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  * Copyright (c) 2002-2007, Jeffrey Roberson <jeff@freebsd.org>
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice unmodified, this list of conditions, and the following
   10  *    disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  *
   15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   25  */
   26 
   27 /*
   28  * This file implements the ULE scheduler.  ULE supports independent CPU
   29  * run queues and fine grain locking.  It has superior interactive
   30  * performance under load even on uni-processor systems.
   31  *
   32  * etymology:
   33  *   ULE is the last three letters in schedule.  It owes its name to a
   34  * generic user created for a scheduling system by Paul Mikesell at
   35  * Isilon Systems and a general lack of creativity on the part of the author.
   36  */
   37 
   38 #include <sys/cdefs.h>
   39 __FBSDID("$FreeBSD: head/sys/kern/sched_ule.c 270423 2014-08-23 17:31:56Z mav $");
   40 
   41 #include "opt_hwpmc_hooks.h"
   42 #include "opt_sched.h"
   43 
   44 #include <sys/param.h>
   45 #include <sys/systm.h>
   46 #include <sys/kdb.h>
   47 #include <sys/kernel.h>
   48 #include <sys/ktr.h>
   49 #include <sys/limits.h>
   50 #include <sys/lock.h>
   51 #include <sys/mutex.h>
   52 #include <sys/proc.h>
   53 #include <sys/resource.h>
   54 #include <sys/resourcevar.h>
   55 #include <sys/sched.h>
   56 #include <sys/sdt.h>
   57 #include <sys/smp.h>
   58 #include <sys/sx.h>
   59 #include <sys/sysctl.h>
   60 #include <sys/sysproto.h>
   61 #include <sys/turnstile.h>
   62 #include <sys/umtx.h>
   63 #include <sys/vmmeter.h>
   64 #include <sys/cpuset.h>
   65 #include <sys/sbuf.h>
   66 
   67 #ifdef HWPMC_HOOKS
   68 #include <sys/pmckern.h>
   69 #endif
   70 
   71 #ifdef KDTRACE_HOOKS
   72 #include <sys/dtrace_bsd.h>
   73 int                             dtrace_vtime_active;
   74 dtrace_vtime_switch_func_t      dtrace_vtime_switch_func;
   75 #endif
   76 
   77 #include <machine/cpu.h>
   78 #include <machine/smp.h>
   79 
   80 #define KTR_ULE 0
   81 
   82 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
   83 #define TDQ_NAME_LEN    (sizeof("sched lock ") + sizeof(__XSTRING(MAXCPU)))
   84 #define TDQ_LOADNAME_LEN        (sizeof("CPU ") + sizeof(__XSTRING(MAXCPU)) - 1 + sizeof(" load"))
   85 
   86 /*
   87  * Thread scheduler specific section.  All fields are protected
   88  * by the thread lock.
   89  */
   90 struct td_sched {       
   91         struct runq     *ts_runq;       /* Run-queue we're queued on. */
   92         short           ts_flags;       /* TSF_* flags. */
   93         u_char          ts_cpu;         /* CPU that we have affinity for. */
   94         int             ts_rltick;      /* Real last tick, for affinity. */
   95         int             ts_slice;       /* Ticks of slice remaining. */
   96         u_int           ts_slptime;     /* Number of ticks we vol. slept */
   97         u_int           ts_runtime;     /* Number of ticks we were running */
   98         int             ts_ltick;       /* Last tick that we were running on */
   99         int             ts_ftick;       /* First tick that we were running on */
  100         int             ts_ticks;       /* Tick count */
  101 #ifdef KTR
  102         char            ts_name[TS_NAME_LEN];
  103 #endif
  104 };
  105 /* flags kept in ts_flags */
  106 #define TSF_BOUND       0x0001          /* Thread can not migrate. */
  107 #define TSF_XFERABLE    0x0002          /* Thread was added as transferable. */
  108 
  109 static struct td_sched td_sched0;
  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 /*
  116  * Priority ranges used for interactive and non-interactive timeshare
  117  * threads.  The timeshare priorities are split up into four ranges.
  118  * The first range handles interactive threads.  The last three ranges
  119  * (NHALF, x, and NHALF) handle non-interactive threads with the outer
  120  * ranges supporting nice values.
  121  */
  122 #define PRI_TIMESHARE_RANGE     (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE + 1)
  123 #define PRI_INTERACT_RANGE      ((PRI_TIMESHARE_RANGE - SCHED_PRI_NRESV) / 2)
  124 #define PRI_BATCH_RANGE         (PRI_TIMESHARE_RANGE - PRI_INTERACT_RANGE)
  125 
  126 #define PRI_MIN_INTERACT        PRI_MIN_TIMESHARE
  127 #define PRI_MAX_INTERACT        (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE - 1)
  128 #define PRI_MIN_BATCH           (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE)
  129 #define PRI_MAX_BATCH           PRI_MAX_TIMESHARE
  130 
  131 /*
  132  * Cpu percentage computation macros and defines.
  133  *
  134  * SCHED_TICK_SECS:     Number of seconds to average the cpu usage across.
  135  * SCHED_TICK_TARG:     Number of hz ticks to average the cpu usage across.
  136  * SCHED_TICK_MAX:      Maximum number of ticks before scaling back.
  137  * SCHED_TICK_SHIFT:    Shift factor to avoid rounding away results.
  138  * SCHED_TICK_HZ:       Compute the number of hz ticks for a given ticks count.
  139  * SCHED_TICK_TOTAL:    Gives the amount of time we've been recording ticks.
  140  */
  141 #define SCHED_TICK_SECS         10
  142 #define SCHED_TICK_TARG         (hz * SCHED_TICK_SECS)
  143 #define SCHED_TICK_MAX          (SCHED_TICK_TARG + hz)
  144 #define SCHED_TICK_SHIFT        10
  145 #define SCHED_TICK_HZ(ts)       ((ts)->ts_ticks >> SCHED_TICK_SHIFT)
  146 #define SCHED_TICK_TOTAL(ts)    (max((ts)->ts_ltick - (ts)->ts_ftick, hz))
  147 
  148 /*
  149  * These macros determine priorities for non-interactive threads.  They are
  150  * assigned a priority based on their recent cpu utilization as expressed
  151  * by the ratio of ticks to the tick total.  NHALF priorities at the start
  152  * and end of the MIN to MAX timeshare range are only reachable with negative
  153  * or positive nice respectively.
  154  *
  155  * PRI_RANGE:   Priority range for utilization dependent priorities.
  156  * PRI_NRESV:   Number of nice values.
  157  * PRI_TICKS:   Compute a priority in PRI_RANGE from the ticks count and total.
  158  * PRI_NICE:    Determines the part of the priority inherited from nice.
  159  */
  160 #define SCHED_PRI_NRESV         (PRIO_MAX - PRIO_MIN)
  161 #define SCHED_PRI_NHALF         (SCHED_PRI_NRESV / 2)
  162 #define SCHED_PRI_MIN           (PRI_MIN_BATCH + SCHED_PRI_NHALF)
  163 #define SCHED_PRI_MAX           (PRI_MAX_BATCH - SCHED_PRI_NHALF)
  164 #define SCHED_PRI_RANGE         (SCHED_PRI_MAX - SCHED_PRI_MIN + 1)
  165 #define SCHED_PRI_TICKS(ts)                                             \
  166     (SCHED_TICK_HZ((ts)) /                                              \
  167     (roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE))
  168 #define SCHED_PRI_NICE(nice)    (nice)
  169 
  170 /*
  171  * These determine the interactivity of a process.  Interactivity differs from
  172  * cpu utilization in that it expresses the voluntary time slept vs time ran
  173  * while cpu utilization includes all time not running.  This more accurately
  174  * models the intent of the thread.
  175  *
  176  * SLP_RUN_MAX: Maximum amount of sleep time + run time we'll accumulate
  177  *              before throttling back.
  178  * SLP_RUN_FORK:        Maximum slp+run time to inherit at fork time.
  179  * INTERACT_MAX:        Maximum interactivity value.  Smaller is better.
  180  * INTERACT_THRESH:     Threshold for placement on the current runq.
  181  */
  182 #define SCHED_SLP_RUN_MAX       ((hz * 5) << SCHED_TICK_SHIFT)
  183 #define SCHED_SLP_RUN_FORK      ((hz / 2) << SCHED_TICK_SHIFT)
  184 #define SCHED_INTERACT_MAX      (100)
  185 #define SCHED_INTERACT_HALF     (SCHED_INTERACT_MAX / 2)
  186 #define SCHED_INTERACT_THRESH   (30)
  187 
  188 /*
  189  * These parameters determine the slice behavior for batch work.
  190  */
  191 #define SCHED_SLICE_DEFAULT_DIVISOR     10      /* ~94 ms, 12 stathz ticks. */
  192 #define SCHED_SLICE_MIN_DIVISOR         6       /* DEFAULT/MIN = ~16 ms. */
  193 
  194 /* Flags kept in td_flags. */
  195 #define TDF_SLICEEND    TDF_SCHED2      /* Thread time slice is over. */
  196 
  197 /*
  198  * tickincr:            Converts a stathz tick into a hz domain scaled by
  199  *                      the shift factor.  Without the shift the error rate
  200  *                      due to rounding would be unacceptably high.
  201  * realstathz:          stathz is sometimes 0 and run off of hz.
  202  * sched_slice:         Runtime of each thread before rescheduling.
  203  * preempt_thresh:      Priority threshold for preemption and remote IPIs.
  204  */
  205 static int sched_interact = SCHED_INTERACT_THRESH;
  206 static int tickincr = 8 << SCHED_TICK_SHIFT;
  207 static int realstathz = 127;    /* reset during boot. */
  208 static int sched_slice = 10;    /* reset during boot. */
  209 static int sched_slice_min = 1; /* reset during boot. */
  210 #ifdef PREEMPTION
  211 #ifdef FULL_PREEMPTION
  212 static int preempt_thresh = PRI_MAX_IDLE;
  213 #else
  214 static int preempt_thresh = PRI_MIN_KERN;
  215 #endif
  216 #else 
  217 static int preempt_thresh = 0;
  218 #endif
  219 static int static_boost = PRI_MIN_BATCH;
  220 static int sched_idlespins = 10000;
  221 static int sched_idlespinthresh = -1;
  222 
  223 /*
  224  * tdq - per processor runqs and statistics.  All fields are protected by the
  225  * tdq_lock.  The load and lowpri may be accessed without to avoid excess
  226  * locking in sched_pickcpu();
  227  */
  228 struct tdq {
  229         /* 
  230          * Ordered to improve efficiency of cpu_search() and switch().
  231          * tdq_lock is padded to avoid false sharing with tdq_load and
  232          * tdq_cpu_idle.
  233          */
  234         struct mtx_padalign tdq_lock;           /* run queue lock. */
  235         struct cpu_group *tdq_cg;               /* Pointer to cpu topology. */
  236         volatile int    tdq_load;               /* Aggregate load. */
  237         volatile int    tdq_cpu_idle;           /* cpu_idle() is active. */
  238         int             tdq_sysload;            /* For loadavg, !ITHD load. */
  239         int             tdq_transferable;       /* Transferable thread count. */
  240         short           tdq_switchcnt;          /* Switches this tick. */
  241         short           tdq_oldswitchcnt;       /* Switches last tick. */
  242         u_char          tdq_lowpri;             /* Lowest priority thread. */
  243         u_char          tdq_ipipending;         /* IPI pending. */
  244         u_char          tdq_idx;                /* Current insert index. */
  245         u_char          tdq_ridx;               /* Current removal index. */
  246         struct runq     tdq_realtime;           /* real-time run queue. */
  247         struct runq     tdq_timeshare;          /* timeshare run queue. */
  248         struct runq     tdq_idle;               /* Queue of IDLE threads. */
  249         char            tdq_name[TDQ_NAME_LEN];
  250 #ifdef KTR
  251         char            tdq_loadname[TDQ_LOADNAME_LEN];
  252 #endif
  253 } __aligned(64);
  254 
  255 /* Idle thread states and config. */
  256 #define TDQ_RUNNING     1
  257 #define TDQ_IDLE        2
  258 
  259 #ifdef SMP
  260 struct cpu_group *cpu_top;              /* CPU topology */
  261 
  262 #define SCHED_AFFINITY_DEFAULT  (max(1, hz / 1000))
  263 #define SCHED_AFFINITY(ts, t)   ((ts)->ts_rltick > ticks - ((t) * affinity))
  264 
  265 /*
  266  * Run-time tunables.
  267  */
  268 static int rebalance = 1;
  269 static int balance_interval = 128;      /* Default set in sched_initticks(). */
  270 static int affinity;
  271 static int steal_idle = 1;
  272 static int steal_thresh = 2;
  273 
  274 /*
  275  * One thread queue per processor.
  276  */
  277 static struct tdq       tdq_cpu[MAXCPU];
  278 static struct tdq       *balance_tdq;
  279 static int balance_ticks;
  280 static DPCPU_DEFINE(uint32_t, randomval);
  281 
  282 #define TDQ_SELF()      (&tdq_cpu[PCPU_GET(cpuid)])
  283 #define TDQ_CPU(x)      (&tdq_cpu[(x)])
  284 #define TDQ_ID(x)       ((int)((x) - tdq_cpu))
  285 #else   /* !SMP */
  286 static struct tdq       tdq_cpu;
  287 
  288 #define TDQ_ID(x)       (0)
  289 #define TDQ_SELF()      (&tdq_cpu)
  290 #define TDQ_CPU(x)      (&tdq_cpu)
  291 #endif
  292 
  293 #define TDQ_LOCK_ASSERT(t, type)        mtx_assert(TDQ_LOCKPTR((t)), (type))
  294 #define TDQ_LOCK(t)             mtx_lock_spin(TDQ_LOCKPTR((t)))
  295 #define TDQ_LOCK_FLAGS(t, f)    mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f))
  296 #define TDQ_UNLOCK(t)           mtx_unlock_spin(TDQ_LOCKPTR((t)))
  297 #define TDQ_LOCKPTR(t)          ((struct mtx *)(&(t)->tdq_lock))
  298 
  299 static void sched_priority(struct thread *);
  300 static void sched_thread_priority(struct thread *, u_char);
  301 static int sched_interact_score(struct thread *);
  302 static void sched_interact_update(struct thread *);
  303 static void sched_interact_fork(struct thread *);
  304 static void sched_pctcpu_update(struct td_sched *, int);
  305 
  306 /* Operations on per processor queues */
  307 static struct thread *tdq_choose(struct tdq *);
  308 static void tdq_setup(struct tdq *);
  309 static void tdq_load_add(struct tdq *, struct thread *);
  310 static void tdq_load_rem(struct tdq *, struct thread *);
  311 static __inline void tdq_runq_add(struct tdq *, struct thread *, int);
  312 static __inline void tdq_runq_rem(struct tdq *, struct thread *);
  313 static inline int sched_shouldpreempt(int, int, int);
  314 void tdq_print(int cpu);
  315 static void runq_print(struct runq *rq);
  316 static void tdq_add(struct tdq *, struct thread *, int);
  317 #ifdef SMP
  318 static int tdq_move(struct tdq *, struct tdq *);
  319 static int tdq_idled(struct tdq *);
  320 static void tdq_notify(struct tdq *, struct thread *);
  321 static struct thread *tdq_steal(struct tdq *, int);
  322 static struct thread *runq_steal(struct runq *, int);
  323 static int sched_pickcpu(struct thread *, int);
  324 static void sched_balance(void);
  325 static int sched_balance_pair(struct tdq *, struct tdq *);
  326 static inline struct tdq *sched_setcpu(struct thread *, int, int);
  327 static inline void thread_unblock_switch(struct thread *, struct mtx *);
  328 static struct mtx *sched_switch_migrate(struct tdq *, struct thread *, int);
  329 static int sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS);
  330 static int sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, 
  331     struct cpu_group *cg, int indent);
  332 #endif
  333 
  334 static void sched_setup(void *dummy);
  335 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
  336 
  337 static void sched_initticks(void *dummy);
  338 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
  339     NULL);
  340 
  341 SDT_PROVIDER_DEFINE(sched);
  342 
  343 SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *", 
  344     "struct proc *", "uint8_t");
  345 SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *", 
  346     "struct proc *", "void *");
  347 SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *", 
  348     "struct proc *", "void *", "int");
  349 SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *", 
  350     "struct proc *", "uint8_t", "struct thread *");
  351 SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int");
  352 SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *", 
  353     "struct proc *");
  354 SDT_PROBE_DEFINE(sched, , , on__cpu);
  355 SDT_PROBE_DEFINE(sched, , , remain__cpu);
  356 SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *", 
  357     "struct proc *");
  358 
  359 /*
  360  * Print the threads waiting on a run-queue.
  361  */
  362 static void
  363 runq_print(struct runq *rq)
  364 {
  365         struct rqhead *rqh;
  366         struct thread *td;
  367         int pri;
  368         int j;
  369         int i;
  370 
  371         for (i = 0; i < RQB_LEN; i++) {
  372                 printf("\t\trunq bits %d 0x%zx\n",
  373                     i, rq->rq_status.rqb_bits[i]);
  374                 for (j = 0; j < RQB_BPW; j++)
  375                         if (rq->rq_status.rqb_bits[i] & (1ul << j)) {
  376                                 pri = j + (i << RQB_L2BPW);
  377                                 rqh = &rq->rq_queues[pri];
  378                                 TAILQ_FOREACH(td, rqh, td_runq) {
  379                                         printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
  380                                             td, td->td_name, td->td_priority,
  381                                             td->td_rqindex, pri);
  382                                 }
  383                         }
  384         }
  385 }
  386 
  387 /*
  388  * Print the status of a per-cpu thread queue.  Should be a ddb show cmd.
  389  */
  390 void
  391 tdq_print(int cpu)
  392 {
  393         struct tdq *tdq;
  394 
  395         tdq = TDQ_CPU(cpu);
  396 
  397         printf("tdq %d:\n", TDQ_ID(tdq));
  398         printf("\tlock            %p\n", TDQ_LOCKPTR(tdq));
  399         printf("\tLock name:      %s\n", tdq->tdq_name);
  400         printf("\tload:           %d\n", tdq->tdq_load);
  401         printf("\tswitch cnt:     %d\n", tdq->tdq_switchcnt);
  402         printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt);
  403         printf("\ttimeshare idx:  %d\n", tdq->tdq_idx);
  404         printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
  405         printf("\tload transferable: %d\n", tdq->tdq_transferable);
  406         printf("\tlowest priority:   %d\n", tdq->tdq_lowpri);
  407         printf("\trealtime runq:\n");
  408         runq_print(&tdq->tdq_realtime);
  409         printf("\ttimeshare runq:\n");
  410         runq_print(&tdq->tdq_timeshare);
  411         printf("\tidle runq:\n");
  412         runq_print(&tdq->tdq_idle);
  413 }
  414 
  415 static inline int
  416 sched_shouldpreempt(int pri, int cpri, int remote)
  417 {
  418         /*
  419          * If the new priority is not better than the current priority there is
  420          * nothing to do.
  421          */
  422         if (pri >= cpri)
  423                 return (0);
  424         /*
  425          * Always preempt idle.
  426          */
  427         if (cpri >= PRI_MIN_IDLE)
  428                 return (1);
  429         /*
  430          * If preemption is disabled don't preempt others.
  431          */
  432         if (preempt_thresh == 0)
  433                 return (0);
  434         /*
  435          * Preempt if we exceed the threshold.
  436          */
  437         if (pri <= preempt_thresh)
  438                 return (1);
  439         /*
  440          * If we're interactive or better and there is non-interactive
  441          * or worse running preempt only remote processors.
  442          */
  443         if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT)
  444                 return (1);
  445         return (0);
  446 }
  447 
  448 /*
  449  * Add a thread to the actual run-queue.  Keeps transferable counts up to
  450  * date with what is actually on the run-queue.  Selects the correct
  451  * queue position for timeshare threads.
  452  */
  453 static __inline void
  454 tdq_runq_add(struct tdq *tdq, struct thread *td, int flags)
  455 {
  456         struct td_sched *ts;
  457         u_char pri;
  458 
  459         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  460         THREAD_LOCK_ASSERT(td, MA_OWNED);
  461 
  462         pri = td->td_priority;
  463         ts = td->td_sched;
  464         TD_SET_RUNQ(td);
  465         if (THREAD_CAN_MIGRATE(td)) {
  466                 tdq->tdq_transferable++;
  467                 ts->ts_flags |= TSF_XFERABLE;
  468         }
  469         if (pri < PRI_MIN_BATCH) {
  470                 ts->ts_runq = &tdq->tdq_realtime;
  471         } else if (pri <= PRI_MAX_BATCH) {
  472                 ts->ts_runq = &tdq->tdq_timeshare;
  473                 KASSERT(pri <= PRI_MAX_BATCH && pri >= PRI_MIN_BATCH,
  474                         ("Invalid priority %d on timeshare runq", pri));
  475                 /*
  476                  * This queue contains only priorities between MIN and MAX
  477                  * realtime.  Use the whole queue to represent these values.
  478                  */
  479                 if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) {
  480                         pri = RQ_NQS * (pri - PRI_MIN_BATCH) / PRI_BATCH_RANGE;
  481                         pri = (pri + tdq->tdq_idx) % RQ_NQS;
  482                         /*
  483                          * This effectively shortens the queue by one so we
  484                          * can have a one slot difference between idx and
  485                          * ridx while we wait for threads to drain.
  486                          */
  487                         if (tdq->tdq_ridx != tdq->tdq_idx &&
  488                             pri == tdq->tdq_ridx)
  489                                 pri = (unsigned char)(pri - 1) % RQ_NQS;
  490                 } else
  491                         pri = tdq->tdq_ridx;
  492                 runq_add_pri(ts->ts_runq, td, pri, flags);
  493                 return;
  494         } else
  495                 ts->ts_runq = &tdq->tdq_idle;
  496         runq_add(ts->ts_runq, td, flags);
  497 }
  498 
  499 /* 
  500  * Remove a thread from a run-queue.  This typically happens when a thread
  501  * is selected to run.  Running threads are not on the queue and the
  502  * transferable count does not reflect them.
  503  */
  504 static __inline void
  505 tdq_runq_rem(struct tdq *tdq, struct thread *td)
  506 {
  507         struct td_sched *ts;
  508 
  509         ts = td->td_sched;
  510         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  511         KASSERT(ts->ts_runq != NULL,
  512             ("tdq_runq_remove: thread %p null ts_runq", td));
  513         if (ts->ts_flags & TSF_XFERABLE) {
  514                 tdq->tdq_transferable--;
  515                 ts->ts_flags &= ~TSF_XFERABLE;
  516         }
  517         if (ts->ts_runq == &tdq->tdq_timeshare) {
  518                 if (tdq->tdq_idx != tdq->tdq_ridx)
  519                         runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx);
  520                 else
  521                         runq_remove_idx(ts->ts_runq, td, NULL);
  522         } else
  523                 runq_remove(ts->ts_runq, td);
  524 }
  525 
  526 /*
  527  * Load is maintained for all threads RUNNING and ON_RUNQ.  Add the load
  528  * for this thread to the referenced thread queue.
  529  */
  530 static void
  531 tdq_load_add(struct tdq *tdq, struct thread *td)
  532 {
  533 
  534         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  535         THREAD_LOCK_ASSERT(td, MA_OWNED);
  536 
  537         tdq->tdq_load++;
  538         if ((td->td_flags & TDF_NOLOAD) == 0)
  539                 tdq->tdq_sysload++;
  540         KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
  541         SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
  542 }
  543 
  544 /*
  545  * Remove the load from a thread that is transitioning to a sleep state or
  546  * exiting.
  547  */
  548 static void
  549 tdq_load_rem(struct tdq *tdq, struct thread *td)
  550 {
  551 
  552         THREAD_LOCK_ASSERT(td, MA_OWNED);
  553         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  554         KASSERT(tdq->tdq_load != 0,
  555             ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
  556 
  557         tdq->tdq_load--;
  558         if ((td->td_flags & TDF_NOLOAD) == 0)
  559                 tdq->tdq_sysload--;
  560         KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
  561         SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
  562 }
  563 
  564 /*
  565  * Bound timeshare latency by decreasing slice size as load increases.  We
  566  * consider the maximum latency as the sum of the threads waiting to run
  567  * aside from curthread and target no more than sched_slice latency but
  568  * no less than sched_slice_min runtime.
  569  */
  570 static inline int
  571 tdq_slice(struct tdq *tdq)
  572 {
  573         int load;
  574 
  575         /*
  576          * It is safe to use sys_load here because this is called from
  577          * contexts where timeshare threads are running and so there
  578          * cannot be higher priority load in the system.
  579          */
  580         load = tdq->tdq_sysload - 1;
  581         if (load >= SCHED_SLICE_MIN_DIVISOR)
  582                 return (sched_slice_min);
  583         if (load <= 1)
  584                 return (sched_slice);
  585         return (sched_slice / load);
  586 }
  587 
  588 /*
  589  * Set lowpri to its exact value by searching the run-queue and
  590  * evaluating curthread.  curthread may be passed as an optimization.
  591  */
  592 static void
  593 tdq_setlowpri(struct tdq *tdq, struct thread *ctd)
  594 {
  595         struct thread *td;
  596 
  597         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  598         if (ctd == NULL)
  599                 ctd = pcpu_find(TDQ_ID(tdq))->pc_curthread;
  600         td = tdq_choose(tdq);
  601         if (td == NULL || td->td_priority > ctd->td_priority)
  602                 tdq->tdq_lowpri = ctd->td_priority;
  603         else
  604                 tdq->tdq_lowpri = td->td_priority;
  605 }
  606 
  607 #ifdef SMP
  608 struct cpu_search {
  609         cpuset_t cs_mask;
  610         u_int   cs_prefer;
  611         int     cs_pri;         /* Min priority for low. */
  612         int     cs_limit;       /* Max load for low, min load for high. */
  613         int     cs_cpu;
  614         int     cs_load;
  615 };
  616 
  617 #define CPU_SEARCH_LOWEST       0x1
  618 #define CPU_SEARCH_HIGHEST      0x2
  619 #define CPU_SEARCH_BOTH         (CPU_SEARCH_LOWEST|CPU_SEARCH_HIGHEST)
  620 
  621 #define CPUSET_FOREACH(cpu, mask)                               \
  622         for ((cpu) = 0; (cpu) <= mp_maxid; (cpu)++)             \
  623                 if (CPU_ISSET(cpu, &mask))
  624 
  625 static __always_inline int cpu_search(const struct cpu_group *cg,
  626     struct cpu_search *low, struct cpu_search *high, const int match);
  627 int __noinline cpu_search_lowest(const struct cpu_group *cg,
  628     struct cpu_search *low);
  629 int __noinline cpu_search_highest(const struct cpu_group *cg,
  630     struct cpu_search *high);
  631 int __noinline cpu_search_both(const struct cpu_group *cg,
  632     struct cpu_search *low, struct cpu_search *high);
  633 
  634 /*
  635  * Search the tree of cpu_groups for the lowest or highest loaded cpu
  636  * according to the match argument.  This routine actually compares the
  637  * load on all paths through the tree and finds the least loaded cpu on
  638  * the least loaded path, which may differ from the least loaded cpu in
  639  * the system.  This balances work among caches and busses.
  640  *
  641  * This inline is instantiated in three forms below using constants for the
  642  * match argument.  It is reduced to the minimum set for each case.  It is
  643  * also recursive to the depth of the tree.
  644  */
  645 static __always_inline int
  646 cpu_search(const struct cpu_group *cg, struct cpu_search *low,
  647     struct cpu_search *high, const int match)
  648 {
  649         struct cpu_search lgroup;
  650         struct cpu_search hgroup;
  651         cpuset_t cpumask;
  652         struct cpu_group *child;
  653         struct tdq *tdq;
  654         int cpu, i, hload, lload, load, total, rnd, *rndptr;
  655 
  656         total = 0;
  657         cpumask = cg->cg_mask;
  658         if (match & CPU_SEARCH_LOWEST) {
  659                 lload = INT_MAX;
  660                 lgroup = *low;
  661         }
  662         if (match & CPU_SEARCH_HIGHEST) {
  663                 hload = INT_MIN;
  664                 hgroup = *high;
  665         }
  666 
  667         /* Iterate through the child CPU groups and then remaining CPUs. */
  668         for (i = cg->cg_children, cpu = mp_maxid; ; ) {
  669                 if (i == 0) {
  670 #ifdef HAVE_INLINE_FFSL
  671                         cpu = CPU_FFS(&cpumask) - 1;
  672 #else
  673                         while (cpu >= 0 && !CPU_ISSET(cpu, &cpumask))
  674                                 cpu--;
  675 #endif
  676                         if (cpu < 0)
  677                                 break;
  678                         child = NULL;
  679                 } else
  680                         child = &cg->cg_child[i - 1];
  681 
  682                 if (match & CPU_SEARCH_LOWEST)
  683                         lgroup.cs_cpu = -1;
  684                 if (match & CPU_SEARCH_HIGHEST)
  685                         hgroup.cs_cpu = -1;
  686                 if (child) {                    /* Handle child CPU group. */
  687                         CPU_NAND(&cpumask, &child->cg_mask);
  688                         switch (match) {
  689                         case CPU_SEARCH_LOWEST:
  690                                 load = cpu_search_lowest(child, &lgroup);
  691                                 break;
  692                         case CPU_SEARCH_HIGHEST:
  693                                 load = cpu_search_highest(child, &hgroup);
  694                                 break;
  695                         case CPU_SEARCH_BOTH:
  696                                 load = cpu_search_both(child, &lgroup, &hgroup);
  697                                 break;
  698                         }
  699                 } else {                        /* Handle child CPU. */
  700                         CPU_CLR(cpu, &cpumask);
  701                         tdq = TDQ_CPU(cpu);
  702                         load = tdq->tdq_load * 256;
  703                         rndptr = DPCPU_PTR(randomval);
  704                         rnd = (*rndptr = *rndptr * 69069 + 5) >> 26;
  705                         if (match & CPU_SEARCH_LOWEST) {
  706                                 if (cpu == low->cs_prefer)
  707                                         load -= 64;
  708                                 /* If that CPU is allowed and get data. */
  709                                 if (tdq->tdq_lowpri > lgroup.cs_pri &&
  710                                     tdq->tdq_load <= lgroup.cs_limit &&
  711                                     CPU_ISSET(cpu, &lgroup.cs_mask)) {
  712                                         lgroup.cs_cpu = cpu;
  713                                         lgroup.cs_load = load - rnd;
  714                                 }
  715                         }
  716                         if (match & CPU_SEARCH_HIGHEST)
  717                                 if (tdq->tdq_load >= hgroup.cs_limit &&
  718                                     tdq->tdq_transferable &&
  719                                     CPU_ISSET(cpu, &hgroup.cs_mask)) {
  720                                         hgroup.cs_cpu = cpu;
  721                                         hgroup.cs_load = load - rnd;
  722                                 }
  723                 }
  724                 total += load;
  725 
  726                 /* We have info about child item. Compare it. */
  727                 if (match & CPU_SEARCH_LOWEST) {
  728                         if (lgroup.cs_cpu >= 0 &&
  729                             (load < lload ||
  730                              (load == lload && lgroup.cs_load < low->cs_load))) {
  731                                 lload = load;
  732                                 low->cs_cpu = lgroup.cs_cpu;
  733                                 low->cs_load = lgroup.cs_load;
  734                         }
  735                 }
  736                 if (match & CPU_SEARCH_HIGHEST)
  737                         if (hgroup.cs_cpu >= 0 &&
  738                             (load > hload ||
  739                              (load == hload && hgroup.cs_load > high->cs_load))) {
  740                                 hload = load;
  741                                 high->cs_cpu = hgroup.cs_cpu;
  742                                 high->cs_load = hgroup.cs_load;
  743                         }
  744                 if (child) {
  745                         i--;
  746                         if (i == 0 && CPU_EMPTY(&cpumask))
  747                                 break;
  748                 }
  749 #ifndef HAVE_INLINE_FFSL
  750                 else
  751                         cpu--;
  752 #endif
  753         }
  754         return (total);
  755 }
  756 
  757 /*
  758  * cpu_search instantiations must pass constants to maintain the inline
  759  * optimization.
  760  */
  761 int
  762 cpu_search_lowest(const struct cpu_group *cg, struct cpu_search *low)
  763 {
  764         return cpu_search(cg, low, NULL, CPU_SEARCH_LOWEST);
  765 }
  766 
  767 int
  768 cpu_search_highest(const struct cpu_group *cg, struct cpu_search *high)
  769 {
  770         return cpu_search(cg, NULL, high, CPU_SEARCH_HIGHEST);
  771 }
  772 
  773 int
  774 cpu_search_both(const struct cpu_group *cg, struct cpu_search *low,
  775     struct cpu_search *high)
  776 {
  777         return cpu_search(cg, low, high, CPU_SEARCH_BOTH);
  778 }
  779 
  780 /*
  781  * Find the cpu with the least load via the least loaded path that has a
  782  * lowpri greater than pri  pri.  A pri of -1 indicates any priority is
  783  * acceptable.
  784  */
  785 static inline int
  786 sched_lowest(const struct cpu_group *cg, cpuset_t mask, int pri, int maxload,
  787     int prefer)
  788 {
  789         struct cpu_search low;
  790 
  791         low.cs_cpu = -1;
  792         low.cs_prefer = prefer;
  793         low.cs_mask = mask;
  794         low.cs_pri = pri;
  795         low.cs_limit = maxload;
  796         cpu_search_lowest(cg, &low);
  797         return low.cs_cpu;
  798 }
  799 
  800 /*
  801  * Find the cpu with the highest load via the highest loaded path.
  802  */
  803 static inline int
  804 sched_highest(const struct cpu_group *cg, cpuset_t mask, int minload)
  805 {
  806         struct cpu_search high;
  807 
  808         high.cs_cpu = -1;
  809         high.cs_mask = mask;
  810         high.cs_limit = minload;
  811         cpu_search_highest(cg, &high);
  812         return high.cs_cpu;
  813 }
  814 
  815 static void
  816 sched_balance_group(struct cpu_group *cg)
  817 {
  818         cpuset_t hmask, lmask;
  819         int high, low, anylow;
  820 
  821         CPU_FILL(&hmask);
  822         for (;;) {
  823                 high = sched_highest(cg, hmask, 1);
  824                 /* Stop if there is no more CPU with transferrable threads. */
  825                 if (high == -1)
  826                         break;
  827                 CPU_CLR(high, &hmask);
  828                 CPU_COPY(&hmask, &lmask);
  829                 /* Stop if there is no more CPU left for low. */
  830                 if (CPU_EMPTY(&lmask))
  831                         break;
  832                 anylow = 1;
  833 nextlow:
  834                 low = sched_lowest(cg, lmask, -1,
  835                     TDQ_CPU(high)->tdq_load - 1, high);
  836                 /* Stop if we looked well and found no less loaded CPU. */
  837                 if (anylow && low == -1)
  838                         break;
  839                 /* Go to next high if we found no less loaded CPU. */
  840                 if (low == -1)
  841                         continue;
  842                 /* Transfer thread from high to low. */
  843                 if (sched_balance_pair(TDQ_CPU(high), TDQ_CPU(low))) {
  844                         /* CPU that got thread can no longer be a donor. */
  845                         CPU_CLR(low, &hmask);
  846                 } else {
  847                         /*
  848                          * If failed, then there is no threads on high
  849                          * that can run on this low. Drop low from low
  850                          * mask and look for different one.
  851                          */
  852                         CPU_CLR(low, &lmask);
  853                         anylow = 0;
  854                         goto nextlow;
  855                 }
  856         }
  857 }
  858 
  859 static void
  860 sched_balance(void)
  861 {
  862         struct tdq *tdq;
  863 
  864         /*
  865          * Select a random time between .5 * balance_interval and
  866          * 1.5 * balance_interval.
  867          */
  868         balance_ticks = max(balance_interval / 2, 1);
  869         balance_ticks += random() % balance_interval;
  870         if (smp_started == 0 || rebalance == 0)
  871                 return;
  872         tdq = TDQ_SELF();
  873         TDQ_UNLOCK(tdq);
  874         sched_balance_group(cpu_top);
  875         TDQ_LOCK(tdq);
  876 }
  877 
  878 /*
  879  * Lock two thread queues using their address to maintain lock order.
  880  */
  881 static void
  882 tdq_lock_pair(struct tdq *one, struct tdq *two)
  883 {
  884         if (one < two) {
  885                 TDQ_LOCK(one);
  886                 TDQ_LOCK_FLAGS(two, MTX_DUPOK);
  887         } else {
  888                 TDQ_LOCK(two);
  889                 TDQ_LOCK_FLAGS(one, MTX_DUPOK);
  890         }
  891 }
  892 
  893 /*
  894  * Unlock two thread queues.  Order is not important here.
  895  */
  896 static void
  897 tdq_unlock_pair(struct tdq *one, struct tdq *two)
  898 {
  899         TDQ_UNLOCK(one);
  900         TDQ_UNLOCK(two);
  901 }
  902 
  903 /*
  904  * Transfer load between two imbalanced thread queues.
  905  */
  906 static int
  907 sched_balance_pair(struct tdq *high, struct tdq *low)
  908 {
  909         int moved;
  910         int cpu;
  911 
  912         tdq_lock_pair(high, low);
  913         moved = 0;
  914         /*
  915          * Determine what the imbalance is and then adjust that to how many
  916          * threads we actually have to give up (transferable).
  917          */
  918         if (high->tdq_transferable != 0 && high->tdq_load > low->tdq_load &&
  919             (moved = tdq_move(high, low)) > 0) {
  920                 /*
  921                  * In case the target isn't the current cpu IPI it to force a
  922                  * reschedule with the new workload.
  923                  */
  924                 cpu = TDQ_ID(low);
  925                 if (cpu != PCPU_GET(cpuid))
  926                         ipi_cpu(cpu, IPI_PREEMPT);
  927         }
  928         tdq_unlock_pair(high, low);
  929         return (moved);
  930 }
  931 
  932 /*
  933  * Move a thread from one thread queue to another.
  934  */
  935 static int
  936 tdq_move(struct tdq *from, struct tdq *to)
  937 {
  938         struct td_sched *ts;
  939         struct thread *td;
  940         struct tdq *tdq;
  941         int cpu;
  942 
  943         TDQ_LOCK_ASSERT(from, MA_OWNED);
  944         TDQ_LOCK_ASSERT(to, MA_OWNED);
  945 
  946         tdq = from;
  947         cpu = TDQ_ID(to);
  948         td = tdq_steal(tdq, cpu);
  949         if (td == NULL)
  950                 return (0);
  951         ts = td->td_sched;
  952         /*
  953          * Although the run queue is locked the thread may be blocked.  Lock
  954          * it to clear this and acquire the run-queue lock.
  955          */
  956         thread_lock(td);
  957         /* Drop recursive lock on from acquired via thread_lock(). */
  958         TDQ_UNLOCK(from);
  959         sched_rem(td);
  960         ts->ts_cpu = cpu;
  961         td->td_lock = TDQ_LOCKPTR(to);
  962         tdq_add(to, td, SRQ_YIELDING);
  963         return (1);
  964 }
  965 
  966 /*
  967  * This tdq has idled.  Try to steal a thread from another cpu and switch
  968  * to it.
  969  */
  970 static int
  971 tdq_idled(struct tdq *tdq)
  972 {
  973         struct cpu_group *cg;
  974         struct tdq *steal;
  975         cpuset_t mask;
  976         int thresh;
  977         int cpu;
  978 
  979         if (smp_started == 0 || steal_idle == 0)
  980                 return (1);
  981         CPU_FILL(&mask);
  982         CPU_CLR(PCPU_GET(cpuid), &mask);
  983         /* We don't want to be preempted while we're iterating. */
  984         spinlock_enter();
  985         for (cg = tdq->tdq_cg; cg != NULL; ) {
  986                 if ((cg->cg_flags & CG_FLAG_THREAD) == 0)
  987                         thresh = steal_thresh;
  988                 else
  989                         thresh = 1;
  990                 cpu = sched_highest(cg, mask, thresh);
  991                 if (cpu == -1) {
  992                         cg = cg->cg_parent;
  993                         continue;
  994                 }
  995                 steal = TDQ_CPU(cpu);
  996                 CPU_CLR(cpu, &mask);
  997                 tdq_lock_pair(tdq, steal);
  998                 if (steal->tdq_load < thresh || steal->tdq_transferable == 0) {
  999                         tdq_unlock_pair(tdq, steal);
 1000                         continue;
 1001                 }
 1002                 /*
 1003                  * If a thread was added while interrupts were disabled don't
 1004                  * steal one here.  If we fail to acquire one due to affinity
 1005                  * restrictions loop again with this cpu removed from the
 1006                  * set.
 1007                  */
 1008                 if (tdq->tdq_load == 0 && tdq_move(steal, tdq) == 0) {
 1009                         tdq_unlock_pair(tdq, steal);
 1010                         continue;
 1011                 }
 1012                 spinlock_exit();
 1013                 TDQ_UNLOCK(steal);
 1014                 mi_switch(SW_VOL | SWT_IDLE, NULL);
 1015                 thread_unlock(curthread);
 1016 
 1017                 return (0);
 1018         }
 1019         spinlock_exit();
 1020         return (1);
 1021 }
 1022 
 1023 /*
 1024  * Notify a remote cpu of new work.  Sends an IPI if criteria are met.
 1025  */
 1026 static void
 1027 tdq_notify(struct tdq *tdq, struct thread *td)
 1028 {
 1029         struct thread *ctd;
 1030         int pri;
 1031         int cpu;
 1032 
 1033         if (tdq->tdq_ipipending)
 1034                 return;
 1035         cpu = td->td_sched->ts_cpu;
 1036         pri = td->td_priority;
 1037         ctd = pcpu_find(cpu)->pc_curthread;
 1038         if (!sched_shouldpreempt(pri, ctd->td_priority, 1))
 1039                 return;
 1040         if (TD_IS_IDLETHREAD(ctd)) {
 1041                 /*
 1042                  * If the MD code has an idle wakeup routine try that before
 1043                  * falling back to IPI.
 1044                  */
 1045                 if (!tdq->tdq_cpu_idle || cpu_idle_wakeup(cpu))
 1046                         return;
 1047         }
 1048         tdq->tdq_ipipending = 1;
 1049         ipi_cpu(cpu, IPI_PREEMPT);
 1050 }
 1051 
 1052 /*
 1053  * Steals load from a timeshare queue.  Honors the rotating queue head
 1054  * index.
 1055  */
 1056 static struct thread *
 1057 runq_steal_from(struct runq *rq, int cpu, u_char start)
 1058 {
 1059         struct rqbits *rqb;
 1060         struct rqhead *rqh;
 1061         struct thread *td, *first;
 1062         int bit;
 1063         int i;
 1064 
 1065         rqb = &rq->rq_status;
 1066         bit = start & (RQB_BPW -1);
 1067         first = NULL;
 1068 again:
 1069         for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
 1070                 if (rqb->rqb_bits[i] == 0)
 1071                         continue;
 1072                 if (bit == 0)
 1073                         bit = RQB_FFS(rqb->rqb_bits[i]);
 1074                 for (; bit < RQB_BPW; bit++) {
 1075                         if ((rqb->rqb_bits[i] & (1ul << bit)) == 0)
 1076                                 continue;
 1077                         rqh = &rq->rq_queues[bit + (i << RQB_L2BPW)];
 1078                         TAILQ_FOREACH(td, rqh, td_runq) {
 1079                                 if (first && THREAD_CAN_MIGRATE(td) &&
 1080                                     THREAD_CAN_SCHED(td, cpu))
 1081                                         return (td);
 1082                                 first = td;
 1083                         }
 1084                 }
 1085         }
 1086         if (start != 0) {
 1087                 start = 0;
 1088                 goto again;
 1089         }
 1090 
 1091         if (first && THREAD_CAN_MIGRATE(first) &&
 1092             THREAD_CAN_SCHED(first, cpu))
 1093                 return (first);
 1094         return (NULL);
 1095 }
 1096 
 1097 /*
 1098  * Steals load from a standard linear queue.
 1099  */
 1100 static struct thread *
 1101 runq_steal(struct runq *rq, int cpu)
 1102 {
 1103         struct rqhead *rqh;
 1104         struct rqbits *rqb;
 1105         struct thread *td;
 1106         int word;
 1107         int bit;
 1108 
 1109         rqb = &rq->rq_status;
 1110         for (word = 0; word < RQB_LEN; word++) {
 1111                 if (rqb->rqb_bits[word] == 0)
 1112                         continue;
 1113                 for (bit = 0; bit < RQB_BPW; bit++) {
 1114                         if ((rqb->rqb_bits[word] & (1ul << bit)) == 0)
 1115                                 continue;
 1116                         rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)];
 1117                         TAILQ_FOREACH(td, rqh, td_runq)
 1118                                 if (THREAD_CAN_MIGRATE(td) &&
 1119                                     THREAD_CAN_SCHED(td, cpu))
 1120                                         return (td);
 1121                 }
 1122         }
 1123         return (NULL);
 1124 }
 1125 
 1126 /*
 1127  * Attempt to steal a thread in priority order from a thread queue.
 1128  */
 1129 static struct thread *
 1130 tdq_steal(struct tdq *tdq, int cpu)
 1131 {
 1132         struct thread *td;
 1133 
 1134         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 1135         if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL)
 1136                 return (td);
 1137         if ((td = runq_steal_from(&tdq->tdq_timeshare,
 1138             cpu, tdq->tdq_ridx)) != NULL)
 1139                 return (td);
 1140         return (runq_steal(&tdq->tdq_idle, cpu));
 1141 }
 1142 
 1143 /*
 1144  * Sets the thread lock and ts_cpu to match the requested cpu.  Unlocks the
 1145  * current lock and returns with the assigned queue locked.
 1146  */
 1147 static inline struct tdq *
 1148 sched_setcpu(struct thread *td, int cpu, int flags)
 1149 {
 1150 
 1151         struct tdq *tdq;
 1152 
 1153         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1154         tdq = TDQ_CPU(cpu);
 1155         td->td_sched->ts_cpu = cpu;
 1156         /*
 1157          * If the lock matches just return the queue.
 1158          */
 1159         if (td->td_lock == TDQ_LOCKPTR(tdq))
 1160                 return (tdq);
 1161 #ifdef notyet
 1162         /*
 1163          * If the thread isn't running its lockptr is a
 1164          * turnstile or a sleepqueue.  We can just lock_set without
 1165          * blocking.
 1166          */
 1167         if (TD_CAN_RUN(td)) {
 1168                 TDQ_LOCK(tdq);
 1169                 thread_lock_set(td, TDQ_LOCKPTR(tdq));
 1170                 return (tdq);
 1171         }
 1172 #endif
 1173         /*
 1174          * The hard case, migration, we need to block the thread first to
 1175          * prevent order reversals with other cpus locks.
 1176          */
 1177         spinlock_enter();
 1178         thread_lock_block(td);
 1179         TDQ_LOCK(tdq);
 1180         thread_lock_unblock(td, TDQ_LOCKPTR(tdq));
 1181         spinlock_exit();
 1182         return (tdq);
 1183 }
 1184 
 1185 SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding");
 1186 SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity");
 1187 SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity");
 1188 SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load");
 1189 SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu");
 1190 SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration");
 1191 
 1192 static int
 1193 sched_pickcpu(struct thread *td, int flags)
 1194 {
 1195         struct cpu_group *cg, *ccg;
 1196         struct td_sched *ts;
 1197         struct tdq *tdq;
 1198         cpuset_t mask;
 1199         int cpu, pri, self;
 1200 
 1201         self = PCPU_GET(cpuid);
 1202         ts = td->td_sched;
 1203         if (smp_started == 0)
 1204                 return (self);
 1205         /*
 1206          * Don't migrate a running thread from sched_switch().
 1207          */
 1208         if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td))
 1209                 return (ts->ts_cpu);
 1210         /*
 1211          * Prefer to run interrupt threads on the processors that generate
 1212          * the interrupt.
 1213          */
 1214         pri = td->td_priority;
 1215         if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) &&
 1216             curthread->td_intr_nesting_level && ts->ts_cpu != self) {
 1217                 SCHED_STAT_INC(pickcpu_intrbind);
 1218                 ts->ts_cpu = self;
 1219                 if (TDQ_CPU(self)->tdq_lowpri > pri) {
 1220                         SCHED_STAT_INC(pickcpu_affinity);
 1221                         return (ts->ts_cpu);
 1222                 }
 1223         }
 1224         /*
 1225          * If the thread can run on the last cpu and the affinity has not
 1226          * expired or it is idle run it there.
 1227          */
 1228         tdq = TDQ_CPU(ts->ts_cpu);
 1229         cg = tdq->tdq_cg;
 1230         if (THREAD_CAN_SCHED(td, ts->ts_cpu) &&
 1231             tdq->tdq_lowpri >= PRI_MIN_IDLE &&
 1232             SCHED_AFFINITY(ts, CG_SHARE_L2)) {
 1233                 if (cg->cg_flags & CG_FLAG_THREAD) {
 1234                         CPUSET_FOREACH(cpu, cg->cg_mask) {
 1235                                 if (TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE)
 1236                                         break;
 1237                         }
 1238                 } else
 1239                         cpu = INT_MAX;
 1240                 if (cpu > mp_maxid) {
 1241                         SCHED_STAT_INC(pickcpu_idle_affinity);
 1242                         return (ts->ts_cpu);
 1243                 }
 1244         }
 1245         /*
 1246          * Search for the last level cache CPU group in the tree.
 1247          * Skip caches with expired affinity time and SMT groups.
 1248          * Affinity to higher level caches will be handled less aggressively.
 1249          */
 1250         for (ccg = NULL; cg != NULL; cg = cg->cg_parent) {
 1251                 if (cg->cg_flags & CG_FLAG_THREAD)
 1252                         continue;
 1253                 if (!SCHED_AFFINITY(ts, cg->cg_level))
 1254                         continue;
 1255                 ccg = cg;
 1256         }
 1257         if (ccg != NULL)
 1258                 cg = ccg;
 1259         cpu = -1;
 1260         /* Search the group for the less loaded idle CPU we can run now. */
 1261         mask = td->td_cpuset->cs_mask;
 1262         if (cg != NULL && cg != cpu_top &&
 1263             CPU_CMP(&cg->cg_mask, &cpu_top->cg_mask) != 0)
 1264                 cpu = sched_lowest(cg, mask, max(pri, PRI_MAX_TIMESHARE),
 1265                     INT_MAX, ts->ts_cpu);
 1266         /* Search globally for the less loaded CPU we can run now. */
 1267         if (cpu == -1)
 1268                 cpu = sched_lowest(cpu_top, mask, pri, INT_MAX, ts->ts_cpu);
 1269         /* Search globally for the less loaded CPU. */
 1270         if (cpu == -1)
 1271                 cpu = sched_lowest(cpu_top, mask, -1, INT_MAX, ts->ts_cpu);
 1272         KASSERT(cpu != -1, ("sched_pickcpu: Failed to find a cpu."));
 1273         /*
 1274          * Compare the lowest loaded cpu to current cpu.
 1275          */
 1276         if (THREAD_CAN_SCHED(td, self) && TDQ_CPU(self)->tdq_lowpri > pri &&
 1277             TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE &&
 1278             TDQ_CPU(self)->tdq_load <= TDQ_CPU(cpu)->tdq_load + 1) {
 1279                 SCHED_STAT_INC(pickcpu_local);
 1280                 cpu = self;
 1281         } else
 1282                 SCHED_STAT_INC(pickcpu_lowest);
 1283         if (cpu != ts->ts_cpu)
 1284                 SCHED_STAT_INC(pickcpu_migration);
 1285         return (cpu);
 1286 }
 1287 #endif
 1288 
 1289 /*
 1290  * Pick the highest priority task we have and return it.
 1291  */
 1292 static struct thread *
 1293 tdq_choose(struct tdq *tdq)
 1294 {
 1295         struct thread *td;
 1296 
 1297         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 1298         td = runq_choose(&tdq->tdq_realtime);
 1299         if (td != NULL)
 1300                 return (td);
 1301         td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
 1302         if (td != NULL) {
 1303                 KASSERT(td->td_priority >= PRI_MIN_BATCH,
 1304                     ("tdq_choose: Invalid priority on timeshare queue %d",
 1305                     td->td_priority));
 1306                 return (td);
 1307         }
 1308         td = runq_choose(&tdq->tdq_idle);
 1309         if (td != NULL) {
 1310                 KASSERT(td->td_priority >= PRI_MIN_IDLE,
 1311                     ("tdq_choose: Invalid priority on idle queue %d",
 1312                     td->td_priority));
 1313                 return (td);
 1314         }
 1315 
 1316         return (NULL);
 1317 }
 1318 
 1319 /*
 1320  * Initialize a thread queue.
 1321  */
 1322 static void
 1323 tdq_setup(struct tdq *tdq)
 1324 {
 1325 
 1326         if (bootverbose)
 1327                 printf("ULE: setup cpu %d\n", TDQ_ID(tdq));
 1328         runq_init(&tdq->tdq_realtime);
 1329         runq_init(&tdq->tdq_timeshare);
 1330         runq_init(&tdq->tdq_idle);
 1331         snprintf(tdq->tdq_name, sizeof(tdq->tdq_name),
 1332             "sched lock %d", (int)TDQ_ID(tdq));
 1333         mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock",
 1334             MTX_SPIN | MTX_RECURSE);
 1335 #ifdef KTR
 1336         snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname),
 1337             "CPU %d load", (int)TDQ_ID(tdq));
 1338 #endif
 1339 }
 1340 
 1341 #ifdef SMP
 1342 static void
 1343 sched_setup_smp(void)
 1344 {
 1345         struct tdq *tdq;
 1346         int i;
 1347 
 1348         cpu_top = smp_topo();
 1349         CPU_FOREACH(i) {
 1350                 tdq = TDQ_CPU(i);
 1351                 tdq_setup(tdq);
 1352                 tdq->tdq_cg = smp_topo_find(cpu_top, i);
 1353                 if (tdq->tdq_cg == NULL)
 1354                         panic("Can't find cpu group for %d\n", i);
 1355         }
 1356         balance_tdq = TDQ_SELF();
 1357         sched_balance();
 1358 }
 1359 #endif
 1360 
 1361 /*
 1362  * Setup the thread queues and initialize the topology based on MD
 1363  * information.
 1364  */
 1365 static void
 1366 sched_setup(void *dummy)
 1367 {
 1368         struct tdq *tdq;
 1369 
 1370         tdq = TDQ_SELF();
 1371 #ifdef SMP
 1372         sched_setup_smp();
 1373 #else
 1374         tdq_setup(tdq);
 1375 #endif
 1376 
 1377         /* Add thread0's load since it's running. */
 1378         TDQ_LOCK(tdq);
 1379         thread0.td_lock = TDQ_LOCKPTR(TDQ_SELF());
 1380         tdq_load_add(tdq, &thread0);
 1381         tdq->tdq_lowpri = thread0.td_priority;
 1382         TDQ_UNLOCK(tdq);
 1383 }
 1384 
 1385 /*
 1386  * This routine determines time constants after stathz and hz are setup.
 1387  */
 1388 /* ARGSUSED */
 1389 static void
 1390 sched_initticks(void *dummy)
 1391 {
 1392         int incr;
 1393 
 1394         realstathz = stathz ? stathz : hz;
 1395         sched_slice = realstathz / SCHED_SLICE_DEFAULT_DIVISOR;
 1396         sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
 1397         hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
 1398             realstathz);
 1399 
 1400         /*
 1401          * tickincr is shifted out by 10 to avoid rounding errors due to
 1402          * hz not being evenly divisible by stathz on all platforms.
 1403          */
 1404         incr = (hz << SCHED_TICK_SHIFT) / realstathz;
 1405         /*
 1406          * This does not work for values of stathz that are more than
 1407          * 1 << SCHED_TICK_SHIFT * hz.  In practice this does not happen.
 1408          */
 1409         if (incr == 0)
 1410                 incr = 1;
 1411         tickincr = incr;
 1412 #ifdef SMP
 1413         /*
 1414          * Set the default balance interval now that we know
 1415          * what realstathz is.
 1416          */
 1417         balance_interval = realstathz;
 1418         affinity = SCHED_AFFINITY_DEFAULT;
 1419 #endif
 1420         if (sched_idlespinthresh < 0)
 1421                 sched_idlespinthresh = 2 * max(10000, 6 * hz) / realstathz;
 1422 }
 1423 
 1424 
 1425 /*
 1426  * This is the core of the interactivity algorithm.  Determines a score based
 1427  * on past behavior.  It is the ratio of sleep time to run time scaled to
 1428  * a [0, 100] integer.  This is the voluntary sleep time of a process, which
 1429  * differs from the cpu usage because it does not account for time spent
 1430  * waiting on a run-queue.  Would be prettier if we had floating point.
 1431  */
 1432 static int
 1433 sched_interact_score(struct thread *td)
 1434 {
 1435         struct td_sched *ts;
 1436         int div;
 1437 
 1438         ts = td->td_sched;
 1439         /*
 1440          * The score is only needed if this is likely to be an interactive
 1441          * task.  Don't go through the expense of computing it if there's
 1442          * no chance.
 1443          */
 1444         if (sched_interact <= SCHED_INTERACT_HALF &&
 1445                 ts->ts_runtime >= ts->ts_slptime)
 1446                         return (SCHED_INTERACT_HALF);
 1447 
 1448         if (ts->ts_runtime > ts->ts_slptime) {
 1449                 div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF);
 1450                 return (SCHED_INTERACT_HALF +
 1451                     (SCHED_INTERACT_HALF - (ts->ts_slptime / div)));
 1452         }
 1453         if (ts->ts_slptime > ts->ts_runtime) {
 1454                 div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF);
 1455                 return (ts->ts_runtime / div);
 1456         }
 1457         /* runtime == slptime */
 1458         if (ts->ts_runtime)
 1459                 return (SCHED_INTERACT_HALF);
 1460 
 1461         /*
 1462          * This can happen if slptime and runtime are 0.
 1463          */
 1464         return (0);
 1465 
 1466 }
 1467 
 1468 /*
 1469  * Scale the scheduling priority according to the "interactivity" of this
 1470  * process.
 1471  */
 1472 static void
 1473 sched_priority(struct thread *td)
 1474 {
 1475         int score;
 1476         int pri;
 1477 
 1478         if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
 1479                 return;
 1480         /*
 1481          * If the score is interactive we place the thread in the realtime
 1482          * queue with a priority that is less than kernel and interrupt
 1483          * priorities.  These threads are not subject to nice restrictions.
 1484          *
 1485          * Scores greater than this are placed on the normal timeshare queue
 1486          * where the priority is partially decided by the most recent cpu
 1487          * utilization and the rest is decided by nice value.
 1488          *
 1489          * The nice value of the process has a linear effect on the calculated
 1490          * score.  Negative nice values make it easier for a thread to be
 1491          * considered interactive.
 1492          */
 1493         score = imax(0, sched_interact_score(td) + td->td_proc->p_nice);
 1494         if (score < sched_interact) {
 1495                 pri = PRI_MIN_INTERACT;
 1496                 pri += ((PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) /
 1497                     sched_interact) * score;
 1498                 KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT,
 1499                     ("sched_priority: invalid interactive priority %d score %d",
 1500                     pri, score));
 1501         } else {
 1502                 pri = SCHED_PRI_MIN;
 1503                 if (td->td_sched->ts_ticks)
 1504                         pri += min(SCHED_PRI_TICKS(td->td_sched),
 1505                             SCHED_PRI_RANGE - 1);
 1506                 pri += SCHED_PRI_NICE(td->td_proc->p_nice);
 1507                 KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH,
 1508                     ("sched_priority: invalid priority %d: nice %d, " 
 1509                     "ticks %d ftick %d ltick %d tick pri %d",
 1510                     pri, td->td_proc->p_nice, td->td_sched->ts_ticks,
 1511                     td->td_sched->ts_ftick, td->td_sched->ts_ltick,
 1512                     SCHED_PRI_TICKS(td->td_sched)));
 1513         }
 1514         sched_user_prio(td, pri);
 1515 
 1516         return;
 1517 }
 1518 
 1519 /*
 1520  * This routine enforces a maximum limit on the amount of scheduling history
 1521  * kept.  It is called after either the slptime or runtime is adjusted.  This
 1522  * function is ugly due to integer math.
 1523  */
 1524 static void
 1525 sched_interact_update(struct thread *td)
 1526 {
 1527         struct td_sched *ts;
 1528         u_int sum;
 1529 
 1530         ts = td->td_sched;
 1531         sum = ts->ts_runtime + ts->ts_slptime;
 1532         if (sum < SCHED_SLP_RUN_MAX)
 1533                 return;
 1534         /*
 1535          * This only happens from two places:
 1536          * 1) We have added an unusual amount of run time from fork_exit.
 1537          * 2) We have added an unusual amount of sleep time from sched_sleep().
 1538          */
 1539         if (sum > SCHED_SLP_RUN_MAX * 2) {
 1540                 if (ts->ts_runtime > ts->ts_slptime) {
 1541                         ts->ts_runtime = SCHED_SLP_RUN_MAX;
 1542                         ts->ts_slptime = 1;
 1543                 } else {
 1544                         ts->ts_slptime = SCHED_SLP_RUN_MAX;
 1545                         ts->ts_runtime = 1;
 1546                 }
 1547                 return;
 1548         }
 1549         /*
 1550          * If we have exceeded by more than 1/5th then the algorithm below
 1551          * will not bring us back into range.  Dividing by two here forces
 1552          * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX]
 1553          */
 1554         if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) {
 1555                 ts->ts_runtime /= 2;
 1556                 ts->ts_slptime /= 2;
 1557                 return;
 1558         }
 1559         ts->ts_runtime = (ts->ts_runtime / 5) * 4;
 1560         ts->ts_slptime = (ts->ts_slptime / 5) * 4;
 1561 }
 1562 
 1563 /*
 1564  * Scale back the interactivity history when a child thread is created.  The
 1565  * history is inherited from the parent but the thread may behave totally
 1566  * differently.  For example, a shell spawning a compiler process.  We want
 1567  * to learn that the compiler is behaving badly very quickly.
 1568  */
 1569 static void
 1570 sched_interact_fork(struct thread *td)
 1571 {
 1572         int ratio;
 1573         int sum;
 1574 
 1575         sum = td->td_sched->ts_runtime + td->td_sched->ts_slptime;
 1576         if (sum > SCHED_SLP_RUN_FORK) {
 1577                 ratio = sum / SCHED_SLP_RUN_FORK;
 1578                 td->td_sched->ts_runtime /= ratio;
 1579                 td->td_sched->ts_slptime /= ratio;
 1580         }
 1581 }
 1582 
 1583 /*
 1584  * Called from proc0_init() to setup the scheduler fields.
 1585  */
 1586 void
 1587 schedinit(void)
 1588 {
 1589 
 1590         /*
 1591          * Set up the scheduler specific parts of proc0.
 1592          */
 1593         proc0.p_sched = NULL; /* XXX */
 1594         thread0.td_sched = &td_sched0;
 1595         td_sched0.ts_ltick = ticks;
 1596         td_sched0.ts_ftick = ticks;
 1597         td_sched0.ts_slice = 0;
 1598 }
 1599 
 1600 /*
 1601  * This is only somewhat accurate since given many processes of the same
 1602  * priority they will switch when their slices run out, which will be
 1603  * at most sched_slice stathz ticks.
 1604  */
 1605 int
 1606 sched_rr_interval(void)
 1607 {
 1608 
 1609         /* Convert sched_slice from stathz to hz. */
 1610         return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz));
 1611 }
 1612 
 1613 /*
 1614  * Update the percent cpu tracking information when it is requested or
 1615  * the total history exceeds the maximum.  We keep a sliding history of
 1616  * tick counts that slowly decays.  This is less precise than the 4BSD
 1617  * mechanism since it happens with less regular and frequent events.
 1618  */
 1619 static void
 1620 sched_pctcpu_update(struct td_sched *ts, int run)
 1621 {
 1622         int t = ticks;
 1623 
 1624         if (t - ts->ts_ltick >= SCHED_TICK_TARG) {
 1625                 ts->ts_ticks = 0;
 1626                 ts->ts_ftick = t - SCHED_TICK_TARG;
 1627         } else if (t - ts->ts_ftick >= SCHED_TICK_MAX) {
 1628                 ts->ts_ticks = (ts->ts_ticks / (ts->ts_ltick - ts->ts_ftick)) *
 1629                     (ts->ts_ltick - (t - SCHED_TICK_TARG));
 1630                 ts->ts_ftick = t - SCHED_TICK_TARG;
 1631         }
 1632         if (run)
 1633                 ts->ts_ticks += (t - ts->ts_ltick) << SCHED_TICK_SHIFT;
 1634         ts->ts_ltick = t;
 1635 }
 1636 
 1637 /*
 1638  * Adjust the priority of a thread.  Move it to the appropriate run-queue
 1639  * if necessary.  This is the back-end for several priority related
 1640  * functions.
 1641  */
 1642 static void
 1643 sched_thread_priority(struct thread *td, u_char prio)
 1644 {
 1645         struct td_sched *ts;
 1646         struct tdq *tdq;
 1647         int oldpri;
 1648 
 1649         KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio",
 1650             "prio:%d", td->td_priority, "new prio:%d", prio,
 1651             KTR_ATTR_LINKED, sched_tdname(curthread));
 1652         SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio);
 1653         if (td != curthread && prio < td->td_priority) {
 1654                 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
 1655                     "lend prio", "prio:%d", td->td_priority, "new prio:%d",
 1656                     prio, KTR_ATTR_LINKED, sched_tdname(td));
 1657                 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio, 
 1658                     curthread);
 1659         } 
 1660         ts = td->td_sched;
 1661         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1662         if (td->td_priority == prio)
 1663                 return;
 1664         /*
 1665          * If the priority has been elevated due to priority
 1666          * propagation, we may have to move ourselves to a new
 1667          * queue.  This could be optimized to not re-add in some
 1668          * cases.
 1669          */
 1670         if (TD_ON_RUNQ(td) && prio < td->td_priority) {
 1671                 sched_rem(td);
 1672                 td->td_priority = prio;
 1673                 sched_add(td, SRQ_BORROWING);
 1674                 return;
 1675         }
 1676         /*
 1677          * If the thread is currently running we may have to adjust the lowpri
 1678          * information so other cpus are aware of our current priority.
 1679          */
 1680         if (TD_IS_RUNNING(td)) {
 1681                 tdq = TDQ_CPU(ts->ts_cpu);
 1682                 oldpri = td->td_priority;
 1683                 td->td_priority = prio;
 1684                 if (prio < tdq->tdq_lowpri)
 1685                         tdq->tdq_lowpri = prio;
 1686                 else if (tdq->tdq_lowpri == oldpri)
 1687                         tdq_setlowpri(tdq, td);
 1688                 return;
 1689         }
 1690         td->td_priority = prio;
 1691 }
 1692 
 1693 /*
 1694  * Update a thread's priority when it is lent another thread's
 1695  * priority.
 1696  */
 1697 void
 1698 sched_lend_prio(struct thread *td, u_char prio)
 1699 {
 1700 
 1701         td->td_flags |= TDF_BORROWING;
 1702         sched_thread_priority(td, prio);
 1703 }
 1704 
 1705 /*
 1706  * Restore a thread's priority when priority propagation is
 1707  * over.  The prio argument is the minimum priority the thread
 1708  * needs to have to satisfy other possible priority lending
 1709  * requests.  If the thread's regular priority is less
 1710  * important than prio, the thread will keep a priority boost
 1711  * of prio.
 1712  */
 1713 void
 1714 sched_unlend_prio(struct thread *td, u_char prio)
 1715 {
 1716         u_char base_pri;
 1717 
 1718         if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
 1719             td->td_base_pri <= PRI_MAX_TIMESHARE)
 1720                 base_pri = td->td_user_pri;
 1721         else
 1722                 base_pri = td->td_base_pri;
 1723         if (prio >= base_pri) {
 1724                 td->td_flags &= ~TDF_BORROWING;
 1725                 sched_thread_priority(td, base_pri);
 1726         } else
 1727                 sched_lend_prio(td, prio);
 1728 }
 1729 
 1730 /*
 1731  * Standard entry for setting the priority to an absolute value.
 1732  */
 1733 void
 1734 sched_prio(struct thread *td, u_char prio)
 1735 {
 1736         u_char oldprio;
 1737 
 1738         /* First, update the base priority. */
 1739         td->td_base_pri = prio;
 1740 
 1741         /*
 1742          * If the thread is borrowing another thread's priority, don't
 1743          * ever lower the priority.
 1744          */
 1745         if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
 1746                 return;
 1747 
 1748         /* Change the real priority. */
 1749         oldprio = td->td_priority;
 1750         sched_thread_priority(td, prio);
 1751 
 1752         /*
 1753          * If the thread is on a turnstile, then let the turnstile update
 1754          * its state.
 1755          */
 1756         if (TD_ON_LOCK(td) && oldprio != prio)
 1757                 turnstile_adjust(td, oldprio);
 1758 }
 1759 
 1760 /*
 1761  * Set the base user priority, does not effect current running priority.
 1762  */
 1763 void
 1764 sched_user_prio(struct thread *td, u_char prio)
 1765 {
 1766 
 1767         td->td_base_user_pri = prio;
 1768         if (td->td_lend_user_pri <= prio)
 1769                 return;
 1770         td->td_user_pri = prio;
 1771 }
 1772 
 1773 void
 1774 sched_lend_user_prio(struct thread *td, u_char prio)
 1775 {
 1776 
 1777         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1778         td->td_lend_user_pri = prio;
 1779         td->td_user_pri = min(prio, td->td_base_user_pri);
 1780         if (td->td_priority > td->td_user_pri)
 1781                 sched_prio(td, td->td_user_pri);
 1782         else if (td->td_priority != td->td_user_pri)
 1783                 td->td_flags |= TDF_NEEDRESCHED;
 1784 }
 1785 
 1786 /*
 1787  * Handle migration from sched_switch().  This happens only for
 1788  * cpu binding.
 1789  */
 1790 static struct mtx *
 1791 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags)
 1792 {
 1793         struct tdq *tdn;
 1794 
 1795         tdn = TDQ_CPU(td->td_sched->ts_cpu);
 1796 #ifdef SMP
 1797         tdq_load_rem(tdq, td);
 1798         /*
 1799          * Do the lock dance required to avoid LOR.  We grab an extra
 1800          * spinlock nesting to prevent preemption while we're
 1801          * not holding either run-queue lock.
 1802          */
 1803         spinlock_enter();
 1804         thread_lock_block(td);  /* This releases the lock on tdq. */
 1805 
 1806         /*
 1807          * Acquire both run-queue locks before placing the thread on the new
 1808          * run-queue to avoid deadlocks created by placing a thread with a
 1809          * blocked lock on the run-queue of a remote processor.  The deadlock
 1810          * occurs when a third processor attempts to lock the two queues in
 1811          * question while the target processor is spinning with its own
 1812          * run-queue lock held while waiting for the blocked lock to clear.
 1813          */
 1814         tdq_lock_pair(tdn, tdq);
 1815         tdq_add(tdn, td, flags);
 1816         tdq_notify(tdn, td);
 1817         TDQ_UNLOCK(tdn);
 1818         spinlock_exit();
 1819 #endif
 1820         return (TDQ_LOCKPTR(tdn));
 1821 }
 1822 
 1823 /*
 1824  * Variadic version of thread_lock_unblock() that does not assume td_lock
 1825  * is blocked.
 1826  */
 1827 static inline void
 1828 thread_unblock_switch(struct thread *td, struct mtx *mtx)
 1829 {
 1830         atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock,
 1831             (uintptr_t)mtx);
 1832 }
 1833 
 1834 /*
 1835  * Switch threads.  This function has to handle threads coming in while
 1836  * blocked for some reason, running, or idle.  It also must deal with
 1837  * migrating a thread from one queue to another as running threads may
 1838  * be assigned elsewhere via binding.
 1839  */
 1840 void
 1841 sched_switch(struct thread *td, struct thread *newtd, int flags)
 1842 {
 1843         struct tdq *tdq;
 1844         struct td_sched *ts;
 1845         struct mtx *mtx;
 1846         int srqflag;
 1847         int cpuid, preempted;
 1848 
 1849         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1850         KASSERT(newtd == NULL, ("sched_switch: Unsupported newtd argument"));
 1851 
 1852         cpuid = PCPU_GET(cpuid);
 1853         tdq = TDQ_CPU(cpuid);
 1854         ts = td->td_sched;
 1855         mtx = td->td_lock;
 1856         sched_pctcpu_update(ts, 1);
 1857         ts->ts_rltick = ticks;
 1858         td->td_lastcpu = td->td_oncpu;
 1859         td->td_oncpu = NOCPU;
 1860         preempted = !((td->td_flags & TDF_SLICEEND) ||
 1861             (flags & SWT_RELINQUISH));
 1862         td->td_flags &= ~(TDF_NEEDRESCHED | TDF_SLICEEND);
 1863         td->td_owepreempt = 0;
 1864         if (!TD_IS_IDLETHREAD(td))
 1865                 tdq->tdq_switchcnt++;
 1866         /*
 1867          * The lock pointer in an idle thread should never change.  Reset it
 1868          * to CAN_RUN as well.
 1869          */
 1870         if (TD_IS_IDLETHREAD(td)) {
 1871                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1872                 TD_SET_CAN_RUN(td);
 1873         } else if (TD_IS_RUNNING(td)) {
 1874                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1875                 srqflag = preempted ?
 1876                     SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
 1877                     SRQ_OURSELF|SRQ_YIELDING;
 1878 #ifdef SMP
 1879                 if (THREAD_CAN_MIGRATE(td) && !THREAD_CAN_SCHED(td, ts->ts_cpu))
 1880                         ts->ts_cpu = sched_pickcpu(td, 0);
 1881 #endif
 1882                 if (ts->ts_cpu == cpuid)
 1883                         tdq_runq_add(tdq, td, srqflag);
 1884                 else {
 1885                         KASSERT(THREAD_CAN_MIGRATE(td) ||
 1886                             (ts->ts_flags & TSF_BOUND) != 0,
 1887                             ("Thread %p shouldn't migrate", td));
 1888                         mtx = sched_switch_migrate(tdq, td, srqflag);
 1889                 }
 1890         } else {
 1891                 /* This thread must be going to sleep. */
 1892                 TDQ_LOCK(tdq);
 1893                 mtx = thread_lock_block(td);
 1894                 tdq_load_rem(tdq, td);
 1895         }
 1896         /*
 1897          * We enter here with the thread blocked and assigned to the
 1898          * appropriate cpu run-queue or sleep-queue and with the current
 1899          * thread-queue locked.
 1900          */
 1901         TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
 1902         newtd = choosethread();
 1903         /*
 1904          * Call the MD code to switch contexts if necessary.
 1905          */
 1906         if (td != newtd) {
 1907 #ifdef  HWPMC_HOOKS
 1908                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 1909                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
 1910 #endif
 1911                 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc);
 1912                 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
 1913                 TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
 1914                 sched_pctcpu_update(newtd->td_sched, 0);
 1915 
 1916 #ifdef KDTRACE_HOOKS
 1917                 /*
 1918                  * If DTrace has set the active vtime enum to anything
 1919                  * other than INACTIVE (0), then it should have set the
 1920                  * function to call.
 1921                  */
 1922                 if (dtrace_vtime_active)
 1923                         (*dtrace_vtime_switch_func)(newtd);
 1924 #endif
 1925 
 1926                 cpu_switch(td, newtd, mtx);
 1927                 /*
 1928                  * We may return from cpu_switch on a different cpu.  However,
 1929                  * we always return with td_lock pointing to the current cpu's
 1930                  * run queue lock.
 1931                  */
 1932                 cpuid = PCPU_GET(cpuid);
 1933                 tdq = TDQ_CPU(cpuid);
 1934                 lock_profile_obtain_lock_success(
 1935                     &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
 1936 
 1937                 SDT_PROBE0(sched, , , on__cpu);
 1938 #ifdef  HWPMC_HOOKS
 1939                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 1940                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
 1941 #endif
 1942         } else {
 1943                 thread_unblock_switch(td, mtx);
 1944                 SDT_PROBE0(sched, , , remain__cpu);
 1945         }
 1946         /*
 1947          * Assert that all went well and return.
 1948          */
 1949         TDQ_LOCK_ASSERT(tdq, MA_OWNED|MA_NOTRECURSED);
 1950         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1951         td->td_oncpu = cpuid;
 1952 }
 1953 
 1954 /*
 1955  * Adjust thread priorities as a result of a nice request.
 1956  */
 1957 void
 1958 sched_nice(struct proc *p, int nice)
 1959 {
 1960         struct thread *td;
 1961 
 1962         PROC_LOCK_ASSERT(p, MA_OWNED);
 1963 
 1964         p->p_nice = nice;
 1965         FOREACH_THREAD_IN_PROC(p, td) {
 1966                 thread_lock(td);
 1967                 sched_priority(td);
 1968                 sched_prio(td, td->td_base_user_pri);
 1969                 thread_unlock(td);
 1970         }
 1971 }
 1972 
 1973 /*
 1974  * Record the sleep time for the interactivity scorer.
 1975  */
 1976 void
 1977 sched_sleep(struct thread *td, int prio)
 1978 {
 1979 
 1980         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1981 
 1982         td->td_slptick = ticks;
 1983         if (TD_IS_SUSPENDED(td) || prio >= PSOCK)
 1984                 td->td_flags |= TDF_CANSWAP;
 1985         if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
 1986                 return;
 1987         if (static_boost == 1 && prio)
 1988                 sched_prio(td, prio);
 1989         else if (static_boost && td->td_priority > static_boost)
 1990                 sched_prio(td, static_boost);
 1991 }
 1992 
 1993 /*
 1994  * Schedule a thread to resume execution and record how long it voluntarily
 1995  * slept.  We also update the pctcpu, interactivity, and priority.
 1996  */
 1997 void
 1998 sched_wakeup(struct thread *td)
 1999 {
 2000         struct td_sched *ts;
 2001         int slptick;
 2002 
 2003         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2004         ts = td->td_sched;
 2005         td->td_flags &= ~TDF_CANSWAP;
 2006         /*
 2007          * If we slept for more than a tick update our interactivity and
 2008          * priority.
 2009          */
 2010         slptick = td->td_slptick;
 2011         td->td_slptick = 0;
 2012         if (slptick && slptick != ticks) {
 2013                 ts->ts_slptime += (ticks - slptick) << SCHED_TICK_SHIFT;
 2014                 sched_interact_update(td);
 2015                 sched_pctcpu_update(ts, 0);
 2016         }
 2017         /*
 2018          * Reset the slice value since we slept and advanced the round-robin.
 2019          */
 2020         ts->ts_slice = 0;
 2021         sched_add(td, SRQ_BORING);
 2022 }
 2023 
 2024 /*
 2025  * Penalize the parent for creating a new child and initialize the child's
 2026  * priority.
 2027  */
 2028 void
 2029 sched_fork(struct thread *td, struct thread *child)
 2030 {
 2031         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2032         sched_pctcpu_update(td->td_sched, 1);
 2033         sched_fork_thread(td, child);
 2034         /*
 2035          * Penalize the parent and child for forking.
 2036          */
 2037         sched_interact_fork(child);
 2038         sched_priority(child);
 2039         td->td_sched->ts_runtime += tickincr;
 2040         sched_interact_update(td);
 2041         sched_priority(td);
 2042 }
 2043 
 2044 /*
 2045  * Fork a new thread, may be within the same process.
 2046  */
 2047 void
 2048 sched_fork_thread(struct thread *td, struct thread *child)
 2049 {
 2050         struct td_sched *ts;
 2051         struct td_sched *ts2;
 2052         struct tdq *tdq;
 2053 
 2054         tdq = TDQ_SELF();
 2055         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2056         /*
 2057          * Initialize child.
 2058          */
 2059         ts = td->td_sched;
 2060         ts2 = child->td_sched;
 2061         child->td_lock = TDQ_LOCKPTR(tdq);
 2062         child->td_cpuset = cpuset_ref(td->td_cpuset);
 2063         ts2->ts_cpu = ts->ts_cpu;
 2064         ts2->ts_flags = 0;
 2065         /*
 2066          * Grab our parents cpu estimation information.
 2067          */
 2068         ts2->ts_ticks = ts->ts_ticks;
 2069         ts2->ts_ltick = ts->ts_ltick;
 2070         ts2->ts_ftick = ts->ts_ftick;
 2071         /*
 2072          * Do not inherit any borrowed priority from the parent.
 2073          */
 2074         child->td_priority = child->td_base_pri;
 2075         /*
 2076          * And update interactivity score.
 2077          */
 2078         ts2->ts_slptime = ts->ts_slptime;
 2079         ts2->ts_runtime = ts->ts_runtime;
 2080         /* Attempt to quickly learn interactivity. */
 2081         ts2->ts_slice = tdq_slice(tdq) - sched_slice_min;
 2082 #ifdef KTR
 2083         bzero(ts2->ts_name, sizeof(ts2->ts_name));
 2084 #endif
 2085 }
 2086 
 2087 /*
 2088  * Adjust the priority class of a thread.
 2089  */
 2090 void
 2091 sched_class(struct thread *td, int class)
 2092 {
 2093 
 2094         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2095         if (td->td_pri_class == class)
 2096                 return;
 2097         td->td_pri_class = class;
 2098 }
 2099 
 2100 /*
 2101  * Return some of the child's priority and interactivity to the parent.
 2102  */
 2103 void
 2104 sched_exit(struct proc *p, struct thread *child)
 2105 {
 2106         struct thread *td;
 2107 
 2108         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit",
 2109             "prio:%d", child->td_priority);
 2110         PROC_LOCK_ASSERT(p, MA_OWNED);
 2111         td = FIRST_THREAD_IN_PROC(p);
 2112         sched_exit_thread(td, child);
 2113 }
 2114 
 2115 /*
 2116  * Penalize another thread for the time spent on this one.  This helps to
 2117  * worsen the priority and interactivity of processes which schedule batch
 2118  * jobs such as make.  This has little effect on the make process itself but
 2119  * causes new processes spawned by it to receive worse scores immediately.
 2120  */
 2121 void
 2122 sched_exit_thread(struct thread *td, struct thread *child)
 2123 {
 2124 
 2125         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit",
 2126             "prio:%d", child->td_priority);
 2127         /*
 2128          * Give the child's runtime to the parent without returning the
 2129          * sleep time as a penalty to the parent.  This causes shells that
 2130          * launch expensive things to mark their children as expensive.
 2131          */
 2132         thread_lock(td);
 2133         td->td_sched->ts_runtime += child->td_sched->ts_runtime;
 2134         sched_interact_update(td);
 2135         sched_priority(td);
 2136         thread_unlock(td);
 2137 }
 2138 
 2139 void
 2140 sched_preempt(struct thread *td)
 2141 {
 2142         struct tdq *tdq;
 2143 
 2144         SDT_PROBE2(sched, , , surrender, td, td->td_proc);
 2145 
 2146         thread_lock(td);
 2147         tdq = TDQ_SELF();
 2148         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2149         tdq->tdq_ipipending = 0;
 2150         if (td->td_priority > tdq->tdq_lowpri) {
 2151                 int flags;
 2152 
 2153                 flags = SW_INVOL | SW_PREEMPT;
 2154                 if (td->td_critnest > 1)
 2155                         td->td_owepreempt = 1;
 2156                 else if (TD_IS_IDLETHREAD(td))
 2157                         mi_switch(flags | SWT_REMOTEWAKEIDLE, NULL);
 2158                 else
 2159                         mi_switch(flags | SWT_REMOTEPREEMPT, NULL);
 2160         }
 2161         thread_unlock(td);
 2162 }
 2163 
 2164 /*
 2165  * Fix priorities on return to user-space.  Priorities may be elevated due
 2166  * to static priorities in msleep() or similar.
 2167  */
 2168 void
 2169 sched_userret(struct thread *td)
 2170 {
 2171         /*
 2172          * XXX we cheat slightly on the locking here to avoid locking in  
 2173          * the usual case.  Setting td_priority here is essentially an
 2174          * incomplete workaround for not setting it properly elsewhere.
 2175          * Now that some interrupt handlers are threads, not setting it
 2176          * properly elsewhere can clobber it in the window between setting
 2177          * it here and returning to user mode, so don't waste time setting
 2178          * it perfectly here.
 2179          */
 2180         KASSERT((td->td_flags & TDF_BORROWING) == 0,
 2181             ("thread with borrowed priority returning to userland"));
 2182         if (td->td_priority != td->td_user_pri) {
 2183                 thread_lock(td);
 2184                 td->td_priority = td->td_user_pri;
 2185                 td->td_base_pri = td->td_user_pri;
 2186                 tdq_setlowpri(TDQ_SELF(), td);
 2187                 thread_unlock(td);
 2188         }
 2189 }
 2190 
 2191 /*
 2192  * Handle a stathz tick.  This is really only relevant for timeshare
 2193  * threads.
 2194  */
 2195 void
 2196 sched_clock(struct thread *td)
 2197 {
 2198         struct tdq *tdq;
 2199         struct td_sched *ts;
 2200 
 2201         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2202         tdq = TDQ_SELF();
 2203 #ifdef SMP
 2204         /*
 2205          * We run the long term load balancer infrequently on the first cpu.
 2206          */
 2207         if (balance_tdq == tdq) {
 2208                 if (balance_ticks && --balance_ticks == 0)
 2209                         sched_balance();
 2210         }
 2211 #endif
 2212         /*
 2213          * Save the old switch count so we have a record of the last ticks
 2214          * activity.   Initialize the new switch count based on our load.
 2215          * If there is some activity seed it to reflect that.
 2216          */
 2217         tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt;
 2218         tdq->tdq_switchcnt = tdq->tdq_load;
 2219         /*
 2220          * Advance the insert index once for each tick to ensure that all
 2221          * threads get a chance to run.
 2222          */
 2223         if (tdq->tdq_idx == tdq->tdq_ridx) {
 2224                 tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS;
 2225                 if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx]))
 2226                         tdq->tdq_ridx = tdq->tdq_idx;
 2227         }
 2228         ts = td->td_sched;
 2229         sched_pctcpu_update(ts, 1);
 2230         if (td->td_pri_class & PRI_FIFO_BIT)
 2231                 return;
 2232         if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) {
 2233                 /*
 2234                  * We used a tick; charge it to the thread so
 2235                  * that we can compute our interactivity.
 2236                  */
 2237                 td->td_sched->ts_runtime += tickincr;
 2238                 sched_interact_update(td);
 2239                 sched_priority(td);
 2240         }
 2241 
 2242         /*
 2243          * Force a context switch if the current thread has used up a full
 2244          * time slice (default is 100ms).
 2245          */
 2246         if (!TD_IS_IDLETHREAD(td) && ++ts->ts_slice >= tdq_slice(tdq)) {
 2247                 ts->ts_slice = 0;
 2248                 td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND;
 2249         }
 2250 }
 2251 
 2252 /*
 2253  * Called once per hz tick.
 2254  */
 2255 void
 2256 sched_tick(int cnt)
 2257 {
 2258 
 2259 }
 2260 
 2261 /*
 2262  * Return whether the current CPU has runnable tasks.  Used for in-kernel
 2263  * cooperative idle threads.
 2264  */
 2265 int
 2266 sched_runnable(void)
 2267 {
 2268         struct tdq *tdq;
 2269         int load;
 2270 
 2271         load = 1;
 2272 
 2273         tdq = TDQ_SELF();
 2274         if ((curthread->td_flags & TDF_IDLETD) != 0) {
 2275                 if (tdq->tdq_load > 0)
 2276                         goto out;
 2277         } else
 2278                 if (tdq->tdq_load - 1 > 0)
 2279                         goto out;
 2280         load = 0;
 2281 out:
 2282         return (load);
 2283 }
 2284 
 2285 /*
 2286  * Choose the highest priority thread to run.  The thread is removed from
 2287  * the run-queue while running however the load remains.  For SMP we set
 2288  * the tdq in the global idle bitmask if it idles here.
 2289  */
 2290 struct thread *
 2291 sched_choose(void)
 2292 {
 2293         struct thread *td;
 2294         struct tdq *tdq;
 2295 
 2296         tdq = TDQ_SELF();
 2297         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2298         td = tdq_choose(tdq);
 2299         if (td) {
 2300                 tdq_runq_rem(tdq, td);
 2301                 tdq->tdq_lowpri = td->td_priority;
 2302                 return (td);
 2303         }
 2304         tdq->tdq_lowpri = PRI_MAX_IDLE;
 2305         return (PCPU_GET(idlethread));
 2306 }
 2307 
 2308 /*
 2309  * Set owepreempt if necessary.  Preemption never happens directly in ULE,
 2310  * we always request it once we exit a critical section.
 2311  */
 2312 static inline void
 2313 sched_setpreempt(struct thread *td)
 2314 {
 2315         struct thread *ctd;
 2316         int cpri;
 2317         int pri;
 2318 
 2319         THREAD_LOCK_ASSERT(curthread, MA_OWNED);
 2320 
 2321         ctd = curthread;
 2322         pri = td->td_priority;
 2323         cpri = ctd->td_priority;
 2324         if (pri < cpri)
 2325                 ctd->td_flags |= TDF_NEEDRESCHED;
 2326         if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
 2327                 return;
 2328         if (!sched_shouldpreempt(pri, cpri, 0))
 2329                 return;
 2330         ctd->td_owepreempt = 1;
 2331 }
 2332 
 2333 /*
 2334  * Add a thread to a thread queue.  Select the appropriate runq and add the
 2335  * thread to it.  This is the internal function called when the tdq is
 2336  * predetermined.
 2337  */
 2338 void
 2339 tdq_add(struct tdq *tdq, struct thread *td, int flags)
 2340 {
 2341 
 2342         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2343         KASSERT((td->td_inhibitors == 0),
 2344             ("sched_add: trying to run inhibited thread"));
 2345         KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
 2346             ("sched_add: bad thread state"));
 2347         KASSERT(td->td_flags & TDF_INMEM,
 2348             ("sched_add: thread swapped out"));
 2349 
 2350         if (td->td_priority < tdq->tdq_lowpri)
 2351                 tdq->tdq_lowpri = td->td_priority;
 2352         tdq_runq_add(tdq, td, flags);
 2353         tdq_load_add(tdq, td);
 2354 }
 2355 
 2356 /*
 2357  * Select the target thread queue and add a thread to it.  Request
 2358  * preemption or IPI a remote processor if required.
 2359  */
 2360 void
 2361 sched_add(struct thread *td, int flags)
 2362 {
 2363         struct tdq *tdq;
 2364 #ifdef SMP
 2365         int cpu;
 2366 #endif
 2367 
 2368         KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
 2369             "prio:%d", td->td_priority, KTR_ATTR_LINKED,
 2370             sched_tdname(curthread));
 2371         KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
 2372             KTR_ATTR_LINKED, sched_tdname(td));
 2373         SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL, 
 2374             flags & SRQ_PREEMPTED);
 2375         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2376         /*
 2377          * Recalculate the priority before we select the target cpu or
 2378          * run-queue.
 2379          */
 2380         if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
 2381                 sched_priority(td);
 2382 #ifdef SMP
 2383         /*
 2384          * Pick the destination cpu and if it isn't ours transfer to the
 2385          * target cpu.
 2386          */
 2387         cpu = sched_pickcpu(td, flags);
 2388         tdq = sched_setcpu(td, cpu, flags);
 2389         tdq_add(tdq, td, flags);
 2390         if (cpu != PCPU_GET(cpuid)) {
 2391                 tdq_notify(tdq, td);
 2392                 return;
 2393         }
 2394 #else
 2395         tdq = TDQ_SELF();
 2396         TDQ_LOCK(tdq);
 2397         /*
 2398          * Now that the thread is moving to the run-queue, set the lock
 2399          * to the scheduler's lock.
 2400          */
 2401         thread_lock_set(td, TDQ_LOCKPTR(tdq));
 2402         tdq_add(tdq, td, flags);
 2403 #endif
 2404         if (!(flags & SRQ_YIELDING))
 2405                 sched_setpreempt(td);
 2406 }
 2407 
 2408 /*
 2409  * Remove a thread from a run-queue without running it.  This is used
 2410  * when we're stealing a thread from a remote queue.  Otherwise all threads
 2411  * exit by calling sched_exit_thread() and sched_throw() themselves.
 2412  */
 2413 void
 2414 sched_rem(struct thread *td)
 2415 {
 2416         struct tdq *tdq;
 2417 
 2418         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
 2419             "prio:%d", td->td_priority);
 2420         SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL);
 2421         tdq = TDQ_CPU(td->td_sched->ts_cpu);
 2422         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2423         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2424         KASSERT(TD_ON_RUNQ(td),
 2425             ("sched_rem: thread not on run queue"));
 2426         tdq_runq_rem(tdq, td);
 2427         tdq_load_rem(tdq, td);
 2428         TD_SET_CAN_RUN(td);
 2429         if (td->td_priority == tdq->tdq_lowpri)
 2430                 tdq_setlowpri(tdq, NULL);
 2431 }
 2432 
 2433 /*
 2434  * Fetch cpu utilization information.  Updates on demand.
 2435  */
 2436 fixpt_t
 2437 sched_pctcpu(struct thread *td)
 2438 {
 2439         fixpt_t pctcpu;
 2440         struct td_sched *ts;
 2441 
 2442         pctcpu = 0;
 2443         ts = td->td_sched;
 2444         if (ts == NULL)
 2445                 return (0);
 2446 
 2447         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2448         sched_pctcpu_update(ts, TD_IS_RUNNING(td));
 2449         if (ts->ts_ticks) {
 2450                 int rtick;
 2451 
 2452                 /* How many rtick per second ? */
 2453                 rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
 2454                 pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
 2455         }
 2456 
 2457         return (pctcpu);
 2458 }
 2459 
 2460 /*
 2461  * Enforce affinity settings for a thread.  Called after adjustments to
 2462  * cpumask.
 2463  */
 2464 void
 2465 sched_affinity(struct thread *td)
 2466 {
 2467 #ifdef SMP
 2468         struct td_sched *ts;
 2469 
 2470         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2471         ts = td->td_sched;
 2472         if (THREAD_CAN_SCHED(td, ts->ts_cpu))
 2473                 return;
 2474         if (TD_ON_RUNQ(td)) {
 2475                 sched_rem(td);
 2476                 sched_add(td, SRQ_BORING);
 2477                 return;
 2478         }
 2479         if (!TD_IS_RUNNING(td))
 2480                 return;
 2481         /*
 2482          * Force a switch before returning to userspace.  If the
 2483          * target thread is not running locally send an ipi to force
 2484          * the issue.
 2485          */
 2486         td->td_flags |= TDF_NEEDRESCHED;
 2487         if (td != curthread)
 2488                 ipi_cpu(ts->ts_cpu, IPI_PREEMPT);
 2489 #endif
 2490 }
 2491 
 2492 /*
 2493  * Bind a thread to a target cpu.
 2494  */
 2495 void
 2496 sched_bind(struct thread *td, int cpu)
 2497 {
 2498         struct td_sched *ts;
 2499 
 2500         THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
 2501         KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
 2502         ts = td->td_sched;
 2503         if (ts->ts_flags & TSF_BOUND)
 2504                 sched_unbind(td);
 2505         KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td));
 2506         ts->ts_flags |= TSF_BOUND;
 2507         sched_pin();
 2508         if (PCPU_GET(cpuid) == cpu)
 2509                 return;
 2510         ts->ts_cpu = cpu;
 2511         /* When we return from mi_switch we'll be on the correct cpu. */
 2512         mi_switch(SW_VOL, NULL);
 2513 }
 2514 
 2515 /*
 2516  * Release a bound thread.
 2517  */
 2518 void
 2519 sched_unbind(struct thread *td)
 2520 {
 2521         struct td_sched *ts;
 2522 
 2523         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2524         KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
 2525         ts = td->td_sched;
 2526         if ((ts->ts_flags & TSF_BOUND) == 0)
 2527                 return;
 2528         ts->ts_flags &= ~TSF_BOUND;
 2529         sched_unpin();
 2530 }
 2531 
 2532 int
 2533 sched_is_bound(struct thread *td)
 2534 {
 2535         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2536         return (td->td_sched->ts_flags & TSF_BOUND);
 2537 }
 2538 
 2539 /*
 2540  * Basic yield call.
 2541  */
 2542 void
 2543 sched_relinquish(struct thread *td)
 2544 {
 2545         thread_lock(td);
 2546         mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
 2547         thread_unlock(td);
 2548 }
 2549 
 2550 /*
 2551  * Return the total system load.
 2552  */
 2553 int
 2554 sched_load(void)
 2555 {
 2556 #ifdef SMP
 2557         int total;
 2558         int i;
 2559 
 2560         total = 0;
 2561         CPU_FOREACH(i)
 2562                 total += TDQ_CPU(i)->tdq_sysload;
 2563         return (total);
 2564 #else
 2565         return (TDQ_SELF()->tdq_sysload);
 2566 #endif
 2567 }
 2568 
 2569 int
 2570 sched_sizeof_proc(void)
 2571 {
 2572         return (sizeof(struct proc));
 2573 }
 2574 
 2575 int
 2576 sched_sizeof_thread(void)
 2577 {
 2578         return (sizeof(struct thread) + sizeof(struct td_sched));
 2579 }
 2580 
 2581 #ifdef SMP
 2582 #define TDQ_IDLESPIN(tdq)                                               \
 2583     ((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0)
 2584 #else
 2585 #define TDQ_IDLESPIN(tdq)       1
 2586 #endif
 2587 
 2588 /*
 2589  * The actual idle process.
 2590  */
 2591 void
 2592 sched_idletd(void *dummy)
 2593 {
 2594         struct thread *td;
 2595         struct tdq *tdq;
 2596         int oldswitchcnt, switchcnt;
 2597         int i;
 2598 
 2599         mtx_assert(&Giant, MA_NOTOWNED);
 2600         td = curthread;
 2601         tdq = TDQ_SELF();
 2602         THREAD_NO_SLEEPING();
 2603         oldswitchcnt = -1;
 2604         for (;;) {
 2605                 if (tdq->tdq_load) {
 2606                         thread_lock(td);
 2607                         mi_switch(SW_VOL | SWT_IDLE, NULL);
 2608                         thread_unlock(td);
 2609                 }
 2610                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2611 #ifdef SMP
 2612                 if (switchcnt != oldswitchcnt) {
 2613                         oldswitchcnt = switchcnt;
 2614                         if (tdq_idled(tdq) == 0)
 2615                                 continue;
 2616                 }
 2617                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2618 #else
 2619                 oldswitchcnt = switchcnt;
 2620 #endif
 2621                 /*
 2622                  * If we're switching very frequently, spin while checking
 2623                  * for load rather than entering a low power state that 
 2624                  * may require an IPI.  However, don't do any busy
 2625                  * loops while on SMT machines as this simply steals
 2626                  * cycles from cores doing useful work.
 2627                  */
 2628                 if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) {
 2629                         for (i = 0; i < sched_idlespins; i++) {
 2630                                 if (tdq->tdq_load)
 2631                                         break;
 2632                                 cpu_spinwait();
 2633                         }
 2634                 }
 2635 
 2636                 /* If there was context switch during spin, restart it. */
 2637                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2638                 if (tdq->tdq_load != 0 || switchcnt != oldswitchcnt)
 2639                         continue;
 2640 
 2641                 /* Run main MD idle handler. */
 2642                 tdq->tdq_cpu_idle = 1;
 2643                 cpu_idle(switchcnt * 4 > sched_idlespinthresh);
 2644                 tdq->tdq_cpu_idle = 0;
 2645 
 2646                 /*
 2647                  * Account thread-less hardware interrupts and
 2648                  * other wakeup reasons equal to context switches.
 2649                  */
 2650                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2651                 if (switchcnt != oldswitchcnt)
 2652                         continue;
 2653                 tdq->tdq_switchcnt++;
 2654                 oldswitchcnt++;
 2655         }
 2656 }
 2657 
 2658 /*
 2659  * A CPU is entering for the first time or a thread is exiting.
 2660  */
 2661 void
 2662 sched_throw(struct thread *td)
 2663 {
 2664         struct thread *newtd;
 2665         struct tdq *tdq;
 2666 
 2667         tdq = TDQ_SELF();
 2668         if (td == NULL) {
 2669                 /* Correct spinlock nesting and acquire the correct lock. */
 2670                 TDQ_LOCK(tdq);
 2671                 spinlock_exit();
 2672                 PCPU_SET(switchtime, cpu_ticks());
 2673                 PCPU_SET(switchticks, ticks);
 2674         } else {
 2675                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2676                 tdq_load_rem(tdq, td);
 2677                 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
 2678         }
 2679         KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
 2680         newtd = choosethread();
 2681         TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
 2682         cpu_throw(td, newtd);           /* doesn't return */
 2683 }
 2684 
 2685 /*
 2686  * This is called from fork_exit().  Just acquire the correct locks and
 2687  * let fork do the rest of the work.
 2688  */
 2689 void
 2690 sched_fork_exit(struct thread *td)
 2691 {
 2692         struct tdq *tdq;
 2693         int cpuid;
 2694 
 2695         /*
 2696          * Finish setting up thread glue so that it begins execution in a
 2697          * non-nested critical section with the scheduler lock held.
 2698          */
 2699         cpuid = PCPU_GET(cpuid);
 2700         tdq = TDQ_CPU(cpuid);
 2701         if (TD_IS_IDLETHREAD(td))
 2702                 td->td_lock = TDQ_LOCKPTR(tdq);
 2703         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2704         td->td_oncpu = cpuid;
 2705         TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
 2706         lock_profile_obtain_lock_success(
 2707             &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
 2708 }
 2709 
 2710 /*
 2711  * Create on first use to catch odd startup conditons.
 2712  */
 2713 char *
 2714 sched_tdname(struct thread *td)
 2715 {
 2716 #ifdef KTR
 2717         struct td_sched *ts;
 2718 
 2719         ts = td->td_sched;
 2720         if (ts->ts_name[0] == '\0')
 2721                 snprintf(ts->ts_name, sizeof(ts->ts_name),
 2722                     "%s tid %d", td->td_name, td->td_tid);
 2723         return (ts->ts_name);
 2724 #else
 2725         return (td->td_name);
 2726 #endif
 2727 }
 2728 
 2729 #ifdef KTR
 2730 void
 2731 sched_clear_tdname(struct thread *td)
 2732 {
 2733         struct td_sched *ts;
 2734 
 2735         ts = td->td_sched;
 2736         ts->ts_name[0] = '\0';
 2737 }
 2738 #endif
 2739 
 2740 #ifdef SMP
 2741 
 2742 /*
 2743  * Build the CPU topology dump string. Is recursively called to collect
 2744  * the topology tree.
 2745  */
 2746 static int
 2747 sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg,
 2748     int indent)
 2749 {
 2750         char cpusetbuf[CPUSETBUFSIZ];
 2751         int i, first;
 2752 
 2753         sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent,
 2754             "", 1 + indent / 2, cg->cg_level);
 2755         sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"%s\">", indent, "",
 2756             cg->cg_count, cpusetobj_strprint(cpusetbuf, &cg->cg_mask));
 2757         first = TRUE;
 2758         for (i = 0; i < MAXCPU; i++) {
 2759                 if (CPU_ISSET(i, &cg->cg_mask)) {
 2760                         if (!first)
 2761                                 sbuf_printf(sb, ", ");
 2762                         else
 2763                                 first = FALSE;
 2764                         sbuf_printf(sb, "%d", i);
 2765                 }
 2766         }
 2767         sbuf_printf(sb, "</cpu>\n");
 2768 
 2769         if (cg->cg_flags != 0) {
 2770                 sbuf_printf(sb, "%*s <flags>", indent, "");
 2771                 if ((cg->cg_flags & CG_FLAG_HTT) != 0)
 2772                         sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>");
 2773                 if ((cg->cg_flags & CG_FLAG_THREAD) != 0)
 2774                         sbuf_printf(sb, "<flag name=\"THREAD\">THREAD group</flag>");
 2775                 if ((cg->cg_flags & CG_FLAG_SMT) != 0)
 2776                         sbuf_printf(sb, "<flag name=\"SMT\">SMT group</flag>");
 2777                 sbuf_printf(sb, "</flags>\n");
 2778         }
 2779 
 2780         if (cg->cg_children > 0) {
 2781                 sbuf_printf(sb, "%*s <children>\n", indent, "");
 2782                 for (i = 0; i < cg->cg_children; i++)
 2783                         sysctl_kern_sched_topology_spec_internal(sb, 
 2784                             &cg->cg_child[i], indent+2);
 2785                 sbuf_printf(sb, "%*s </children>\n", indent, "");
 2786         }
 2787         sbuf_printf(sb, "%*s</group>\n", indent, "");
 2788         return (0);
 2789 }
 2790 
 2791 /*
 2792  * Sysctl handler for retrieving topology dump. It's a wrapper for
 2793  * the recursive sysctl_kern_smp_topology_spec_internal().
 2794  */
 2795 static int
 2796 sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS)
 2797 {
 2798         struct sbuf *topo;
 2799         int err;
 2800 
 2801         KASSERT(cpu_top != NULL, ("cpu_top isn't initialized"));
 2802 
 2803         topo = sbuf_new(NULL, NULL, 500, SBUF_AUTOEXTEND);
 2804         if (topo == NULL)
 2805                 return (ENOMEM);
 2806 
 2807         sbuf_printf(topo, "<groups>\n");
 2808         err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1);
 2809         sbuf_printf(topo, "</groups>\n");
 2810 
 2811         if (err == 0) {
 2812                 sbuf_finish(topo);
 2813                 err = SYSCTL_OUT(req, sbuf_data(topo), sbuf_len(topo));
 2814         }
 2815         sbuf_delete(topo);
 2816         return (err);
 2817 }
 2818 
 2819 #endif
 2820 
 2821 static int
 2822 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
 2823 {
 2824         int error, new_val, period;
 2825 
 2826         period = 1000000 / realstathz;
 2827         new_val = period * sched_slice;
 2828         error = sysctl_handle_int(oidp, &new_val, 0, req);
 2829         if (error != 0 || req->newptr == NULL)
 2830                 return (error);
 2831         if (new_val <= 0)
 2832                 return (EINVAL);
 2833         sched_slice = imax(1, (new_val + period / 2) / period);
 2834         sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
 2835         hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
 2836             realstathz);
 2837         return (0);
 2838 }
 2839 
 2840 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW, 0, "Scheduler");
 2841 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0,
 2842     "Scheduler name");
 2843 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW,
 2844     NULL, 0, sysctl_kern_quantum, "I",
 2845     "Quantum for timeshare threads in microseconds");
 2846 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
 2847     "Quantum for timeshare threads in stathz ticks");
 2848 SYSCTL_INT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0,
 2849     "Interactivity score threshold");
 2850 SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW,
 2851     &preempt_thresh, 0,
 2852     "Maximal (lowest) priority for preemption");
 2853 SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost, 0,
 2854     "Assign static kernel priorities to sleeping threads");
 2855 SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins, 0,
 2856     "Number of times idle thread will spin waiting for new work");
 2857 SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW,
 2858     &sched_idlespinthresh, 0,
 2859     "Threshold before we will permit idle thread spinning");
 2860 #ifdef SMP
 2861 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0,
 2862     "Number of hz ticks to keep thread affinity for");
 2863 SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0,
 2864     "Enables the long-term load balancer");
 2865 SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW,
 2866     &balance_interval, 0,
 2867     "Average period in stathz ticks to run the long-term balancer");
 2868 SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0,
 2869     "Attempts to steal work from other cores before idling");
 2870 SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0,
 2871     "Minimum load on remote CPU before we'll steal");
 2872 SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING |
 2873     CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A",
 2874     "XML dump of detected CPU topology");
 2875 #endif
 2876 
 2877 /* ps compat.  All cpu percentages from ULE are weighted. */
 2878 static int ccpu = 0;
 2879 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");

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