The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/sched_ule.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright (c) 2002-2007, Jeffrey Roberson <jeff@freebsd.org>
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice unmodified, this list of conditions, and the following
   12  *    disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   20  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   27  */
   28 
   29 /*
   30  * This file implements the ULE scheduler.  ULE supports independent CPU
   31  * run queues and fine grain locking.  It has superior interactive
   32  * performance under load even on uni-processor systems.
   33  *
   34  * etymology:
   35  *   ULE is the last three letters in schedule.  It owes its name to a
   36  * generic user created for a scheduling system by Paul Mikesell at
   37  * Isilon Systems and a general lack of creativity on the part of the author.
   38  */
   39 
   40 #include <sys/cdefs.h>
   41 __FBSDID("$FreeBSD: head/sys/kern/sched_ule.c 336855 2018-07-29 00:30:06Z truckman $");
   42 
   43 #include "opt_hwpmc_hooks.h"
   44 #include "opt_sched.h"
   45 
   46 #include <sys/param.h>
   47 #include <sys/systm.h>
   48 #include <sys/kdb.h>
   49 #include <sys/kernel.h>
   50 #include <sys/ktr.h>
   51 #include <sys/limits.h>
   52 #include <sys/lock.h>
   53 #include <sys/mutex.h>
   54 #include <sys/proc.h>
   55 #include <sys/resource.h>
   56 #include <sys/resourcevar.h>
   57 #include <sys/sched.h>
   58 #include <sys/sdt.h>
   59 #include <sys/smp.h>
   60 #include <sys/sx.h>
   61 #include <sys/sysctl.h>
   62 #include <sys/sysproto.h>
   63 #include <sys/turnstile.h>
   64 #include <sys/umtx.h>
   65 #include <sys/vmmeter.h>
   66 #include <sys/cpuset.h>
   67 #include <sys/sbuf.h>
   68 
   69 #ifdef HWPMC_HOOKS
   70 #include <sys/pmckern.h>
   71 #endif
   72 
   73 #ifdef KDTRACE_HOOKS
   74 #include <sys/dtrace_bsd.h>
   75 int                             dtrace_vtime_active;
   76 dtrace_vtime_switch_func_t      dtrace_vtime_switch_func;
   77 #endif
   78 
   79 #include <machine/cpu.h>
   80 #include <machine/smp.h>
   81 
   82 #define KTR_ULE 0
   83 
   84 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
   85 #define TDQ_NAME_LEN    (sizeof("sched lock ") + sizeof(__XSTRING(MAXCPU)))
   86 #define TDQ_LOADNAME_LEN        (sizeof("CPU ") + sizeof(__XSTRING(MAXCPU)) - 1 + sizeof(" load"))
   87 
   88 /*
   89  * Thread scheduler specific section.  All fields are protected
   90  * by the thread lock.
   91  */
   92 struct td_sched {       
   93         struct runq     *ts_runq;       /* Run-queue we're queued on. */
   94         short           ts_flags;       /* TSF_* flags. */
   95         int             ts_cpu;         /* CPU that we have affinity for. */
   96         int             ts_rltick;      /* Real last tick, for affinity. */
   97         int             ts_slice;       /* Ticks of slice remaining. */
   98         u_int           ts_slptime;     /* Number of ticks we vol. slept */
   99         u_int           ts_runtime;     /* Number of ticks we were running */
  100         int             ts_ltick;       /* Last tick that we were running on */
  101         int             ts_ftick;       /* First tick that we were running on */
  102         int             ts_ticks;       /* Tick count */
  103 #ifdef KTR
  104         char            ts_name[TS_NAME_LEN];
  105 #endif
  106 };
  107 /* flags kept in ts_flags */
  108 #define TSF_BOUND       0x0001          /* Thread can not migrate. */
  109 #define TSF_XFERABLE    0x0002          /* Thread was added as transferable. */
  110 
  111 #define THREAD_CAN_MIGRATE(td)  ((td)->td_pinned == 0)
  112 #define THREAD_CAN_SCHED(td, cpu)       \
  113     CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
  114 
  115 _Static_assert(sizeof(struct thread) + sizeof(struct td_sched) <=
  116     sizeof(struct thread0_storage),
  117     "increase struct thread0_storage.t0st_sched size");
  118 
  119 /*
  120  * Priority ranges used for interactive and non-interactive timeshare
  121  * threads.  The timeshare priorities are split up into four ranges.
  122  * The first range handles interactive threads.  The last three ranges
  123  * (NHALF, x, and NHALF) handle non-interactive threads with the outer
  124  * ranges supporting nice values.
  125  */
  126 #define PRI_TIMESHARE_RANGE     (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE + 1)
  127 #define PRI_INTERACT_RANGE      ((PRI_TIMESHARE_RANGE - SCHED_PRI_NRESV) / 2)
  128 #define PRI_BATCH_RANGE         (PRI_TIMESHARE_RANGE - PRI_INTERACT_RANGE)
  129 
  130 #define PRI_MIN_INTERACT        PRI_MIN_TIMESHARE
  131 #define PRI_MAX_INTERACT        (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE - 1)
  132 #define PRI_MIN_BATCH           (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE)
  133 #define PRI_MAX_BATCH           PRI_MAX_TIMESHARE
  134 
  135 /*
  136  * Cpu percentage computation macros and defines.
  137  *
  138  * SCHED_TICK_SECS:     Number of seconds to average the cpu usage across.
  139  * SCHED_TICK_TARG:     Number of hz ticks to average the cpu usage across.
  140  * SCHED_TICK_MAX:      Maximum number of ticks before scaling back.
  141  * SCHED_TICK_SHIFT:    Shift factor to avoid rounding away results.
  142  * SCHED_TICK_HZ:       Compute the number of hz ticks for a given ticks count.
  143  * SCHED_TICK_TOTAL:    Gives the amount of time we've been recording ticks.
  144  */
  145 #define SCHED_TICK_SECS         10
  146 #define SCHED_TICK_TARG         (hz * SCHED_TICK_SECS)
  147 #define SCHED_TICK_MAX          (SCHED_TICK_TARG + hz)
  148 #define SCHED_TICK_SHIFT        10
  149 #define SCHED_TICK_HZ(ts)       ((ts)->ts_ticks >> SCHED_TICK_SHIFT)
  150 #define SCHED_TICK_TOTAL(ts)    (max((ts)->ts_ltick - (ts)->ts_ftick, hz))
  151 
  152 /*
  153  * These macros determine priorities for non-interactive threads.  They are
  154  * assigned a priority based on their recent cpu utilization as expressed
  155  * by the ratio of ticks to the tick total.  NHALF priorities at the start
  156  * and end of the MIN to MAX timeshare range are only reachable with negative
  157  * or positive nice respectively.
  158  *
  159  * PRI_RANGE:   Priority range for utilization dependent priorities.
  160  * PRI_NRESV:   Number of nice values.
  161  * PRI_TICKS:   Compute a priority in PRI_RANGE from the ticks count and total.
  162  * PRI_NICE:    Determines the part of the priority inherited from nice.
  163  */
  164 #define SCHED_PRI_NRESV         (PRIO_MAX - PRIO_MIN)
  165 #define SCHED_PRI_NHALF         (SCHED_PRI_NRESV / 2)
  166 #define SCHED_PRI_MIN           (PRI_MIN_BATCH + SCHED_PRI_NHALF)
  167 #define SCHED_PRI_MAX           (PRI_MAX_BATCH - SCHED_PRI_NHALF)
  168 #define SCHED_PRI_RANGE         (SCHED_PRI_MAX - SCHED_PRI_MIN + 1)
  169 #define SCHED_PRI_TICKS(ts)                                             \
  170     (SCHED_TICK_HZ((ts)) /                                              \
  171     (roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE))
  172 #define SCHED_PRI_NICE(nice)    (nice)
  173 
  174 /*
  175  * These determine the interactivity of a process.  Interactivity differs from
  176  * cpu utilization in that it expresses the voluntary time slept vs time ran
  177  * while cpu utilization includes all time not running.  This more accurately
  178  * models the intent of the thread.
  179  *
  180  * SLP_RUN_MAX: Maximum amount of sleep time + run time we'll accumulate
  181  *              before throttling back.
  182  * SLP_RUN_FORK:        Maximum slp+run time to inherit at fork time.
  183  * INTERACT_MAX:        Maximum interactivity value.  Smaller is better.
  184  * INTERACT_THRESH:     Threshold for placement on the current runq.
  185  */
  186 #define SCHED_SLP_RUN_MAX       ((hz * 5) << SCHED_TICK_SHIFT)
  187 #define SCHED_SLP_RUN_FORK      ((hz / 2) << SCHED_TICK_SHIFT)
  188 #define SCHED_INTERACT_MAX      (100)
  189 #define SCHED_INTERACT_HALF     (SCHED_INTERACT_MAX / 2)
  190 #define SCHED_INTERACT_THRESH   (30)
  191 
  192 /*
  193  * These parameters determine the slice behavior for batch work.
  194  */
  195 #define SCHED_SLICE_DEFAULT_DIVISOR     10      /* ~94 ms, 12 stathz ticks. */
  196 #define SCHED_SLICE_MIN_DIVISOR         6       /* DEFAULT/MIN = ~16 ms. */
  197 
  198 /* Flags kept in td_flags. */
  199 #define TDF_SLICEEND    TDF_SCHED2      /* Thread time slice is over. */
  200 
  201 /*
  202  * tickincr:            Converts a stathz tick into a hz domain scaled by
  203  *                      the shift factor.  Without the shift the error rate
  204  *                      due to rounding would be unacceptably high.
  205  * realstathz:          stathz is sometimes 0 and run off of hz.
  206  * sched_slice:         Runtime of each thread before rescheduling.
  207  * preempt_thresh:      Priority threshold for preemption and remote IPIs.
  208  */
  209 static int sched_interact = SCHED_INTERACT_THRESH;
  210 static int tickincr = 8 << SCHED_TICK_SHIFT;
  211 static int realstathz = 127;    /* reset during boot. */
  212 static int sched_slice = 10;    /* reset during boot. */
  213 static int sched_slice_min = 1; /* reset during boot. */
  214 #ifdef PREEMPTION
  215 #ifdef FULL_PREEMPTION
  216 static int preempt_thresh = PRI_MAX_IDLE;
  217 #else
  218 static int preempt_thresh = PRI_MIN_KERN;
  219 #endif
  220 #else 
  221 static int preempt_thresh = 0;
  222 #endif
  223 static int static_boost = PRI_MIN_BATCH;
  224 static int sched_idlespins = 10000;
  225 static int sched_idlespinthresh = -1;
  226 
  227 /*
  228  * tdq - per processor runqs and statistics.  All fields are protected by the
  229  * tdq_lock.  The load and lowpri may be accessed without to avoid excess
  230  * locking in sched_pickcpu();
  231  */
  232 struct tdq {
  233         /* 
  234          * Ordered to improve efficiency of cpu_search() and switch().
  235          * tdq_lock is padded to avoid false sharing with tdq_load and
  236          * tdq_cpu_idle.
  237          */
  238         struct mtx_padalign tdq_lock;           /* run queue lock. */
  239         struct cpu_group *tdq_cg;               /* Pointer to cpu topology. */
  240         volatile int    tdq_load;               /* Aggregate load. */
  241         volatile int    tdq_cpu_idle;           /* cpu_idle() is active. */
  242         int             tdq_sysload;            /* For loadavg, !ITHD load. */
  243         volatile int    tdq_transferable;       /* Transferable thread count. */
  244         volatile short  tdq_switchcnt;          /* Switches this tick. */
  245         volatile short  tdq_oldswitchcnt;       /* Switches last tick. */
  246         u_char          tdq_lowpri;             /* Lowest priority thread. */
  247         u_char          tdq_ipipending;         /* IPI pending. */
  248         u_char          tdq_idx;                /* Current insert index. */
  249         u_char          tdq_ridx;               /* Current removal index. */
  250         struct runq     tdq_realtime;           /* real-time run queue. */
  251         struct runq     tdq_timeshare;          /* timeshare run queue. */
  252         struct runq     tdq_idle;               /* Queue of IDLE threads. */
  253         char            tdq_name[TDQ_NAME_LEN];
  254 #ifdef KTR
  255         char            tdq_loadname[TDQ_LOADNAME_LEN];
  256 #endif
  257 } __aligned(64);
  258 
  259 /* Idle thread states and config. */
  260 #define TDQ_RUNNING     1
  261 #define TDQ_IDLE        2
  262 
  263 #ifdef SMP
  264 struct cpu_group *cpu_top;              /* CPU topology */
  265 
  266 #define SCHED_AFFINITY_DEFAULT  (max(1, hz / 1000))
  267 #define SCHED_AFFINITY(ts, t)   ((ts)->ts_rltick > ticks - ((t) * affinity))
  268 
  269 /*
  270  * Run-time tunables.
  271  */
  272 static int rebalance = 1;
  273 static int balance_interval = 128;      /* Default set in sched_initticks(). */
  274 static int affinity;
  275 static int steal_idle = 1;
  276 static int steal_thresh = 2;
  277 static int always_steal = 0;
  278 static int trysteal_limit = 2;
  279 
  280 /*
  281  * One thread queue per processor.
  282  */
  283 static struct tdq       tdq_cpu[MAXCPU];
  284 static struct tdq       *balance_tdq;
  285 static int balance_ticks;
  286 DPCPU_DEFINE_STATIC(uint32_t, randomval);
  287 
  288 #define TDQ_SELF()      (&tdq_cpu[PCPU_GET(cpuid)])
  289 #define TDQ_CPU(x)      (&tdq_cpu[(x)])
  290 #define TDQ_ID(x)       ((int)((x) - tdq_cpu))
  291 #else   /* !SMP */
  292 static struct tdq       tdq_cpu;
  293 
  294 #define TDQ_ID(x)       (0)
  295 #define TDQ_SELF()      (&tdq_cpu)
  296 #define TDQ_CPU(x)      (&tdq_cpu)
  297 #endif
  298 
  299 #define TDQ_LOCK_ASSERT(t, type)        mtx_assert(TDQ_LOCKPTR((t)), (type))
  300 #define TDQ_LOCK(t)             mtx_lock_spin(TDQ_LOCKPTR((t)))
  301 #define TDQ_LOCK_FLAGS(t, f)    mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f))
  302 #define TDQ_UNLOCK(t)           mtx_unlock_spin(TDQ_LOCKPTR((t)))
  303 #define TDQ_LOCKPTR(t)          ((struct mtx *)(&(t)->tdq_lock))
  304 
  305 static void sched_priority(struct thread *);
  306 static void sched_thread_priority(struct thread *, u_char);
  307 static int sched_interact_score(struct thread *);
  308 static void sched_interact_update(struct thread *);
  309 static void sched_interact_fork(struct thread *);
  310 static void sched_pctcpu_update(struct td_sched *, int);
  311 
  312 /* Operations on per processor queues */
  313 static struct thread *tdq_choose(struct tdq *);
  314 static void tdq_setup(struct tdq *);
  315 static void tdq_load_add(struct tdq *, struct thread *);
  316 static void tdq_load_rem(struct tdq *, struct thread *);
  317 static __inline void tdq_runq_add(struct tdq *, struct thread *, int);
  318 static __inline void tdq_runq_rem(struct tdq *, struct thread *);
  319 static inline int sched_shouldpreempt(int, int, int);
  320 void tdq_print(int cpu);
  321 static void runq_print(struct runq *rq);
  322 static void tdq_add(struct tdq *, struct thread *, int);
  323 #ifdef SMP
  324 static struct thread *tdq_move(struct tdq *, struct tdq *);
  325 static int tdq_idled(struct tdq *);
  326 static void tdq_notify(struct tdq *, struct thread *);
  327 static struct thread *tdq_steal(struct tdq *, int);
  328 static struct thread *runq_steal(struct runq *, int);
  329 static int sched_pickcpu(struct thread *, int);
  330 static void sched_balance(void);
  331 static int sched_balance_pair(struct tdq *, struct tdq *);
  332 static inline struct tdq *sched_setcpu(struct thread *, int, int);
  333 static inline void thread_unblock_switch(struct thread *, struct mtx *);
  334 static struct mtx *sched_switch_migrate(struct tdq *, struct thread *, int);
  335 static int sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS);
  336 static int sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, 
  337     struct cpu_group *cg, int indent);
  338 #endif
  339 
  340 static void sched_setup(void *dummy);
  341 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
  342 
  343 static void sched_initticks(void *dummy);
  344 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
  345     NULL);
  346 
  347 SDT_PROVIDER_DEFINE(sched);
  348 
  349 SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *", 
  350     "struct proc *", "uint8_t");
  351 SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *", 
  352     "struct proc *", "void *");
  353 SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *", 
  354     "struct proc *", "void *", "int");
  355 SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *", 
  356     "struct proc *", "uint8_t", "struct thread *");
  357 SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int");
  358 SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *", 
  359     "struct proc *");
  360 SDT_PROBE_DEFINE(sched, , , on__cpu);
  361 SDT_PROBE_DEFINE(sched, , , remain__cpu);
  362 SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *", 
  363     "struct proc *");
  364 
  365 /*
  366  * Print the threads waiting on a run-queue.
  367  */
  368 static void
  369 runq_print(struct runq *rq)
  370 {
  371         struct rqhead *rqh;
  372         struct thread *td;
  373         int pri;
  374         int j;
  375         int i;
  376 
  377         for (i = 0; i < RQB_LEN; i++) {
  378                 printf("\t\trunq bits %d 0x%zx\n",
  379                     i, rq->rq_status.rqb_bits[i]);
  380                 for (j = 0; j < RQB_BPW; j++)
  381                         if (rq->rq_status.rqb_bits[i] & (1ul << j)) {
  382                                 pri = j + (i << RQB_L2BPW);
  383                                 rqh = &rq->rq_queues[pri];
  384                                 TAILQ_FOREACH(td, rqh, td_runq) {
  385                                         printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
  386                                             td, td->td_name, td->td_priority,
  387                                             td->td_rqindex, pri);
  388                                 }
  389                         }
  390         }
  391 }
  392 
  393 /*
  394  * Print the status of a per-cpu thread queue.  Should be a ddb show cmd.
  395  */
  396 void
  397 tdq_print(int cpu)
  398 {
  399         struct tdq *tdq;
  400 
  401         tdq = TDQ_CPU(cpu);
  402 
  403         printf("tdq %d:\n", TDQ_ID(tdq));
  404         printf("\tlock            %p\n", TDQ_LOCKPTR(tdq));
  405         printf("\tLock name:      %s\n", tdq->tdq_name);
  406         printf("\tload:           %d\n", tdq->tdq_load);
  407         printf("\tswitch cnt:     %d\n", tdq->tdq_switchcnt);
  408         printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt);
  409         printf("\ttimeshare idx:  %d\n", tdq->tdq_idx);
  410         printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
  411         printf("\tload transferable: %d\n", tdq->tdq_transferable);
  412         printf("\tlowest priority:   %d\n", tdq->tdq_lowpri);
  413         printf("\trealtime runq:\n");
  414         runq_print(&tdq->tdq_realtime);
  415         printf("\ttimeshare runq:\n");
  416         runq_print(&tdq->tdq_timeshare);
  417         printf("\tidle runq:\n");
  418         runq_print(&tdq->tdq_idle);
  419 }
  420 
  421 static inline int
  422 sched_shouldpreempt(int pri, int cpri, int remote)
  423 {
  424         /*
  425          * If the new priority is not better than the current priority there is
  426          * nothing to do.
  427          */
  428         if (pri >= cpri)
  429                 return (0);
  430         /*
  431          * Always preempt idle.
  432          */
  433         if (cpri >= PRI_MIN_IDLE)
  434                 return (1);
  435         /*
  436          * If preemption is disabled don't preempt others.
  437          */
  438         if (preempt_thresh == 0)
  439                 return (0);
  440         /*
  441          * Preempt if we exceed the threshold.
  442          */
  443         if (pri <= preempt_thresh)
  444                 return (1);
  445         /*
  446          * If we're interactive or better and there is non-interactive
  447          * or worse running preempt only remote processors.
  448          */
  449         if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT)
  450                 return (1);
  451         return (0);
  452 }
  453 
  454 /*
  455  * Add a thread to the actual run-queue.  Keeps transferable counts up to
  456  * date with what is actually on the run-queue.  Selects the correct
  457  * queue position for timeshare threads.
  458  */
  459 static __inline void
  460 tdq_runq_add(struct tdq *tdq, struct thread *td, int flags)
  461 {
  462         struct td_sched *ts;
  463         u_char pri;
  464 
  465         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  466         THREAD_LOCK_ASSERT(td, MA_OWNED);
  467 
  468         pri = td->td_priority;
  469         ts = td_get_sched(td);
  470         TD_SET_RUNQ(td);
  471         if (THREAD_CAN_MIGRATE(td)) {
  472                 tdq->tdq_transferable++;
  473                 ts->ts_flags |= TSF_XFERABLE;
  474         }
  475         if (pri < PRI_MIN_BATCH) {
  476                 ts->ts_runq = &tdq->tdq_realtime;
  477         } else if (pri <= PRI_MAX_BATCH) {
  478                 ts->ts_runq = &tdq->tdq_timeshare;
  479                 KASSERT(pri <= PRI_MAX_BATCH && pri >= PRI_MIN_BATCH,
  480                         ("Invalid priority %d on timeshare runq", pri));
  481                 /*
  482                  * This queue contains only priorities between MIN and MAX
  483                  * realtime.  Use the whole queue to represent these values.
  484                  */
  485                 if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) {
  486                         pri = RQ_NQS * (pri - PRI_MIN_BATCH) / PRI_BATCH_RANGE;
  487                         pri = (pri + tdq->tdq_idx) % RQ_NQS;
  488                         /*
  489                          * This effectively shortens the queue by one so we
  490                          * can have a one slot difference between idx and
  491                          * ridx while we wait for threads to drain.
  492                          */
  493                         if (tdq->tdq_ridx != tdq->tdq_idx &&
  494                             pri == tdq->tdq_ridx)
  495                                 pri = (unsigned char)(pri - 1) % RQ_NQS;
  496                 } else
  497                         pri = tdq->tdq_ridx;
  498                 runq_add_pri(ts->ts_runq, td, pri, flags);
  499                 return;
  500         } else
  501                 ts->ts_runq = &tdq->tdq_idle;
  502         runq_add(ts->ts_runq, td, flags);
  503 }
  504 
  505 /* 
  506  * Remove a thread from a run-queue.  This typically happens when a thread
  507  * is selected to run.  Running threads are not on the queue and the
  508  * transferable count does not reflect them.
  509  */
  510 static __inline void
  511 tdq_runq_rem(struct tdq *tdq, struct thread *td)
  512 {
  513         struct td_sched *ts;
  514 
  515         ts = td_get_sched(td);
  516         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  517         KASSERT(ts->ts_runq != NULL,
  518             ("tdq_runq_remove: thread %p null ts_runq", td));
  519         if (ts->ts_flags & TSF_XFERABLE) {
  520                 tdq->tdq_transferable--;
  521                 ts->ts_flags &= ~TSF_XFERABLE;
  522         }
  523         if (ts->ts_runq == &tdq->tdq_timeshare) {
  524                 if (tdq->tdq_idx != tdq->tdq_ridx)
  525                         runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx);
  526                 else
  527                         runq_remove_idx(ts->ts_runq, td, NULL);
  528         } else
  529                 runq_remove(ts->ts_runq, td);
  530 }
  531 
  532 /*
  533  * Load is maintained for all threads RUNNING and ON_RUNQ.  Add the load
  534  * for this thread to the referenced thread queue.
  535  */
  536 static void
  537 tdq_load_add(struct tdq *tdq, struct thread *td)
  538 {
  539 
  540         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  541         THREAD_LOCK_ASSERT(td, MA_OWNED);
  542 
  543         tdq->tdq_load++;
  544         if ((td->td_flags & TDF_NOLOAD) == 0)
  545                 tdq->tdq_sysload++;
  546         KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
  547         SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
  548 }
  549 
  550 /*
  551  * Remove the load from a thread that is transitioning to a sleep state or
  552  * exiting.
  553  */
  554 static void
  555 tdq_load_rem(struct tdq *tdq, struct thread *td)
  556 {
  557 
  558         THREAD_LOCK_ASSERT(td, MA_OWNED);
  559         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  560         KASSERT(tdq->tdq_load != 0,
  561             ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
  562 
  563         tdq->tdq_load--;
  564         if ((td->td_flags & TDF_NOLOAD) == 0)
  565                 tdq->tdq_sysload--;
  566         KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
  567         SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
  568 }
  569 
  570 /*
  571  * Bound timeshare latency by decreasing slice size as load increases.  We
  572  * consider the maximum latency as the sum of the threads waiting to run
  573  * aside from curthread and target no more than sched_slice latency but
  574  * no less than sched_slice_min runtime.
  575  */
  576 static inline int
  577 tdq_slice(struct tdq *tdq)
  578 {
  579         int load;
  580 
  581         /*
  582          * It is safe to use sys_load here because this is called from
  583          * contexts where timeshare threads are running and so there
  584          * cannot be higher priority load in the system.
  585          */
  586         load = tdq->tdq_sysload - 1;
  587         if (load >= SCHED_SLICE_MIN_DIVISOR)
  588                 return (sched_slice_min);
  589         if (load <= 1)
  590                 return (sched_slice);
  591         return (sched_slice / load);
  592 }
  593 
  594 /*
  595  * Set lowpri to its exact value by searching the run-queue and
  596  * evaluating curthread.  curthread may be passed as an optimization.
  597  */
  598 static void
  599 tdq_setlowpri(struct tdq *tdq, struct thread *ctd)
  600 {
  601         struct thread *td;
  602 
  603         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  604         if (ctd == NULL)
  605                 ctd = pcpu_find(TDQ_ID(tdq))->pc_curthread;
  606         td = tdq_choose(tdq);
  607         if (td == NULL || td->td_priority > ctd->td_priority)
  608                 tdq->tdq_lowpri = ctd->td_priority;
  609         else
  610                 tdq->tdq_lowpri = td->td_priority;
  611 }
  612 
  613 #ifdef SMP
  614 /*
  615  * We need some randomness. Implement a classic Linear Congruential
  616  * Generator X_{n+1}=(aX_n+c) mod m. These values are optimized for
  617  * m = 2^32, a = 69069 and c = 5. We only return the upper 16 bits
  618  * of the random state (in the low bits of our answer) to keep
  619  * the maximum randomness.
  620  */
  621 static uint32_t
  622 sched_random(void)
  623 {
  624         uint32_t *rndptr;
  625 
  626         rndptr = DPCPU_PTR(randomval);
  627         *rndptr = *rndptr * 69069 + 5;
  628 
  629         return (*rndptr >> 16);
  630 }
  631 
  632 struct cpu_search {
  633         cpuset_t cs_mask;
  634         u_int   cs_prefer;
  635         int     cs_pri;         /* Min priority for low. */
  636         int     cs_limit;       /* Max load for low, min load for high. */
  637         int     cs_cpu;
  638         int     cs_load;
  639 };
  640 
  641 #define CPU_SEARCH_LOWEST       0x1
  642 #define CPU_SEARCH_HIGHEST      0x2
  643 #define CPU_SEARCH_BOTH         (CPU_SEARCH_LOWEST|CPU_SEARCH_HIGHEST)
  644 
  645 #define CPUSET_FOREACH(cpu, mask)                               \
  646         for ((cpu) = 0; (cpu) <= mp_maxid; (cpu)++)             \
  647                 if (CPU_ISSET(cpu, &mask))
  648 
  649 static __always_inline int cpu_search(const struct cpu_group *cg,
  650     struct cpu_search *low, struct cpu_search *high, const int match);
  651 int __noinline cpu_search_lowest(const struct cpu_group *cg,
  652     struct cpu_search *low);
  653 int __noinline cpu_search_highest(const struct cpu_group *cg,
  654     struct cpu_search *high);
  655 int __noinline cpu_search_both(const struct cpu_group *cg,
  656     struct cpu_search *low, struct cpu_search *high);
  657 
  658 /*
  659  * Search the tree of cpu_groups for the lowest or highest loaded cpu
  660  * according to the match argument.  This routine actually compares the
  661  * load on all paths through the tree and finds the least loaded cpu on
  662  * the least loaded path, which may differ from the least loaded cpu in
  663  * the system.  This balances work among caches and buses.
  664  *
  665  * This inline is instantiated in three forms below using constants for the
  666  * match argument.  It is reduced to the minimum set for each case.  It is
  667  * also recursive to the depth of the tree.
  668  */
  669 static __always_inline int
  670 cpu_search(const struct cpu_group *cg, struct cpu_search *low,
  671     struct cpu_search *high, const int match)
  672 {
  673         struct cpu_search lgroup;
  674         struct cpu_search hgroup;
  675         cpuset_t cpumask;
  676         struct cpu_group *child;
  677         struct tdq *tdq;
  678         int cpu, i, hload, lload, load, total, rnd;
  679 
  680         total = 0;
  681         cpumask = cg->cg_mask;
  682         if (match & CPU_SEARCH_LOWEST) {
  683                 lload = INT_MAX;
  684                 lgroup = *low;
  685         }
  686         if (match & CPU_SEARCH_HIGHEST) {
  687                 hload = INT_MIN;
  688                 hgroup = *high;
  689         }
  690 
  691         /* Iterate through the child CPU groups and then remaining CPUs. */
  692         for (i = cg->cg_children, cpu = mp_maxid; ; ) {
  693                 if (i == 0) {
  694 #ifdef HAVE_INLINE_FFSL
  695                         cpu = CPU_FFS(&cpumask) - 1;
  696 #else
  697                         while (cpu >= 0 && !CPU_ISSET(cpu, &cpumask))
  698                                 cpu--;
  699 #endif
  700                         if (cpu < 0)
  701                                 break;
  702                         child = NULL;
  703                 } else
  704                         child = &cg->cg_child[i - 1];
  705 
  706                 if (match & CPU_SEARCH_LOWEST)
  707                         lgroup.cs_cpu = -1;
  708                 if (match & CPU_SEARCH_HIGHEST)
  709                         hgroup.cs_cpu = -1;
  710                 if (child) {                    /* Handle child CPU group. */
  711                         CPU_NAND(&cpumask, &child->cg_mask);
  712                         switch (match) {
  713                         case CPU_SEARCH_LOWEST:
  714                                 load = cpu_search_lowest(child, &lgroup);
  715                                 break;
  716                         case CPU_SEARCH_HIGHEST:
  717                                 load = cpu_search_highest(child, &hgroup);
  718                                 break;
  719                         case CPU_SEARCH_BOTH:
  720                                 load = cpu_search_both(child, &lgroup, &hgroup);
  721                                 break;
  722                         }
  723                 } else {                        /* Handle child CPU. */
  724                         CPU_CLR(cpu, &cpumask);
  725                         tdq = TDQ_CPU(cpu);
  726                         load = tdq->tdq_load * 256;
  727                         rnd = sched_random() % 32;
  728                         if (match & CPU_SEARCH_LOWEST) {
  729                                 if (cpu == low->cs_prefer)
  730                                         load -= 64;
  731                                 /* If that CPU is allowed and get data. */
  732                                 if (tdq->tdq_lowpri > lgroup.cs_pri &&
  733                                     tdq->tdq_load <= lgroup.cs_limit &&
  734                                     CPU_ISSET(cpu, &lgroup.cs_mask)) {
  735                                         lgroup.cs_cpu = cpu;
  736                                         lgroup.cs_load = load - rnd;
  737                                 }
  738                         }
  739                         if (match & CPU_SEARCH_HIGHEST)
  740                                 if (tdq->tdq_load >= hgroup.cs_limit &&
  741                                     tdq->tdq_transferable &&
  742                                     CPU_ISSET(cpu, &hgroup.cs_mask)) {
  743                                         hgroup.cs_cpu = cpu;
  744                                         hgroup.cs_load = load - rnd;
  745                                 }
  746                 }
  747                 total += load;
  748 
  749                 /* We have info about child item. Compare it. */
  750                 if (match & CPU_SEARCH_LOWEST) {
  751                         if (lgroup.cs_cpu >= 0 &&
  752                             (load < lload ||
  753                              (load == lload && lgroup.cs_load < low->cs_load))) {
  754                                 lload = load;
  755                                 low->cs_cpu = lgroup.cs_cpu;
  756                                 low->cs_load = lgroup.cs_load;
  757                         }
  758                 }
  759                 if (match & CPU_SEARCH_HIGHEST)
  760                         if (hgroup.cs_cpu >= 0 &&
  761                             (load > hload ||
  762                              (load == hload && hgroup.cs_load > high->cs_load))) {
  763                                 hload = load;
  764                                 high->cs_cpu = hgroup.cs_cpu;
  765                                 high->cs_load = hgroup.cs_load;
  766                         }
  767                 if (child) {
  768                         i--;
  769                         if (i == 0 && CPU_EMPTY(&cpumask))
  770                                 break;
  771                 }
  772 #ifndef HAVE_INLINE_FFSL
  773                 else
  774                         cpu--;
  775 #endif
  776         }
  777         return (total);
  778 }
  779 
  780 /*
  781  * cpu_search instantiations must pass constants to maintain the inline
  782  * optimization.
  783  */
  784 int
  785 cpu_search_lowest(const struct cpu_group *cg, struct cpu_search *low)
  786 {
  787         return cpu_search(cg, low, NULL, CPU_SEARCH_LOWEST);
  788 }
  789 
  790 int
  791 cpu_search_highest(const struct cpu_group *cg, struct cpu_search *high)
  792 {
  793         return cpu_search(cg, NULL, high, CPU_SEARCH_HIGHEST);
  794 }
  795 
  796 int
  797 cpu_search_both(const struct cpu_group *cg, struct cpu_search *low,
  798     struct cpu_search *high)
  799 {
  800         return cpu_search(cg, low, high, CPU_SEARCH_BOTH);
  801 }
  802 
  803 /*
  804  * Find the cpu with the least load via the least loaded path that has a
  805  * lowpri greater than pri  pri.  A pri of -1 indicates any priority is
  806  * acceptable.
  807  */
  808 static inline int
  809 sched_lowest(const struct cpu_group *cg, cpuset_t mask, int pri, int maxload,
  810     int prefer)
  811 {
  812         struct cpu_search low;
  813 
  814         low.cs_cpu = -1;
  815         low.cs_prefer = prefer;
  816         low.cs_mask = mask;
  817         low.cs_pri = pri;
  818         low.cs_limit = maxload;
  819         cpu_search_lowest(cg, &low);
  820         return low.cs_cpu;
  821 }
  822 
  823 /*
  824  * Find the cpu with the highest load via the highest loaded path.
  825  */
  826 static inline int
  827 sched_highest(const struct cpu_group *cg, cpuset_t mask, int minload)
  828 {
  829         struct cpu_search high;
  830 
  831         high.cs_cpu = -1;
  832         high.cs_mask = mask;
  833         high.cs_limit = minload;
  834         cpu_search_highest(cg, &high);
  835         return high.cs_cpu;
  836 }
  837 
  838 static void
  839 sched_balance_group(struct cpu_group *cg)
  840 {
  841         cpuset_t hmask, lmask;
  842         int high, low, anylow;
  843 
  844         CPU_FILL(&hmask);
  845         for (;;) {
  846                 high = sched_highest(cg, hmask, 2);
  847                 /* Stop if there is no more CPU with transferrable threads. */
  848                 if (high == -1)
  849                         break;
  850                 CPU_CLR(high, &hmask);
  851                 CPU_COPY(&hmask, &lmask);
  852                 /* Stop if there is no more CPU left for low. */
  853                 if (CPU_EMPTY(&lmask))
  854                         break;
  855                 anylow = 1;
  856 nextlow:
  857                 low = sched_lowest(cg, lmask, -1,
  858                     TDQ_CPU(high)->tdq_load - 1, high);
  859                 /* Stop if we looked well and found no less loaded CPU. */
  860                 if (anylow && low == -1)
  861                         break;
  862                 /* Go to next high if we found no less loaded CPU. */
  863                 if (low == -1)
  864                         continue;
  865                 /* Transfer thread from high to low. */
  866                 if (sched_balance_pair(TDQ_CPU(high), TDQ_CPU(low))) {
  867                         /* CPU that got thread can no longer be a donor. */
  868                         CPU_CLR(low, &hmask);
  869                 } else {
  870                         /*
  871                          * If failed, then there is no threads on high
  872                          * that can run on this low. Drop low from low
  873                          * mask and look for different one.
  874                          */
  875                         CPU_CLR(low, &lmask);
  876                         anylow = 0;
  877                         goto nextlow;
  878                 }
  879         }
  880 }
  881 
  882 static void
  883 sched_balance(void)
  884 {
  885         struct tdq *tdq;
  886 
  887         balance_ticks = max(balance_interval / 2, 1) +
  888             (sched_random() % balance_interval);
  889         tdq = TDQ_SELF();
  890         TDQ_UNLOCK(tdq);
  891         sched_balance_group(cpu_top);
  892         TDQ_LOCK(tdq);
  893 }
  894 
  895 /*
  896  * Lock two thread queues using their address to maintain lock order.
  897  */
  898 static void
  899 tdq_lock_pair(struct tdq *one, struct tdq *two)
  900 {
  901         if (one < two) {
  902                 TDQ_LOCK(one);
  903                 TDQ_LOCK_FLAGS(two, MTX_DUPOK);
  904         } else {
  905                 TDQ_LOCK(two);
  906                 TDQ_LOCK_FLAGS(one, MTX_DUPOK);
  907         }
  908 }
  909 
  910 /*
  911  * Unlock two thread queues.  Order is not important here.
  912  */
  913 static void
  914 tdq_unlock_pair(struct tdq *one, struct tdq *two)
  915 {
  916         TDQ_UNLOCK(one);
  917         TDQ_UNLOCK(two);
  918 }
  919 
  920 /*
  921  * Transfer load between two imbalanced thread queues.
  922  */
  923 static int
  924 sched_balance_pair(struct tdq *high, struct tdq *low)
  925 {
  926         struct thread *td;
  927         int cpu;
  928 
  929         tdq_lock_pair(high, low);
  930         td = NULL;
  931         /*
  932          * Transfer a thread from high to low.
  933          */
  934         if (high->tdq_transferable != 0 && high->tdq_load > low->tdq_load &&
  935             (td = tdq_move(high, low)) != NULL) {
  936                 /*
  937                  * In case the target isn't the current cpu notify it of the
  938                  * new load, possibly sending an IPI to force it to reschedule.
  939                  */
  940                 cpu = TDQ_ID(low);
  941                 if (cpu != PCPU_GET(cpuid))
  942                         tdq_notify(low, td);
  943         }
  944         tdq_unlock_pair(high, low);
  945         return (td != NULL);
  946 }
  947 
  948 /*
  949  * Move a thread from one thread queue to another.
  950  */
  951 static struct thread *
  952 tdq_move(struct tdq *from, struct tdq *to)
  953 {
  954         struct td_sched *ts;
  955         struct thread *td;
  956         struct tdq *tdq;
  957         int cpu;
  958 
  959         TDQ_LOCK_ASSERT(from, MA_OWNED);
  960         TDQ_LOCK_ASSERT(to, MA_OWNED);
  961 
  962         tdq = from;
  963         cpu = TDQ_ID(to);
  964         td = tdq_steal(tdq, cpu);
  965         if (td == NULL)
  966                 return (NULL);
  967         ts = td_get_sched(td);
  968         /*
  969          * Although the run queue is locked the thread may be blocked.  Lock
  970          * it to clear this and acquire the run-queue lock.
  971          */
  972         thread_lock(td);
  973         /* Drop recursive lock on from acquired via thread_lock(). */
  974         TDQ_UNLOCK(from);
  975         sched_rem(td);
  976         ts->ts_cpu = cpu;
  977         td->td_lock = TDQ_LOCKPTR(to);
  978         tdq_add(to, td, SRQ_YIELDING);
  979         return (td);
  980 }
  981 
  982 /*
  983  * This tdq has idled.  Try to steal a thread from another cpu and switch
  984  * to it.
  985  */
  986 static int
  987 tdq_idled(struct tdq *tdq)
  988 {
  989         struct cpu_group *cg;
  990         struct tdq *steal;
  991         cpuset_t mask;
  992         int cpu, switchcnt;
  993 
  994         if (smp_started == 0 || steal_idle == 0 || tdq->tdq_cg == NULL)
  995                 return (1);
  996         CPU_FILL(&mask);
  997         CPU_CLR(PCPU_GET(cpuid), &mask);
  998     restart:
  999         switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 1000         for (cg = tdq->tdq_cg; ; ) {
 1001                 cpu = sched_highest(cg, mask, steal_thresh);
 1002                 /*
 1003                  * We were assigned a thread but not preempted.  Returning
 1004                  * 0 here will cause our caller to switch to it.
 1005                  */
 1006                 if (tdq->tdq_load)
 1007                         return (0);
 1008                 if (cpu == -1) {
 1009                         cg = cg->cg_parent;
 1010                         if (cg == NULL)
 1011                                 return (1);
 1012                         continue;
 1013                 }
 1014                 steal = TDQ_CPU(cpu);
 1015                 /*
 1016                  * The data returned by sched_highest() is stale and
 1017                  * the chosen CPU no longer has an eligible thread.
 1018                  *
 1019                  * Testing this ahead of tdq_lock_pair() only catches
 1020                  * this situation about 20% of the time on an 8 core
 1021                  * 16 thread Ryzen 7, but it still helps performance.
 1022                  */
 1023                 if (steal->tdq_load < steal_thresh ||
 1024                     steal->tdq_transferable == 0)
 1025                         goto restart;
 1026                 tdq_lock_pair(tdq, steal);
 1027                 /*
 1028                  * We were assigned a thread while waiting for the locks.
 1029                  * Switch to it now instead of stealing a thread.
 1030                  */
 1031                 if (tdq->tdq_load)
 1032                         break;
 1033                 /*
 1034                  * The data returned by sched_highest() is stale and
 1035                  * the chosen CPU no longer has an eligible thread, or
 1036                  * we were preempted and the CPU loading info may be out
 1037                  * of date.  The latter is rare.  In either case restart
 1038                  * the search.
 1039                  */
 1040                 if (steal->tdq_load < steal_thresh ||
 1041                     steal->tdq_transferable == 0 ||
 1042                     switchcnt != tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt) {
 1043                         tdq_unlock_pair(tdq, steal);
 1044                         goto restart;
 1045                 }
 1046                 /*
 1047                  * Steal the thread and switch to it.
 1048                  */
 1049                 if (tdq_move(steal, tdq) != NULL)
 1050                         break;
 1051                 /*
 1052                  * We failed to acquire a thread even though it looked
 1053                  * like one was available.  This could be due to affinity
 1054                  * restrictions or for other reasons.  Loop again after
 1055                  * removing this CPU from the set.  The restart logic
 1056                  * above does not restore this CPU to the set due to the
 1057                  * likelyhood of failing here again.
 1058                  */
 1059                 CPU_CLR(cpu, &mask);
 1060                 tdq_unlock_pair(tdq, steal);
 1061         }
 1062         TDQ_UNLOCK(steal);
 1063         mi_switch(SW_VOL | SWT_IDLE, NULL);
 1064         thread_unlock(curthread);
 1065         return (0);
 1066 }
 1067 
 1068 /*
 1069  * Notify a remote cpu of new work.  Sends an IPI if criteria are met.
 1070  */
 1071 static void
 1072 tdq_notify(struct tdq *tdq, struct thread *td)
 1073 {
 1074         struct thread *ctd;
 1075         int pri;
 1076         int cpu;
 1077 
 1078         if (tdq->tdq_ipipending)
 1079                 return;
 1080         cpu = td_get_sched(td)->ts_cpu;
 1081         pri = td->td_priority;
 1082         ctd = pcpu_find(cpu)->pc_curthread;
 1083         if (!sched_shouldpreempt(pri, ctd->td_priority, 1))
 1084                 return;
 1085 
 1086         /*
 1087          * Make sure that our caller's earlier update to tdq_load is
 1088          * globally visible before we read tdq_cpu_idle.  Idle thread
 1089          * accesses both of them without locks, and the order is important.
 1090          */
 1091         atomic_thread_fence_seq_cst();
 1092 
 1093         if (TD_IS_IDLETHREAD(ctd)) {
 1094                 /*
 1095                  * If the MD code has an idle wakeup routine try that before
 1096                  * falling back to IPI.
 1097                  */
 1098                 if (!tdq->tdq_cpu_idle || cpu_idle_wakeup(cpu))
 1099                         return;
 1100         }
 1101         tdq->tdq_ipipending = 1;
 1102         ipi_cpu(cpu, IPI_PREEMPT);
 1103 }
 1104 
 1105 /*
 1106  * Steals load from a timeshare queue.  Honors the rotating queue head
 1107  * index.
 1108  */
 1109 static struct thread *
 1110 runq_steal_from(struct runq *rq, int cpu, u_char start)
 1111 {
 1112         struct rqbits *rqb;
 1113         struct rqhead *rqh;
 1114         struct thread *td, *first;
 1115         int bit;
 1116         int i;
 1117 
 1118         rqb = &rq->rq_status;
 1119         bit = start & (RQB_BPW -1);
 1120         first = NULL;
 1121 again:
 1122         for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
 1123                 if (rqb->rqb_bits[i] == 0)
 1124                         continue;
 1125                 if (bit == 0)
 1126                         bit = RQB_FFS(rqb->rqb_bits[i]);
 1127                 for (; bit < RQB_BPW; bit++) {
 1128                         if ((rqb->rqb_bits[i] & (1ul << bit)) == 0)
 1129                                 continue;
 1130                         rqh = &rq->rq_queues[bit + (i << RQB_L2BPW)];
 1131                         TAILQ_FOREACH(td, rqh, td_runq) {
 1132                                 if (first && THREAD_CAN_MIGRATE(td) &&
 1133                                     THREAD_CAN_SCHED(td, cpu))
 1134                                         return (td);
 1135                                 first = td;
 1136                         }
 1137                 }
 1138         }
 1139         if (start != 0) {
 1140                 start = 0;
 1141                 goto again;
 1142         }
 1143 
 1144         if (first && THREAD_CAN_MIGRATE(first) &&
 1145             THREAD_CAN_SCHED(first, cpu))
 1146                 return (first);
 1147         return (NULL);
 1148 }
 1149 
 1150 /*
 1151  * Steals load from a standard linear queue.
 1152  */
 1153 static struct thread *
 1154 runq_steal(struct runq *rq, int cpu)
 1155 {
 1156         struct rqhead *rqh;
 1157         struct rqbits *rqb;
 1158         struct thread *td;
 1159         int word;
 1160         int bit;
 1161 
 1162         rqb = &rq->rq_status;
 1163         for (word = 0; word < RQB_LEN; word++) {
 1164                 if (rqb->rqb_bits[word] == 0)
 1165                         continue;
 1166                 for (bit = 0; bit < RQB_BPW; bit++) {
 1167                         if ((rqb->rqb_bits[word] & (1ul << bit)) == 0)
 1168                                 continue;
 1169                         rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)];
 1170                         TAILQ_FOREACH(td, rqh, td_runq)
 1171                                 if (THREAD_CAN_MIGRATE(td) &&
 1172                                     THREAD_CAN_SCHED(td, cpu))
 1173                                         return (td);
 1174                 }
 1175         }
 1176         return (NULL);
 1177 }
 1178 
 1179 /*
 1180  * Attempt to steal a thread in priority order from a thread queue.
 1181  */
 1182 static struct thread *
 1183 tdq_steal(struct tdq *tdq, int cpu)
 1184 {
 1185         struct thread *td;
 1186 
 1187         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 1188         if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL)
 1189                 return (td);
 1190         if ((td = runq_steal_from(&tdq->tdq_timeshare,
 1191             cpu, tdq->tdq_ridx)) != NULL)
 1192                 return (td);
 1193         return (runq_steal(&tdq->tdq_idle, cpu));
 1194 }
 1195 
 1196 /*
 1197  * Sets the thread lock and ts_cpu to match the requested cpu.  Unlocks the
 1198  * current lock and returns with the assigned queue locked.
 1199  */
 1200 static inline struct tdq *
 1201 sched_setcpu(struct thread *td, int cpu, int flags)
 1202 {
 1203 
 1204         struct tdq *tdq;
 1205 
 1206         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1207         tdq = TDQ_CPU(cpu);
 1208         td_get_sched(td)->ts_cpu = cpu;
 1209         /*
 1210          * If the lock matches just return the queue.
 1211          */
 1212         if (td->td_lock == TDQ_LOCKPTR(tdq))
 1213                 return (tdq);
 1214 #ifdef notyet
 1215         /*
 1216          * If the thread isn't running its lockptr is a
 1217          * turnstile or a sleepqueue.  We can just lock_set without
 1218          * blocking.
 1219          */
 1220         if (TD_CAN_RUN(td)) {
 1221                 TDQ_LOCK(tdq);
 1222                 thread_lock_set(td, TDQ_LOCKPTR(tdq));
 1223                 return (tdq);
 1224         }
 1225 #endif
 1226         /*
 1227          * The hard case, migration, we need to block the thread first to
 1228          * prevent order reversals with other cpus locks.
 1229          */
 1230         spinlock_enter();
 1231         thread_lock_block(td);
 1232         TDQ_LOCK(tdq);
 1233         thread_lock_unblock(td, TDQ_LOCKPTR(tdq));
 1234         spinlock_exit();
 1235         return (tdq);
 1236 }
 1237 
 1238 SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding");
 1239 SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity");
 1240 SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity");
 1241 SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load");
 1242 SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu");
 1243 SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration");
 1244 
 1245 static int
 1246 sched_pickcpu(struct thread *td, int flags)
 1247 {
 1248         struct cpu_group *cg, *ccg;
 1249         struct td_sched *ts;
 1250         struct tdq *tdq;
 1251         cpuset_t mask;
 1252         int cpu, pri, self;
 1253 
 1254         self = PCPU_GET(cpuid);
 1255         ts = td_get_sched(td);
 1256         KASSERT(!CPU_ABSENT(ts->ts_cpu), ("sched_pickcpu: Start scheduler on "
 1257             "absent CPU %d for thread %s.", ts->ts_cpu, td->td_name));
 1258         if (smp_started == 0)
 1259                 return (self);
 1260         /*
 1261          * Don't migrate a running thread from sched_switch().
 1262          */
 1263         if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td))
 1264                 return (ts->ts_cpu);
 1265         /*
 1266          * Prefer to run interrupt threads on the processors that generate
 1267          * the interrupt.
 1268          */
 1269         pri = td->td_priority;
 1270         if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) &&
 1271             curthread->td_intr_nesting_level && ts->ts_cpu != self) {
 1272                 SCHED_STAT_INC(pickcpu_intrbind);
 1273                 ts->ts_cpu = self;
 1274                 if (TDQ_CPU(self)->tdq_lowpri > pri) {
 1275                         SCHED_STAT_INC(pickcpu_affinity);
 1276                         return (ts->ts_cpu);
 1277                 }
 1278         }
 1279         /*
 1280          * If the thread can run on the last cpu and the affinity has not
 1281          * expired and it is idle, run it there.
 1282          */
 1283         tdq = TDQ_CPU(ts->ts_cpu);
 1284         cg = tdq->tdq_cg;
 1285         if (THREAD_CAN_SCHED(td, ts->ts_cpu) &&
 1286             tdq->tdq_lowpri >= PRI_MIN_IDLE &&
 1287             SCHED_AFFINITY(ts, CG_SHARE_L2)) {
 1288                 if (cg->cg_flags & CG_FLAG_THREAD) {
 1289                         CPUSET_FOREACH(cpu, cg->cg_mask) {
 1290                                 if (TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE)
 1291                                         break;
 1292                         }
 1293                 } else
 1294                         cpu = INT_MAX;
 1295                 if (cpu > mp_maxid) {
 1296                         SCHED_STAT_INC(pickcpu_idle_affinity);
 1297                         return (ts->ts_cpu);
 1298                 }
 1299         }
 1300         /*
 1301          * Search for the last level cache CPU group in the tree.
 1302          * Skip caches with expired affinity time and SMT groups.
 1303          * Affinity to higher level caches will be handled less aggressively.
 1304          */
 1305         for (ccg = NULL; cg != NULL; cg = cg->cg_parent) {
 1306                 if (cg->cg_flags & CG_FLAG_THREAD)
 1307                         continue;
 1308                 if (!SCHED_AFFINITY(ts, cg->cg_level))
 1309                         continue;
 1310                 ccg = cg;
 1311         }
 1312         if (ccg != NULL)
 1313                 cg = ccg;
 1314         cpu = -1;
 1315         /* Search the group for the less loaded idle CPU we can run now. */
 1316         mask = td->td_cpuset->cs_mask;
 1317         if (cg != NULL && cg != cpu_top &&
 1318             CPU_CMP(&cg->cg_mask, &cpu_top->cg_mask) != 0)
 1319                 cpu = sched_lowest(cg, mask, max(pri, PRI_MAX_TIMESHARE),
 1320                     INT_MAX, ts->ts_cpu);
 1321         /* Search globally for the less loaded CPU we can run now. */
 1322         if (cpu == -1)
 1323                 cpu = sched_lowest(cpu_top, mask, pri, INT_MAX, ts->ts_cpu);
 1324         /* Search globally for the less loaded CPU. */
 1325         if (cpu == -1)
 1326                 cpu = sched_lowest(cpu_top, mask, -1, INT_MAX, ts->ts_cpu);
 1327         KASSERT(cpu != -1, ("sched_pickcpu: Failed to find a cpu."));
 1328         KASSERT(!CPU_ABSENT(cpu), ("sched_pickcpu: Picked absent CPU %d.", cpu));
 1329         /*
 1330          * Compare the lowest loaded cpu to current cpu.
 1331          */
 1332         if (THREAD_CAN_SCHED(td, self) && TDQ_CPU(self)->tdq_lowpri > pri &&
 1333             TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE &&
 1334             TDQ_CPU(self)->tdq_load <= TDQ_CPU(cpu)->tdq_load + 1) {
 1335                 SCHED_STAT_INC(pickcpu_local);
 1336                 cpu = self;
 1337         } else
 1338                 SCHED_STAT_INC(pickcpu_lowest);
 1339         if (cpu != ts->ts_cpu)
 1340                 SCHED_STAT_INC(pickcpu_migration);
 1341         return (cpu);
 1342 }
 1343 #endif
 1344 
 1345 /*
 1346  * Pick the highest priority task we have and return it.
 1347  */
 1348 static struct thread *
 1349 tdq_choose(struct tdq *tdq)
 1350 {
 1351         struct thread *td;
 1352 
 1353         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 1354         td = runq_choose(&tdq->tdq_realtime);
 1355         if (td != NULL)
 1356                 return (td);
 1357         td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
 1358         if (td != NULL) {
 1359                 KASSERT(td->td_priority >= PRI_MIN_BATCH,
 1360                     ("tdq_choose: Invalid priority on timeshare queue %d",
 1361                     td->td_priority));
 1362                 return (td);
 1363         }
 1364         td = runq_choose(&tdq->tdq_idle);
 1365         if (td != NULL) {
 1366                 KASSERT(td->td_priority >= PRI_MIN_IDLE,
 1367                     ("tdq_choose: Invalid priority on idle queue %d",
 1368                     td->td_priority));
 1369                 return (td);
 1370         }
 1371 
 1372         return (NULL);
 1373 }
 1374 
 1375 /*
 1376  * Initialize a thread queue.
 1377  */
 1378 static void
 1379 tdq_setup(struct tdq *tdq)
 1380 {
 1381 
 1382         if (bootverbose)
 1383                 printf("ULE: setup cpu %d\n", TDQ_ID(tdq));
 1384         runq_init(&tdq->tdq_realtime);
 1385         runq_init(&tdq->tdq_timeshare);
 1386         runq_init(&tdq->tdq_idle);
 1387         snprintf(tdq->tdq_name, sizeof(tdq->tdq_name),
 1388             "sched lock %d", (int)TDQ_ID(tdq));
 1389         mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock",
 1390             MTX_SPIN | MTX_RECURSE);
 1391 #ifdef KTR
 1392         snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname),
 1393             "CPU %d load", (int)TDQ_ID(tdq));
 1394 #endif
 1395 }
 1396 
 1397 #ifdef SMP
 1398 static void
 1399 sched_setup_smp(void)
 1400 {
 1401         struct tdq *tdq;
 1402         int i;
 1403 
 1404         cpu_top = smp_topo();
 1405         CPU_FOREACH(i) {
 1406                 tdq = TDQ_CPU(i);
 1407                 tdq_setup(tdq);
 1408                 tdq->tdq_cg = smp_topo_find(cpu_top, i);
 1409                 if (tdq->tdq_cg == NULL)
 1410                         panic("Can't find cpu group for %d\n", i);
 1411         }
 1412         balance_tdq = TDQ_SELF();
 1413 }
 1414 #endif
 1415 
 1416 /*
 1417  * Setup the thread queues and initialize the topology based on MD
 1418  * information.
 1419  */
 1420 static void
 1421 sched_setup(void *dummy)
 1422 {
 1423         struct tdq *tdq;
 1424 
 1425         tdq = TDQ_SELF();
 1426 #ifdef SMP
 1427         sched_setup_smp();
 1428 #else
 1429         tdq_setup(tdq);
 1430 #endif
 1431 
 1432         /* Add thread0's load since it's running. */
 1433         TDQ_LOCK(tdq);
 1434         thread0.td_lock = TDQ_LOCKPTR(TDQ_SELF());
 1435         tdq_load_add(tdq, &thread0);
 1436         tdq->tdq_lowpri = thread0.td_priority;
 1437         TDQ_UNLOCK(tdq);
 1438 }
 1439 
 1440 /*
 1441  * This routine determines time constants after stathz and hz are setup.
 1442  */
 1443 /* ARGSUSED */
 1444 static void
 1445 sched_initticks(void *dummy)
 1446 {
 1447         int incr;
 1448 
 1449         realstathz = stathz ? stathz : hz;
 1450         sched_slice = realstathz / SCHED_SLICE_DEFAULT_DIVISOR;
 1451         sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
 1452         hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
 1453             realstathz);
 1454 
 1455         /*
 1456          * tickincr is shifted out by 10 to avoid rounding errors due to
 1457          * hz not being evenly divisible by stathz on all platforms.
 1458          */
 1459         incr = (hz << SCHED_TICK_SHIFT) / realstathz;
 1460         /*
 1461          * This does not work for values of stathz that are more than
 1462          * 1 << SCHED_TICK_SHIFT * hz.  In practice this does not happen.
 1463          */
 1464         if (incr == 0)
 1465                 incr = 1;
 1466         tickincr = incr;
 1467 #ifdef SMP
 1468         /*
 1469          * Set the default balance interval now that we know
 1470          * what realstathz is.
 1471          */
 1472         balance_interval = realstathz;
 1473         balance_ticks = balance_interval;
 1474         affinity = SCHED_AFFINITY_DEFAULT;
 1475 #endif
 1476         if (sched_idlespinthresh < 0)
 1477                 sched_idlespinthresh = 2 * max(10000, 6 * hz) / realstathz;
 1478 }
 1479 
 1480 
 1481 /*
 1482  * This is the core of the interactivity algorithm.  Determines a score based
 1483  * on past behavior.  It is the ratio of sleep time to run time scaled to
 1484  * a [0, 100] integer.  This is the voluntary sleep time of a process, which
 1485  * differs from the cpu usage because it does not account for time spent
 1486  * waiting on a run-queue.  Would be prettier if we had floating point.
 1487  *
 1488  * When a thread's sleep time is greater than its run time the
 1489  * calculation is:
 1490  *
 1491  *                           scaling factor 
 1492  * interactivity score =  ---------------------
 1493  *                        sleep time / run time
 1494  *
 1495  *
 1496  * When a thread's run time is greater than its sleep time the
 1497  * calculation is:
 1498  *
 1499  *                           scaling factor 
 1500  * interactivity score =  ---------------------    + scaling factor
 1501  *                        run time / sleep time
 1502  */
 1503 static int
 1504 sched_interact_score(struct thread *td)
 1505 {
 1506         struct td_sched *ts;
 1507         int div;
 1508 
 1509         ts = td_get_sched(td);
 1510         /*
 1511          * The score is only needed if this is likely to be an interactive
 1512          * task.  Don't go through the expense of computing it if there's
 1513          * no chance.
 1514          */
 1515         if (sched_interact <= SCHED_INTERACT_HALF &&
 1516                 ts->ts_runtime >= ts->ts_slptime)
 1517                         return (SCHED_INTERACT_HALF);
 1518 
 1519         if (ts->ts_runtime > ts->ts_slptime) {
 1520                 div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF);
 1521                 return (SCHED_INTERACT_HALF +
 1522                     (SCHED_INTERACT_HALF - (ts->ts_slptime / div)));
 1523         }
 1524         if (ts->ts_slptime > ts->ts_runtime) {
 1525                 div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF);
 1526                 return (ts->ts_runtime / div);
 1527         }
 1528         /* runtime == slptime */
 1529         if (ts->ts_runtime)
 1530                 return (SCHED_INTERACT_HALF);
 1531 
 1532         /*
 1533          * This can happen if slptime and runtime are 0.
 1534          */
 1535         return (0);
 1536 
 1537 }
 1538 
 1539 /*
 1540  * Scale the scheduling priority according to the "interactivity" of this
 1541  * process.
 1542  */
 1543 static void
 1544 sched_priority(struct thread *td)
 1545 {
 1546         int score;
 1547         int pri;
 1548 
 1549         if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
 1550                 return;
 1551         /*
 1552          * If the score is interactive we place the thread in the realtime
 1553          * queue with a priority that is less than kernel and interrupt
 1554          * priorities.  These threads are not subject to nice restrictions.
 1555          *
 1556          * Scores greater than this are placed on the normal timeshare queue
 1557          * where the priority is partially decided by the most recent cpu
 1558          * utilization and the rest is decided by nice value.
 1559          *
 1560          * The nice value of the process has a linear effect on the calculated
 1561          * score.  Negative nice values make it easier for a thread to be
 1562          * considered interactive.
 1563          */
 1564         score = imax(0, sched_interact_score(td) + td->td_proc->p_nice);
 1565         if (score < sched_interact) {
 1566                 pri = PRI_MIN_INTERACT;
 1567                 pri += ((PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) /
 1568                     sched_interact) * score;
 1569                 KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT,
 1570                     ("sched_priority: invalid interactive priority %d score %d",
 1571                     pri, score));
 1572         } else {
 1573                 pri = SCHED_PRI_MIN;
 1574                 if (td_get_sched(td)->ts_ticks)
 1575                         pri += min(SCHED_PRI_TICKS(td_get_sched(td)),
 1576                             SCHED_PRI_RANGE - 1);
 1577                 pri += SCHED_PRI_NICE(td->td_proc->p_nice);
 1578                 KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH,
 1579                     ("sched_priority: invalid priority %d: nice %d, " 
 1580                     "ticks %d ftick %d ltick %d tick pri %d",
 1581                     pri, td->td_proc->p_nice, td_get_sched(td)->ts_ticks,
 1582                     td_get_sched(td)->ts_ftick, td_get_sched(td)->ts_ltick,
 1583                     SCHED_PRI_TICKS(td_get_sched(td))));
 1584         }
 1585         sched_user_prio(td, pri);
 1586 
 1587         return;
 1588 }
 1589 
 1590 /*
 1591  * This routine enforces a maximum limit on the amount of scheduling history
 1592  * kept.  It is called after either the slptime or runtime is adjusted.  This
 1593  * function is ugly due to integer math.
 1594  */
 1595 static void
 1596 sched_interact_update(struct thread *td)
 1597 {
 1598         struct td_sched *ts;
 1599         u_int sum;
 1600 
 1601         ts = td_get_sched(td);
 1602         sum = ts->ts_runtime + ts->ts_slptime;
 1603         if (sum < SCHED_SLP_RUN_MAX)
 1604                 return;
 1605         /*
 1606          * This only happens from two places:
 1607          * 1) We have added an unusual amount of run time from fork_exit.
 1608          * 2) We have added an unusual amount of sleep time from sched_sleep().
 1609          */
 1610         if (sum > SCHED_SLP_RUN_MAX * 2) {
 1611                 if (ts->ts_runtime > ts->ts_slptime) {
 1612                         ts->ts_runtime = SCHED_SLP_RUN_MAX;
 1613                         ts->ts_slptime = 1;
 1614                 } else {
 1615                         ts->ts_slptime = SCHED_SLP_RUN_MAX;
 1616                         ts->ts_runtime = 1;
 1617                 }
 1618                 return;
 1619         }
 1620         /*
 1621          * If we have exceeded by more than 1/5th then the algorithm below
 1622          * will not bring us back into range.  Dividing by two here forces
 1623          * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX]
 1624          */
 1625         if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) {
 1626                 ts->ts_runtime /= 2;
 1627                 ts->ts_slptime /= 2;
 1628                 return;
 1629         }
 1630         ts->ts_runtime = (ts->ts_runtime / 5) * 4;
 1631         ts->ts_slptime = (ts->ts_slptime / 5) * 4;
 1632 }
 1633 
 1634 /*
 1635  * Scale back the interactivity history when a child thread is created.  The
 1636  * history is inherited from the parent but the thread may behave totally
 1637  * differently.  For example, a shell spawning a compiler process.  We want
 1638  * to learn that the compiler is behaving badly very quickly.
 1639  */
 1640 static void
 1641 sched_interact_fork(struct thread *td)
 1642 {
 1643         struct td_sched *ts;
 1644         int ratio;
 1645         int sum;
 1646 
 1647         ts = td_get_sched(td);
 1648         sum = ts->ts_runtime + ts->ts_slptime;
 1649         if (sum > SCHED_SLP_RUN_FORK) {
 1650                 ratio = sum / SCHED_SLP_RUN_FORK;
 1651                 ts->ts_runtime /= ratio;
 1652                 ts->ts_slptime /= ratio;
 1653         }
 1654 }
 1655 
 1656 /*
 1657  * Called from proc0_init() to setup the scheduler fields.
 1658  */
 1659 void
 1660 schedinit(void)
 1661 {
 1662         struct td_sched *ts0;
 1663 
 1664         /*
 1665          * Set up the scheduler specific parts of thread0.
 1666          */
 1667         ts0 = td_get_sched(&thread0);
 1668         ts0->ts_ltick = ticks;
 1669         ts0->ts_ftick = ticks;
 1670         ts0->ts_slice = 0;
 1671         ts0->ts_cpu = curcpu;   /* set valid CPU number */
 1672 }
 1673 
 1674 /*
 1675  * This is only somewhat accurate since given many processes of the same
 1676  * priority they will switch when their slices run out, which will be
 1677  * at most sched_slice stathz ticks.
 1678  */
 1679 int
 1680 sched_rr_interval(void)
 1681 {
 1682 
 1683         /* Convert sched_slice from stathz to hz. */
 1684         return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz));
 1685 }
 1686 
 1687 /*
 1688  * Update the percent cpu tracking information when it is requested or
 1689  * the total history exceeds the maximum.  We keep a sliding history of
 1690  * tick counts that slowly decays.  This is less precise than the 4BSD
 1691  * mechanism since it happens with less regular and frequent events.
 1692  */
 1693 static void
 1694 sched_pctcpu_update(struct td_sched *ts, int run)
 1695 {
 1696         int t = ticks;
 1697 
 1698         /*
 1699          * The signed difference may be negative if the thread hasn't run for
 1700          * over half of the ticks rollover period.
 1701          */
 1702         if ((u_int)(t - ts->ts_ltick) >= SCHED_TICK_TARG) {
 1703                 ts->ts_ticks = 0;
 1704                 ts->ts_ftick = t - SCHED_TICK_TARG;
 1705         } else if (t - ts->ts_ftick >= SCHED_TICK_MAX) {
 1706                 ts->ts_ticks = (ts->ts_ticks / (ts->ts_ltick - ts->ts_ftick)) *
 1707                     (ts->ts_ltick - (t - SCHED_TICK_TARG));
 1708                 ts->ts_ftick = t - SCHED_TICK_TARG;
 1709         }
 1710         if (run)
 1711                 ts->ts_ticks += (t - ts->ts_ltick) << SCHED_TICK_SHIFT;
 1712         ts->ts_ltick = t;
 1713 }
 1714 
 1715 /*
 1716  * Adjust the priority of a thread.  Move it to the appropriate run-queue
 1717  * if necessary.  This is the back-end for several priority related
 1718  * functions.
 1719  */
 1720 static void
 1721 sched_thread_priority(struct thread *td, u_char prio)
 1722 {
 1723         struct td_sched *ts;
 1724         struct tdq *tdq;
 1725         int oldpri;
 1726 
 1727         KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio",
 1728             "prio:%d", td->td_priority, "new prio:%d", prio,
 1729             KTR_ATTR_LINKED, sched_tdname(curthread));
 1730         SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio);
 1731         if (td != curthread && prio < td->td_priority) {
 1732                 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
 1733                     "lend prio", "prio:%d", td->td_priority, "new prio:%d",
 1734                     prio, KTR_ATTR_LINKED, sched_tdname(td));
 1735                 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio, 
 1736                     curthread);
 1737         } 
 1738         ts = td_get_sched(td);
 1739         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1740         if (td->td_priority == prio)
 1741                 return;
 1742         /*
 1743          * If the priority has been elevated due to priority
 1744          * propagation, we may have to move ourselves to a new
 1745          * queue.  This could be optimized to not re-add in some
 1746          * cases.
 1747          */
 1748         if (TD_ON_RUNQ(td) && prio < td->td_priority) {
 1749                 sched_rem(td);
 1750                 td->td_priority = prio;
 1751                 sched_add(td, SRQ_BORROWING);
 1752                 return;
 1753         }
 1754         /*
 1755          * If the thread is currently running we may have to adjust the lowpri
 1756          * information so other cpus are aware of our current priority.
 1757          */
 1758         if (TD_IS_RUNNING(td)) {
 1759                 tdq = TDQ_CPU(ts->ts_cpu);
 1760                 oldpri = td->td_priority;
 1761                 td->td_priority = prio;
 1762                 if (prio < tdq->tdq_lowpri)
 1763                         tdq->tdq_lowpri = prio;
 1764                 else if (tdq->tdq_lowpri == oldpri)
 1765                         tdq_setlowpri(tdq, td);
 1766                 return;
 1767         }
 1768         td->td_priority = prio;
 1769 }
 1770 
 1771 /*
 1772  * Update a thread's priority when it is lent another thread's
 1773  * priority.
 1774  */
 1775 void
 1776 sched_lend_prio(struct thread *td, u_char prio)
 1777 {
 1778 
 1779         td->td_flags |= TDF_BORROWING;
 1780         sched_thread_priority(td, prio);
 1781 }
 1782 
 1783 /*
 1784  * Restore a thread's priority when priority propagation is
 1785  * over.  The prio argument is the minimum priority the thread
 1786  * needs to have to satisfy other possible priority lending
 1787  * requests.  If the thread's regular priority is less
 1788  * important than prio, the thread will keep a priority boost
 1789  * of prio.
 1790  */
 1791 void
 1792 sched_unlend_prio(struct thread *td, u_char prio)
 1793 {
 1794         u_char base_pri;
 1795 
 1796         if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
 1797             td->td_base_pri <= PRI_MAX_TIMESHARE)
 1798                 base_pri = td->td_user_pri;
 1799         else
 1800                 base_pri = td->td_base_pri;
 1801         if (prio >= base_pri) {
 1802                 td->td_flags &= ~TDF_BORROWING;
 1803                 sched_thread_priority(td, base_pri);
 1804         } else
 1805                 sched_lend_prio(td, prio);
 1806 }
 1807 
 1808 /*
 1809  * Standard entry for setting the priority to an absolute value.
 1810  */
 1811 void
 1812 sched_prio(struct thread *td, u_char prio)
 1813 {
 1814         u_char oldprio;
 1815 
 1816         /* First, update the base priority. */
 1817         td->td_base_pri = prio;
 1818 
 1819         /*
 1820          * If the thread is borrowing another thread's priority, don't
 1821          * ever lower the priority.
 1822          */
 1823         if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
 1824                 return;
 1825 
 1826         /* Change the real priority. */
 1827         oldprio = td->td_priority;
 1828         sched_thread_priority(td, prio);
 1829 
 1830         /*
 1831          * If the thread is on a turnstile, then let the turnstile update
 1832          * its state.
 1833          */
 1834         if (TD_ON_LOCK(td) && oldprio != prio)
 1835                 turnstile_adjust(td, oldprio);
 1836 }
 1837 
 1838 /*
 1839  * Set the base user priority, does not effect current running priority.
 1840  */
 1841 void
 1842 sched_user_prio(struct thread *td, u_char prio)
 1843 {
 1844 
 1845         td->td_base_user_pri = prio;
 1846         if (td->td_lend_user_pri <= prio)
 1847                 return;
 1848         td->td_user_pri = prio;
 1849 }
 1850 
 1851 void
 1852 sched_lend_user_prio(struct thread *td, u_char prio)
 1853 {
 1854 
 1855         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1856         td->td_lend_user_pri = prio;
 1857         td->td_user_pri = min(prio, td->td_base_user_pri);
 1858         if (td->td_priority > td->td_user_pri)
 1859                 sched_prio(td, td->td_user_pri);
 1860         else if (td->td_priority != td->td_user_pri)
 1861                 td->td_flags |= TDF_NEEDRESCHED;
 1862 }
 1863 
 1864 #ifdef SMP
 1865 /*
 1866  * This tdq is about to idle.  Try to steal a thread from another CPU before
 1867  * choosing the idle thread.
 1868  */
 1869 static void
 1870 tdq_trysteal(struct tdq *tdq)
 1871 {
 1872         struct cpu_group *cg;
 1873         struct tdq *steal;
 1874         cpuset_t mask;
 1875         int cpu, i;
 1876 
 1877         if (smp_started == 0 || trysteal_limit == 0 || tdq->tdq_cg == NULL)
 1878                 return;
 1879         CPU_FILL(&mask);
 1880         CPU_CLR(PCPU_GET(cpuid), &mask);
 1881         /* We don't want to be preempted while we're iterating. */
 1882         spinlock_enter();
 1883         TDQ_UNLOCK(tdq);
 1884         for (i = 1, cg = tdq->tdq_cg; ; ) {
 1885                 cpu = sched_highest(cg, mask, steal_thresh);
 1886                 /*
 1887                  * If a thread was added while interrupts were disabled don't
 1888                  * steal one here.
 1889                  */
 1890                 if (tdq->tdq_load > 0) {
 1891                         TDQ_LOCK(tdq);
 1892                         break;
 1893                 }
 1894                 if (cpu == -1) {
 1895                         i++;
 1896                         cg = cg->cg_parent;
 1897                         if (cg == NULL || i > trysteal_limit) {
 1898                                 TDQ_LOCK(tdq);
 1899                                 break;
 1900                         }
 1901                         continue;
 1902                 }
 1903                 steal = TDQ_CPU(cpu);
 1904                 /*
 1905                  * The data returned by sched_highest() is stale and
 1906                  * the chosen CPU no longer has an eligible thread.
 1907                  */
 1908                 if (steal->tdq_load < steal_thresh ||
 1909                     steal->tdq_transferable == 0)
 1910                         continue;
 1911                 tdq_lock_pair(tdq, steal);
 1912                 /*
 1913                  * If we get to this point, unconditonally exit the loop
 1914                  * to bound the time spent in the critcal section.
 1915                  *
 1916                  * If a thread was added while interrupts were disabled don't
 1917                  * steal one here.
 1918                  */
 1919                 if (tdq->tdq_load > 0) {
 1920                         TDQ_UNLOCK(steal);
 1921                         break;
 1922                 }
 1923                 /*
 1924                  * The data returned by sched_highest() is stale and
 1925                  * the chosen CPU no longer has an eligible thread.
 1926                  */
 1927                 if (steal->tdq_load < steal_thresh ||
 1928                     steal->tdq_transferable == 0) {
 1929                         TDQ_UNLOCK(steal);
 1930                         break;
 1931                 }
 1932                 /*
 1933                  * If we fail to acquire one due to affinity restrictions,
 1934                  * bail out and let the idle thread to a more complete search
 1935                  * outside of a critical section.
 1936                  */
 1937                 if (tdq_move(steal, tdq) == NULL) {
 1938                         TDQ_UNLOCK(steal);
 1939                         break;
 1940                 }
 1941                 TDQ_UNLOCK(steal);
 1942                 break;
 1943         }
 1944         spinlock_exit();
 1945 }
 1946 #endif
 1947 
 1948 /*
 1949  * Handle migration from sched_switch().  This happens only for
 1950  * cpu binding.
 1951  */
 1952 static struct mtx *
 1953 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags)
 1954 {
 1955         struct tdq *tdn;
 1956 
 1957         KASSERT(!CPU_ABSENT(td_get_sched(td)->ts_cpu), ("sched_switch_migrate: "
 1958             "thread %s queued on absent CPU %d.", td->td_name,
 1959             td_get_sched(td)->ts_cpu));
 1960         tdn = TDQ_CPU(td_get_sched(td)->ts_cpu);
 1961 #ifdef SMP
 1962         tdq_load_rem(tdq, td);
 1963         /*
 1964          * Do the lock dance required to avoid LOR.  We grab an extra
 1965          * spinlock nesting to prevent preemption while we're
 1966          * not holding either run-queue lock.
 1967          */
 1968         spinlock_enter();
 1969         thread_lock_block(td);  /* This releases the lock on tdq. */
 1970 
 1971         /*
 1972          * Acquire both run-queue locks before placing the thread on the new
 1973          * run-queue to avoid deadlocks created by placing a thread with a
 1974          * blocked lock on the run-queue of a remote processor.  The deadlock
 1975          * occurs when a third processor attempts to lock the two queues in
 1976          * question while the target processor is spinning with its own
 1977          * run-queue lock held while waiting for the blocked lock to clear.
 1978          */
 1979         tdq_lock_pair(tdn, tdq);
 1980         tdq_add(tdn, td, flags);
 1981         tdq_notify(tdn, td);
 1982         TDQ_UNLOCK(tdn);
 1983         spinlock_exit();
 1984 #endif
 1985         return (TDQ_LOCKPTR(tdn));
 1986 }
 1987 
 1988 /*
 1989  * Variadic version of thread_lock_unblock() that does not assume td_lock
 1990  * is blocked.
 1991  */
 1992 static inline void
 1993 thread_unblock_switch(struct thread *td, struct mtx *mtx)
 1994 {
 1995         atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock,
 1996             (uintptr_t)mtx);
 1997 }
 1998 
 1999 /*
 2000  * Switch threads.  This function has to handle threads coming in while
 2001  * blocked for some reason, running, or idle.  It also must deal with
 2002  * migrating a thread from one queue to another as running threads may
 2003  * be assigned elsewhere via binding.
 2004  */
 2005 void
 2006 sched_switch(struct thread *td, struct thread *newtd, int flags)
 2007 {
 2008         struct tdq *tdq;
 2009         struct td_sched *ts;
 2010         struct mtx *mtx;
 2011         int srqflag;
 2012         int cpuid, preempted;
 2013 
 2014         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2015         KASSERT(newtd == NULL, ("sched_switch: Unsupported newtd argument"));
 2016 
 2017         cpuid = PCPU_GET(cpuid);
 2018         tdq = TDQ_CPU(cpuid);
 2019         ts = td_get_sched(td);
 2020         mtx = td->td_lock;
 2021         sched_pctcpu_update(ts, 1);
 2022         ts->ts_rltick = ticks;
 2023         td->td_lastcpu = td->td_oncpu;
 2024         td->td_oncpu = NOCPU;
 2025         preempted = (td->td_flags & TDF_SLICEEND) == 0 &&
 2026             (flags & SW_PREEMPT) != 0;
 2027         td->td_flags &= ~(TDF_NEEDRESCHED | TDF_SLICEEND);
 2028         td->td_owepreempt = 0;
 2029         if (!TD_IS_IDLETHREAD(td))
 2030                 tdq->tdq_switchcnt++;
 2031         /*
 2032          * The lock pointer in an idle thread should never change.  Reset it
 2033          * to CAN_RUN as well.
 2034          */
 2035         if (TD_IS_IDLETHREAD(td)) {
 2036                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2037                 TD_SET_CAN_RUN(td);
 2038         } else if (TD_IS_RUNNING(td)) {
 2039                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2040                 srqflag = preempted ?
 2041                     SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
 2042                     SRQ_OURSELF|SRQ_YIELDING;
 2043 #ifdef SMP
 2044                 if (THREAD_CAN_MIGRATE(td) && !THREAD_CAN_SCHED(td, ts->ts_cpu))
 2045                         ts->ts_cpu = sched_pickcpu(td, 0);
 2046 #endif
 2047                 if (ts->ts_cpu == cpuid)
 2048                         tdq_runq_add(tdq, td, srqflag);
 2049                 else {
 2050                         KASSERT(THREAD_CAN_MIGRATE(td) ||
 2051                             (ts->ts_flags & TSF_BOUND) != 0,
 2052                             ("Thread %p shouldn't migrate", td));
 2053                         mtx = sched_switch_migrate(tdq, td, srqflag);
 2054                 }
 2055         } else {
 2056                 /* This thread must be going to sleep. */
 2057                 TDQ_LOCK(tdq);
 2058                 mtx = thread_lock_block(td);
 2059                 tdq_load_rem(tdq, td);
 2060 #ifdef SMP
 2061                 if (tdq->tdq_load == 0)
 2062                         tdq_trysteal(tdq);
 2063 #endif
 2064         }
 2065 
 2066 #if (KTR_COMPILE & KTR_SCHED) != 0
 2067         if (TD_IS_IDLETHREAD(td))
 2068                 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle",
 2069                     "prio:%d", td->td_priority);
 2070         else
 2071                 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td),
 2072                     "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg,
 2073                     "lockname:\"%s\"", td->td_lockname);
 2074 #endif
 2075 
 2076         /*
 2077          * We enter here with the thread blocked and assigned to the
 2078          * appropriate cpu run-queue or sleep-queue and with the current
 2079          * thread-queue locked.
 2080          */
 2081         TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
 2082         newtd = choosethread();
 2083         /*
 2084          * Call the MD code to switch contexts if necessary.
 2085          */
 2086         if (td != newtd) {
 2087 #ifdef  HWPMC_HOOKS
 2088                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 2089                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
 2090 #endif
 2091                 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc);
 2092                 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
 2093                 TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
 2094                 sched_pctcpu_update(td_get_sched(newtd), 0);
 2095 
 2096 #ifdef KDTRACE_HOOKS
 2097                 /*
 2098                  * If DTrace has set the active vtime enum to anything
 2099                  * other than INACTIVE (0), then it should have set the
 2100                  * function to call.
 2101                  */
 2102                 if (dtrace_vtime_active)
 2103                         (*dtrace_vtime_switch_func)(newtd);
 2104 #endif
 2105 
 2106                 cpu_switch(td, newtd, mtx);
 2107                 /*
 2108                  * We may return from cpu_switch on a different cpu.  However,
 2109                  * we always return with td_lock pointing to the current cpu's
 2110                  * run queue lock.
 2111                  */
 2112                 cpuid = PCPU_GET(cpuid);
 2113                 tdq = TDQ_CPU(cpuid);
 2114                 lock_profile_obtain_lock_success(
 2115                     &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
 2116 
 2117                 SDT_PROBE0(sched, , , on__cpu);
 2118 #ifdef  HWPMC_HOOKS
 2119                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 2120                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
 2121 #endif
 2122         } else {
 2123                 thread_unblock_switch(td, mtx);
 2124                 SDT_PROBE0(sched, , , remain__cpu);
 2125         }
 2126 
 2127         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
 2128             "prio:%d", td->td_priority);
 2129 
 2130         /*
 2131          * Assert that all went well and return.
 2132          */
 2133         TDQ_LOCK_ASSERT(tdq, MA_OWNED|MA_NOTRECURSED);
 2134         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2135         td->td_oncpu = cpuid;
 2136 }
 2137 
 2138 /*
 2139  * Adjust thread priorities as a result of a nice request.
 2140  */
 2141 void
 2142 sched_nice(struct proc *p, int nice)
 2143 {
 2144         struct thread *td;
 2145 
 2146         PROC_LOCK_ASSERT(p, MA_OWNED);
 2147 
 2148         p->p_nice = nice;
 2149         FOREACH_THREAD_IN_PROC(p, td) {
 2150                 thread_lock(td);
 2151                 sched_priority(td);
 2152                 sched_prio(td, td->td_base_user_pri);
 2153                 thread_unlock(td);
 2154         }
 2155 }
 2156 
 2157 /*
 2158  * Record the sleep time for the interactivity scorer.
 2159  */
 2160 void
 2161 sched_sleep(struct thread *td, int prio)
 2162 {
 2163 
 2164         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2165 
 2166         td->td_slptick = ticks;
 2167         if (TD_IS_SUSPENDED(td) || prio >= PSOCK)
 2168                 td->td_flags |= TDF_CANSWAP;
 2169         if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
 2170                 return;
 2171         if (static_boost == 1 && prio)
 2172                 sched_prio(td, prio);
 2173         else if (static_boost && td->td_priority > static_boost)
 2174                 sched_prio(td, static_boost);
 2175 }
 2176 
 2177 /*
 2178  * Schedule a thread to resume execution and record how long it voluntarily
 2179  * slept.  We also update the pctcpu, interactivity, and priority.
 2180  */
 2181 void
 2182 sched_wakeup(struct thread *td)
 2183 {
 2184         struct td_sched *ts;
 2185         int slptick;
 2186 
 2187         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2188         ts = td_get_sched(td);
 2189         td->td_flags &= ~TDF_CANSWAP;
 2190         /*
 2191          * If we slept for more than a tick update our interactivity and
 2192          * priority.
 2193          */
 2194         slptick = td->td_slptick;
 2195         td->td_slptick = 0;
 2196         if (slptick && slptick != ticks) {
 2197                 ts->ts_slptime += (ticks - slptick) << SCHED_TICK_SHIFT;
 2198                 sched_interact_update(td);
 2199                 sched_pctcpu_update(ts, 0);
 2200         }
 2201         /*
 2202          * Reset the slice value since we slept and advanced the round-robin.
 2203          */
 2204         ts->ts_slice = 0;
 2205         sched_add(td, SRQ_BORING);
 2206 }
 2207 
 2208 /*
 2209  * Penalize the parent for creating a new child and initialize the child's
 2210  * priority.
 2211  */
 2212 void
 2213 sched_fork(struct thread *td, struct thread *child)
 2214 {
 2215         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2216         sched_pctcpu_update(td_get_sched(td), 1);
 2217         sched_fork_thread(td, child);
 2218         /*
 2219          * Penalize the parent and child for forking.
 2220          */
 2221         sched_interact_fork(child);
 2222         sched_priority(child);
 2223         td_get_sched(td)->ts_runtime += tickincr;
 2224         sched_interact_update(td);
 2225         sched_priority(td);
 2226 }
 2227 
 2228 /*
 2229  * Fork a new thread, may be within the same process.
 2230  */
 2231 void
 2232 sched_fork_thread(struct thread *td, struct thread *child)
 2233 {
 2234         struct td_sched *ts;
 2235         struct td_sched *ts2;
 2236         struct tdq *tdq;
 2237 
 2238         tdq = TDQ_SELF();
 2239         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2240         /*
 2241          * Initialize child.
 2242          */
 2243         ts = td_get_sched(td);
 2244         ts2 = td_get_sched(child);
 2245         child->td_oncpu = NOCPU;
 2246         child->td_lastcpu = NOCPU;
 2247         child->td_lock = TDQ_LOCKPTR(tdq);
 2248         child->td_cpuset = cpuset_ref(td->td_cpuset);
 2249         child->td_domain.dr_policy = td->td_cpuset->cs_domain;
 2250         ts2->ts_cpu = ts->ts_cpu;
 2251         ts2->ts_flags = 0;
 2252         /*
 2253          * Grab our parents cpu estimation information.
 2254          */
 2255         ts2->ts_ticks = ts->ts_ticks;
 2256         ts2->ts_ltick = ts->ts_ltick;
 2257         ts2->ts_ftick = ts->ts_ftick;
 2258         /*
 2259          * Do not inherit any borrowed priority from the parent.
 2260          */
 2261         child->td_priority = child->td_base_pri;
 2262         /*
 2263          * And update interactivity score.
 2264          */
 2265         ts2->ts_slptime = ts->ts_slptime;
 2266         ts2->ts_runtime = ts->ts_runtime;
 2267         /* Attempt to quickly learn interactivity. */
 2268         ts2->ts_slice = tdq_slice(tdq) - sched_slice_min;
 2269 #ifdef KTR
 2270         bzero(ts2->ts_name, sizeof(ts2->ts_name));
 2271 #endif
 2272 }
 2273 
 2274 /*
 2275  * Adjust the priority class of a thread.
 2276  */
 2277 void
 2278 sched_class(struct thread *td, int class)
 2279 {
 2280 
 2281         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2282         if (td->td_pri_class == class)
 2283                 return;
 2284         td->td_pri_class = class;
 2285 }
 2286 
 2287 /*
 2288  * Return some of the child's priority and interactivity to the parent.
 2289  */
 2290 void
 2291 sched_exit(struct proc *p, struct thread *child)
 2292 {
 2293         struct thread *td;
 2294 
 2295         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit",
 2296             "prio:%d", child->td_priority);
 2297         PROC_LOCK_ASSERT(p, MA_OWNED);
 2298         td = FIRST_THREAD_IN_PROC(p);
 2299         sched_exit_thread(td, child);
 2300 }
 2301 
 2302 /*
 2303  * Penalize another thread for the time spent on this one.  This helps to
 2304  * worsen the priority and interactivity of processes which schedule batch
 2305  * jobs such as make.  This has little effect on the make process itself but
 2306  * causes new processes spawned by it to receive worse scores immediately.
 2307  */
 2308 void
 2309 sched_exit_thread(struct thread *td, struct thread *child)
 2310 {
 2311 
 2312         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit",
 2313             "prio:%d", child->td_priority);
 2314         /*
 2315          * Give the child's runtime to the parent without returning the
 2316          * sleep time as a penalty to the parent.  This causes shells that
 2317          * launch expensive things to mark their children as expensive.
 2318          */
 2319         thread_lock(td);
 2320         td_get_sched(td)->ts_runtime += td_get_sched(child)->ts_runtime;
 2321         sched_interact_update(td);
 2322         sched_priority(td);
 2323         thread_unlock(td);
 2324 }
 2325 
 2326 void
 2327 sched_preempt(struct thread *td)
 2328 {
 2329         struct tdq *tdq;
 2330 
 2331         SDT_PROBE2(sched, , , surrender, td, td->td_proc);
 2332 
 2333         thread_lock(td);
 2334         tdq = TDQ_SELF();
 2335         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2336         tdq->tdq_ipipending = 0;
 2337         if (td->td_priority > tdq->tdq_lowpri) {
 2338                 int flags;
 2339 
 2340                 flags = SW_INVOL | SW_PREEMPT;
 2341                 if (td->td_critnest > 1)
 2342                         td->td_owepreempt = 1;
 2343                 else if (TD_IS_IDLETHREAD(td))
 2344                         mi_switch(flags | SWT_REMOTEWAKEIDLE, NULL);
 2345                 else
 2346                         mi_switch(flags | SWT_REMOTEPREEMPT, NULL);
 2347         }
 2348         thread_unlock(td);
 2349 }
 2350 
 2351 /*
 2352  * Fix priorities on return to user-space.  Priorities may be elevated due
 2353  * to static priorities in msleep() or similar.
 2354  */
 2355 void
 2356 sched_userret_slowpath(struct thread *td)
 2357 {
 2358 
 2359         thread_lock(td);
 2360         td->td_priority = td->td_user_pri;
 2361         td->td_base_pri = td->td_user_pri;
 2362         tdq_setlowpri(TDQ_SELF(), td);
 2363         thread_unlock(td);
 2364 }
 2365 
 2366 /*
 2367  * Handle a stathz tick.  This is really only relevant for timeshare
 2368  * threads.
 2369  */
 2370 void
 2371 sched_clock(struct thread *td)
 2372 {
 2373         struct tdq *tdq;
 2374         struct td_sched *ts;
 2375 
 2376         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2377         tdq = TDQ_SELF();
 2378 #ifdef SMP
 2379         /*
 2380          * We run the long term load balancer infrequently on the first cpu.
 2381          */
 2382         if (balance_tdq == tdq && smp_started != 0 && rebalance != 0) {
 2383                 if (balance_ticks && --balance_ticks == 0)
 2384                         sched_balance();
 2385         }
 2386 #endif
 2387         /*
 2388          * Save the old switch count so we have a record of the last ticks
 2389          * activity.   Initialize the new switch count based on our load.
 2390          * If there is some activity seed it to reflect that.
 2391          */
 2392         tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt;
 2393         tdq->tdq_switchcnt = tdq->tdq_load;
 2394         /*
 2395          * Advance the insert index once for each tick to ensure that all
 2396          * threads get a chance to run.
 2397          */
 2398         if (tdq->tdq_idx == tdq->tdq_ridx) {
 2399                 tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS;
 2400                 if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx]))
 2401                         tdq->tdq_ridx = tdq->tdq_idx;
 2402         }
 2403         ts = td_get_sched(td);
 2404         sched_pctcpu_update(ts, 1);
 2405         if (td->td_pri_class & PRI_FIFO_BIT)
 2406                 return;
 2407         if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) {
 2408                 /*
 2409                  * We used a tick; charge it to the thread so
 2410                  * that we can compute our interactivity.
 2411                  */
 2412                 td_get_sched(td)->ts_runtime += tickincr;
 2413                 sched_interact_update(td);
 2414                 sched_priority(td);
 2415         }
 2416 
 2417         /*
 2418          * Force a context switch if the current thread has used up a full
 2419          * time slice (default is 100ms).
 2420          */
 2421         if (!TD_IS_IDLETHREAD(td) && ++ts->ts_slice >= tdq_slice(tdq)) {
 2422                 ts->ts_slice = 0;
 2423                 td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND;
 2424         }
 2425 }
 2426 
 2427 u_int
 2428 sched_estcpu(struct thread *td __unused)
 2429 {
 2430 
 2431         return (0);
 2432 }
 2433 
 2434 /*
 2435  * Return whether the current CPU has runnable tasks.  Used for in-kernel
 2436  * cooperative idle threads.
 2437  */
 2438 int
 2439 sched_runnable(void)
 2440 {
 2441         struct tdq *tdq;
 2442         int load;
 2443 
 2444         load = 1;
 2445 
 2446         tdq = TDQ_SELF();
 2447         if ((curthread->td_flags & TDF_IDLETD) != 0) {
 2448                 if (tdq->tdq_load > 0)
 2449                         goto out;
 2450         } else
 2451                 if (tdq->tdq_load - 1 > 0)
 2452                         goto out;
 2453         load = 0;
 2454 out:
 2455         return (load);
 2456 }
 2457 
 2458 /*
 2459  * Choose the highest priority thread to run.  The thread is removed from
 2460  * the run-queue while running however the load remains.  For SMP we set
 2461  * the tdq in the global idle bitmask if it idles here.
 2462  */
 2463 struct thread *
 2464 sched_choose(void)
 2465 {
 2466         struct thread *td;
 2467         struct tdq *tdq;
 2468 
 2469         tdq = TDQ_SELF();
 2470         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2471         td = tdq_choose(tdq);
 2472         if (td) {
 2473                 tdq_runq_rem(tdq, td);
 2474                 tdq->tdq_lowpri = td->td_priority;
 2475                 return (td);
 2476         }
 2477         tdq->tdq_lowpri = PRI_MAX_IDLE;
 2478         return (PCPU_GET(idlethread));
 2479 }
 2480 
 2481 /*
 2482  * Set owepreempt if necessary.  Preemption never happens directly in ULE,
 2483  * we always request it once we exit a critical section.
 2484  */
 2485 static inline void
 2486 sched_setpreempt(struct thread *td)
 2487 {
 2488         struct thread *ctd;
 2489         int cpri;
 2490         int pri;
 2491 
 2492         THREAD_LOCK_ASSERT(curthread, MA_OWNED);
 2493 
 2494         ctd = curthread;
 2495         pri = td->td_priority;
 2496         cpri = ctd->td_priority;
 2497         if (pri < cpri)
 2498                 ctd->td_flags |= TDF_NEEDRESCHED;
 2499         if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
 2500                 return;
 2501         if (!sched_shouldpreempt(pri, cpri, 0))
 2502                 return;
 2503         ctd->td_owepreempt = 1;
 2504 }
 2505 
 2506 /*
 2507  * Add a thread to a thread queue.  Select the appropriate runq and add the
 2508  * thread to it.  This is the internal function called when the tdq is
 2509  * predetermined.
 2510  */
 2511 void
 2512 tdq_add(struct tdq *tdq, struct thread *td, int flags)
 2513 {
 2514 
 2515         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2516         KASSERT((td->td_inhibitors == 0),
 2517             ("sched_add: trying to run inhibited thread"));
 2518         KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
 2519             ("sched_add: bad thread state"));
 2520         KASSERT(td->td_flags & TDF_INMEM,
 2521             ("sched_add: thread swapped out"));
 2522 
 2523         if (td->td_priority < tdq->tdq_lowpri)
 2524                 tdq->tdq_lowpri = td->td_priority;
 2525         tdq_runq_add(tdq, td, flags);
 2526         tdq_load_add(tdq, td);
 2527 }
 2528 
 2529 /*
 2530  * Select the target thread queue and add a thread to it.  Request
 2531  * preemption or IPI a remote processor if required.
 2532  */
 2533 void
 2534 sched_add(struct thread *td, int flags)
 2535 {
 2536         struct tdq *tdq;
 2537 #ifdef SMP
 2538         int cpu;
 2539 #endif
 2540 
 2541         KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
 2542             "prio:%d", td->td_priority, KTR_ATTR_LINKED,
 2543             sched_tdname(curthread));
 2544         KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
 2545             KTR_ATTR_LINKED, sched_tdname(td));
 2546         SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL, 
 2547             flags & SRQ_PREEMPTED);
 2548         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2549         /*
 2550          * Recalculate the priority before we select the target cpu or
 2551          * run-queue.
 2552          */
 2553         if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
 2554                 sched_priority(td);
 2555 #ifdef SMP
 2556         /*
 2557          * Pick the destination cpu and if it isn't ours transfer to the
 2558          * target cpu.
 2559          */
 2560         cpu = sched_pickcpu(td, flags);
 2561         tdq = sched_setcpu(td, cpu, flags);
 2562         tdq_add(tdq, td, flags);
 2563         if (cpu != PCPU_GET(cpuid)) {
 2564                 tdq_notify(tdq, td);
 2565                 return;
 2566         }
 2567 #else
 2568         tdq = TDQ_SELF();
 2569         TDQ_LOCK(tdq);
 2570         /*
 2571          * Now that the thread is moving to the run-queue, set the lock
 2572          * to the scheduler's lock.
 2573          */
 2574         thread_lock_set(td, TDQ_LOCKPTR(tdq));
 2575         tdq_add(tdq, td, flags);
 2576 #endif
 2577         if (!(flags & SRQ_YIELDING))
 2578                 sched_setpreempt(td);
 2579 }
 2580 
 2581 /*
 2582  * Remove a thread from a run-queue without running it.  This is used
 2583  * when we're stealing a thread from a remote queue.  Otherwise all threads
 2584  * exit by calling sched_exit_thread() and sched_throw() themselves.
 2585  */
 2586 void
 2587 sched_rem(struct thread *td)
 2588 {
 2589         struct tdq *tdq;
 2590 
 2591         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
 2592             "prio:%d", td->td_priority);
 2593         SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL);
 2594         tdq = TDQ_CPU(td_get_sched(td)->ts_cpu);
 2595         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2596         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2597         KASSERT(TD_ON_RUNQ(td),
 2598             ("sched_rem: thread not on run queue"));
 2599         tdq_runq_rem(tdq, td);
 2600         tdq_load_rem(tdq, td);
 2601         TD_SET_CAN_RUN(td);
 2602         if (td->td_priority == tdq->tdq_lowpri)
 2603                 tdq_setlowpri(tdq, NULL);
 2604 }
 2605 
 2606 /*
 2607  * Fetch cpu utilization information.  Updates on demand.
 2608  */
 2609 fixpt_t
 2610 sched_pctcpu(struct thread *td)
 2611 {
 2612         fixpt_t pctcpu;
 2613         struct td_sched *ts;
 2614 
 2615         pctcpu = 0;
 2616         ts = td_get_sched(td);
 2617 
 2618         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2619         sched_pctcpu_update(ts, TD_IS_RUNNING(td));
 2620         if (ts->ts_ticks) {
 2621                 int rtick;
 2622 
 2623                 /* How many rtick per second ? */
 2624                 rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
 2625                 pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
 2626         }
 2627 
 2628         return (pctcpu);
 2629 }
 2630 
 2631 /*
 2632  * Enforce affinity settings for a thread.  Called after adjustments to
 2633  * cpumask.
 2634  */
 2635 void
 2636 sched_affinity(struct thread *td)
 2637 {
 2638 #ifdef SMP
 2639         struct td_sched *ts;
 2640 
 2641         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2642         ts = td_get_sched(td);
 2643         if (THREAD_CAN_SCHED(td, ts->ts_cpu))
 2644                 return;
 2645         if (TD_ON_RUNQ(td)) {
 2646                 sched_rem(td);
 2647                 sched_add(td, SRQ_BORING);
 2648                 return;
 2649         }
 2650         if (!TD_IS_RUNNING(td))
 2651                 return;
 2652         /*
 2653          * Force a switch before returning to userspace.  If the
 2654          * target thread is not running locally send an ipi to force
 2655          * the issue.
 2656          */
 2657         td->td_flags |= TDF_NEEDRESCHED;
 2658         if (td != curthread)
 2659                 ipi_cpu(ts->ts_cpu, IPI_PREEMPT);
 2660 #endif
 2661 }
 2662 
 2663 /*
 2664  * Bind a thread to a target cpu.
 2665  */
 2666 void
 2667 sched_bind(struct thread *td, int cpu)
 2668 {
 2669         struct td_sched *ts;
 2670 
 2671         THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
 2672         KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
 2673         ts = td_get_sched(td);
 2674         if (ts->ts_flags & TSF_BOUND)
 2675                 sched_unbind(td);
 2676         KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td));
 2677         ts->ts_flags |= TSF_BOUND;
 2678         sched_pin();
 2679         if (PCPU_GET(cpuid) == cpu)
 2680                 return;
 2681         ts->ts_cpu = cpu;
 2682         /* When we return from mi_switch we'll be on the correct cpu. */
 2683         mi_switch(SW_VOL, NULL);
 2684 }
 2685 
 2686 /*
 2687  * Release a bound thread.
 2688  */
 2689 void
 2690 sched_unbind(struct thread *td)
 2691 {
 2692         struct td_sched *ts;
 2693 
 2694         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2695         KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
 2696         ts = td_get_sched(td);
 2697         if ((ts->ts_flags & TSF_BOUND) == 0)
 2698                 return;
 2699         ts->ts_flags &= ~TSF_BOUND;
 2700         sched_unpin();
 2701 }
 2702 
 2703 int
 2704 sched_is_bound(struct thread *td)
 2705 {
 2706         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2707         return (td_get_sched(td)->ts_flags & TSF_BOUND);
 2708 }
 2709 
 2710 /*
 2711  * Basic yield call.
 2712  */
 2713 void
 2714 sched_relinquish(struct thread *td)
 2715 {
 2716         thread_lock(td);
 2717         mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
 2718         thread_unlock(td);
 2719 }
 2720 
 2721 /*
 2722  * Return the total system load.
 2723  */
 2724 int
 2725 sched_load(void)
 2726 {
 2727 #ifdef SMP
 2728         int total;
 2729         int i;
 2730 
 2731         total = 0;
 2732         CPU_FOREACH(i)
 2733                 total += TDQ_CPU(i)->tdq_sysload;
 2734         return (total);
 2735 #else
 2736         return (TDQ_SELF()->tdq_sysload);
 2737 #endif
 2738 }
 2739 
 2740 int
 2741 sched_sizeof_proc(void)
 2742 {
 2743         return (sizeof(struct proc));
 2744 }
 2745 
 2746 int
 2747 sched_sizeof_thread(void)
 2748 {
 2749         return (sizeof(struct thread) + sizeof(struct td_sched));
 2750 }
 2751 
 2752 #ifdef SMP
 2753 #define TDQ_IDLESPIN(tdq)                                               \
 2754     ((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0)
 2755 #else
 2756 #define TDQ_IDLESPIN(tdq)       1
 2757 #endif
 2758 
 2759 /*
 2760  * The actual idle process.
 2761  */
 2762 void
 2763 sched_idletd(void *dummy)
 2764 {
 2765         struct thread *td;
 2766         struct tdq *tdq;
 2767         int oldswitchcnt, switchcnt;
 2768         int i;
 2769 
 2770         mtx_assert(&Giant, MA_NOTOWNED);
 2771         td = curthread;
 2772         tdq = TDQ_SELF();
 2773         THREAD_NO_SLEEPING();
 2774         oldswitchcnt = -1;
 2775         for (;;) {
 2776                 if (tdq->tdq_load) {
 2777                         thread_lock(td);
 2778                         mi_switch(SW_VOL | SWT_IDLE, NULL);
 2779                         thread_unlock(td);
 2780                 }
 2781                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2782 #ifdef SMP
 2783                 if (always_steal || switchcnt != oldswitchcnt) {
 2784                         oldswitchcnt = switchcnt;
 2785                         if (tdq_idled(tdq) == 0)
 2786                                 continue;
 2787                 }
 2788                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2789 #else
 2790                 oldswitchcnt = switchcnt;
 2791 #endif
 2792                 /*
 2793                  * If we're switching very frequently, spin while checking
 2794                  * for load rather than entering a low power state that 
 2795                  * may require an IPI.  However, don't do any busy
 2796                  * loops while on SMT machines as this simply steals
 2797                  * cycles from cores doing useful work.
 2798                  */
 2799                 if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) {
 2800                         for (i = 0; i < sched_idlespins; i++) {
 2801                                 if (tdq->tdq_load)
 2802                                         break;
 2803                                 cpu_spinwait();
 2804                         }
 2805                 }
 2806 
 2807                 /* If there was context switch during spin, restart it. */
 2808                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2809                 if (tdq->tdq_load != 0 || switchcnt != oldswitchcnt)
 2810                         continue;
 2811 
 2812                 /* Run main MD idle handler. */
 2813                 tdq->tdq_cpu_idle = 1;
 2814                 /*
 2815                  * Make sure that tdq_cpu_idle update is globally visible
 2816                  * before cpu_idle() read tdq_load.  The order is important
 2817                  * to avoid race with tdq_notify.
 2818                  */
 2819                 atomic_thread_fence_seq_cst();
 2820                 /*
 2821                  * Checking for again after the fence picks up assigned
 2822                  * threads often enough to make it worthwhile to do so in
 2823                  * order to avoid calling cpu_idle().
 2824                  */
 2825                 if (tdq->tdq_load != 0) {
 2826                         tdq->tdq_cpu_idle = 0;
 2827                         continue;
 2828                 }
 2829                 cpu_idle(switchcnt * 4 > sched_idlespinthresh);
 2830                 tdq->tdq_cpu_idle = 0;
 2831 
 2832                 /*
 2833                  * Account thread-less hardware interrupts and
 2834                  * other wakeup reasons equal to context switches.
 2835                  */
 2836                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2837                 if (switchcnt != oldswitchcnt)
 2838                         continue;
 2839                 tdq->tdq_switchcnt++;
 2840                 oldswitchcnt++;
 2841         }
 2842 }
 2843 
 2844 /*
 2845  * A CPU is entering for the first time or a thread is exiting.
 2846  */
 2847 void
 2848 sched_throw(struct thread *td)
 2849 {
 2850         struct thread *newtd;
 2851         struct tdq *tdq;
 2852 
 2853         tdq = TDQ_SELF();
 2854         if (td == NULL) {
 2855                 /* Correct spinlock nesting and acquire the correct lock. */
 2856                 TDQ_LOCK(tdq);
 2857                 spinlock_exit();
 2858                 PCPU_SET(switchtime, cpu_ticks());
 2859                 PCPU_SET(switchticks, ticks);
 2860         } else {
 2861                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2862                 tdq_load_rem(tdq, td);
 2863                 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
 2864                 td->td_lastcpu = td->td_oncpu;
 2865                 td->td_oncpu = NOCPU;
 2866         }
 2867         KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
 2868         newtd = choosethread();
 2869         TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
 2870         cpu_throw(td, newtd);           /* doesn't return */
 2871 }
 2872 
 2873 /*
 2874  * This is called from fork_exit().  Just acquire the correct locks and
 2875  * let fork do the rest of the work.
 2876  */
 2877 void
 2878 sched_fork_exit(struct thread *td)
 2879 {
 2880         struct tdq *tdq;
 2881         int cpuid;
 2882 
 2883         /*
 2884          * Finish setting up thread glue so that it begins execution in a
 2885          * non-nested critical section with the scheduler lock held.
 2886          */
 2887         cpuid = PCPU_GET(cpuid);
 2888         tdq = TDQ_CPU(cpuid);
 2889         if (TD_IS_IDLETHREAD(td))
 2890                 td->td_lock = TDQ_LOCKPTR(tdq);
 2891         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2892         td->td_oncpu = cpuid;
 2893         TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
 2894         lock_profile_obtain_lock_success(
 2895             &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
 2896 
 2897         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
 2898             "prio:%d", td->td_priority);
 2899         SDT_PROBE0(sched, , , on__cpu);
 2900 }
 2901 
 2902 /*
 2903  * Create on first use to catch odd startup conditons.
 2904  */
 2905 char *
 2906 sched_tdname(struct thread *td)
 2907 {
 2908 #ifdef KTR
 2909         struct td_sched *ts;
 2910 
 2911         ts = td_get_sched(td);
 2912         if (ts->ts_name[0] == '\0')
 2913                 snprintf(ts->ts_name, sizeof(ts->ts_name),
 2914                     "%s tid %d", td->td_name, td->td_tid);
 2915         return (ts->ts_name);
 2916 #else
 2917         return (td->td_name);
 2918 #endif
 2919 }
 2920 
 2921 #ifdef KTR
 2922 void
 2923 sched_clear_tdname(struct thread *td)
 2924 {
 2925         struct td_sched *ts;
 2926 
 2927         ts = td_get_sched(td);
 2928         ts->ts_name[0] = '\0';
 2929 }
 2930 #endif
 2931 
 2932 #ifdef SMP
 2933 
 2934 /*
 2935  * Build the CPU topology dump string. Is recursively called to collect
 2936  * the topology tree.
 2937  */
 2938 static int
 2939 sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg,
 2940     int indent)
 2941 {
 2942         char cpusetbuf[CPUSETBUFSIZ];
 2943         int i, first;
 2944 
 2945         sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent,
 2946             "", 1 + indent / 2, cg->cg_level);
 2947         sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"%s\">", indent, "",
 2948             cg->cg_count, cpusetobj_strprint(cpusetbuf, &cg->cg_mask));
 2949         first = TRUE;
 2950         for (i = 0; i < MAXCPU; i++) {
 2951                 if (CPU_ISSET(i, &cg->cg_mask)) {
 2952                         if (!first)
 2953                                 sbuf_printf(sb, ", ");
 2954                         else
 2955                                 first = FALSE;
 2956                         sbuf_printf(sb, "%d", i);
 2957                 }
 2958         }
 2959         sbuf_printf(sb, "</cpu>\n");
 2960 
 2961         if (cg->cg_flags != 0) {
 2962                 sbuf_printf(sb, "%*s <flags>", indent, "");
 2963                 if ((cg->cg_flags & CG_FLAG_HTT) != 0)
 2964                         sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>");
 2965                 if ((cg->cg_flags & CG_FLAG_THREAD) != 0)
 2966                         sbuf_printf(sb, "<flag name=\"THREAD\">THREAD group</flag>");
 2967                 if ((cg->cg_flags & CG_FLAG_SMT) != 0)
 2968                         sbuf_printf(sb, "<flag name=\"SMT\">SMT group</flag>");
 2969                 sbuf_printf(sb, "</flags>\n");
 2970         }
 2971 
 2972         if (cg->cg_children > 0) {
 2973                 sbuf_printf(sb, "%*s <children>\n", indent, "");
 2974                 for (i = 0; i < cg->cg_children; i++)
 2975                         sysctl_kern_sched_topology_spec_internal(sb, 
 2976                             &cg->cg_child[i], indent+2);
 2977                 sbuf_printf(sb, "%*s </children>\n", indent, "");
 2978         }
 2979         sbuf_printf(sb, "%*s</group>\n", indent, "");
 2980         return (0);
 2981 }
 2982 
 2983 /*
 2984  * Sysctl handler for retrieving topology dump. It's a wrapper for
 2985  * the recursive sysctl_kern_smp_topology_spec_internal().
 2986  */
 2987 static int
 2988 sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS)
 2989 {
 2990         struct sbuf *topo;
 2991         int err;
 2992 
 2993         KASSERT(cpu_top != NULL, ("cpu_top isn't initialized"));
 2994 
 2995         topo = sbuf_new_for_sysctl(NULL, NULL, 512, req);
 2996         if (topo == NULL)
 2997                 return (ENOMEM);
 2998 
 2999         sbuf_printf(topo, "<groups>\n");
 3000         err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1);
 3001         sbuf_printf(topo, "</groups>\n");
 3002 
 3003         if (err == 0) {
 3004                 err = sbuf_finish(topo);
 3005         }
 3006         sbuf_delete(topo);
 3007         return (err);
 3008 }
 3009 
 3010 #endif
 3011 
 3012 static int
 3013 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
 3014 {
 3015         int error, new_val, period;
 3016 
 3017         period = 1000000 / realstathz;
 3018         new_val = period * sched_slice;
 3019         error = sysctl_handle_int(oidp, &new_val, 0, req);
 3020         if (error != 0 || req->newptr == NULL)
 3021                 return (error);
 3022         if (new_val <= 0)
 3023                 return (EINVAL);
 3024         sched_slice = imax(1, (new_val + period / 2) / period);
 3025         sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
 3026         hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
 3027             realstathz);
 3028         return (0);
 3029 }
 3030 
 3031 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW, 0, "Scheduler");
 3032 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0,
 3033     "Scheduler name");
 3034 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW,
 3035     NULL, 0, sysctl_kern_quantum, "I",
 3036     "Quantum for timeshare threads in microseconds");
 3037 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
 3038     "Quantum for timeshare threads in stathz ticks");
 3039 SYSCTL_INT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0,
 3040     "Interactivity score threshold");
 3041 SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW,
 3042     &preempt_thresh, 0,
 3043     "Maximal (lowest) priority for preemption");
 3044 SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost, 0,
 3045     "Assign static kernel priorities to sleeping threads");
 3046 SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins, 0,
 3047     "Number of times idle thread will spin waiting for new work");
 3048 SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW,
 3049     &sched_idlespinthresh, 0,
 3050     "Threshold before we will permit idle thread spinning");
 3051 #ifdef SMP
 3052 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0,
 3053     "Number of hz ticks to keep thread affinity for");
 3054 SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0,
 3055     "Enables the long-term load balancer");
 3056 SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW,
 3057     &balance_interval, 0,
 3058     "Average period in stathz ticks to run the long-term balancer");
 3059 SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0,
 3060     "Attempts to steal work from other cores before idling");
 3061 SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0,
 3062     "Minimum load on remote CPU before we'll steal");
 3063 SYSCTL_INT(_kern_sched, OID_AUTO, trysteal_limit, CTLFLAG_RW, &trysteal_limit,
 3064     0, "Topological distance limit for stealing threads in sched_switch()");
 3065 SYSCTL_INT(_kern_sched, OID_AUTO, always_steal, CTLFLAG_RW, &always_steal, 0,
 3066     "Always run the stealer from the idle thread");
 3067 SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING |
 3068     CTLFLAG_MPSAFE | CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A",
 3069     "XML dump of detected CPU topology");
 3070 #endif
 3071 
 3072 /* ps compat.  All cpu percentages from ULE are weighted. */
 3073 static int ccpu = 0;
 3074 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");

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