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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 261357 2014-02-01 20:46:35Z nwhitehorn $");
   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/lock.h>
   50 #include <sys/mutex.h>
   51 #include <sys/proc.h>
   52 #include <sys/resource.h>
   53 #include <sys/resourcevar.h>
   54 #include <sys/sched.h>
   55 #include <sys/sdt.h>
   56 #include <sys/smp.h>
   57 #include <sys/sx.h>
   58 #include <sys/sysctl.h>
   59 #include <sys/sysproto.h>
   60 #include <sys/turnstile.h>
   61 #include <sys/umtx.h>
   62 #include <sys/vmmeter.h>
   63 #include <sys/cpuset.h>
   64 #include <sys/sbuf.h>
   65 
   66 #ifdef HWPMC_HOOKS
   67 #include <sys/pmckern.h>
   68 #endif
   69 
   70 #ifdef KDTRACE_HOOKS
   71 #include <sys/dtrace_bsd.h>
   72 int                             dtrace_vtime_active;
   73 dtrace_vtime_switch_func_t      dtrace_vtime_switch_func;
   74 #endif
   75 
   76 #include <machine/cpu.h>
   77 #include <machine/smp.h>
   78 
   79 #define KTR_ULE 0
   80 
   81 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
   82 #define TDQ_NAME_LEN    (sizeof("sched lock ") + sizeof(__XSTRING(MAXCPU)))
   83 #define TDQ_LOADNAME_LEN        (sizeof("CPU ") + sizeof(__XSTRING(MAXCPU)) - 1 + sizeof(" load"))
   84 
   85 /*
   86  * Thread scheduler specific section.  All fields are protected
   87  * by the thread lock.
   88  */
   89 struct td_sched {       
   90         struct runq     *ts_runq;       /* Run-queue we're queued on. */
   91         short           ts_flags;       /* TSF_* flags. */
   92         u_char          ts_cpu;         /* CPU that we have affinity for. */
   93         int             ts_rltick;      /* Real last tick, for affinity. */
   94         int             ts_slice;       /* Ticks of slice remaining. */
   95         u_int           ts_slptime;     /* Number of ticks we vol. slept */
   96         u_int           ts_runtime;     /* Number of ticks we were running */
   97         int             ts_ltick;       /* Last tick that we were running on */
   98         int             ts_ftick;       /* First tick that we were running on */
   99         int             ts_ticks;       /* Tick count */
  100 #ifdef KTR
  101         char            ts_name[TS_NAME_LEN];
  102 #endif
  103 };
  104 /* flags kept in ts_flags */
  105 #define TSF_BOUND       0x0001          /* Thread can not migrate. */
  106 #define TSF_XFERABLE    0x0002          /* Thread was added as transferable. */
  107 
  108 static struct td_sched td_sched0;
  109 
  110 #define THREAD_CAN_MIGRATE(td)  ((td)->td_pinned == 0)
  111 #define THREAD_CAN_SCHED(td, cpu)       \
  112     CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
  113 
  114 /*
  115  * Priority ranges used for interactive and non-interactive timeshare
  116  * threads.  The timeshare priorities are split up into four ranges.
  117  * The first range handles interactive threads.  The last three ranges
  118  * (NHALF, x, and NHALF) handle non-interactive threads with the outer
  119  * ranges supporting nice values.
  120  */
  121 #define PRI_TIMESHARE_RANGE     (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE + 1)
  122 #define PRI_INTERACT_RANGE      ((PRI_TIMESHARE_RANGE - SCHED_PRI_NRESV) / 2)
  123 #define PRI_BATCH_RANGE         (PRI_TIMESHARE_RANGE - PRI_INTERACT_RANGE)
  124 
  125 #define PRI_MIN_INTERACT        PRI_MIN_TIMESHARE
  126 #define PRI_MAX_INTERACT        (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE - 1)
  127 #define PRI_MIN_BATCH           (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE)
  128 #define PRI_MAX_BATCH           PRI_MAX_TIMESHARE
  129 
  130 /*
  131  * Cpu percentage computation macros and defines.
  132  *
  133  * SCHED_TICK_SECS:     Number of seconds to average the cpu usage across.
  134  * SCHED_TICK_TARG:     Number of hz ticks to average the cpu usage across.
  135  * SCHED_TICK_MAX:      Maximum number of ticks before scaling back.
  136  * SCHED_TICK_SHIFT:    Shift factor to avoid rounding away results.
  137  * SCHED_TICK_HZ:       Compute the number of hz ticks for a given ticks count.
  138  * SCHED_TICK_TOTAL:    Gives the amount of time we've been recording ticks.
  139  */
  140 #define SCHED_TICK_SECS         10
  141 #define SCHED_TICK_TARG         (hz * SCHED_TICK_SECS)
  142 #define SCHED_TICK_MAX          (SCHED_TICK_TARG + hz)
  143 #define SCHED_TICK_SHIFT        10
  144 #define SCHED_TICK_HZ(ts)       ((ts)->ts_ticks >> SCHED_TICK_SHIFT)
  145 #define SCHED_TICK_TOTAL(ts)    (max((ts)->ts_ltick - (ts)->ts_ftick, hz))
  146 
  147 /*
  148  * These macros determine priorities for non-interactive threads.  They are
  149  * assigned a priority based on their recent cpu utilization as expressed
  150  * by the ratio of ticks to the tick total.  NHALF priorities at the start
  151  * and end of the MIN to MAX timeshare range are only reachable with negative
  152  * or positive nice respectively.
  153  *
  154  * PRI_RANGE:   Priority range for utilization dependent priorities.
  155  * PRI_NRESV:   Number of nice values.
  156  * PRI_TICKS:   Compute a priority in PRI_RANGE from the ticks count and total.
  157  * PRI_NICE:    Determines the part of the priority inherited from nice.
  158  */
  159 #define SCHED_PRI_NRESV         (PRIO_MAX - PRIO_MIN)
  160 #define SCHED_PRI_NHALF         (SCHED_PRI_NRESV / 2)
  161 #define SCHED_PRI_MIN           (PRI_MIN_BATCH + SCHED_PRI_NHALF)
  162 #define SCHED_PRI_MAX           (PRI_MAX_BATCH - SCHED_PRI_NHALF)
  163 #define SCHED_PRI_RANGE         (SCHED_PRI_MAX - SCHED_PRI_MIN + 1)
  164 #define SCHED_PRI_TICKS(ts)                                             \
  165     (SCHED_TICK_HZ((ts)) /                                              \
  166     (roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE))
  167 #define SCHED_PRI_NICE(nice)    (nice)
  168 
  169 /*
  170  * These determine the interactivity of a process.  Interactivity differs from
  171  * cpu utilization in that it expresses the voluntary time slept vs time ran
  172  * while cpu utilization includes all time not running.  This more accurately
  173  * models the intent of the thread.
  174  *
  175  * SLP_RUN_MAX: Maximum amount of sleep time + run time we'll accumulate
  176  *              before throttling back.
  177  * SLP_RUN_FORK:        Maximum slp+run time to inherit at fork time.
  178  * INTERACT_MAX:        Maximum interactivity value.  Smaller is better.
  179  * INTERACT_THRESH:     Threshold for placement on the current runq.
  180  */
  181 #define SCHED_SLP_RUN_MAX       ((hz * 5) << SCHED_TICK_SHIFT)
  182 #define SCHED_SLP_RUN_FORK      ((hz / 2) << SCHED_TICK_SHIFT)
  183 #define SCHED_INTERACT_MAX      (100)
  184 #define SCHED_INTERACT_HALF     (SCHED_INTERACT_MAX / 2)
  185 #define SCHED_INTERACT_THRESH   (30)
  186 
  187 /*
  188  * These parameters determine the slice behavior for batch work.
  189  */
  190 #define SCHED_SLICE_DEFAULT_DIVISOR     10      /* ~94 ms, 12 stathz ticks. */
  191 #define SCHED_SLICE_MIN_DIVISOR         6       /* DEFAULT/MIN = ~16 ms. */
  192 
  193 /* Flags kept in td_flags. */
  194 #define TDF_SLICEEND    TDF_SCHED2      /* Thread time slice is over. */
  195 
  196 /*
  197  * tickincr:            Converts a stathz tick into a hz domain scaled by
  198  *                      the shift factor.  Without the shift the error rate
  199  *                      due to rounding would be unacceptably high.
  200  * realstathz:          stathz is sometimes 0 and run off of hz.
  201  * sched_slice:         Runtime of each thread before rescheduling.
  202  * preempt_thresh:      Priority threshold for preemption and remote IPIs.
  203  */
  204 static int sched_interact = SCHED_INTERACT_THRESH;
  205 static int tickincr = 8 << SCHED_TICK_SHIFT;
  206 static int realstathz = 127;    /* reset during boot. */
  207 static int sched_slice = 10;    /* reset during boot. */
  208 static int sched_slice_min = 1; /* reset during boot. */
  209 #ifdef PREEMPTION
  210 #ifdef FULL_PREEMPTION
  211 static int preempt_thresh = PRI_MAX_IDLE;
  212 #else
  213 static int preempt_thresh = PRI_MIN_KERN;
  214 #endif
  215 #else 
  216 static int preempt_thresh = 0;
  217 #endif
  218 static int static_boost = PRI_MIN_BATCH;
  219 static int sched_idlespins = 10000;
  220 static int sched_idlespinthresh = -1;
  221 
  222 /*
  223  * tdq - per processor runqs and statistics.  All fields are protected by the
  224  * tdq_lock.  The load and lowpri may be accessed without to avoid excess
  225  * locking in sched_pickcpu();
  226  */
  227 struct tdq {
  228         /* 
  229          * Ordered to improve efficiency of cpu_search() and switch().
  230          * tdq_lock is padded to avoid false sharing with tdq_load and
  231          * tdq_cpu_idle.
  232          */
  233         struct mtx_padalign tdq_lock;           /* run queue lock. */
  234         struct cpu_group *tdq_cg;               /* Pointer to cpu topology. */
  235         volatile int    tdq_load;               /* Aggregate load. */
  236         volatile int    tdq_cpu_idle;           /* cpu_idle() is active. */
  237         int             tdq_sysload;            /* For loadavg, !ITHD load. */
  238         int             tdq_transferable;       /* Transferable thread count. */
  239         short           tdq_switchcnt;          /* Switches this tick. */
  240         short           tdq_oldswitchcnt;       /* Switches last tick. */
  241         u_char          tdq_lowpri;             /* Lowest priority thread. */
  242         u_char          tdq_ipipending;         /* IPI pending. */
  243         u_char          tdq_idx;                /* Current insert index. */
  244         u_char          tdq_ridx;               /* Current removal index. */
  245         struct runq     tdq_realtime;           /* real-time run queue. */
  246         struct runq     tdq_timeshare;          /* timeshare run queue. */
  247         struct runq     tdq_idle;               /* Queue of IDLE threads. */
  248         char            tdq_name[TDQ_NAME_LEN];
  249 #ifdef KTR
  250         char            tdq_loadname[TDQ_LOADNAME_LEN];
  251 #endif
  252 } __aligned(64);
  253 
  254 /* Idle thread states and config. */
  255 #define TDQ_RUNNING     1
  256 #define TDQ_IDLE        2
  257 
  258 #ifdef SMP
  259 struct cpu_group *cpu_top;              /* CPU topology */
  260 
  261 #define SCHED_AFFINITY_DEFAULT  (max(1, hz / 1000))
  262 #define SCHED_AFFINITY(ts, t)   ((ts)->ts_rltick > ticks - ((t) * affinity))
  263 
  264 /*
  265  * Run-time tunables.
  266  */
  267 static int rebalance = 1;
  268 static int balance_interval = 128;      /* Default set in sched_initticks(). */
  269 static int affinity;
  270 static int steal_idle = 1;
  271 static int steal_thresh = 2;
  272 
  273 /*
  274  * One thread queue per processor.
  275  */
  276 static struct tdq       tdq_cpu[MAXCPU];
  277 static struct tdq       *balance_tdq;
  278 static int balance_ticks;
  279 static DPCPU_DEFINE(uint32_t, randomval);
  280 
  281 #define TDQ_SELF()      (&tdq_cpu[PCPU_GET(cpuid)])
  282 #define TDQ_CPU(x)      (&tdq_cpu[(x)])
  283 #define TDQ_ID(x)       ((int)((x) - tdq_cpu))
  284 #else   /* !SMP */
  285 static struct tdq       tdq_cpu;
  286 
  287 #define TDQ_ID(x)       (0)
  288 #define TDQ_SELF()      (&tdq_cpu)
  289 #define TDQ_CPU(x)      (&tdq_cpu)
  290 #endif
  291 
  292 #define TDQ_LOCK_ASSERT(t, type)        mtx_assert(TDQ_LOCKPTR((t)), (type))
  293 #define TDQ_LOCK(t)             mtx_lock_spin(TDQ_LOCKPTR((t)))
  294 #define TDQ_LOCK_FLAGS(t, f)    mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f))
  295 #define TDQ_UNLOCK(t)           mtx_unlock_spin(TDQ_LOCKPTR((t)))
  296 #define TDQ_LOCKPTR(t)          ((struct mtx *)(&(t)->tdq_lock))
  297 
  298 static void sched_priority(struct thread *);
  299 static void sched_thread_priority(struct thread *, u_char);
  300 static int sched_interact_score(struct thread *);
  301 static void sched_interact_update(struct thread *);
  302 static void sched_interact_fork(struct thread *);
  303 static void sched_pctcpu_update(struct td_sched *, int);
  304 
  305 /* Operations on per processor queues */
  306 static struct thread *tdq_choose(struct tdq *);
  307 static void tdq_setup(struct tdq *);
  308 static void tdq_load_add(struct tdq *, struct thread *);
  309 static void tdq_load_rem(struct tdq *, struct thread *);
  310 static __inline void tdq_runq_add(struct tdq *, struct thread *, int);
  311 static __inline void tdq_runq_rem(struct tdq *, struct thread *);
  312 static inline int sched_shouldpreempt(int, int, int);
  313 void tdq_print(int cpu);
  314 static void runq_print(struct runq *rq);
  315 static void tdq_add(struct tdq *, struct thread *, int);
  316 #ifdef SMP
  317 static int tdq_move(struct tdq *, struct tdq *);
  318 static int tdq_idled(struct tdq *);
  319 static void tdq_notify(struct tdq *, struct thread *);
  320 static struct thread *tdq_steal(struct tdq *, int);
  321 static struct thread *runq_steal(struct runq *, int);
  322 static int sched_pickcpu(struct thread *, int);
  323 static void sched_balance(void);
  324 static int sched_balance_pair(struct tdq *, struct tdq *);
  325 static inline struct tdq *sched_setcpu(struct thread *, int, int);
  326 static inline void thread_unblock_switch(struct thread *, struct mtx *);
  327 static struct mtx *sched_switch_migrate(struct tdq *, struct thread *, int);
  328 static int sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS);
  329 static int sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, 
  330     struct cpu_group *cg, int indent);
  331 #endif
  332 
  333 static void sched_setup(void *dummy);
  334 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
  335 
  336 static void sched_initticks(void *dummy);
  337 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
  338     NULL);
  339 
  340 SDT_PROVIDER_DEFINE(sched);
  341 
  342 SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *", 
  343     "struct proc *", "uint8_t");
  344 SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *", 
  345     "struct proc *", "void *");
  346 SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *", 
  347     "struct proc *", "void *", "int");
  348 SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *", 
  349     "struct proc *", "uint8_t", "struct thread *");
  350 SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int");
  351 SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *", 
  352     "struct proc *");
  353 SDT_PROBE_DEFINE(sched, , , on__cpu);
  354 SDT_PROBE_DEFINE(sched, , , remain__cpu);
  355 SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *", 
  356     "struct proc *");
  357 
  358 /*
  359  * Print the threads waiting on a run-queue.
  360  */
  361 static void
  362 runq_print(struct runq *rq)
  363 {
  364         struct rqhead *rqh;
  365         struct thread *td;
  366         int pri;
  367         int j;
  368         int i;
  369 
  370         for (i = 0; i < RQB_LEN; i++) {
  371                 printf("\t\trunq bits %d 0x%zx\n",
  372                     i, rq->rq_status.rqb_bits[i]);
  373                 for (j = 0; j < RQB_BPW; j++)
  374                         if (rq->rq_status.rqb_bits[i] & (1ul << j)) {
  375                                 pri = j + (i << RQB_L2BPW);
  376                                 rqh = &rq->rq_queues[pri];
  377                                 TAILQ_FOREACH(td, rqh, td_runq) {
  378                                         printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
  379                                             td, td->td_name, td->td_priority,
  380                                             td->td_rqindex, pri);
  381                                 }
  382                         }
  383         }
  384 }
  385 
  386 /*
  387  * Print the status of a per-cpu thread queue.  Should be a ddb show cmd.
  388  */
  389 void
  390 tdq_print(int cpu)
  391 {
  392         struct tdq *tdq;
  393 
  394         tdq = TDQ_CPU(cpu);
  395 
  396         printf("tdq %d:\n", TDQ_ID(tdq));
  397         printf("\tlock            %p\n", TDQ_LOCKPTR(tdq));
  398         printf("\tLock name:      %s\n", tdq->tdq_name);
  399         printf("\tload:           %d\n", tdq->tdq_load);
  400         printf("\tswitch cnt:     %d\n", tdq->tdq_switchcnt);
  401         printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt);
  402         printf("\ttimeshare idx:  %d\n", tdq->tdq_idx);
  403         printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
  404         printf("\tload transferable: %d\n", tdq->tdq_transferable);
  405         printf("\tlowest priority:   %d\n", tdq->tdq_lowpri);
  406         printf("\trealtime runq:\n");
  407         runq_print(&tdq->tdq_realtime);
  408         printf("\ttimeshare runq:\n");
  409         runq_print(&tdq->tdq_timeshare);
  410         printf("\tidle runq:\n");
  411         runq_print(&tdq->tdq_idle);
  412 }
  413 
  414 static inline int
  415 sched_shouldpreempt(int pri, int cpri, int remote)
  416 {
  417         /*
  418          * If the new priority is not better than the current priority there is
  419          * nothing to do.
  420          */
  421         if (pri >= cpri)
  422                 return (0);
  423         /*
  424          * Always preempt idle.
  425          */
  426         if (cpri >= PRI_MIN_IDLE)
  427                 return (1);
  428         /*
  429          * If preemption is disabled don't preempt others.
  430          */
  431         if (preempt_thresh == 0)
  432                 return (0);
  433         /*
  434          * Preempt if we exceed the threshold.
  435          */
  436         if (pri <= preempt_thresh)
  437                 return (1);
  438         /*
  439          * If we're interactive or better and there is non-interactive
  440          * or worse running preempt only remote processors.
  441          */
  442         if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT)
  443                 return (1);
  444         return (0);
  445 }
  446 
  447 /*
  448  * Add a thread to the actual run-queue.  Keeps transferable counts up to
  449  * date with what is actually on the run-queue.  Selects the correct
  450  * queue position for timeshare threads.
  451  */
  452 static __inline void
  453 tdq_runq_add(struct tdq *tdq, struct thread *td, int flags)
  454 {
  455         struct td_sched *ts;
  456         u_char pri;
  457 
  458         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  459         THREAD_LOCK_ASSERT(td, MA_OWNED);
  460 
  461         pri = td->td_priority;
  462         ts = td->td_sched;
  463         TD_SET_RUNQ(td);
  464         if (THREAD_CAN_MIGRATE(td)) {
  465                 tdq->tdq_transferable++;
  466                 ts->ts_flags |= TSF_XFERABLE;
  467         }
  468         if (pri < PRI_MIN_BATCH) {
  469                 ts->ts_runq = &tdq->tdq_realtime;
  470         } else if (pri <= PRI_MAX_BATCH) {
  471                 ts->ts_runq = &tdq->tdq_timeshare;
  472                 KASSERT(pri <= PRI_MAX_BATCH && pri >= PRI_MIN_BATCH,
  473                         ("Invalid priority %d on timeshare runq", pri));
  474                 /*
  475                  * This queue contains only priorities between MIN and MAX
  476                  * realtime.  Use the whole queue to represent these values.
  477                  */
  478                 if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) {
  479                         pri = RQ_NQS * (pri - PRI_MIN_BATCH) / PRI_BATCH_RANGE;
  480                         pri = (pri + tdq->tdq_idx) % RQ_NQS;
  481                         /*
  482                          * This effectively shortens the queue by one so we
  483                          * can have a one slot difference between idx and
  484                          * ridx while we wait for threads to drain.
  485                          */
  486                         if (tdq->tdq_ridx != tdq->tdq_idx &&
  487                             pri == tdq->tdq_ridx)
  488                                 pri = (unsigned char)(pri - 1) % RQ_NQS;
  489                 } else
  490                         pri = tdq->tdq_ridx;
  491                 runq_add_pri(ts->ts_runq, td, pri, flags);
  492                 return;
  493         } else
  494                 ts->ts_runq = &tdq->tdq_idle;
  495         runq_add(ts->ts_runq, td, flags);
  496 }
  497 
  498 /* 
  499  * Remove a thread from a run-queue.  This typically happens when a thread
  500  * is selected to run.  Running threads are not on the queue and the
  501  * transferable count does not reflect them.
  502  */
  503 static __inline void
  504 tdq_runq_rem(struct tdq *tdq, struct thread *td)
  505 {
  506         struct td_sched *ts;
  507 
  508         ts = td->td_sched;
  509         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  510         KASSERT(ts->ts_runq != NULL,
  511             ("tdq_runq_remove: thread %p null ts_runq", td));
  512         if (ts->ts_flags & TSF_XFERABLE) {
  513                 tdq->tdq_transferable--;
  514                 ts->ts_flags &= ~TSF_XFERABLE;
  515         }
  516         if (ts->ts_runq == &tdq->tdq_timeshare) {
  517                 if (tdq->tdq_idx != tdq->tdq_ridx)
  518                         runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx);
  519                 else
  520                         runq_remove_idx(ts->ts_runq, td, NULL);
  521         } else
  522                 runq_remove(ts->ts_runq, td);
  523 }
  524 
  525 /*
  526  * Load is maintained for all threads RUNNING and ON_RUNQ.  Add the load
  527  * for this thread to the referenced thread queue.
  528  */
  529 static void
  530 tdq_load_add(struct tdq *tdq, struct thread *td)
  531 {
  532 
  533         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  534         THREAD_LOCK_ASSERT(td, MA_OWNED);
  535 
  536         tdq->tdq_load++;
  537         if ((td->td_flags & TDF_NOLOAD) == 0)
  538                 tdq->tdq_sysload++;
  539         KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
  540         SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
  541 }
  542 
  543 /*
  544  * Remove the load from a thread that is transitioning to a sleep state or
  545  * exiting.
  546  */
  547 static void
  548 tdq_load_rem(struct tdq *tdq, struct thread *td)
  549 {
  550 
  551         THREAD_LOCK_ASSERT(td, MA_OWNED);
  552         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  553         KASSERT(tdq->tdq_load != 0,
  554             ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
  555 
  556         tdq->tdq_load--;
  557         if ((td->td_flags & TDF_NOLOAD) == 0)
  558                 tdq->tdq_sysload--;
  559         KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
  560         SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
  561 }
  562 
  563 /*
  564  * Bound timeshare latency by decreasing slice size as load increases.  We
  565  * consider the maximum latency as the sum of the threads waiting to run
  566  * aside from curthread and target no more than sched_slice latency but
  567  * no less than sched_slice_min runtime.
  568  */
  569 static inline int
  570 tdq_slice(struct tdq *tdq)
  571 {
  572         int load;
  573 
  574         /*
  575          * It is safe to use sys_load here because this is called from
  576          * contexts where timeshare threads are running and so there
  577          * cannot be higher priority load in the system.
  578          */
  579         load = tdq->tdq_sysload - 1;
  580         if (load >= SCHED_SLICE_MIN_DIVISOR)
  581                 return (sched_slice_min);
  582         if (load <= 1)
  583                 return (sched_slice);
  584         return (sched_slice / load);
  585 }
  586 
  587 /*
  588  * Set lowpri to its exact value by searching the run-queue and
  589  * evaluating curthread.  curthread may be passed as an optimization.
  590  */
  591 static void
  592 tdq_setlowpri(struct tdq *tdq, struct thread *ctd)
  593 {
  594         struct thread *td;
  595 
  596         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  597         if (ctd == NULL)
  598                 ctd = pcpu_find(TDQ_ID(tdq))->pc_curthread;
  599         td = tdq_choose(tdq);
  600         if (td == NULL || td->td_priority > ctd->td_priority)
  601                 tdq->tdq_lowpri = ctd->td_priority;
  602         else
  603                 tdq->tdq_lowpri = td->td_priority;
  604 }
  605 
  606 #ifdef SMP
  607 struct cpu_search {
  608         cpuset_t cs_mask;
  609         u_int   cs_prefer;
  610         int     cs_pri;         /* Min priority for low. */
  611         int     cs_limit;       /* Max load for low, min load for high. */
  612         int     cs_cpu;
  613         int     cs_load;
  614 };
  615 
  616 #define CPU_SEARCH_LOWEST       0x1
  617 #define CPU_SEARCH_HIGHEST      0x2
  618 #define CPU_SEARCH_BOTH         (CPU_SEARCH_LOWEST|CPU_SEARCH_HIGHEST)
  619 
  620 #define CPUSET_FOREACH(cpu, mask)                               \
  621         for ((cpu) = 0; (cpu) <= mp_maxid; (cpu)++)             \
  622                 if (CPU_ISSET(cpu, &mask))
  623 
  624 static __inline int cpu_search(const struct cpu_group *cg, struct cpu_search *low,
  625     struct cpu_search *high, const int match);
  626 int cpu_search_lowest(const struct cpu_group *cg, struct cpu_search *low);
  627 int cpu_search_highest(const struct cpu_group *cg, struct cpu_search *high);
  628 int cpu_search_both(const struct cpu_group *cg, struct cpu_search *low,
  629     struct cpu_search *high);
  630 
  631 /*
  632  * Search the tree of cpu_groups for the lowest or highest loaded cpu
  633  * according to the match argument.  This routine actually compares the
  634  * load on all paths through the tree and finds the least loaded cpu on
  635  * the least loaded path, which may differ from the least loaded cpu in
  636  * the system.  This balances work among caches and busses.
  637  *
  638  * This inline is instantiated in three forms below using constants for the
  639  * match argument.  It is reduced to the minimum set for each case.  It is
  640  * also recursive to the depth of the tree.
  641  */
  642 static __inline int
  643 cpu_search(const struct cpu_group *cg, struct cpu_search *low,
  644     struct cpu_search *high, const int match)
  645 {
  646         struct cpu_search lgroup;
  647         struct cpu_search hgroup;
  648         cpuset_t cpumask;
  649         struct cpu_group *child;
  650         struct tdq *tdq;
  651         int cpu, i, hload, lload, load, total, rnd, *rndptr;
  652 
  653         total = 0;
  654         cpumask = cg->cg_mask;
  655         if (match & CPU_SEARCH_LOWEST) {
  656                 lload = INT_MAX;
  657                 lgroup = *low;
  658         }
  659         if (match & CPU_SEARCH_HIGHEST) {
  660                 hload = INT_MIN;
  661                 hgroup = *high;
  662         }
  663 
  664         /* Iterate through the child CPU groups and then remaining CPUs. */
  665         for (i = cg->cg_children, cpu = mp_maxid; ; ) {
  666                 if (i == 0) {
  667 #ifdef HAVE_INLINE_FFSL
  668                         cpu = CPU_FFS(&cpumask) - 1;
  669 #else
  670                         while (cpu >= 0 && !CPU_ISSET(cpu, &cpumask))
  671                                 cpu--;
  672 #endif
  673                         if (cpu < 0)
  674                                 break;
  675                         child = NULL;
  676                 } else
  677                         child = &cg->cg_child[i - 1];
  678 
  679                 if (match & CPU_SEARCH_LOWEST)
  680                         lgroup.cs_cpu = -1;
  681                 if (match & CPU_SEARCH_HIGHEST)
  682                         hgroup.cs_cpu = -1;
  683                 if (child) {                    /* Handle child CPU group. */
  684                         CPU_NAND(&cpumask, &child->cg_mask);
  685                         switch (match) {
  686                         case CPU_SEARCH_LOWEST:
  687                                 load = cpu_search_lowest(child, &lgroup);
  688                                 break;
  689                         case CPU_SEARCH_HIGHEST:
  690                                 load = cpu_search_highest(child, &hgroup);
  691                                 break;
  692                         case CPU_SEARCH_BOTH:
  693                                 load = cpu_search_both(child, &lgroup, &hgroup);
  694                                 break;
  695                         }
  696                 } else {                        /* Handle child CPU. */
  697                         CPU_CLR(cpu, &cpumask);
  698                         tdq = TDQ_CPU(cpu);
  699                         load = tdq->tdq_load * 256;
  700                         rndptr = DPCPU_PTR(randomval);
  701                         rnd = (*rndptr = *rndptr * 69069 + 5) >> 26;
  702                         if (match & CPU_SEARCH_LOWEST) {
  703                                 if (cpu == low->cs_prefer)
  704                                         load -= 64;
  705                                 /* If that CPU is allowed and get data. */
  706                                 if (tdq->tdq_lowpri > lgroup.cs_pri &&
  707                                     tdq->tdq_load <= lgroup.cs_limit &&
  708                                     CPU_ISSET(cpu, &lgroup.cs_mask)) {
  709                                         lgroup.cs_cpu = cpu;
  710                                         lgroup.cs_load = load - rnd;
  711                                 }
  712                         }
  713                         if (match & CPU_SEARCH_HIGHEST)
  714                                 if (tdq->tdq_load >= hgroup.cs_limit &&
  715                                     tdq->tdq_transferable &&
  716                                     CPU_ISSET(cpu, &hgroup.cs_mask)) {
  717                                         hgroup.cs_cpu = cpu;
  718                                         hgroup.cs_load = load - rnd;
  719                                 }
  720                 }
  721                 total += load;
  722 
  723                 /* We have info about child item. Compare it. */
  724                 if (match & CPU_SEARCH_LOWEST) {
  725                         if (lgroup.cs_cpu >= 0 &&
  726                             (load < lload ||
  727                              (load == lload && lgroup.cs_load < low->cs_load))) {
  728                                 lload = load;
  729                                 low->cs_cpu = lgroup.cs_cpu;
  730                                 low->cs_load = lgroup.cs_load;
  731                         }
  732                 }
  733                 if (match & CPU_SEARCH_HIGHEST)
  734                         if (hgroup.cs_cpu >= 0 &&
  735                             (load > hload ||
  736                              (load == hload && hgroup.cs_load > high->cs_load))) {
  737                                 hload = load;
  738                                 high->cs_cpu = hgroup.cs_cpu;
  739                                 high->cs_load = hgroup.cs_load;
  740                         }
  741                 if (child) {
  742                         i--;
  743                         if (i == 0 && CPU_EMPTY(&cpumask))
  744                                 break;
  745                 }
  746 #ifndef HAVE_INLINE_FFSL
  747                 else
  748                         cpu--;
  749 #endif
  750         }
  751         return (total);
  752 }
  753 
  754 /*
  755  * cpu_search instantiations must pass constants to maintain the inline
  756  * optimization.
  757  */
  758 int
  759 cpu_search_lowest(const struct cpu_group *cg, struct cpu_search *low)
  760 {
  761         return cpu_search(cg, low, NULL, CPU_SEARCH_LOWEST);
  762 }
  763 
  764 int
  765 cpu_search_highest(const struct cpu_group *cg, struct cpu_search *high)
  766 {
  767         return cpu_search(cg, NULL, high, CPU_SEARCH_HIGHEST);
  768 }
  769 
  770 int
  771 cpu_search_both(const struct cpu_group *cg, struct cpu_search *low,
  772     struct cpu_search *high)
  773 {
  774         return cpu_search(cg, low, high, CPU_SEARCH_BOTH);
  775 }
  776 
  777 /*
  778  * Find the cpu with the least load via the least loaded path that has a
  779  * lowpri greater than pri  pri.  A pri of -1 indicates any priority is
  780  * acceptable.
  781  */
  782 static inline int
  783 sched_lowest(const struct cpu_group *cg, cpuset_t mask, int pri, int maxload,
  784     int prefer)
  785 {
  786         struct cpu_search low;
  787 
  788         low.cs_cpu = -1;
  789         low.cs_prefer = prefer;
  790         low.cs_mask = mask;
  791         low.cs_pri = pri;
  792         low.cs_limit = maxload;
  793         cpu_search_lowest(cg, &low);
  794         return low.cs_cpu;
  795 }
  796 
  797 /*
  798  * Find the cpu with the highest load via the highest loaded path.
  799  */
  800 static inline int
  801 sched_highest(const struct cpu_group *cg, cpuset_t mask, int minload)
  802 {
  803         struct cpu_search high;
  804 
  805         high.cs_cpu = -1;
  806         high.cs_mask = mask;
  807         high.cs_limit = minload;
  808         cpu_search_highest(cg, &high);
  809         return high.cs_cpu;
  810 }
  811 
  812 static void
  813 sched_balance_group(struct cpu_group *cg)
  814 {
  815         cpuset_t hmask, lmask;
  816         int high, low, anylow;
  817 
  818         CPU_FILL(&hmask);
  819         for (;;) {
  820                 high = sched_highest(cg, hmask, 1);
  821                 /* Stop if there is no more CPU with transferrable threads. */
  822                 if (high == -1)
  823                         break;
  824                 CPU_CLR(high, &hmask);
  825                 CPU_COPY(&hmask, &lmask);
  826                 /* Stop if there is no more CPU left for low. */
  827                 if (CPU_EMPTY(&lmask))
  828                         break;
  829                 anylow = 1;
  830 nextlow:
  831                 low = sched_lowest(cg, lmask, -1,
  832                     TDQ_CPU(high)->tdq_load - 1, high);
  833                 /* Stop if we looked well and found no less loaded CPU. */
  834                 if (anylow && low == -1)
  835                         break;
  836                 /* Go to next high if we found no less loaded CPU. */
  837                 if (low == -1)
  838                         continue;
  839                 /* Transfer thread from high to low. */
  840                 if (sched_balance_pair(TDQ_CPU(high), TDQ_CPU(low))) {
  841                         /* CPU that got thread can no longer be a donor. */
  842                         CPU_CLR(low, &hmask);
  843                 } else {
  844                         /*
  845                          * If failed, then there is no threads on high
  846                          * that can run on this low. Drop low from low
  847                          * mask and look for different one.
  848                          */
  849                         CPU_CLR(low, &lmask);
  850                         anylow = 0;
  851                         goto nextlow;
  852                 }
  853         }
  854 }
  855 
  856 static void
  857 sched_balance(void)
  858 {
  859         struct tdq *tdq;
  860 
  861         /*
  862          * Select a random time between .5 * balance_interval and
  863          * 1.5 * balance_interval.
  864          */
  865         balance_ticks = max(balance_interval / 2, 1);
  866         balance_ticks += random() % balance_interval;
  867         if (smp_started == 0 || rebalance == 0)
  868                 return;
  869         tdq = TDQ_SELF();
  870         TDQ_UNLOCK(tdq);
  871         sched_balance_group(cpu_top);
  872         TDQ_LOCK(tdq);
  873 }
  874 
  875 /*
  876  * Lock two thread queues using their address to maintain lock order.
  877  */
  878 static void
  879 tdq_lock_pair(struct tdq *one, struct tdq *two)
  880 {
  881         if (one < two) {
  882                 TDQ_LOCK(one);
  883                 TDQ_LOCK_FLAGS(two, MTX_DUPOK);
  884         } else {
  885                 TDQ_LOCK(two);
  886                 TDQ_LOCK_FLAGS(one, MTX_DUPOK);
  887         }
  888 }
  889 
  890 /*
  891  * Unlock two thread queues.  Order is not important here.
  892  */
  893 static void
  894 tdq_unlock_pair(struct tdq *one, struct tdq *two)
  895 {
  896         TDQ_UNLOCK(one);
  897         TDQ_UNLOCK(two);
  898 }
  899 
  900 /*
  901  * Transfer load between two imbalanced thread queues.
  902  */
  903 static int
  904 sched_balance_pair(struct tdq *high, struct tdq *low)
  905 {
  906         int moved;
  907         int cpu;
  908 
  909         tdq_lock_pair(high, low);
  910         moved = 0;
  911         /*
  912          * Determine what the imbalance is and then adjust that to how many
  913          * threads we actually have to give up (transferable).
  914          */
  915         if (high->tdq_transferable != 0 && high->tdq_load > low->tdq_load &&
  916             (moved = tdq_move(high, low)) > 0) {
  917                 /*
  918                  * In case the target isn't the current cpu IPI it to force a
  919                  * reschedule with the new workload.
  920                  */
  921                 cpu = TDQ_ID(low);
  922                 if (cpu != PCPU_GET(cpuid))
  923                         ipi_cpu(cpu, IPI_PREEMPT);
  924         }
  925         tdq_unlock_pair(high, low);
  926         return (moved);
  927 }
  928 
  929 /*
  930  * Move a thread from one thread queue to another.
  931  */
  932 static int
  933 tdq_move(struct tdq *from, struct tdq *to)
  934 {
  935         struct td_sched *ts;
  936         struct thread *td;
  937         struct tdq *tdq;
  938         int cpu;
  939 
  940         TDQ_LOCK_ASSERT(from, MA_OWNED);
  941         TDQ_LOCK_ASSERT(to, MA_OWNED);
  942 
  943         tdq = from;
  944         cpu = TDQ_ID(to);
  945         td = tdq_steal(tdq, cpu);
  946         if (td == NULL)
  947                 return (0);
  948         ts = td->td_sched;
  949         /*
  950          * Although the run queue is locked the thread may be blocked.  Lock
  951          * it to clear this and acquire the run-queue lock.
  952          */
  953         thread_lock(td);
  954         /* Drop recursive lock on from acquired via thread_lock(). */
  955         TDQ_UNLOCK(from);
  956         sched_rem(td);
  957         ts->ts_cpu = cpu;
  958         td->td_lock = TDQ_LOCKPTR(to);
  959         tdq_add(to, td, SRQ_YIELDING);
  960         return (1);
  961 }
  962 
  963 /*
  964  * This tdq has idled.  Try to steal a thread from another cpu and switch
  965  * to it.
  966  */
  967 static int
  968 tdq_idled(struct tdq *tdq)
  969 {
  970         struct cpu_group *cg;
  971         struct tdq *steal;
  972         cpuset_t mask;
  973         int thresh;
  974         int cpu;
  975 
  976         if (smp_started == 0 || steal_idle == 0)
  977                 return (1);
  978         CPU_FILL(&mask);
  979         CPU_CLR(PCPU_GET(cpuid), &mask);
  980         /* We don't want to be preempted while we're iterating. */
  981         spinlock_enter();
  982         for (cg = tdq->tdq_cg; cg != NULL; ) {
  983                 if ((cg->cg_flags & CG_FLAG_THREAD) == 0)
  984                         thresh = steal_thresh;
  985                 else
  986                         thresh = 1;
  987                 cpu = sched_highest(cg, mask, thresh);
  988                 if (cpu == -1) {
  989                         cg = cg->cg_parent;
  990                         continue;
  991                 }
  992                 steal = TDQ_CPU(cpu);
  993                 CPU_CLR(cpu, &mask);
  994                 tdq_lock_pair(tdq, steal);
  995                 if (steal->tdq_load < thresh || steal->tdq_transferable == 0) {
  996                         tdq_unlock_pair(tdq, steal);
  997                         continue;
  998                 }
  999                 /*
 1000                  * If a thread was added while interrupts were disabled don't
 1001                  * steal one here.  If we fail to acquire one due to affinity
 1002                  * restrictions loop again with this cpu removed from the
 1003                  * set.
 1004                  */
 1005                 if (tdq->tdq_load == 0 && tdq_move(steal, tdq) == 0) {
 1006                         tdq_unlock_pair(tdq, steal);
 1007                         continue;
 1008                 }
 1009                 spinlock_exit();
 1010                 TDQ_UNLOCK(steal);
 1011                 mi_switch(SW_VOL | SWT_IDLE, NULL);
 1012                 thread_unlock(curthread);
 1013 
 1014                 return (0);
 1015         }
 1016         spinlock_exit();
 1017         return (1);
 1018 }
 1019 
 1020 /*
 1021  * Notify a remote cpu of new work.  Sends an IPI if criteria are met.
 1022  */
 1023 static void
 1024 tdq_notify(struct tdq *tdq, struct thread *td)
 1025 {
 1026         struct thread *ctd;
 1027         int pri;
 1028         int cpu;
 1029 
 1030         if (tdq->tdq_ipipending)
 1031                 return;
 1032         cpu = td->td_sched->ts_cpu;
 1033         pri = td->td_priority;
 1034         ctd = pcpu_find(cpu)->pc_curthread;
 1035         if (!sched_shouldpreempt(pri, ctd->td_priority, 1))
 1036                 return;
 1037         if (TD_IS_IDLETHREAD(ctd)) {
 1038                 /*
 1039                  * If the MD code has an idle wakeup routine try that before
 1040                  * falling back to IPI.
 1041                  */
 1042                 if (!tdq->tdq_cpu_idle || cpu_idle_wakeup(cpu))
 1043                         return;
 1044         }
 1045         tdq->tdq_ipipending = 1;
 1046         ipi_cpu(cpu, IPI_PREEMPT);
 1047 }
 1048 
 1049 /*
 1050  * Steals load from a timeshare queue.  Honors the rotating queue head
 1051  * index.
 1052  */
 1053 static struct thread *
 1054 runq_steal_from(struct runq *rq, int cpu, u_char start)
 1055 {
 1056         struct rqbits *rqb;
 1057         struct rqhead *rqh;
 1058         struct thread *td, *first;
 1059         int bit;
 1060         int pri;
 1061         int i;
 1062 
 1063         rqb = &rq->rq_status;
 1064         bit = start & (RQB_BPW -1);
 1065         pri = 0;
 1066         first = NULL;
 1067 again:
 1068         for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
 1069                 if (rqb->rqb_bits[i] == 0)
 1070                         continue;
 1071                 if (bit != 0) {
 1072                         for (pri = bit; pri < RQB_BPW; pri++)
 1073                                 if (rqb->rqb_bits[i] & (1ul << pri))
 1074                                         break;
 1075                         if (pri >= RQB_BPW)
 1076                                 continue;
 1077                 } else
 1078                         pri = RQB_FFS(rqb->rqb_bits[i]);
 1079                 pri += (i << RQB_L2BPW);
 1080                 rqh = &rq->rq_queues[pri];
 1081                 TAILQ_FOREACH(td, rqh, td_runq) {
 1082                         if (first && THREAD_CAN_MIGRATE(td) &&
 1083                             THREAD_CAN_SCHED(td, cpu))
 1084                                 return (td);
 1085                         first = td;
 1086                 }
 1087         }
 1088         if (start != 0) {
 1089                 start = 0;
 1090                 goto again;
 1091         }
 1092 
 1093         if (first && THREAD_CAN_MIGRATE(first) &&
 1094             THREAD_CAN_SCHED(first, cpu))
 1095                 return (first);
 1096         return (NULL);
 1097 }
 1098 
 1099 /*
 1100  * Steals load from a standard linear queue.
 1101  */
 1102 static struct thread *
 1103 runq_steal(struct runq *rq, int cpu)
 1104 {
 1105         struct rqhead *rqh;
 1106         struct rqbits *rqb;
 1107         struct thread *td;
 1108         int word;
 1109         int bit;
 1110 
 1111         rqb = &rq->rq_status;
 1112         for (word = 0; word < RQB_LEN; word++) {
 1113                 if (rqb->rqb_bits[word] == 0)
 1114                         continue;
 1115                 for (bit = 0; bit < RQB_BPW; bit++) {
 1116                         if ((rqb->rqb_bits[word] & (1ul << bit)) == 0)
 1117                                 continue;
 1118                         rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)];
 1119                         TAILQ_FOREACH(td, rqh, td_runq)
 1120                                 if (THREAD_CAN_MIGRATE(td) &&
 1121                                     THREAD_CAN_SCHED(td, cpu))
 1122                                         return (td);
 1123                 }
 1124         }
 1125         return (NULL);
 1126 }
 1127 
 1128 /*
 1129  * Attempt to steal a thread in priority order from a thread queue.
 1130  */
 1131 static struct thread *
 1132 tdq_steal(struct tdq *tdq, int cpu)
 1133 {
 1134         struct thread *td;
 1135 
 1136         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 1137         if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL)
 1138                 return (td);
 1139         if ((td = runq_steal_from(&tdq->tdq_timeshare,
 1140             cpu, tdq->tdq_ridx)) != NULL)
 1141                 return (td);
 1142         return (runq_steal(&tdq->tdq_idle, cpu));
 1143 }
 1144 
 1145 /*
 1146  * Sets the thread lock and ts_cpu to match the requested cpu.  Unlocks the
 1147  * current lock and returns with the assigned queue locked.
 1148  */
 1149 static inline struct tdq *
 1150 sched_setcpu(struct thread *td, int cpu, int flags)
 1151 {
 1152 
 1153         struct tdq *tdq;
 1154 
 1155         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1156         tdq = TDQ_CPU(cpu);
 1157         td->td_sched->ts_cpu = cpu;
 1158         /*
 1159          * If the lock matches just return the queue.
 1160          */
 1161         if (td->td_lock == TDQ_LOCKPTR(tdq))
 1162                 return (tdq);
 1163 #ifdef notyet
 1164         /*
 1165          * If the thread isn't running its lockptr is a
 1166          * turnstile or a sleepqueue.  We can just lock_set without
 1167          * blocking.
 1168          */
 1169         if (TD_CAN_RUN(td)) {
 1170                 TDQ_LOCK(tdq);
 1171                 thread_lock_set(td, TDQ_LOCKPTR(tdq));
 1172                 return (tdq);
 1173         }
 1174 #endif
 1175         /*
 1176          * The hard case, migration, we need to block the thread first to
 1177          * prevent order reversals with other cpus locks.
 1178          */
 1179         spinlock_enter();
 1180         thread_lock_block(td);
 1181         TDQ_LOCK(tdq);
 1182         thread_lock_unblock(td, TDQ_LOCKPTR(tdq));
 1183         spinlock_exit();
 1184         return (tdq);
 1185 }
 1186 
 1187 SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding");
 1188 SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity");
 1189 SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity");
 1190 SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load");
 1191 SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu");
 1192 SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration");
 1193 
 1194 static int
 1195 sched_pickcpu(struct thread *td, int flags)
 1196 {
 1197         struct cpu_group *cg, *ccg;
 1198         struct td_sched *ts;
 1199         struct tdq *tdq;
 1200         cpuset_t mask;
 1201         int cpu, pri, self;
 1202 
 1203         self = PCPU_GET(cpuid);
 1204         ts = td->td_sched;
 1205         if (smp_started == 0)
 1206                 return (self);
 1207         /*
 1208          * Don't migrate a running thread from sched_switch().
 1209          */
 1210         if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td))
 1211                 return (ts->ts_cpu);
 1212         /*
 1213          * Prefer to run interrupt threads on the processors that generate
 1214          * the interrupt.
 1215          */
 1216         pri = td->td_priority;
 1217         if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) &&
 1218             curthread->td_intr_nesting_level && ts->ts_cpu != self) {
 1219                 SCHED_STAT_INC(pickcpu_intrbind);
 1220                 ts->ts_cpu = self;
 1221                 if (TDQ_CPU(self)->tdq_lowpri > pri) {
 1222                         SCHED_STAT_INC(pickcpu_affinity);
 1223                         return (ts->ts_cpu);
 1224                 }
 1225         }
 1226         /*
 1227          * If the thread can run on the last cpu and the affinity has not
 1228          * expired or it is idle run it there.
 1229          */
 1230         tdq = TDQ_CPU(ts->ts_cpu);
 1231         cg = tdq->tdq_cg;
 1232         if (THREAD_CAN_SCHED(td, ts->ts_cpu) &&
 1233             tdq->tdq_lowpri >= PRI_MIN_IDLE &&
 1234             SCHED_AFFINITY(ts, CG_SHARE_L2)) {
 1235                 if (cg->cg_flags & CG_FLAG_THREAD) {
 1236                         CPUSET_FOREACH(cpu, cg->cg_mask) {
 1237                                 if (TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE)
 1238                                         break;
 1239                         }
 1240                 } else
 1241                         cpu = INT_MAX;
 1242                 if (cpu > mp_maxid) {
 1243                         SCHED_STAT_INC(pickcpu_idle_affinity);
 1244                         return (ts->ts_cpu);
 1245                 }
 1246         }
 1247         /*
 1248          * Search for the last level cache CPU group in the tree.
 1249          * Skip caches with expired affinity time and SMT groups.
 1250          * Affinity to higher level caches will be handled less aggressively.
 1251          */
 1252         for (ccg = NULL; cg != NULL; cg = cg->cg_parent) {
 1253                 if (cg->cg_flags & CG_FLAG_THREAD)
 1254                         continue;
 1255                 if (!SCHED_AFFINITY(ts, cg->cg_level))
 1256                         continue;
 1257                 ccg = cg;
 1258         }
 1259         if (ccg != NULL)
 1260                 cg = ccg;
 1261         cpu = -1;
 1262         /* Search the group for the less loaded idle CPU we can run now. */
 1263         mask = td->td_cpuset->cs_mask;
 1264         if (cg != NULL && cg != cpu_top &&
 1265             CPU_CMP(&cg->cg_mask, &cpu_top->cg_mask) != 0)
 1266                 cpu = sched_lowest(cg, mask, max(pri, PRI_MAX_TIMESHARE),
 1267                     INT_MAX, ts->ts_cpu);
 1268         /* Search globally for the less loaded CPU we can run now. */
 1269         if (cpu == -1)
 1270                 cpu = sched_lowest(cpu_top, mask, pri, INT_MAX, ts->ts_cpu);
 1271         /* Search globally for the less loaded CPU. */
 1272         if (cpu == -1)
 1273                 cpu = sched_lowest(cpu_top, mask, -1, INT_MAX, ts->ts_cpu);
 1274         KASSERT(cpu != -1, ("sched_pickcpu: Failed to find a cpu."));
 1275         /*
 1276          * Compare the lowest loaded cpu to current cpu.
 1277          */
 1278         if (THREAD_CAN_SCHED(td, self) && TDQ_CPU(self)->tdq_lowpri > pri &&
 1279             TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE &&
 1280             TDQ_CPU(self)->tdq_load <= TDQ_CPU(cpu)->tdq_load + 1) {
 1281                 SCHED_STAT_INC(pickcpu_local);
 1282                 cpu = self;
 1283         } else
 1284                 SCHED_STAT_INC(pickcpu_lowest);
 1285         if (cpu != ts->ts_cpu)
 1286                 SCHED_STAT_INC(pickcpu_migration);
 1287         return (cpu);
 1288 }
 1289 #endif
 1290 
 1291 /*
 1292  * Pick the highest priority task we have and return it.
 1293  */
 1294 static struct thread *
 1295 tdq_choose(struct tdq *tdq)
 1296 {
 1297         struct thread *td;
 1298 
 1299         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 1300         td = runq_choose(&tdq->tdq_realtime);
 1301         if (td != NULL)
 1302                 return (td);
 1303         td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
 1304         if (td != NULL) {
 1305                 KASSERT(td->td_priority >= PRI_MIN_BATCH,
 1306                     ("tdq_choose: Invalid priority on timeshare queue %d",
 1307                     td->td_priority));
 1308                 return (td);
 1309         }
 1310         td = runq_choose(&tdq->tdq_idle);
 1311         if (td != NULL) {
 1312                 KASSERT(td->td_priority >= PRI_MIN_IDLE,
 1313                     ("tdq_choose: Invalid priority on idle queue %d",
 1314                     td->td_priority));
 1315                 return (td);
 1316         }
 1317 
 1318         return (NULL);
 1319 }
 1320 
 1321 /*
 1322  * Initialize a thread queue.
 1323  */
 1324 static void
 1325 tdq_setup(struct tdq *tdq)
 1326 {
 1327 
 1328         if (bootverbose)
 1329                 printf("ULE: setup cpu %d\n", TDQ_ID(tdq));
 1330         runq_init(&tdq->tdq_realtime);
 1331         runq_init(&tdq->tdq_timeshare);
 1332         runq_init(&tdq->tdq_idle);
 1333         snprintf(tdq->tdq_name, sizeof(tdq->tdq_name),
 1334             "sched lock %d", (int)TDQ_ID(tdq));
 1335         mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock",
 1336             MTX_SPIN | MTX_RECURSE);
 1337 #ifdef KTR
 1338         snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname),
 1339             "CPU %d load", (int)TDQ_ID(tdq));
 1340 #endif
 1341 }
 1342 
 1343 #ifdef SMP
 1344 static void
 1345 sched_setup_smp(void)
 1346 {
 1347         struct tdq *tdq;
 1348         int i;
 1349 
 1350         cpu_top = smp_topo();
 1351         CPU_FOREACH(i) {
 1352                 tdq = TDQ_CPU(i);
 1353                 tdq_setup(tdq);
 1354                 tdq->tdq_cg = smp_topo_find(cpu_top, i);
 1355                 if (tdq->tdq_cg == NULL)
 1356                         panic("Can't find cpu group for %d\n", i);
 1357         }
 1358         balance_tdq = TDQ_SELF();
 1359         sched_balance();
 1360 }
 1361 #endif
 1362 
 1363 /*
 1364  * Setup the thread queues and initialize the topology based on MD
 1365  * information.
 1366  */
 1367 static void
 1368 sched_setup(void *dummy)
 1369 {
 1370         struct tdq *tdq;
 1371 
 1372         tdq = TDQ_SELF();
 1373 #ifdef SMP
 1374         sched_setup_smp();
 1375 #else
 1376         tdq_setup(tdq);
 1377 #endif
 1378 
 1379         /* Add thread0's load since it's running. */
 1380         TDQ_LOCK(tdq);
 1381         thread0.td_lock = TDQ_LOCKPTR(TDQ_SELF());
 1382         tdq_load_add(tdq, &thread0);
 1383         tdq->tdq_lowpri = thread0.td_priority;
 1384         TDQ_UNLOCK(tdq);
 1385 }
 1386 
 1387 /*
 1388  * This routine determines time constants after stathz and hz are setup.
 1389  */
 1390 /* ARGSUSED */
 1391 static void
 1392 sched_initticks(void *dummy)
 1393 {
 1394         int incr;
 1395 
 1396         realstathz = stathz ? stathz : hz;
 1397         sched_slice = realstathz / SCHED_SLICE_DEFAULT_DIVISOR;
 1398         sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
 1399         hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
 1400             realstathz);
 1401 
 1402         /*
 1403          * tickincr is shifted out by 10 to avoid rounding errors due to
 1404          * hz not being evenly divisible by stathz on all platforms.
 1405          */
 1406         incr = (hz << SCHED_TICK_SHIFT) / realstathz;
 1407         /*
 1408          * This does not work for values of stathz that are more than
 1409          * 1 << SCHED_TICK_SHIFT * hz.  In practice this does not happen.
 1410          */
 1411         if (incr == 0)
 1412                 incr = 1;
 1413         tickincr = incr;
 1414 #ifdef SMP
 1415         /*
 1416          * Set the default balance interval now that we know
 1417          * what realstathz is.
 1418          */
 1419         balance_interval = realstathz;
 1420         affinity = SCHED_AFFINITY_DEFAULT;
 1421 #endif
 1422         if (sched_idlespinthresh < 0)
 1423                 sched_idlespinthresh = 2 * max(10000, 6 * hz) / realstathz;
 1424 }
 1425 
 1426 
 1427 /*
 1428  * This is the core of the interactivity algorithm.  Determines a score based
 1429  * on past behavior.  It is the ratio of sleep time to run time scaled to
 1430  * a [0, 100] integer.  This is the voluntary sleep time of a process, which
 1431  * differs from the cpu usage because it does not account for time spent
 1432  * waiting on a run-queue.  Would be prettier if we had floating point.
 1433  */
 1434 static int
 1435 sched_interact_score(struct thread *td)
 1436 {
 1437         struct td_sched *ts;
 1438         int div;
 1439 
 1440         ts = td->td_sched;
 1441         /*
 1442          * The score is only needed if this is likely to be an interactive
 1443          * task.  Don't go through the expense of computing it if there's
 1444          * no chance.
 1445          */
 1446         if (sched_interact <= SCHED_INTERACT_HALF &&
 1447                 ts->ts_runtime >= ts->ts_slptime)
 1448                         return (SCHED_INTERACT_HALF);
 1449 
 1450         if (ts->ts_runtime > ts->ts_slptime) {
 1451                 div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF);
 1452                 return (SCHED_INTERACT_HALF +
 1453                     (SCHED_INTERACT_HALF - (ts->ts_slptime / div)));
 1454         }
 1455         if (ts->ts_slptime > ts->ts_runtime) {
 1456                 div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF);
 1457                 return (ts->ts_runtime / div);
 1458         }
 1459         /* runtime == slptime */
 1460         if (ts->ts_runtime)
 1461                 return (SCHED_INTERACT_HALF);
 1462 
 1463         /*
 1464          * This can happen if slptime and runtime are 0.
 1465          */
 1466         return (0);
 1467 
 1468 }
 1469 
 1470 /*
 1471  * Scale the scheduling priority according to the "interactivity" of this
 1472  * process.
 1473  */
 1474 static void
 1475 sched_priority(struct thread *td)
 1476 {
 1477         int score;
 1478         int pri;
 1479 
 1480         if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
 1481                 return;
 1482         /*
 1483          * If the score is interactive we place the thread in the realtime
 1484          * queue with a priority that is less than kernel and interrupt
 1485          * priorities.  These threads are not subject to nice restrictions.
 1486          *
 1487          * Scores greater than this are placed on the normal timeshare queue
 1488          * where the priority is partially decided by the most recent cpu
 1489          * utilization and the rest is decided by nice value.
 1490          *
 1491          * The nice value of the process has a linear effect on the calculated
 1492          * score.  Negative nice values make it easier for a thread to be
 1493          * considered interactive.
 1494          */
 1495         score = imax(0, sched_interact_score(td) + td->td_proc->p_nice);
 1496         if (score < sched_interact) {
 1497                 pri = PRI_MIN_INTERACT;
 1498                 pri += ((PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) /
 1499                     sched_interact) * score;
 1500                 KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT,
 1501                     ("sched_priority: invalid interactive priority %d score %d",
 1502                     pri, score));
 1503         } else {
 1504                 pri = SCHED_PRI_MIN;
 1505                 if (td->td_sched->ts_ticks)
 1506                         pri += min(SCHED_PRI_TICKS(td->td_sched),
 1507                             SCHED_PRI_RANGE - 1);
 1508                 pri += SCHED_PRI_NICE(td->td_proc->p_nice);
 1509                 KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH,
 1510                     ("sched_priority: invalid priority %d: nice %d, " 
 1511                     "ticks %d ftick %d ltick %d tick pri %d",
 1512                     pri, td->td_proc->p_nice, td->td_sched->ts_ticks,
 1513                     td->td_sched->ts_ftick, td->td_sched->ts_ltick,
 1514                     SCHED_PRI_TICKS(td->td_sched)));
 1515         }
 1516         sched_user_prio(td, pri);
 1517 
 1518         return;
 1519 }
 1520 
 1521 /*
 1522  * This routine enforces a maximum limit on the amount of scheduling history
 1523  * kept.  It is called after either the slptime or runtime is adjusted.  This
 1524  * function is ugly due to integer math.
 1525  */
 1526 static void
 1527 sched_interact_update(struct thread *td)
 1528 {
 1529         struct td_sched *ts;
 1530         u_int sum;
 1531 
 1532         ts = td->td_sched;
 1533         sum = ts->ts_runtime + ts->ts_slptime;
 1534         if (sum < SCHED_SLP_RUN_MAX)
 1535                 return;
 1536         /*
 1537          * This only happens from two places:
 1538          * 1) We have added an unusual amount of run time from fork_exit.
 1539          * 2) We have added an unusual amount of sleep time from sched_sleep().
 1540          */
 1541         if (sum > SCHED_SLP_RUN_MAX * 2) {
 1542                 if (ts->ts_runtime > ts->ts_slptime) {
 1543                         ts->ts_runtime = SCHED_SLP_RUN_MAX;
 1544                         ts->ts_slptime = 1;
 1545                 } else {
 1546                         ts->ts_slptime = SCHED_SLP_RUN_MAX;
 1547                         ts->ts_runtime = 1;
 1548                 }
 1549                 return;
 1550         }
 1551         /*
 1552          * If we have exceeded by more than 1/5th then the algorithm below
 1553          * will not bring us back into range.  Dividing by two here forces
 1554          * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX]
 1555          */
 1556         if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) {
 1557                 ts->ts_runtime /= 2;
 1558                 ts->ts_slptime /= 2;
 1559                 return;
 1560         }
 1561         ts->ts_runtime = (ts->ts_runtime / 5) * 4;
 1562         ts->ts_slptime = (ts->ts_slptime / 5) * 4;
 1563 }
 1564 
 1565 /*
 1566  * Scale back the interactivity history when a child thread is created.  The
 1567  * history is inherited from the parent but the thread may behave totally
 1568  * differently.  For example, a shell spawning a compiler process.  We want
 1569  * to learn that the compiler is behaving badly very quickly.
 1570  */
 1571 static void
 1572 sched_interact_fork(struct thread *td)
 1573 {
 1574         int ratio;
 1575         int sum;
 1576 
 1577         sum = td->td_sched->ts_runtime + td->td_sched->ts_slptime;
 1578         if (sum > SCHED_SLP_RUN_FORK) {
 1579                 ratio = sum / SCHED_SLP_RUN_FORK;
 1580                 td->td_sched->ts_runtime /= ratio;
 1581                 td->td_sched->ts_slptime /= ratio;
 1582         }
 1583 }
 1584 
 1585 /*
 1586  * Called from proc0_init() to setup the scheduler fields.
 1587  */
 1588 void
 1589 schedinit(void)
 1590 {
 1591 
 1592         /*
 1593          * Set up the scheduler specific parts of proc0.
 1594          */
 1595         proc0.p_sched = NULL; /* XXX */
 1596         thread0.td_sched = &td_sched0;
 1597         td_sched0.ts_ltick = ticks;
 1598         td_sched0.ts_ftick = ticks;
 1599         td_sched0.ts_slice = 0;
 1600 }
 1601 
 1602 /*
 1603  * This is only somewhat accurate since given many processes of the same
 1604  * priority they will switch when their slices run out, which will be
 1605  * at most sched_slice stathz ticks.
 1606  */
 1607 int
 1608 sched_rr_interval(void)
 1609 {
 1610 
 1611         /* Convert sched_slice from stathz to hz. */
 1612         return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz));
 1613 }
 1614 
 1615 /*
 1616  * Update the percent cpu tracking information when it is requested or
 1617  * the total history exceeds the maximum.  We keep a sliding history of
 1618  * tick counts that slowly decays.  This is less precise than the 4BSD
 1619  * mechanism since it happens with less regular and frequent events.
 1620  */
 1621 static void
 1622 sched_pctcpu_update(struct td_sched *ts, int run)
 1623 {
 1624         int t = ticks;
 1625 
 1626         if (t - ts->ts_ltick >= SCHED_TICK_TARG) {
 1627                 ts->ts_ticks = 0;
 1628                 ts->ts_ftick = t - SCHED_TICK_TARG;
 1629         } else if (t - ts->ts_ftick >= SCHED_TICK_MAX) {
 1630                 ts->ts_ticks = (ts->ts_ticks / (ts->ts_ltick - ts->ts_ftick)) *
 1631                     (ts->ts_ltick - (t - SCHED_TICK_TARG));
 1632                 ts->ts_ftick = t - SCHED_TICK_TARG;
 1633         }
 1634         if (run)
 1635                 ts->ts_ticks += (t - ts->ts_ltick) << SCHED_TICK_SHIFT;
 1636         ts->ts_ltick = t;
 1637 }
 1638 
 1639 /*
 1640  * Adjust the priority of a thread.  Move it to the appropriate run-queue
 1641  * if necessary.  This is the back-end for several priority related
 1642  * functions.
 1643  */
 1644 static void
 1645 sched_thread_priority(struct thread *td, u_char prio)
 1646 {
 1647         struct td_sched *ts;
 1648         struct tdq *tdq;
 1649         int oldpri;
 1650 
 1651         KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio",
 1652             "prio:%d", td->td_priority, "new prio:%d", prio,
 1653             KTR_ATTR_LINKED, sched_tdname(curthread));
 1654         SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio);
 1655         if (td != curthread && prio < td->td_priority) {
 1656                 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
 1657                     "lend prio", "prio:%d", td->td_priority, "new prio:%d",
 1658                     prio, KTR_ATTR_LINKED, sched_tdname(td));
 1659                 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio, 
 1660                     curthread);
 1661         } 
 1662         ts = td->td_sched;
 1663         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1664         if (td->td_priority == prio)
 1665                 return;
 1666         /*
 1667          * If the priority has been elevated due to priority
 1668          * propagation, we may have to move ourselves to a new
 1669          * queue.  This could be optimized to not re-add in some
 1670          * cases.
 1671          */
 1672         if (TD_ON_RUNQ(td) && prio < td->td_priority) {
 1673                 sched_rem(td);
 1674                 td->td_priority = prio;
 1675                 sched_add(td, SRQ_BORROWING);
 1676                 return;
 1677         }
 1678         /*
 1679          * If the thread is currently running we may have to adjust the lowpri
 1680          * information so other cpus are aware of our current priority.
 1681          */
 1682         if (TD_IS_RUNNING(td)) {
 1683                 tdq = TDQ_CPU(ts->ts_cpu);
 1684                 oldpri = td->td_priority;
 1685                 td->td_priority = prio;
 1686                 if (prio < tdq->tdq_lowpri)
 1687                         tdq->tdq_lowpri = prio;
 1688                 else if (tdq->tdq_lowpri == oldpri)
 1689                         tdq_setlowpri(tdq, td);
 1690                 return;
 1691         }
 1692         td->td_priority = prio;
 1693 }
 1694 
 1695 /*
 1696  * Update a thread's priority when it is lent another thread's
 1697  * priority.
 1698  */
 1699 void
 1700 sched_lend_prio(struct thread *td, u_char prio)
 1701 {
 1702 
 1703         td->td_flags |= TDF_BORROWING;
 1704         sched_thread_priority(td, prio);
 1705 }
 1706 
 1707 /*
 1708  * Restore a thread's priority when priority propagation is
 1709  * over.  The prio argument is the minimum priority the thread
 1710  * needs to have to satisfy other possible priority lending
 1711  * requests.  If the thread's regular priority is less
 1712  * important than prio, the thread will keep a priority boost
 1713  * of prio.
 1714  */
 1715 void
 1716 sched_unlend_prio(struct thread *td, u_char prio)
 1717 {
 1718         u_char base_pri;
 1719 
 1720         if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
 1721             td->td_base_pri <= PRI_MAX_TIMESHARE)
 1722                 base_pri = td->td_user_pri;
 1723         else
 1724                 base_pri = td->td_base_pri;
 1725         if (prio >= base_pri) {
 1726                 td->td_flags &= ~TDF_BORROWING;
 1727                 sched_thread_priority(td, base_pri);
 1728         } else
 1729                 sched_lend_prio(td, prio);
 1730 }
 1731 
 1732 /*
 1733  * Standard entry for setting the priority to an absolute value.
 1734  */
 1735 void
 1736 sched_prio(struct thread *td, u_char prio)
 1737 {
 1738         u_char oldprio;
 1739 
 1740         /* First, update the base priority. */
 1741         td->td_base_pri = prio;
 1742 
 1743         /*
 1744          * If the thread is borrowing another thread's priority, don't
 1745          * ever lower the priority.
 1746          */
 1747         if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
 1748                 return;
 1749 
 1750         /* Change the real priority. */
 1751         oldprio = td->td_priority;
 1752         sched_thread_priority(td, prio);
 1753 
 1754         /*
 1755          * If the thread is on a turnstile, then let the turnstile update
 1756          * its state.
 1757          */
 1758         if (TD_ON_LOCK(td) && oldprio != prio)
 1759                 turnstile_adjust(td, oldprio);
 1760 }
 1761 
 1762 /*
 1763  * Set the base user priority, does not effect current running priority.
 1764  */
 1765 void
 1766 sched_user_prio(struct thread *td, u_char prio)
 1767 {
 1768 
 1769         td->td_base_user_pri = prio;
 1770         if (td->td_lend_user_pri <= prio)
 1771                 return;
 1772         td->td_user_pri = prio;
 1773 }
 1774 
 1775 void
 1776 sched_lend_user_prio(struct thread *td, u_char prio)
 1777 {
 1778 
 1779         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1780         td->td_lend_user_pri = prio;
 1781         td->td_user_pri = min(prio, td->td_base_user_pri);
 1782         if (td->td_priority > td->td_user_pri)
 1783                 sched_prio(td, td->td_user_pri);
 1784         else if (td->td_priority != td->td_user_pri)
 1785                 td->td_flags |= TDF_NEEDRESCHED;
 1786 }
 1787 
 1788 /*
 1789  * Handle migration from sched_switch().  This happens only for
 1790  * cpu binding.
 1791  */
 1792 static struct mtx *
 1793 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags)
 1794 {
 1795         struct tdq *tdn;
 1796 
 1797         tdn = TDQ_CPU(td->td_sched->ts_cpu);
 1798 #ifdef SMP
 1799         tdq_load_rem(tdq, td);
 1800         /*
 1801          * Do the lock dance required to avoid LOR.  We grab an extra
 1802          * spinlock nesting to prevent preemption while we're
 1803          * not holding either run-queue lock.
 1804          */
 1805         spinlock_enter();
 1806         thread_lock_block(td);  /* This releases the lock on tdq. */
 1807 
 1808         /*
 1809          * Acquire both run-queue locks before placing the thread on the new
 1810          * run-queue to avoid deadlocks created by placing a thread with a
 1811          * blocked lock on the run-queue of a remote processor.  The deadlock
 1812          * occurs when a third processor attempts to lock the two queues in
 1813          * question while the target processor is spinning with its own
 1814          * run-queue lock held while waiting for the blocked lock to clear.
 1815          */
 1816         tdq_lock_pair(tdn, tdq);
 1817         tdq_add(tdn, td, flags);
 1818         tdq_notify(tdn, td);
 1819         TDQ_UNLOCK(tdn);
 1820         spinlock_exit();
 1821 #endif
 1822         return (TDQ_LOCKPTR(tdn));
 1823 }
 1824 
 1825 /*
 1826  * Variadic version of thread_lock_unblock() that does not assume td_lock
 1827  * is blocked.
 1828  */
 1829 static inline void
 1830 thread_unblock_switch(struct thread *td, struct mtx *mtx)
 1831 {
 1832         atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock,
 1833             (uintptr_t)mtx);
 1834 }
 1835 
 1836 /*
 1837  * Switch threads.  This function has to handle threads coming in while
 1838  * blocked for some reason, running, or idle.  It also must deal with
 1839  * migrating a thread from one queue to another as running threads may
 1840  * be assigned elsewhere via binding.
 1841  */
 1842 void
 1843 sched_switch(struct thread *td, struct thread *newtd, int flags)
 1844 {
 1845         struct tdq *tdq;
 1846         struct td_sched *ts;
 1847         struct mtx *mtx;
 1848         int srqflag;
 1849         int cpuid, preempted;
 1850 
 1851         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1852         KASSERT(newtd == NULL, ("sched_switch: Unsupported newtd argument"));
 1853 
 1854         cpuid = PCPU_GET(cpuid);
 1855         tdq = TDQ_CPU(cpuid);
 1856         ts = td->td_sched;
 1857         mtx = td->td_lock;
 1858         sched_pctcpu_update(ts, 1);
 1859         ts->ts_rltick = ticks;
 1860         td->td_lastcpu = td->td_oncpu;
 1861         td->td_oncpu = NOCPU;
 1862         preempted = !(td->td_flags & TDF_SLICEEND);
 1863         td->td_flags &= ~(TDF_NEEDRESCHED | TDF_SLICEEND);
 1864         td->td_owepreempt = 0;
 1865         if (!TD_IS_IDLETHREAD(td))
 1866                 tdq->tdq_switchcnt++;
 1867         /*
 1868          * The lock pointer in an idle thread should never change.  Reset it
 1869          * to CAN_RUN as well.
 1870          */
 1871         if (TD_IS_IDLETHREAD(td)) {
 1872                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1873                 TD_SET_CAN_RUN(td);
 1874         } else if (TD_IS_RUNNING(td)) {
 1875                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1876                 srqflag = preempted ?
 1877                     SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
 1878                     SRQ_OURSELF|SRQ_YIELDING;
 1879 #ifdef SMP
 1880                 if (THREAD_CAN_MIGRATE(td) && !THREAD_CAN_SCHED(td, ts->ts_cpu))
 1881                         ts->ts_cpu = sched_pickcpu(td, 0);
 1882 #endif
 1883                 if (ts->ts_cpu == cpuid)
 1884                         tdq_runq_add(tdq, td, srqflag);
 1885                 else {
 1886                         KASSERT(THREAD_CAN_MIGRATE(td) ||
 1887                             (ts->ts_flags & TSF_BOUND) != 0,
 1888                             ("Thread %p shouldn't migrate", td));
 1889                         mtx = sched_switch_migrate(tdq, td, srqflag);
 1890                 }
 1891         } else {
 1892                 /* This thread must be going to sleep. */
 1893                 TDQ_LOCK(tdq);
 1894                 mtx = thread_lock_block(td);
 1895                 tdq_load_rem(tdq, td);
 1896         }
 1897         /*
 1898          * We enter here with the thread blocked and assigned to the
 1899          * appropriate cpu run-queue or sleep-queue and with the current
 1900          * thread-queue locked.
 1901          */
 1902         TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
 1903         newtd = choosethread();
 1904         /*
 1905          * Call the MD code to switch contexts if necessary.
 1906          */
 1907         if (td != newtd) {
 1908 #ifdef  HWPMC_HOOKS
 1909                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 1910                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
 1911 #endif
 1912                 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc);
 1913                 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
 1914                 TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
 1915                 sched_pctcpu_update(newtd->td_sched, 0);
 1916 
 1917 #ifdef KDTRACE_HOOKS
 1918                 /*
 1919                  * If DTrace has set the active vtime enum to anything
 1920                  * other than INACTIVE (0), then it should have set the
 1921                  * function to call.
 1922                  */
 1923                 if (dtrace_vtime_active)
 1924                         (*dtrace_vtime_switch_func)(newtd);
 1925 #endif
 1926 
 1927                 cpu_switch(td, newtd, mtx);
 1928                 /*
 1929                  * We may return from cpu_switch on a different cpu.  However,
 1930                  * we always return with td_lock pointing to the current cpu's
 1931                  * run queue lock.
 1932                  */
 1933                 cpuid = PCPU_GET(cpuid);
 1934                 tdq = TDQ_CPU(cpuid);
 1935                 lock_profile_obtain_lock_success(
 1936                     &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
 1937 
 1938                 SDT_PROBE0(sched, , , on__cpu);
 1939 #ifdef  HWPMC_HOOKS
 1940                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 1941                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
 1942 #endif
 1943         } else {
 1944                 thread_unblock_switch(td, mtx);
 1945                 SDT_PROBE0(sched, , , remain__cpu);
 1946         }
 1947         /*
 1948          * Assert that all went well and return.
 1949          */
 1950         TDQ_LOCK_ASSERT(tdq, MA_OWNED|MA_NOTRECURSED);
 1951         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1952         td->td_oncpu = cpuid;
 1953 }
 1954 
 1955 /*
 1956  * Adjust thread priorities as a result of a nice request.
 1957  */
 1958 void
 1959 sched_nice(struct proc *p, int nice)
 1960 {
 1961         struct thread *td;
 1962 
 1963         PROC_LOCK_ASSERT(p, MA_OWNED);
 1964 
 1965         p->p_nice = nice;
 1966         FOREACH_THREAD_IN_PROC(p, td) {
 1967                 thread_lock(td);
 1968                 sched_priority(td);
 1969                 sched_prio(td, td->td_base_user_pri);
 1970                 thread_unlock(td);
 1971         }
 1972 }
 1973 
 1974 /*
 1975  * Record the sleep time for the interactivity scorer.
 1976  */
 1977 void
 1978 sched_sleep(struct thread *td, int prio)
 1979 {
 1980 
 1981         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1982 
 1983         td->td_slptick = ticks;
 1984         if (TD_IS_SUSPENDED(td) || prio >= PSOCK)
 1985                 td->td_flags |= TDF_CANSWAP;
 1986         if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
 1987                 return;
 1988         if (static_boost == 1 && prio)
 1989                 sched_prio(td, prio);
 1990         else if (static_boost && td->td_priority > static_boost)
 1991                 sched_prio(td, static_boost);
 1992 }
 1993 
 1994 /*
 1995  * Schedule a thread to resume execution and record how long it voluntarily
 1996  * slept.  We also update the pctcpu, interactivity, and priority.
 1997  */
 1998 void
 1999 sched_wakeup(struct thread *td)
 2000 {
 2001         struct td_sched *ts;
 2002         int slptick;
 2003 
 2004         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2005         ts = td->td_sched;
 2006         td->td_flags &= ~TDF_CANSWAP;
 2007         /*
 2008          * If we slept for more than a tick update our interactivity and
 2009          * priority.
 2010          */
 2011         slptick = td->td_slptick;
 2012         td->td_slptick = 0;
 2013         if (slptick && slptick != ticks) {
 2014                 ts->ts_slptime += (ticks - slptick) << SCHED_TICK_SHIFT;
 2015                 sched_interact_update(td);
 2016                 sched_pctcpu_update(ts, 0);
 2017         }
 2018         /*
 2019          * Reset the slice value since we slept and advanced the round-robin.
 2020          */
 2021         ts->ts_slice = 0;
 2022         sched_add(td, SRQ_BORING);
 2023 }
 2024 
 2025 /*
 2026  * Penalize the parent for creating a new child and initialize the child's
 2027  * priority.
 2028  */
 2029 void
 2030 sched_fork(struct thread *td, struct thread *child)
 2031 {
 2032         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2033         sched_pctcpu_update(td->td_sched, 1);
 2034         sched_fork_thread(td, child);
 2035         /*
 2036          * Penalize the parent and child for forking.
 2037          */
 2038         sched_interact_fork(child);
 2039         sched_priority(child);
 2040         td->td_sched->ts_runtime += tickincr;
 2041         sched_interact_update(td);
 2042         sched_priority(td);
 2043 }
 2044 
 2045 /*
 2046  * Fork a new thread, may be within the same process.
 2047  */
 2048 void
 2049 sched_fork_thread(struct thread *td, struct thread *child)
 2050 {
 2051         struct td_sched *ts;
 2052         struct td_sched *ts2;
 2053         struct tdq *tdq;
 2054 
 2055         tdq = TDQ_SELF();
 2056         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2057         /*
 2058          * Initialize child.
 2059          */
 2060         ts = td->td_sched;
 2061         ts2 = child->td_sched;
 2062         child->td_lock = TDQ_LOCKPTR(tdq);
 2063         child->td_cpuset = cpuset_ref(td->td_cpuset);
 2064         ts2->ts_cpu = ts->ts_cpu;
 2065         ts2->ts_flags = 0;
 2066         /*
 2067          * Grab our parents cpu estimation information.
 2068          */
 2069         ts2->ts_ticks = ts->ts_ticks;
 2070         ts2->ts_ltick = ts->ts_ltick;
 2071         ts2->ts_ftick = ts->ts_ftick;
 2072         /*
 2073          * Do not inherit any borrowed priority from the parent.
 2074          */
 2075         child->td_priority = child->td_base_pri;
 2076         /*
 2077          * And update interactivity score.
 2078          */
 2079         ts2->ts_slptime = ts->ts_slptime;
 2080         ts2->ts_runtime = ts->ts_runtime;
 2081         /* Attempt to quickly learn interactivity. */
 2082         ts2->ts_slice = tdq_slice(tdq) - sched_slice_min;
 2083 #ifdef KTR
 2084         bzero(ts2->ts_name, sizeof(ts2->ts_name));
 2085 #endif
 2086 }
 2087 
 2088 /*
 2089  * Adjust the priority class of a thread.
 2090  */
 2091 void
 2092 sched_class(struct thread *td, int class)
 2093 {
 2094 
 2095         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2096         if (td->td_pri_class == class)
 2097                 return;
 2098         td->td_pri_class = class;
 2099 }
 2100 
 2101 /*
 2102  * Return some of the child's priority and interactivity to the parent.
 2103  */
 2104 void
 2105 sched_exit(struct proc *p, struct thread *child)
 2106 {
 2107         struct thread *td;
 2108 
 2109         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit",
 2110             "prio:%d", child->td_priority);
 2111         PROC_LOCK_ASSERT(p, MA_OWNED);
 2112         td = FIRST_THREAD_IN_PROC(p);
 2113         sched_exit_thread(td, child);
 2114 }
 2115 
 2116 /*
 2117  * Penalize another thread for the time spent on this one.  This helps to
 2118  * worsen the priority and interactivity of processes which schedule batch
 2119  * jobs such as make.  This has little effect on the make process itself but
 2120  * causes new processes spawned by it to receive worse scores immediately.
 2121  */
 2122 void
 2123 sched_exit_thread(struct thread *td, struct thread *child)
 2124 {
 2125 
 2126         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit",
 2127             "prio:%d", child->td_priority);
 2128         /*
 2129          * Give the child's runtime to the parent without returning the
 2130          * sleep time as a penalty to the parent.  This causes shells that
 2131          * launch expensive things to mark their children as expensive.
 2132          */
 2133         thread_lock(td);
 2134         td->td_sched->ts_runtime += child->td_sched->ts_runtime;
 2135         sched_interact_update(td);
 2136         sched_priority(td);
 2137         thread_unlock(td);
 2138 }
 2139 
 2140 void
 2141 sched_preempt(struct thread *td)
 2142 {
 2143         struct tdq *tdq;
 2144 
 2145         SDT_PROBE2(sched, , , surrender, td, td->td_proc);
 2146 
 2147         thread_lock(td);
 2148         tdq = TDQ_SELF();
 2149         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2150         tdq->tdq_ipipending = 0;
 2151         if (td->td_priority > tdq->tdq_lowpri) {
 2152                 int flags;
 2153 
 2154                 flags = SW_INVOL | SW_PREEMPT;
 2155                 if (td->td_critnest > 1)
 2156                         td->td_owepreempt = 1;
 2157                 else if (TD_IS_IDLETHREAD(td))
 2158                         mi_switch(flags | SWT_REMOTEWAKEIDLE, NULL);
 2159                 else
 2160                         mi_switch(flags | SWT_REMOTEPREEMPT, NULL);
 2161         }
 2162         thread_unlock(td);
 2163 }
 2164 
 2165 /*
 2166  * Fix priorities on return to user-space.  Priorities may be elevated due
 2167  * to static priorities in msleep() or similar.
 2168  */
 2169 void
 2170 sched_userret(struct thread *td)
 2171 {
 2172         /*
 2173          * XXX we cheat slightly on the locking here to avoid locking in  
 2174          * the usual case.  Setting td_priority here is essentially an
 2175          * incomplete workaround for not setting it properly elsewhere.
 2176          * Now that some interrupt handlers are threads, not setting it
 2177          * properly elsewhere can clobber it in the window between setting
 2178          * it here and returning to user mode, so don't waste time setting
 2179          * it perfectly here.
 2180          */
 2181         KASSERT((td->td_flags & TDF_BORROWING) == 0,
 2182             ("thread with borrowed priority returning to userland"));
 2183         if (td->td_priority != td->td_user_pri) {
 2184                 thread_lock(td);
 2185                 td->td_priority = td->td_user_pri;
 2186                 td->td_base_pri = td->td_user_pri;
 2187                 tdq_setlowpri(TDQ_SELF(), td);
 2188                 thread_unlock(td);
 2189         }
 2190 }
 2191 
 2192 /*
 2193  * Handle a stathz tick.  This is really only relevant for timeshare
 2194  * threads.
 2195  */
 2196 void
 2197 sched_clock(struct thread *td)
 2198 {
 2199         struct tdq *tdq;
 2200         struct td_sched *ts;
 2201 
 2202         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2203         tdq = TDQ_SELF();
 2204 #ifdef SMP
 2205         /*
 2206          * We run the long term load balancer infrequently on the first cpu.
 2207          */
 2208         if (balance_tdq == tdq) {
 2209                 if (balance_ticks && --balance_ticks == 0)
 2210                         sched_balance();
 2211         }
 2212 #endif
 2213         /*
 2214          * Save the old switch count so we have a record of the last ticks
 2215          * activity.   Initialize the new switch count based on our load.
 2216          * If there is some activity seed it to reflect that.
 2217          */
 2218         tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt;
 2219         tdq->tdq_switchcnt = tdq->tdq_load;
 2220         /*
 2221          * Advance the insert index once for each tick to ensure that all
 2222          * threads get a chance to run.
 2223          */
 2224         if (tdq->tdq_idx == tdq->tdq_ridx) {
 2225                 tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS;
 2226                 if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx]))
 2227                         tdq->tdq_ridx = tdq->tdq_idx;
 2228         }
 2229         ts = td->td_sched;
 2230         sched_pctcpu_update(ts, 1);
 2231         if (td->td_pri_class & PRI_FIFO_BIT)
 2232                 return;
 2233         if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) {
 2234                 /*
 2235                  * We used a tick; charge it to the thread so
 2236                  * that we can compute our interactivity.
 2237                  */
 2238                 td->td_sched->ts_runtime += tickincr;
 2239                 sched_interact_update(td);
 2240                 sched_priority(td);
 2241         }
 2242 
 2243         /*
 2244          * Force a context switch if the current thread has used up a full
 2245          * time slice (default is 100ms).
 2246          */
 2247         if (!TD_IS_IDLETHREAD(td) && ++ts->ts_slice >= tdq_slice(tdq)) {
 2248                 ts->ts_slice = 0;
 2249                 td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND;
 2250         }
 2251 }
 2252 
 2253 /*
 2254  * Called once per hz tick.
 2255  */
 2256 void
 2257 sched_tick(int cnt)
 2258 {
 2259 
 2260 }
 2261 
 2262 /*
 2263  * Return whether the current CPU has runnable tasks.  Used for in-kernel
 2264  * cooperative idle threads.
 2265  */
 2266 int
 2267 sched_runnable(void)
 2268 {
 2269         struct tdq *tdq;
 2270         int load;
 2271 
 2272         load = 1;
 2273 
 2274         tdq = TDQ_SELF();
 2275         if ((curthread->td_flags & TDF_IDLETD) != 0) {
 2276                 if (tdq->tdq_load > 0)
 2277                         goto out;
 2278         } else
 2279                 if (tdq->tdq_load - 1 > 0)
 2280                         goto out;
 2281         load = 0;
 2282 out:
 2283         return (load);
 2284 }
 2285 
 2286 /*
 2287  * Choose the highest priority thread to run.  The thread is removed from
 2288  * the run-queue while running however the load remains.  For SMP we set
 2289  * the tdq in the global idle bitmask if it idles here.
 2290  */
 2291 struct thread *
 2292 sched_choose(void)
 2293 {
 2294         struct thread *td;
 2295         struct tdq *tdq;
 2296 
 2297         tdq = TDQ_SELF();
 2298         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2299         td = tdq_choose(tdq);
 2300         if (td) {
 2301                 tdq_runq_rem(tdq, td);
 2302                 tdq->tdq_lowpri = td->td_priority;
 2303                 return (td);
 2304         }
 2305         tdq->tdq_lowpri = PRI_MAX_IDLE;
 2306         return (PCPU_GET(idlethread));
 2307 }
 2308 
 2309 /*
 2310  * Set owepreempt if necessary.  Preemption never happens directly in ULE,
 2311  * we always request it once we exit a critical section.
 2312  */
 2313 static inline void
 2314 sched_setpreempt(struct thread *td)
 2315 {
 2316         struct thread *ctd;
 2317         int cpri;
 2318         int pri;
 2319 
 2320         THREAD_LOCK_ASSERT(curthread, MA_OWNED);
 2321 
 2322         ctd = curthread;
 2323         pri = td->td_priority;
 2324         cpri = ctd->td_priority;
 2325         if (pri < cpri)
 2326                 ctd->td_flags |= TDF_NEEDRESCHED;
 2327         if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
 2328                 return;
 2329         if (!sched_shouldpreempt(pri, cpri, 0))
 2330                 return;
 2331         ctd->td_owepreempt = 1;
 2332 }
 2333 
 2334 /*
 2335  * Add a thread to a thread queue.  Select the appropriate runq and add the
 2336  * thread to it.  This is the internal function called when the tdq is
 2337  * predetermined.
 2338  */
 2339 void
 2340 tdq_add(struct tdq *tdq, struct thread *td, int flags)
 2341 {
 2342 
 2343         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2344         KASSERT((td->td_inhibitors == 0),
 2345             ("sched_add: trying to run inhibited thread"));
 2346         KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
 2347             ("sched_add: bad thread state"));
 2348         KASSERT(td->td_flags & TDF_INMEM,
 2349             ("sched_add: thread swapped out"));
 2350 
 2351         if (td->td_priority < tdq->tdq_lowpri)
 2352                 tdq->tdq_lowpri = td->td_priority;
 2353         tdq_runq_add(tdq, td, flags);
 2354         tdq_load_add(tdq, td);
 2355 }
 2356 
 2357 /*
 2358  * Select the target thread queue and add a thread to it.  Request
 2359  * preemption or IPI a remote processor if required.
 2360  */
 2361 void
 2362 sched_add(struct thread *td, int flags)
 2363 {
 2364         struct tdq *tdq;
 2365 #ifdef SMP
 2366         int cpu;
 2367 #endif
 2368 
 2369         KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
 2370             "prio:%d", td->td_priority, KTR_ATTR_LINKED,
 2371             sched_tdname(curthread));
 2372         KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
 2373             KTR_ATTR_LINKED, sched_tdname(td));
 2374         SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL, 
 2375             flags & SRQ_PREEMPTED);
 2376         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2377         /*
 2378          * Recalculate the priority before we select the target cpu or
 2379          * run-queue.
 2380          */
 2381         if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
 2382                 sched_priority(td);
 2383 #ifdef SMP
 2384         /*
 2385          * Pick the destination cpu and if it isn't ours transfer to the
 2386          * target cpu.
 2387          */
 2388         cpu = sched_pickcpu(td, flags);
 2389         tdq = sched_setcpu(td, cpu, flags);
 2390         tdq_add(tdq, td, flags);
 2391         if (cpu != PCPU_GET(cpuid)) {
 2392                 tdq_notify(tdq, td);
 2393                 return;
 2394         }
 2395 #else
 2396         tdq = TDQ_SELF();
 2397         TDQ_LOCK(tdq);
 2398         /*
 2399          * Now that the thread is moving to the run-queue, set the lock
 2400          * to the scheduler's lock.
 2401          */
 2402         thread_lock_set(td, TDQ_LOCKPTR(tdq));
 2403         tdq_add(tdq, td, flags);
 2404 #endif
 2405         if (!(flags & SRQ_YIELDING))
 2406                 sched_setpreempt(td);
 2407 }
 2408 
 2409 /*
 2410  * Remove a thread from a run-queue without running it.  This is used
 2411  * when we're stealing a thread from a remote queue.  Otherwise all threads
 2412  * exit by calling sched_exit_thread() and sched_throw() themselves.
 2413  */
 2414 void
 2415 sched_rem(struct thread *td)
 2416 {
 2417         struct tdq *tdq;
 2418 
 2419         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
 2420             "prio:%d", td->td_priority);
 2421         SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL);
 2422         tdq = TDQ_CPU(td->td_sched->ts_cpu);
 2423         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2424         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2425         KASSERT(TD_ON_RUNQ(td),
 2426             ("sched_rem: thread not on run queue"));
 2427         tdq_runq_rem(tdq, td);
 2428         tdq_load_rem(tdq, td);
 2429         TD_SET_CAN_RUN(td);
 2430         if (td->td_priority == tdq->tdq_lowpri)
 2431                 tdq_setlowpri(tdq, NULL);
 2432 }
 2433 
 2434 /*
 2435  * Fetch cpu utilization information.  Updates on demand.
 2436  */
 2437 fixpt_t
 2438 sched_pctcpu(struct thread *td)
 2439 {
 2440         fixpt_t pctcpu;
 2441         struct td_sched *ts;
 2442 
 2443         pctcpu = 0;
 2444         ts = td->td_sched;
 2445         if (ts == NULL)
 2446                 return (0);
 2447 
 2448         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2449         sched_pctcpu_update(ts, TD_IS_RUNNING(td));
 2450         if (ts->ts_ticks) {
 2451                 int rtick;
 2452 
 2453                 /* How many rtick per second ? */
 2454                 rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
 2455                 pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
 2456         }
 2457 
 2458         return (pctcpu);
 2459 }
 2460 
 2461 /*
 2462  * Enforce affinity settings for a thread.  Called after adjustments to
 2463  * cpumask.
 2464  */
 2465 void
 2466 sched_affinity(struct thread *td)
 2467 {
 2468 #ifdef SMP
 2469         struct td_sched *ts;
 2470 
 2471         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2472         ts = td->td_sched;
 2473         if (THREAD_CAN_SCHED(td, ts->ts_cpu))
 2474                 return;
 2475         if (TD_ON_RUNQ(td)) {
 2476                 sched_rem(td);
 2477                 sched_add(td, SRQ_BORING);
 2478                 return;
 2479         }
 2480         if (!TD_IS_RUNNING(td))
 2481                 return;
 2482         /*
 2483          * Force a switch before returning to userspace.  If the
 2484          * target thread is not running locally send an ipi to force
 2485          * the issue.
 2486          */
 2487         td->td_flags |= TDF_NEEDRESCHED;
 2488         if (td != curthread)
 2489                 ipi_cpu(ts->ts_cpu, IPI_PREEMPT);
 2490 #endif
 2491 }
 2492 
 2493 /*
 2494  * Bind a thread to a target cpu.
 2495  */
 2496 void
 2497 sched_bind(struct thread *td, int cpu)
 2498 {
 2499         struct td_sched *ts;
 2500 
 2501         THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
 2502         KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
 2503         ts = td->td_sched;
 2504         if (ts->ts_flags & TSF_BOUND)
 2505                 sched_unbind(td);
 2506         KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td));
 2507         ts->ts_flags |= TSF_BOUND;
 2508         sched_pin();
 2509         if (PCPU_GET(cpuid) == cpu)
 2510                 return;
 2511         ts->ts_cpu = cpu;
 2512         /* When we return from mi_switch we'll be on the correct cpu. */
 2513         mi_switch(SW_VOL, NULL);
 2514 }
 2515 
 2516 /*
 2517  * Release a bound thread.
 2518  */
 2519 void
 2520 sched_unbind(struct thread *td)
 2521 {
 2522         struct td_sched *ts;
 2523 
 2524         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2525         KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
 2526         ts = td->td_sched;
 2527         if ((ts->ts_flags & TSF_BOUND) == 0)
 2528                 return;
 2529         ts->ts_flags &= ~TSF_BOUND;
 2530         sched_unpin();
 2531 }
 2532 
 2533 int
 2534 sched_is_bound(struct thread *td)
 2535 {
 2536         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2537         return (td->td_sched->ts_flags & TSF_BOUND);
 2538 }
 2539 
 2540 /*
 2541  * Basic yield call.
 2542  */
 2543 void
 2544 sched_relinquish(struct thread *td)
 2545 {
 2546         thread_lock(td);
 2547         mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
 2548         thread_unlock(td);
 2549 }
 2550 
 2551 /*
 2552  * Return the total system load.
 2553  */
 2554 int
 2555 sched_load(void)
 2556 {
 2557 #ifdef SMP
 2558         int total;
 2559         int i;
 2560 
 2561         total = 0;
 2562         CPU_FOREACH(i)
 2563                 total += TDQ_CPU(i)->tdq_sysload;
 2564         return (total);
 2565 #else
 2566         return (TDQ_SELF()->tdq_sysload);
 2567 #endif
 2568 }
 2569 
 2570 int
 2571 sched_sizeof_proc(void)
 2572 {
 2573         return (sizeof(struct proc));
 2574 }
 2575 
 2576 int
 2577 sched_sizeof_thread(void)
 2578 {
 2579         return (sizeof(struct thread) + sizeof(struct td_sched));
 2580 }
 2581 
 2582 #ifdef SMP
 2583 #define TDQ_IDLESPIN(tdq)                                               \
 2584     ((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0)
 2585 #else
 2586 #define TDQ_IDLESPIN(tdq)       1
 2587 #endif
 2588 
 2589 /*
 2590  * The actual idle process.
 2591  */
 2592 void
 2593 sched_idletd(void *dummy)
 2594 {
 2595         struct thread *td;
 2596         struct tdq *tdq;
 2597         int oldswitchcnt, switchcnt;
 2598         int i;
 2599 
 2600         mtx_assert(&Giant, MA_NOTOWNED);
 2601         td = curthread;
 2602         tdq = TDQ_SELF();
 2603         THREAD_NO_SLEEPING();
 2604         oldswitchcnt = -1;
 2605         for (;;) {
 2606                 if (tdq->tdq_load) {
 2607                         thread_lock(td);
 2608                         mi_switch(SW_VOL | SWT_IDLE, NULL);
 2609                         thread_unlock(td);
 2610                 }
 2611                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2612 #ifdef SMP
 2613                 if (switchcnt != oldswitchcnt) {
 2614                         oldswitchcnt = switchcnt;
 2615                         if (tdq_idled(tdq) == 0)
 2616                                 continue;
 2617                 }
 2618                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2619 #else
 2620                 oldswitchcnt = switchcnt;
 2621 #endif
 2622                 /*
 2623                  * If we're switching very frequently, spin while checking
 2624                  * for load rather than entering a low power state that 
 2625                  * may require an IPI.  However, don't do any busy
 2626                  * loops while on SMT machines as this simply steals
 2627                  * cycles from cores doing useful work.
 2628                  */
 2629                 if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) {
 2630                         for (i = 0; i < sched_idlespins; i++) {
 2631                                 if (tdq->tdq_load)
 2632                                         break;
 2633                                 cpu_spinwait();
 2634                         }
 2635                 }
 2636 
 2637                 /* If there was context switch during spin, restart it. */
 2638                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2639                 if (tdq->tdq_load != 0 || switchcnt != oldswitchcnt)
 2640                         continue;
 2641 
 2642                 /* Run main MD idle handler. */
 2643                 tdq->tdq_cpu_idle = 1;
 2644                 cpu_idle(switchcnt * 4 > sched_idlespinthresh);
 2645                 tdq->tdq_cpu_idle = 0;
 2646 
 2647                 /*
 2648                  * Account thread-less hardware interrupts and
 2649                  * other wakeup reasons equal to context switches.
 2650                  */
 2651                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2652                 if (switchcnt != oldswitchcnt)
 2653                         continue;
 2654                 tdq->tdq_switchcnt++;
 2655                 oldswitchcnt++;
 2656         }
 2657 }
 2658 
 2659 /*
 2660  * A CPU is entering for the first time or a thread is exiting.
 2661  */
 2662 void
 2663 sched_throw(struct thread *td)
 2664 {
 2665         struct thread *newtd;
 2666         struct tdq *tdq;
 2667 
 2668         tdq = TDQ_SELF();
 2669         if (td == NULL) {
 2670                 /* Correct spinlock nesting and acquire the correct lock. */
 2671                 TDQ_LOCK(tdq);
 2672                 spinlock_exit();
 2673                 PCPU_SET(switchtime, cpu_ticks());
 2674                 PCPU_SET(switchticks, ticks);
 2675         } else {
 2676                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2677                 tdq_load_rem(tdq, td);
 2678                 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
 2679         }
 2680         KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
 2681         newtd = choosethread();
 2682         TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
 2683         cpu_throw(td, newtd);           /* doesn't return */
 2684 }
 2685 
 2686 /*
 2687  * This is called from fork_exit().  Just acquire the correct locks and
 2688  * let fork do the rest of the work.
 2689  */
 2690 void
 2691 sched_fork_exit(struct thread *td)
 2692 {
 2693         struct td_sched *ts;
 2694         struct tdq *tdq;
 2695         int cpuid;
 2696 
 2697         /*
 2698          * Finish setting up thread glue so that it begins execution in a
 2699          * non-nested critical section with the scheduler lock held.
 2700          */
 2701         cpuid = PCPU_GET(cpuid);
 2702         tdq = TDQ_CPU(cpuid);
 2703         ts = td->td_sched;
 2704         if (TD_IS_IDLETHREAD(td))
 2705                 td->td_lock = TDQ_LOCKPTR(tdq);
 2706         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2707         td->td_oncpu = cpuid;
 2708         TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
 2709         lock_profile_obtain_lock_success(
 2710             &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
 2711 }
 2712 
 2713 /*
 2714  * Create on first use to catch odd startup conditons.
 2715  */
 2716 char *
 2717 sched_tdname(struct thread *td)
 2718 {
 2719 #ifdef KTR
 2720         struct td_sched *ts;
 2721 
 2722         ts = td->td_sched;
 2723         if (ts->ts_name[0] == '\0')
 2724                 snprintf(ts->ts_name, sizeof(ts->ts_name),
 2725                     "%s tid %d", td->td_name, td->td_tid);
 2726         return (ts->ts_name);
 2727 #else
 2728         return (td->td_name);
 2729 #endif
 2730 }
 2731 
 2732 #ifdef KTR
 2733 void
 2734 sched_clear_tdname(struct thread *td)
 2735 {
 2736         struct td_sched *ts;
 2737 
 2738         ts = td->td_sched;
 2739         ts->ts_name[0] = '\0';
 2740 }
 2741 #endif
 2742 
 2743 #ifdef SMP
 2744 
 2745 /*
 2746  * Build the CPU topology dump string. Is recursively called to collect
 2747  * the topology tree.
 2748  */
 2749 static int
 2750 sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg,
 2751     int indent)
 2752 {
 2753         char cpusetbuf[CPUSETBUFSIZ];
 2754         int i, first;
 2755 
 2756         sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent,
 2757             "", 1 + indent / 2, cg->cg_level);
 2758         sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"%s\">", indent, "",
 2759             cg->cg_count, cpusetobj_strprint(cpusetbuf, &cg->cg_mask));
 2760         first = TRUE;
 2761         for (i = 0; i < MAXCPU; i++) {
 2762                 if (CPU_ISSET(i, &cg->cg_mask)) {
 2763                         if (!first)
 2764                                 sbuf_printf(sb, ", ");
 2765                         else
 2766                                 first = FALSE;
 2767                         sbuf_printf(sb, "%d", i);
 2768                 }
 2769         }
 2770         sbuf_printf(sb, "</cpu>\n");
 2771 
 2772         if (cg->cg_flags != 0) {
 2773                 sbuf_printf(sb, "%*s <flags>", indent, "");
 2774                 if ((cg->cg_flags & CG_FLAG_HTT) != 0)
 2775                         sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>");
 2776                 if ((cg->cg_flags & CG_FLAG_THREAD) != 0)
 2777                         sbuf_printf(sb, "<flag name=\"THREAD\">THREAD group</flag>");
 2778                 if ((cg->cg_flags & CG_FLAG_SMT) != 0)
 2779                         sbuf_printf(sb, "<flag name=\"SMT\">SMT group</flag>");
 2780                 sbuf_printf(sb, "</flags>\n");
 2781         }
 2782 
 2783         if (cg->cg_children > 0) {
 2784                 sbuf_printf(sb, "%*s <children>\n", indent, "");
 2785                 for (i = 0; i < cg->cg_children; i++)
 2786                         sysctl_kern_sched_topology_spec_internal(sb, 
 2787                             &cg->cg_child[i], indent+2);
 2788                 sbuf_printf(sb, "%*s </children>\n", indent, "");
 2789         }
 2790         sbuf_printf(sb, "%*s</group>\n", indent, "");
 2791         return (0);
 2792 }
 2793 
 2794 /*
 2795  * Sysctl handler for retrieving topology dump. It's a wrapper for
 2796  * the recursive sysctl_kern_smp_topology_spec_internal().
 2797  */
 2798 static int
 2799 sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS)
 2800 {
 2801         struct sbuf *topo;
 2802         int err;
 2803 
 2804         KASSERT(cpu_top != NULL, ("cpu_top isn't initialized"));
 2805 
 2806         topo = sbuf_new(NULL, NULL, 500, SBUF_AUTOEXTEND);
 2807         if (topo == NULL)
 2808                 return (ENOMEM);
 2809 
 2810         sbuf_printf(topo, "<groups>\n");
 2811         err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1);
 2812         sbuf_printf(topo, "</groups>\n");
 2813 
 2814         if (err == 0) {
 2815                 sbuf_finish(topo);
 2816                 err = SYSCTL_OUT(req, sbuf_data(topo), sbuf_len(topo));
 2817         }
 2818         sbuf_delete(topo);
 2819         return (err);
 2820 }
 2821 
 2822 #endif
 2823 
 2824 static int
 2825 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
 2826 {
 2827         int error, new_val, period;
 2828 
 2829         period = 1000000 / realstathz;
 2830         new_val = period * sched_slice;
 2831         error = sysctl_handle_int(oidp, &new_val, 0, req);
 2832         if (error != 0 || req->newptr == NULL)
 2833                 return (error);
 2834         if (new_val <= 0)
 2835                 return (EINVAL);
 2836         sched_slice = imax(1, (new_val + period / 2) / period);
 2837         sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
 2838         hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
 2839             realstathz);
 2840         return (0);
 2841 }
 2842 
 2843 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW, 0, "Scheduler");
 2844 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0,
 2845     "Scheduler name");
 2846 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW,
 2847     NULL, 0, sysctl_kern_quantum, "I",
 2848     "Quantum for timeshare threads in microseconds");
 2849 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
 2850     "Quantum for timeshare threads in stathz ticks");
 2851 SYSCTL_INT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0,
 2852     "Interactivity score threshold");
 2853 SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW,
 2854     &preempt_thresh, 0,
 2855     "Maximal (lowest) priority for preemption");
 2856 SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost, 0,
 2857     "Assign static kernel priorities to sleeping threads");
 2858 SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins, 0,
 2859     "Number of times idle thread will spin waiting for new work");
 2860 SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW,
 2861     &sched_idlespinthresh, 0,
 2862     "Threshold before we will permit idle thread spinning");
 2863 #ifdef SMP
 2864 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0,
 2865     "Number of hz ticks to keep thread affinity for");
 2866 SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0,
 2867     "Enables the long-term load balancer");
 2868 SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW,
 2869     &balance_interval, 0,
 2870     "Average period in stathz ticks to run the long-term balancer");
 2871 SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0,
 2872     "Attempts to steal work from other cores before idling");
 2873 SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0,
 2874     "Minimum load on remote CPU before we'll steal");
 2875 SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING |
 2876     CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A",
 2877     "XML dump of detected CPU topology");
 2878 #endif
 2879 
 2880 /* ps compat.  All cpu percentages from ULE are weighted. */
 2881 static int ccpu = 0;
 2882 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");

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