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


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

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    1 /*-
    2  * 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 285353 2015-07-10 08:54:12Z kib $");
   40 
   41 #include "opt_hwpmc_hooks.h"
   42 #include "opt_sched.h"
   43 
   44 #include <sys/param.h>
   45 #include <sys/systm.h>
   46 #include <sys/kdb.h>
   47 #include <sys/kernel.h>
   48 #include <sys/ktr.h>
   49 #include <sys/limits.h>
   50 #include <sys/lock.h>
   51 #include <sys/mutex.h>
   52 #include <sys/proc.h>
   53 #include <sys/resource.h>
   54 #include <sys/resourcevar.h>
   55 #include <sys/sched.h>
   56 #include <sys/sdt.h>
   57 #include <sys/smp.h>
   58 #include <sys/sx.h>
   59 #include <sys/sysctl.h>
   60 #include <sys/sysproto.h>
   61 #include <sys/turnstile.h>
   62 #include <sys/umtx.h>
   63 #include <sys/vmmeter.h>
   64 #include <sys/cpuset.h>
   65 #include <sys/sbuf.h>
   66 
   67 #ifdef HWPMC_HOOKS
   68 #include <sys/pmckern.h>
   69 #endif
   70 
   71 #ifdef KDTRACE_HOOKS
   72 #include <sys/dtrace_bsd.h>
   73 int                             dtrace_vtime_active;
   74 dtrace_vtime_switch_func_t      dtrace_vtime_switch_func;
   75 #endif
   76 
   77 #include <machine/cpu.h>
   78 #include <machine/smp.h>
   79 
   80 #define KTR_ULE 0
   81 
   82 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
   83 #define TDQ_NAME_LEN    (sizeof("sched lock ") + sizeof(__XSTRING(MAXCPU)))
   84 #define TDQ_LOADNAME_LEN        (sizeof("CPU ") + sizeof(__XSTRING(MAXCPU)) - 1 + sizeof(" load"))
   85 
   86 /*
   87  * Thread scheduler specific section.  All fields are protected
   88  * by the thread lock.
   89  */
   90 struct td_sched {       
   91         struct runq     *ts_runq;       /* Run-queue we're queued on. */
   92         short           ts_flags;       /* TSF_* flags. */
   93         int             ts_cpu;         /* CPU that we have affinity for. */
   94         int             ts_rltick;      /* Real last tick, for affinity. */
   95         int             ts_slice;       /* Ticks of slice remaining. */
   96         u_int           ts_slptime;     /* Number of ticks we vol. slept */
   97         u_int           ts_runtime;     /* Number of ticks we were running */
   98         int             ts_ltick;       /* Last tick that we were running on */
   99         int             ts_ftick;       /* First tick that we were running on */
  100         int             ts_ticks;       /* Tick count */
  101 #ifdef KTR
  102         char            ts_name[TS_NAME_LEN];
  103 #endif
  104 };
  105 /* flags kept in ts_flags */
  106 #define TSF_BOUND       0x0001          /* Thread can not migrate. */
  107 #define TSF_XFERABLE    0x0002          /* Thread was added as transferable. */
  108 
  109 static struct td_sched td_sched0;
  110 
  111 #define THREAD_CAN_MIGRATE(td)  ((td)->td_pinned == 0)
  112 #define THREAD_CAN_SCHED(td, cpu)       \
  113     CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
  114 
  115 /*
  116  * Priority ranges used for interactive and non-interactive timeshare
  117  * threads.  The timeshare priorities are split up into four ranges.
  118  * The first range handles interactive threads.  The last three ranges
  119  * (NHALF, x, and NHALF) handle non-interactive threads with the outer
  120  * ranges supporting nice values.
  121  */
  122 #define PRI_TIMESHARE_RANGE     (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE + 1)
  123 #define PRI_INTERACT_RANGE      ((PRI_TIMESHARE_RANGE - SCHED_PRI_NRESV) / 2)
  124 #define PRI_BATCH_RANGE         (PRI_TIMESHARE_RANGE - PRI_INTERACT_RANGE)
  125 
  126 #define PRI_MIN_INTERACT        PRI_MIN_TIMESHARE
  127 #define PRI_MAX_INTERACT        (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE - 1)
  128 #define PRI_MIN_BATCH           (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE)
  129 #define PRI_MAX_BATCH           PRI_MAX_TIMESHARE
  130 
  131 /*
  132  * Cpu percentage computation macros and defines.
  133  *
  134  * SCHED_TICK_SECS:     Number of seconds to average the cpu usage across.
  135  * SCHED_TICK_TARG:     Number of hz ticks to average the cpu usage across.
  136  * SCHED_TICK_MAX:      Maximum number of ticks before scaling back.
  137  * SCHED_TICK_SHIFT:    Shift factor to avoid rounding away results.
  138  * SCHED_TICK_HZ:       Compute the number of hz ticks for a given ticks count.
  139  * SCHED_TICK_TOTAL:    Gives the amount of time we've been recording ticks.
  140  */
  141 #define SCHED_TICK_SECS         10
  142 #define SCHED_TICK_TARG         (hz * SCHED_TICK_SECS)
  143 #define SCHED_TICK_MAX          (SCHED_TICK_TARG + hz)
  144 #define SCHED_TICK_SHIFT        10
  145 #define SCHED_TICK_HZ(ts)       ((ts)->ts_ticks >> SCHED_TICK_SHIFT)
  146 #define SCHED_TICK_TOTAL(ts)    (max((ts)->ts_ltick - (ts)->ts_ftick, hz))
  147 
  148 /*
  149  * These macros determine priorities for non-interactive threads.  They are
  150  * assigned a priority based on their recent cpu utilization as expressed
  151  * by the ratio of ticks to the tick total.  NHALF priorities at the start
  152  * and end of the MIN to MAX timeshare range are only reachable with negative
  153  * or positive nice respectively.
  154  *
  155  * PRI_RANGE:   Priority range for utilization dependent priorities.
  156  * PRI_NRESV:   Number of nice values.
  157  * PRI_TICKS:   Compute a priority in PRI_RANGE from the ticks count and total.
  158  * PRI_NICE:    Determines the part of the priority inherited from nice.
  159  */
  160 #define SCHED_PRI_NRESV         (PRIO_MAX - PRIO_MIN)
  161 #define SCHED_PRI_NHALF         (SCHED_PRI_NRESV / 2)
  162 #define SCHED_PRI_MIN           (PRI_MIN_BATCH + SCHED_PRI_NHALF)
  163 #define SCHED_PRI_MAX           (PRI_MAX_BATCH - SCHED_PRI_NHALF)
  164 #define SCHED_PRI_RANGE         (SCHED_PRI_MAX - SCHED_PRI_MIN + 1)
  165 #define SCHED_PRI_TICKS(ts)                                             \
  166     (SCHED_TICK_HZ((ts)) /                                              \
  167     (roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE))
  168 #define SCHED_PRI_NICE(nice)    (nice)
  169 
  170 /*
  171  * These determine the interactivity of a process.  Interactivity differs from
  172  * cpu utilization in that it expresses the voluntary time slept vs time ran
  173  * while cpu utilization includes all time not running.  This more accurately
  174  * models the intent of the thread.
  175  *
  176  * SLP_RUN_MAX: Maximum amount of sleep time + run time we'll accumulate
  177  *              before throttling back.
  178  * SLP_RUN_FORK:        Maximum slp+run time to inherit at fork time.
  179  * INTERACT_MAX:        Maximum interactivity value.  Smaller is better.
  180  * INTERACT_THRESH:     Threshold for placement on the current runq.
  181  */
  182 #define SCHED_SLP_RUN_MAX       ((hz * 5) << SCHED_TICK_SHIFT)
  183 #define SCHED_SLP_RUN_FORK      ((hz / 2) << SCHED_TICK_SHIFT)
  184 #define SCHED_INTERACT_MAX      (100)
  185 #define SCHED_INTERACT_HALF     (SCHED_INTERACT_MAX / 2)
  186 #define SCHED_INTERACT_THRESH   (30)
  187 
  188 /*
  189  * These parameters determine the slice behavior for batch work.
  190  */
  191 #define SCHED_SLICE_DEFAULT_DIVISOR     10      /* ~94 ms, 12 stathz ticks. */
  192 #define SCHED_SLICE_MIN_DIVISOR         6       /* DEFAULT/MIN = ~16 ms. */
  193 
  194 /* Flags kept in td_flags. */
  195 #define TDF_SLICEEND    TDF_SCHED2      /* Thread time slice is over. */
  196 
  197 /*
  198  * tickincr:            Converts a stathz tick into a hz domain scaled by
  199  *                      the shift factor.  Without the shift the error rate
  200  *                      due to rounding would be unacceptably high.
  201  * realstathz:          stathz is sometimes 0 and run off of hz.
  202  * sched_slice:         Runtime of each thread before rescheduling.
  203  * preempt_thresh:      Priority threshold for preemption and remote IPIs.
  204  */
  205 static int sched_interact = SCHED_INTERACT_THRESH;
  206 static int tickincr = 8 << SCHED_TICK_SHIFT;
  207 static int realstathz = 127;    /* reset during boot. */
  208 static int sched_slice = 10;    /* reset during boot. */
  209 static int sched_slice_min = 1; /* reset during boot. */
  210 #ifdef PREEMPTION
  211 #ifdef FULL_PREEMPTION
  212 static int preempt_thresh = PRI_MAX_IDLE;
  213 #else
  214 static int preempt_thresh = PRI_MIN_KERN;
  215 #endif
  216 #else 
  217 static int preempt_thresh = 0;
  218 #endif
  219 static int static_boost = PRI_MIN_BATCH;
  220 static int sched_idlespins = 10000;
  221 static int sched_idlespinthresh = -1;
  222 
  223 /*
  224  * tdq - per processor runqs and statistics.  All fields are protected by the
  225  * tdq_lock.  The load and lowpri may be accessed without to avoid excess
  226  * locking in sched_pickcpu();
  227  */
  228 struct tdq {
  229         /* 
  230          * Ordered to improve efficiency of cpu_search() and switch().
  231          * tdq_lock is padded to avoid false sharing with tdq_load and
  232          * tdq_cpu_idle.
  233          */
  234         struct mtx_padalign tdq_lock;           /* run queue lock. */
  235         struct cpu_group *tdq_cg;               /* Pointer to cpu topology. */
  236         volatile int    tdq_load;               /* Aggregate load. */
  237         volatile int    tdq_cpu_idle;           /* cpu_idle() is active. */
  238         int             tdq_sysload;            /* For loadavg, !ITHD load. */
  239         int             tdq_transferable;       /* Transferable thread count. */
  240         short           tdq_switchcnt;          /* Switches this tick. */
  241         short           tdq_oldswitchcnt;       /* Switches last tick. */
  242         u_char          tdq_lowpri;             /* Lowest priority thread. */
  243         u_char          tdq_ipipending;         /* IPI pending. */
  244         u_char          tdq_idx;                /* Current insert index. */
  245         u_char          tdq_ridx;               /* Current removal index. */
  246         struct runq     tdq_realtime;           /* real-time run queue. */
  247         struct runq     tdq_timeshare;          /* timeshare run queue. */
  248         struct runq     tdq_idle;               /* Queue of IDLE threads. */
  249         char            tdq_name[TDQ_NAME_LEN];
  250 #ifdef KTR
  251         char            tdq_loadname[TDQ_LOADNAME_LEN];
  252 #endif
  253 } __aligned(64);
  254 
  255 /* Idle thread states and config. */
  256 #define TDQ_RUNNING     1
  257 #define TDQ_IDLE        2
  258 
  259 #ifdef SMP
  260 struct cpu_group *cpu_top;              /* CPU topology */
  261 
  262 #define SCHED_AFFINITY_DEFAULT  (max(1, hz / 1000))
  263 #define SCHED_AFFINITY(ts, t)   ((ts)->ts_rltick > ticks - ((t) * affinity))
  264 
  265 /*
  266  * Run-time tunables.
  267  */
  268 static int rebalance = 1;
  269 static int balance_interval = 128;      /* Default set in sched_initticks(). */
  270 static int affinity;
  271 static int steal_idle = 1;
  272 static int steal_thresh = 2;
  273 
  274 /*
  275  * One thread queue per processor.
  276  */
  277 static struct tdq       tdq_cpu[MAXCPU];
  278 static struct tdq       *balance_tdq;
  279 static int balance_ticks;
  280 static DPCPU_DEFINE(uint32_t, randomval);
  281 
  282 #define TDQ_SELF()      (&tdq_cpu[PCPU_GET(cpuid)])
  283 #define TDQ_CPU(x)      (&tdq_cpu[(x)])
  284 #define TDQ_ID(x)       ((int)((x) - tdq_cpu))
  285 #else   /* !SMP */
  286 static struct tdq       tdq_cpu;
  287 
  288 #define TDQ_ID(x)       (0)
  289 #define TDQ_SELF()      (&tdq_cpu)
  290 #define TDQ_CPU(x)      (&tdq_cpu)
  291 #endif
  292 
  293 #define TDQ_LOCK_ASSERT(t, type)        mtx_assert(TDQ_LOCKPTR((t)), (type))
  294 #define TDQ_LOCK(t)             mtx_lock_spin(TDQ_LOCKPTR((t)))
  295 #define TDQ_LOCK_FLAGS(t, f)    mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f))
  296 #define TDQ_UNLOCK(t)           mtx_unlock_spin(TDQ_LOCKPTR((t)))
  297 #define TDQ_LOCKPTR(t)          ((struct mtx *)(&(t)->tdq_lock))
  298 
  299 static void sched_priority(struct thread *);
  300 static void sched_thread_priority(struct thread *, u_char);
  301 static int sched_interact_score(struct thread *);
  302 static void sched_interact_update(struct thread *);
  303 static void sched_interact_fork(struct thread *);
  304 static void sched_pctcpu_update(struct td_sched *, int);
  305 
  306 /* Operations on per processor queues */
  307 static struct thread *tdq_choose(struct tdq *);
  308 static void tdq_setup(struct tdq *);
  309 static void tdq_load_add(struct tdq *, struct thread *);
  310 static void tdq_load_rem(struct tdq *, struct thread *);
  311 static __inline void tdq_runq_add(struct tdq *, struct thread *, int);
  312 static __inline void tdq_runq_rem(struct tdq *, struct thread *);
  313 static inline int sched_shouldpreempt(int, int, int);
  314 void tdq_print(int cpu);
  315 static void runq_print(struct runq *rq);
  316 static void tdq_add(struct tdq *, struct thread *, int);
  317 #ifdef SMP
  318 static int tdq_move(struct tdq *, struct tdq *);
  319 static int tdq_idled(struct tdq *);
  320 static void tdq_notify(struct tdq *, struct thread *);
  321 static struct thread *tdq_steal(struct tdq *, int);
  322 static struct thread *runq_steal(struct runq *, int);
  323 static int sched_pickcpu(struct thread *, int);
  324 static void sched_balance(void);
  325 static int sched_balance_pair(struct tdq *, struct tdq *);
  326 static inline struct tdq *sched_setcpu(struct thread *, int, int);
  327 static inline void thread_unblock_switch(struct thread *, struct mtx *);
  328 static struct mtx *sched_switch_migrate(struct tdq *, struct thread *, int);
  329 static int sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS);
  330 static int sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, 
  331     struct cpu_group *cg, int indent);
  332 #endif
  333 
  334 static void sched_setup(void *dummy);
  335 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
  336 
  337 static void sched_initticks(void *dummy);
  338 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
  339     NULL);
  340 
  341 SDT_PROVIDER_DEFINE(sched);
  342 
  343 SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *", 
  344     "struct proc *", "uint8_t");
  345 SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *", 
  346     "struct proc *", "void *");
  347 SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *", 
  348     "struct proc *", "void *", "int");
  349 SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *", 
  350     "struct proc *", "uint8_t", "struct thread *");
  351 SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int");
  352 SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *", 
  353     "struct proc *");
  354 SDT_PROBE_DEFINE(sched, , , on__cpu);
  355 SDT_PROBE_DEFINE(sched, , , remain__cpu);
  356 SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *", 
  357     "struct proc *");
  358 
  359 /*
  360  * Print the threads waiting on a run-queue.
  361  */
  362 static void
  363 runq_print(struct runq *rq)
  364 {
  365         struct rqhead *rqh;
  366         struct thread *td;
  367         int pri;
  368         int j;
  369         int i;
  370 
  371         for (i = 0; i < RQB_LEN; i++) {
  372                 printf("\t\trunq bits %d 0x%zx\n",
  373                     i, rq->rq_status.rqb_bits[i]);
  374                 for (j = 0; j < RQB_BPW; j++)
  375                         if (rq->rq_status.rqb_bits[i] & (1ul << j)) {
  376                                 pri = j + (i << RQB_L2BPW);
  377                                 rqh = &rq->rq_queues[pri];
  378                                 TAILQ_FOREACH(td, rqh, td_runq) {
  379                                         printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
  380                                             td, td->td_name, td->td_priority,
  381                                             td->td_rqindex, pri);
  382                                 }
  383                         }
  384         }
  385 }
  386 
  387 /*
  388  * Print the status of a per-cpu thread queue.  Should be a ddb show cmd.
  389  */
  390 void
  391 tdq_print(int cpu)
  392 {
  393         struct tdq *tdq;
  394 
  395         tdq = TDQ_CPU(cpu);
  396 
  397         printf("tdq %d:\n", TDQ_ID(tdq));
  398         printf("\tlock            %p\n", TDQ_LOCKPTR(tdq));
  399         printf("\tLock name:      %s\n", tdq->tdq_name);
  400         printf("\tload:           %d\n", tdq->tdq_load);
  401         printf("\tswitch cnt:     %d\n", tdq->tdq_switchcnt);
  402         printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt);
  403         printf("\ttimeshare idx:  %d\n", tdq->tdq_idx);
  404         printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
  405         printf("\tload transferable: %d\n", tdq->tdq_transferable);
  406         printf("\tlowest priority:   %d\n", tdq->tdq_lowpri);
  407         printf("\trealtime runq:\n");
  408         runq_print(&tdq->tdq_realtime);
  409         printf("\ttimeshare runq:\n");
  410         runq_print(&tdq->tdq_timeshare);
  411         printf("\tidle runq:\n");
  412         runq_print(&tdq->tdq_idle);
  413 }
  414 
  415 static inline int
  416 sched_shouldpreempt(int pri, int cpri, int remote)
  417 {
  418         /*
  419          * If the new priority is not better than the current priority there is
  420          * nothing to do.
  421          */
  422         if (pri >= cpri)
  423                 return (0);
  424         /*
  425          * Always preempt idle.
  426          */
  427         if (cpri >= PRI_MIN_IDLE)
  428                 return (1);
  429         /*
  430          * If preemption is disabled don't preempt others.
  431          */
  432         if (preempt_thresh == 0)
  433                 return (0);
  434         /*
  435          * Preempt if we exceed the threshold.
  436          */
  437         if (pri <= preempt_thresh)
  438                 return (1);
  439         /*
  440          * If we're interactive or better and there is non-interactive
  441          * or worse running preempt only remote processors.
  442          */
  443         if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT)
  444                 return (1);
  445         return (0);
  446 }
  447 
  448 /*
  449  * Add a thread to the actual run-queue.  Keeps transferable counts up to
  450  * date with what is actually on the run-queue.  Selects the correct
  451  * queue position for timeshare threads.
  452  */
  453 static __inline void
  454 tdq_runq_add(struct tdq *tdq, struct thread *td, int flags)
  455 {
  456         struct td_sched *ts;
  457         u_char pri;
  458 
  459         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  460         THREAD_LOCK_ASSERT(td, MA_OWNED);
  461 
  462         pri = td->td_priority;
  463         ts = td->td_sched;
  464         TD_SET_RUNQ(td);
  465         if (THREAD_CAN_MIGRATE(td)) {
  466                 tdq->tdq_transferable++;
  467                 ts->ts_flags |= TSF_XFERABLE;
  468         }
  469         if (pri < PRI_MIN_BATCH) {
  470                 ts->ts_runq = &tdq->tdq_realtime;
  471         } else if (pri <= PRI_MAX_BATCH) {
  472                 ts->ts_runq = &tdq->tdq_timeshare;
  473                 KASSERT(pri <= PRI_MAX_BATCH && pri >= PRI_MIN_BATCH,
  474                         ("Invalid priority %d on timeshare runq", pri));
  475                 /*
  476                  * This queue contains only priorities between MIN and MAX
  477                  * realtime.  Use the whole queue to represent these values.
  478                  */
  479                 if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) {
  480                         pri = RQ_NQS * (pri - PRI_MIN_BATCH) / PRI_BATCH_RANGE;
  481                         pri = (pri + tdq->tdq_idx) % RQ_NQS;
  482                         /*
  483                          * This effectively shortens the queue by one so we
  484                          * can have a one slot difference between idx and
  485                          * ridx while we wait for threads to drain.
  486                          */
  487                         if (tdq->tdq_ridx != tdq->tdq_idx &&
  488                             pri == tdq->tdq_ridx)
  489                                 pri = (unsigned char)(pri - 1) % RQ_NQS;
  490                 } else
  491                         pri = tdq->tdq_ridx;
  492                 runq_add_pri(ts->ts_runq, td, pri, flags);
  493                 return;
  494         } else
  495                 ts->ts_runq = &tdq->tdq_idle;
  496         runq_add(ts->ts_runq, td, flags);
  497 }
  498 
  499 /* 
  500  * Remove a thread from a run-queue.  This typically happens when a thread
  501  * is selected to run.  Running threads are not on the queue and the
  502  * transferable count does not reflect them.
  503  */
  504 static __inline void
  505 tdq_runq_rem(struct tdq *tdq, struct thread *td)
  506 {
  507         struct td_sched *ts;
  508 
  509         ts = td->td_sched;
  510         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  511         KASSERT(ts->ts_runq != NULL,
  512             ("tdq_runq_remove: thread %p null ts_runq", td));
  513         if (ts->ts_flags & TSF_XFERABLE) {
  514                 tdq->tdq_transferable--;
  515                 ts->ts_flags &= ~TSF_XFERABLE;
  516         }
  517         if (ts->ts_runq == &tdq->tdq_timeshare) {
  518                 if (tdq->tdq_idx != tdq->tdq_ridx)
  519                         runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx);
  520                 else
  521                         runq_remove_idx(ts->ts_runq, td, NULL);
  522         } else
  523                 runq_remove(ts->ts_runq, td);
  524 }
  525 
  526 /*
  527  * Load is maintained for all threads RUNNING and ON_RUNQ.  Add the load
  528  * for this thread to the referenced thread queue.
  529  */
  530 static void
  531 tdq_load_add(struct tdq *tdq, struct thread *td)
  532 {
  533 
  534         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  535         THREAD_LOCK_ASSERT(td, MA_OWNED);
  536 
  537         tdq->tdq_load++;
  538         if ((td->td_flags & TDF_NOLOAD) == 0)
  539                 tdq->tdq_sysload++;
  540         KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
  541         SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
  542 }
  543 
  544 /*
  545  * Remove the load from a thread that is transitioning to a sleep state or
  546  * exiting.
  547  */
  548 static void
  549 tdq_load_rem(struct tdq *tdq, struct thread *td)
  550 {
  551 
  552         THREAD_LOCK_ASSERT(td, MA_OWNED);
  553         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  554         KASSERT(tdq->tdq_load != 0,
  555             ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
  556 
  557         tdq->tdq_load--;
  558         if ((td->td_flags & TDF_NOLOAD) == 0)
  559                 tdq->tdq_sysload--;
  560         KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
  561         SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
  562 }
  563 
  564 /*
  565  * Bound timeshare latency by decreasing slice size as load increases.  We
  566  * consider the maximum latency as the sum of the threads waiting to run
  567  * aside from curthread and target no more than sched_slice latency but
  568  * no less than sched_slice_min runtime.
  569  */
  570 static inline int
  571 tdq_slice(struct tdq *tdq)
  572 {
  573         int load;
  574 
  575         /*
  576          * It is safe to use sys_load here because this is called from
  577          * contexts where timeshare threads are running and so there
  578          * cannot be higher priority load in the system.
  579          */
  580         load = tdq->tdq_sysload - 1;
  581         if (load >= SCHED_SLICE_MIN_DIVISOR)
  582                 return (sched_slice_min);
  583         if (load <= 1)
  584                 return (sched_slice);
  585         return (sched_slice / load);
  586 }
  587 
  588 /*
  589  * Set lowpri to its exact value by searching the run-queue and
  590  * evaluating curthread.  curthread may be passed as an optimization.
  591  */
  592 static void
  593 tdq_setlowpri(struct tdq *tdq, struct thread *ctd)
  594 {
  595         struct thread *td;
  596 
  597         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  598         if (ctd == NULL)
  599                 ctd = pcpu_find(TDQ_ID(tdq))->pc_curthread;
  600         td = tdq_choose(tdq);
  601         if (td == NULL || td->td_priority > ctd->td_priority)
  602                 tdq->tdq_lowpri = ctd->td_priority;
  603         else
  604                 tdq->tdq_lowpri = td->td_priority;
  605 }
  606 
  607 #ifdef SMP
  608 /*
  609  * We need some randomness. Implement a classic Linear Congruential
  610  * Generator X_{n+1}=(aX_n+c) mod m. These values are optimized for
  611  * m = 2^32, a = 69069 and c = 5. We only return the upper 16 bits
  612  * of the random state (in the low bits of our answer) to keep
  613  * the maximum randomness.
  614  */
  615 static uint32_t
  616 sched_random(void)
  617 {
  618         uint32_t *rndptr;
  619 
  620         rndptr = DPCPU_PTR(randomval);
  621         *rndptr = *rndptr * 69069 + 5;
  622 
  623         return (*rndptr >> 16);
  624 }
  625 
  626 struct cpu_search {
  627         cpuset_t cs_mask;
  628         u_int   cs_prefer;
  629         int     cs_pri;         /* Min priority for low. */
  630         int     cs_limit;       /* Max load for low, min load for high. */
  631         int     cs_cpu;
  632         int     cs_load;
  633 };
  634 
  635 #define CPU_SEARCH_LOWEST       0x1
  636 #define CPU_SEARCH_HIGHEST      0x2
  637 #define CPU_SEARCH_BOTH         (CPU_SEARCH_LOWEST|CPU_SEARCH_HIGHEST)
  638 
  639 #define CPUSET_FOREACH(cpu, mask)                               \
  640         for ((cpu) = 0; (cpu) <= mp_maxid; (cpu)++)             \
  641                 if (CPU_ISSET(cpu, &mask))
  642 
  643 static __always_inline int cpu_search(const struct cpu_group *cg,
  644     struct cpu_search *low, struct cpu_search *high, const int match);
  645 int __noinline cpu_search_lowest(const struct cpu_group *cg,
  646     struct cpu_search *low);
  647 int __noinline cpu_search_highest(const struct cpu_group *cg,
  648     struct cpu_search *high);
  649 int __noinline cpu_search_both(const struct cpu_group *cg,
  650     struct cpu_search *low, struct cpu_search *high);
  651 
  652 /*
  653  * Search the tree of cpu_groups for the lowest or highest loaded cpu
  654  * according to the match argument.  This routine actually compares the
  655  * load on all paths through the tree and finds the least loaded cpu on
  656  * the least loaded path, which may differ from the least loaded cpu in
  657  * the system.  This balances work among caches and busses.
  658  *
  659  * This inline is instantiated in three forms below using constants for the
  660  * match argument.  It is reduced to the minimum set for each case.  It is
  661  * also recursive to the depth of the tree.
  662  */
  663 static __always_inline int
  664 cpu_search(const struct cpu_group *cg, struct cpu_search *low,
  665     struct cpu_search *high, const int match)
  666 {
  667         struct cpu_search lgroup;
  668         struct cpu_search hgroup;
  669         cpuset_t cpumask;
  670         struct cpu_group *child;
  671         struct tdq *tdq;
  672         int cpu, i, hload, lload, load, total, rnd;
  673 
  674         total = 0;
  675         cpumask = cg->cg_mask;
  676         if (match & CPU_SEARCH_LOWEST) {
  677                 lload = INT_MAX;
  678                 lgroup = *low;
  679         }
  680         if (match & CPU_SEARCH_HIGHEST) {
  681                 hload = INT_MIN;
  682                 hgroup = *high;
  683         }
  684 
  685         /* Iterate through the child CPU groups and then remaining CPUs. */
  686         for (i = cg->cg_children, cpu = mp_maxid; ; ) {
  687                 if (i == 0) {
  688 #ifdef HAVE_INLINE_FFSL
  689                         cpu = CPU_FFS(&cpumask) - 1;
  690 #else
  691                         while (cpu >= 0 && !CPU_ISSET(cpu, &cpumask))
  692                                 cpu--;
  693 #endif
  694                         if (cpu < 0)
  695                                 break;
  696                         child = NULL;
  697                 } else
  698                         child = &cg->cg_child[i - 1];
  699 
  700                 if (match & CPU_SEARCH_LOWEST)
  701                         lgroup.cs_cpu = -1;
  702                 if (match & CPU_SEARCH_HIGHEST)
  703                         hgroup.cs_cpu = -1;
  704                 if (child) {                    /* Handle child CPU group. */
  705                         CPU_NAND(&cpumask, &child->cg_mask);
  706                         switch (match) {
  707                         case CPU_SEARCH_LOWEST:
  708                                 load = cpu_search_lowest(child, &lgroup);
  709                                 break;
  710                         case CPU_SEARCH_HIGHEST:
  711                                 load = cpu_search_highest(child, &hgroup);
  712                                 break;
  713                         case CPU_SEARCH_BOTH:
  714                                 load = cpu_search_both(child, &lgroup, &hgroup);
  715                                 break;
  716                         }
  717                 } else {                        /* Handle child CPU. */
  718                         CPU_CLR(cpu, &cpumask);
  719                         tdq = TDQ_CPU(cpu);
  720                         load = tdq->tdq_load * 256;
  721                         rnd = sched_random() % 32;
  722                         if (match & CPU_SEARCH_LOWEST) {
  723                                 if (cpu == low->cs_prefer)
  724                                         load -= 64;
  725                                 /* If that CPU is allowed and get data. */
  726                                 if (tdq->tdq_lowpri > lgroup.cs_pri &&
  727                                     tdq->tdq_load <= lgroup.cs_limit &&
  728                                     CPU_ISSET(cpu, &lgroup.cs_mask)) {
  729                                         lgroup.cs_cpu = cpu;
  730                                         lgroup.cs_load = load - rnd;
  731                                 }
  732                         }
  733                         if (match & CPU_SEARCH_HIGHEST)
  734                                 if (tdq->tdq_load >= hgroup.cs_limit &&
  735                                     tdq->tdq_transferable &&
  736                                     CPU_ISSET(cpu, &hgroup.cs_mask)) {
  737                                         hgroup.cs_cpu = cpu;
  738                                         hgroup.cs_load = load - rnd;
  739                                 }
  740                 }
  741                 total += load;
  742 
  743                 /* We have info about child item. Compare it. */
  744                 if (match & CPU_SEARCH_LOWEST) {
  745                         if (lgroup.cs_cpu >= 0 &&
  746                             (load < lload ||
  747                              (load == lload && lgroup.cs_load < low->cs_load))) {
  748                                 lload = load;
  749                                 low->cs_cpu = lgroup.cs_cpu;
  750                                 low->cs_load = lgroup.cs_load;
  751                         }
  752                 }
  753                 if (match & CPU_SEARCH_HIGHEST)
  754                         if (hgroup.cs_cpu >= 0 &&
  755                             (load > hload ||
  756                              (load == hload && hgroup.cs_load > high->cs_load))) {
  757                                 hload = load;
  758                                 high->cs_cpu = hgroup.cs_cpu;
  759                                 high->cs_load = hgroup.cs_load;
  760                         }
  761                 if (child) {
  762                         i--;
  763                         if (i == 0 && CPU_EMPTY(&cpumask))
  764                                 break;
  765                 }
  766 #ifndef HAVE_INLINE_FFSL
  767                 else
  768                         cpu--;
  769 #endif
  770         }
  771         return (total);
  772 }
  773 
  774 /*
  775  * cpu_search instantiations must pass constants to maintain the inline
  776  * optimization.
  777  */
  778 int
  779 cpu_search_lowest(const struct cpu_group *cg, struct cpu_search *low)
  780 {
  781         return cpu_search(cg, low, NULL, CPU_SEARCH_LOWEST);
  782 }
  783 
  784 int
  785 cpu_search_highest(const struct cpu_group *cg, struct cpu_search *high)
  786 {
  787         return cpu_search(cg, NULL, high, CPU_SEARCH_HIGHEST);
  788 }
  789 
  790 int
  791 cpu_search_both(const struct cpu_group *cg, struct cpu_search *low,
  792     struct cpu_search *high)
  793 {
  794         return cpu_search(cg, low, high, CPU_SEARCH_BOTH);
  795 }
  796 
  797 /*
  798  * Find the cpu with the least load via the least loaded path that has a
  799  * lowpri greater than pri  pri.  A pri of -1 indicates any priority is
  800  * acceptable.
  801  */
  802 static inline int
  803 sched_lowest(const struct cpu_group *cg, cpuset_t mask, int pri, int maxload,
  804     int prefer)
  805 {
  806         struct cpu_search low;
  807 
  808         low.cs_cpu = -1;
  809         low.cs_prefer = prefer;
  810         low.cs_mask = mask;
  811         low.cs_pri = pri;
  812         low.cs_limit = maxload;
  813         cpu_search_lowest(cg, &low);
  814         return low.cs_cpu;
  815 }
  816 
  817 /*
  818  * Find the cpu with the highest load via the highest loaded path.
  819  */
  820 static inline int
  821 sched_highest(const struct cpu_group *cg, cpuset_t mask, int minload)
  822 {
  823         struct cpu_search high;
  824 
  825         high.cs_cpu = -1;
  826         high.cs_mask = mask;
  827         high.cs_limit = minload;
  828         cpu_search_highest(cg, &high);
  829         return high.cs_cpu;
  830 }
  831 
  832 static void
  833 sched_balance_group(struct cpu_group *cg)
  834 {
  835         cpuset_t hmask, lmask;
  836         int high, low, anylow;
  837 
  838         CPU_FILL(&hmask);
  839         for (;;) {
  840                 high = sched_highest(cg, hmask, 1);
  841                 /* Stop if there is no more CPU with transferrable threads. */
  842                 if (high == -1)
  843                         break;
  844                 CPU_CLR(high, &hmask);
  845                 CPU_COPY(&hmask, &lmask);
  846                 /* Stop if there is no more CPU left for low. */
  847                 if (CPU_EMPTY(&lmask))
  848                         break;
  849                 anylow = 1;
  850 nextlow:
  851                 low = sched_lowest(cg, lmask, -1,
  852                     TDQ_CPU(high)->tdq_load - 1, high);
  853                 /* Stop if we looked well and found no less loaded CPU. */
  854                 if (anylow && low == -1)
  855                         break;
  856                 /* Go to next high if we found no less loaded CPU. */
  857                 if (low == -1)
  858                         continue;
  859                 /* Transfer thread from high to low. */
  860                 if (sched_balance_pair(TDQ_CPU(high), TDQ_CPU(low))) {
  861                         /* CPU that got thread can no longer be a donor. */
  862                         CPU_CLR(low, &hmask);
  863                 } else {
  864                         /*
  865                          * If failed, then there is no threads on high
  866                          * that can run on this low. Drop low from low
  867                          * mask and look for different one.
  868                          */
  869                         CPU_CLR(low, &lmask);
  870                         anylow = 0;
  871                         goto nextlow;
  872                 }
  873         }
  874 }
  875 
  876 static void
  877 sched_balance(void)
  878 {
  879         struct tdq *tdq;
  880 
  881         if (smp_started == 0 || rebalance == 0)
  882                 return;
  883 
  884         balance_ticks = max(balance_interval / 2, 1) +
  885             (sched_random() % balance_interval);
  886         tdq = TDQ_SELF();
  887         TDQ_UNLOCK(tdq);
  888         sched_balance_group(cpu_top);
  889         TDQ_LOCK(tdq);
  890 }
  891 
  892 /*
  893  * Lock two thread queues using their address to maintain lock order.
  894  */
  895 static void
  896 tdq_lock_pair(struct tdq *one, struct tdq *two)
  897 {
  898         if (one < two) {
  899                 TDQ_LOCK(one);
  900                 TDQ_LOCK_FLAGS(two, MTX_DUPOK);
  901         } else {
  902                 TDQ_LOCK(two);
  903                 TDQ_LOCK_FLAGS(one, MTX_DUPOK);
  904         }
  905 }
  906 
  907 /*
  908  * Unlock two thread queues.  Order is not important here.
  909  */
  910 static void
  911 tdq_unlock_pair(struct tdq *one, struct tdq *two)
  912 {
  913         TDQ_UNLOCK(one);
  914         TDQ_UNLOCK(two);
  915 }
  916 
  917 /*
  918  * Transfer load between two imbalanced thread queues.
  919  */
  920 static int
  921 sched_balance_pair(struct tdq *high, struct tdq *low)
  922 {
  923         int moved;
  924         int cpu;
  925 
  926         tdq_lock_pair(high, low);
  927         moved = 0;
  928         /*
  929          * Determine what the imbalance is and then adjust that to how many
  930          * threads we actually have to give up (transferable).
  931          */
  932         if (high->tdq_transferable != 0 && high->tdq_load > low->tdq_load &&
  933             (moved = tdq_move(high, low)) > 0) {
  934                 /*
  935                  * In case the target isn't the current cpu IPI it to force a
  936                  * reschedule with the new workload.
  937                  */
  938                 cpu = TDQ_ID(low);
  939                 if (cpu != PCPU_GET(cpuid))
  940                         ipi_cpu(cpu, IPI_PREEMPT);
  941         }
  942         tdq_unlock_pair(high, low);
  943         return (moved);
  944 }
  945 
  946 /*
  947  * Move a thread from one thread queue to another.
  948  */
  949 static int
  950 tdq_move(struct tdq *from, struct tdq *to)
  951 {
  952         struct td_sched *ts;
  953         struct thread *td;
  954         struct tdq *tdq;
  955         int cpu;
  956 
  957         TDQ_LOCK_ASSERT(from, MA_OWNED);
  958         TDQ_LOCK_ASSERT(to, MA_OWNED);
  959 
  960         tdq = from;
  961         cpu = TDQ_ID(to);
  962         td = tdq_steal(tdq, cpu);
  963         if (td == NULL)
  964                 return (0);
  965         ts = td->td_sched;
  966         /*
  967          * Although the run queue is locked the thread may be blocked.  Lock
  968          * it to clear this and acquire the run-queue lock.
  969          */
  970         thread_lock(td);
  971         /* Drop recursive lock on from acquired via thread_lock(). */
  972         TDQ_UNLOCK(from);
  973         sched_rem(td);
  974         ts->ts_cpu = cpu;
  975         td->td_lock = TDQ_LOCKPTR(to);
  976         tdq_add(to, td, SRQ_YIELDING);
  977         return (1);
  978 }
  979 
  980 /*
  981  * This tdq has idled.  Try to steal a thread from another cpu and switch
  982  * to it.
  983  */
  984 static int
  985 tdq_idled(struct tdq *tdq)
  986 {
  987         struct cpu_group *cg;
  988         struct tdq *steal;
  989         cpuset_t mask;
  990         int thresh;
  991         int cpu;
  992 
  993         if (smp_started == 0 || steal_idle == 0)
  994                 return (1);
  995         CPU_FILL(&mask);
  996         CPU_CLR(PCPU_GET(cpuid), &mask);
  997         /* We don't want to be preempted while we're iterating. */
  998         spinlock_enter();
  999         for (cg = tdq->tdq_cg; cg != NULL; ) {
 1000                 if ((cg->cg_flags & CG_FLAG_THREAD) == 0)
 1001                         thresh = steal_thresh;
 1002                 else
 1003                         thresh = 1;
 1004                 cpu = sched_highest(cg, mask, thresh);
 1005                 if (cpu == -1) {
 1006                         cg = cg->cg_parent;
 1007                         continue;
 1008                 }
 1009                 steal = TDQ_CPU(cpu);
 1010                 CPU_CLR(cpu, &mask);
 1011                 tdq_lock_pair(tdq, steal);
 1012                 if (steal->tdq_load < thresh || steal->tdq_transferable == 0) {
 1013                         tdq_unlock_pair(tdq, steal);
 1014                         continue;
 1015                 }
 1016                 /*
 1017                  * If a thread was added while interrupts were disabled don't
 1018                  * steal one here.  If we fail to acquire one due to affinity
 1019                  * restrictions loop again with this cpu removed from the
 1020                  * set.
 1021                  */
 1022                 if (tdq->tdq_load == 0 && tdq_move(steal, tdq) == 0) {
 1023                         tdq_unlock_pair(tdq, steal);
 1024                         continue;
 1025                 }
 1026                 spinlock_exit();
 1027                 TDQ_UNLOCK(steal);
 1028                 mi_switch(SW_VOL | SWT_IDLE, NULL);
 1029                 thread_unlock(curthread);
 1030 
 1031                 return (0);
 1032         }
 1033         spinlock_exit();
 1034         return (1);
 1035 }
 1036 
 1037 /*
 1038  * Notify a remote cpu of new work.  Sends an IPI if criteria are met.
 1039  */
 1040 static void
 1041 tdq_notify(struct tdq *tdq, struct thread *td)
 1042 {
 1043         struct thread *ctd;
 1044         int pri;
 1045         int cpu;
 1046 
 1047         if (tdq->tdq_ipipending)
 1048                 return;
 1049         cpu = td->td_sched->ts_cpu;
 1050         pri = td->td_priority;
 1051         ctd = pcpu_find(cpu)->pc_curthread;
 1052         if (!sched_shouldpreempt(pri, ctd->td_priority, 1))
 1053                 return;
 1054 
 1055         /*
 1056          * Make sure that our caller's earlier update to tdq_load is
 1057          * globally visible before we read tdq_cpu_idle.  Idle thread
 1058          * accesses both of them without locks, and the order is important.
 1059          */
 1060         atomic_thread_fence_seq_cst();
 1061 
 1062         if (TD_IS_IDLETHREAD(ctd)) {
 1063                 /*
 1064                  * If the MD code has an idle wakeup routine try that before
 1065                  * falling back to IPI.
 1066                  */
 1067                 if (!tdq->tdq_cpu_idle || cpu_idle_wakeup(cpu))
 1068                         return;
 1069         }
 1070         tdq->tdq_ipipending = 1;
 1071         ipi_cpu(cpu, IPI_PREEMPT);
 1072 }
 1073 
 1074 /*
 1075  * Steals load from a timeshare queue.  Honors the rotating queue head
 1076  * index.
 1077  */
 1078 static struct thread *
 1079 runq_steal_from(struct runq *rq, int cpu, u_char start)
 1080 {
 1081         struct rqbits *rqb;
 1082         struct rqhead *rqh;
 1083         struct thread *td, *first;
 1084         int bit;
 1085         int i;
 1086 
 1087         rqb = &rq->rq_status;
 1088         bit = start & (RQB_BPW -1);
 1089         first = NULL;
 1090 again:
 1091         for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
 1092                 if (rqb->rqb_bits[i] == 0)
 1093                         continue;
 1094                 if (bit == 0)
 1095                         bit = RQB_FFS(rqb->rqb_bits[i]);
 1096                 for (; bit < RQB_BPW; bit++) {
 1097                         if ((rqb->rqb_bits[i] & (1ul << bit)) == 0)
 1098                                 continue;
 1099                         rqh = &rq->rq_queues[bit + (i << RQB_L2BPW)];
 1100                         TAILQ_FOREACH(td, rqh, td_runq) {
 1101                                 if (first && THREAD_CAN_MIGRATE(td) &&
 1102                                     THREAD_CAN_SCHED(td, cpu))
 1103                                         return (td);
 1104                                 first = td;
 1105                         }
 1106                 }
 1107         }
 1108         if (start != 0) {
 1109                 start = 0;
 1110                 goto again;
 1111         }
 1112 
 1113         if (first && THREAD_CAN_MIGRATE(first) &&
 1114             THREAD_CAN_SCHED(first, cpu))
 1115                 return (first);
 1116         return (NULL);
 1117 }
 1118 
 1119 /*
 1120  * Steals load from a standard linear queue.
 1121  */
 1122 static struct thread *
 1123 runq_steal(struct runq *rq, int cpu)
 1124 {
 1125         struct rqhead *rqh;
 1126         struct rqbits *rqb;
 1127         struct thread *td;
 1128         int word;
 1129         int bit;
 1130 
 1131         rqb = &rq->rq_status;
 1132         for (word = 0; word < RQB_LEN; word++) {
 1133                 if (rqb->rqb_bits[word] == 0)
 1134                         continue;
 1135                 for (bit = 0; bit < RQB_BPW; bit++) {
 1136                         if ((rqb->rqb_bits[word] & (1ul << bit)) == 0)
 1137                                 continue;
 1138                         rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)];
 1139                         TAILQ_FOREACH(td, rqh, td_runq)
 1140                                 if (THREAD_CAN_MIGRATE(td) &&
 1141                                     THREAD_CAN_SCHED(td, cpu))
 1142                                         return (td);
 1143                 }
 1144         }
 1145         return (NULL);
 1146 }
 1147 
 1148 /*
 1149  * Attempt to steal a thread in priority order from a thread queue.
 1150  */
 1151 static struct thread *
 1152 tdq_steal(struct tdq *tdq, int cpu)
 1153 {
 1154         struct thread *td;
 1155 
 1156         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 1157         if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL)
 1158                 return (td);
 1159         if ((td = runq_steal_from(&tdq->tdq_timeshare,
 1160             cpu, tdq->tdq_ridx)) != NULL)
 1161                 return (td);
 1162         return (runq_steal(&tdq->tdq_idle, cpu));
 1163 }
 1164 
 1165 /*
 1166  * Sets the thread lock and ts_cpu to match the requested cpu.  Unlocks the
 1167  * current lock and returns with the assigned queue locked.
 1168  */
 1169 static inline struct tdq *
 1170 sched_setcpu(struct thread *td, int cpu, int flags)
 1171 {
 1172 
 1173         struct tdq *tdq;
 1174 
 1175         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1176         tdq = TDQ_CPU(cpu);
 1177         td->td_sched->ts_cpu = cpu;
 1178         /*
 1179          * If the lock matches just return the queue.
 1180          */
 1181         if (td->td_lock == TDQ_LOCKPTR(tdq))
 1182                 return (tdq);
 1183 #ifdef notyet
 1184         /*
 1185          * If the thread isn't running its lockptr is a
 1186          * turnstile or a sleepqueue.  We can just lock_set without
 1187          * blocking.
 1188          */
 1189         if (TD_CAN_RUN(td)) {
 1190                 TDQ_LOCK(tdq);
 1191                 thread_lock_set(td, TDQ_LOCKPTR(tdq));
 1192                 return (tdq);
 1193         }
 1194 #endif
 1195         /*
 1196          * The hard case, migration, we need to block the thread first to
 1197          * prevent order reversals with other cpus locks.
 1198          */
 1199         spinlock_enter();
 1200         thread_lock_block(td);
 1201         TDQ_LOCK(tdq);
 1202         thread_lock_unblock(td, TDQ_LOCKPTR(tdq));
 1203         spinlock_exit();
 1204         return (tdq);
 1205 }
 1206 
 1207 SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding");
 1208 SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity");
 1209 SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity");
 1210 SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load");
 1211 SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu");
 1212 SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration");
 1213 
 1214 static int
 1215 sched_pickcpu(struct thread *td, int flags)
 1216 {
 1217         struct cpu_group *cg, *ccg;
 1218         struct td_sched *ts;
 1219         struct tdq *tdq;
 1220         cpuset_t mask;
 1221         int cpu, pri, self;
 1222 
 1223         self = PCPU_GET(cpuid);
 1224         ts = td->td_sched;
 1225         if (smp_started == 0)
 1226                 return (self);
 1227         /*
 1228          * Don't migrate a running thread from sched_switch().
 1229          */
 1230         if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td))
 1231                 return (ts->ts_cpu);
 1232         /*
 1233          * Prefer to run interrupt threads on the processors that generate
 1234          * the interrupt.
 1235          */
 1236         pri = td->td_priority;
 1237         if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) &&
 1238             curthread->td_intr_nesting_level && ts->ts_cpu != self) {
 1239                 SCHED_STAT_INC(pickcpu_intrbind);
 1240                 ts->ts_cpu = self;
 1241                 if (TDQ_CPU(self)->tdq_lowpri > pri) {
 1242                         SCHED_STAT_INC(pickcpu_affinity);
 1243                         return (ts->ts_cpu);
 1244                 }
 1245         }
 1246         /*
 1247          * If the thread can run on the last cpu and the affinity has not
 1248          * expired or it is idle run it there.
 1249          */
 1250         tdq = TDQ_CPU(ts->ts_cpu);
 1251         cg = tdq->tdq_cg;
 1252         if (THREAD_CAN_SCHED(td, ts->ts_cpu) &&
 1253             tdq->tdq_lowpri >= PRI_MIN_IDLE &&
 1254             SCHED_AFFINITY(ts, CG_SHARE_L2)) {
 1255                 if (cg->cg_flags & CG_FLAG_THREAD) {
 1256                         CPUSET_FOREACH(cpu, cg->cg_mask) {
 1257                                 if (TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE)
 1258                                         break;
 1259                         }
 1260                 } else
 1261                         cpu = INT_MAX;
 1262                 if (cpu > mp_maxid) {
 1263                         SCHED_STAT_INC(pickcpu_idle_affinity);
 1264                         return (ts->ts_cpu);
 1265                 }
 1266         }
 1267         /*
 1268          * Search for the last level cache CPU group in the tree.
 1269          * Skip caches with expired affinity time and SMT groups.
 1270          * Affinity to higher level caches will be handled less aggressively.
 1271          */
 1272         for (ccg = NULL; cg != NULL; cg = cg->cg_parent) {
 1273                 if (cg->cg_flags & CG_FLAG_THREAD)
 1274                         continue;
 1275                 if (!SCHED_AFFINITY(ts, cg->cg_level))
 1276                         continue;
 1277                 ccg = cg;
 1278         }
 1279         if (ccg != NULL)
 1280                 cg = ccg;
 1281         cpu = -1;
 1282         /* Search the group for the less loaded idle CPU we can run now. */
 1283         mask = td->td_cpuset->cs_mask;
 1284         if (cg != NULL && cg != cpu_top &&
 1285             CPU_CMP(&cg->cg_mask, &cpu_top->cg_mask) != 0)
 1286                 cpu = sched_lowest(cg, mask, max(pri, PRI_MAX_TIMESHARE),
 1287                     INT_MAX, ts->ts_cpu);
 1288         /* Search globally for the less loaded CPU we can run now. */
 1289         if (cpu == -1)
 1290                 cpu = sched_lowest(cpu_top, mask, pri, INT_MAX, ts->ts_cpu);
 1291         /* Search globally for the less loaded CPU. */
 1292         if (cpu == -1)
 1293                 cpu = sched_lowest(cpu_top, mask, -1, INT_MAX, ts->ts_cpu);
 1294         KASSERT(cpu != -1, ("sched_pickcpu: Failed to find a cpu."));
 1295         /*
 1296          * Compare the lowest loaded cpu to current cpu.
 1297          */
 1298         if (THREAD_CAN_SCHED(td, self) && TDQ_CPU(self)->tdq_lowpri > pri &&
 1299             TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE &&
 1300             TDQ_CPU(self)->tdq_load <= TDQ_CPU(cpu)->tdq_load + 1) {
 1301                 SCHED_STAT_INC(pickcpu_local);
 1302                 cpu = self;
 1303         } else
 1304                 SCHED_STAT_INC(pickcpu_lowest);
 1305         if (cpu != ts->ts_cpu)
 1306                 SCHED_STAT_INC(pickcpu_migration);
 1307         return (cpu);
 1308 }
 1309 #endif
 1310 
 1311 /*
 1312  * Pick the highest priority task we have and return it.
 1313  */
 1314 static struct thread *
 1315 tdq_choose(struct tdq *tdq)
 1316 {
 1317         struct thread *td;
 1318 
 1319         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 1320         td = runq_choose(&tdq->tdq_realtime);
 1321         if (td != NULL)
 1322                 return (td);
 1323         td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
 1324         if (td != NULL) {
 1325                 KASSERT(td->td_priority >= PRI_MIN_BATCH,
 1326                     ("tdq_choose: Invalid priority on timeshare queue %d",
 1327                     td->td_priority));
 1328                 return (td);
 1329         }
 1330         td = runq_choose(&tdq->tdq_idle);
 1331         if (td != NULL) {
 1332                 KASSERT(td->td_priority >= PRI_MIN_IDLE,
 1333                     ("tdq_choose: Invalid priority on idle queue %d",
 1334                     td->td_priority));
 1335                 return (td);
 1336         }
 1337 
 1338         return (NULL);
 1339 }
 1340 
 1341 /*
 1342  * Initialize a thread queue.
 1343  */
 1344 static void
 1345 tdq_setup(struct tdq *tdq)
 1346 {
 1347 
 1348         if (bootverbose)
 1349                 printf("ULE: setup cpu %d\n", TDQ_ID(tdq));
 1350         runq_init(&tdq->tdq_realtime);
 1351         runq_init(&tdq->tdq_timeshare);
 1352         runq_init(&tdq->tdq_idle);
 1353         snprintf(tdq->tdq_name, sizeof(tdq->tdq_name),
 1354             "sched lock %d", (int)TDQ_ID(tdq));
 1355         mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock",
 1356             MTX_SPIN | MTX_RECURSE);
 1357 #ifdef KTR
 1358         snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname),
 1359             "CPU %d load", (int)TDQ_ID(tdq));
 1360 #endif
 1361 }
 1362 
 1363 #ifdef SMP
 1364 static void
 1365 sched_setup_smp(void)
 1366 {
 1367         struct tdq *tdq;
 1368         int i;
 1369 
 1370         cpu_top = smp_topo();
 1371         CPU_FOREACH(i) {
 1372                 tdq = TDQ_CPU(i);
 1373                 tdq_setup(tdq);
 1374                 tdq->tdq_cg = smp_topo_find(cpu_top, i);
 1375                 if (tdq->tdq_cg == NULL)
 1376                         panic("Can't find cpu group for %d\n", i);
 1377         }
 1378         balance_tdq = TDQ_SELF();
 1379         sched_balance();
 1380 }
 1381 #endif
 1382 
 1383 /*
 1384  * Setup the thread queues and initialize the topology based on MD
 1385  * information.
 1386  */
 1387 static void
 1388 sched_setup(void *dummy)
 1389 {
 1390         struct tdq *tdq;
 1391 
 1392         tdq = TDQ_SELF();
 1393 #ifdef SMP
 1394         sched_setup_smp();
 1395 #else
 1396         tdq_setup(tdq);
 1397 #endif
 1398 
 1399         /* Add thread0's load since it's running. */
 1400         TDQ_LOCK(tdq);
 1401         thread0.td_lock = TDQ_LOCKPTR(TDQ_SELF());
 1402         tdq_load_add(tdq, &thread0);
 1403         tdq->tdq_lowpri = thread0.td_priority;
 1404         TDQ_UNLOCK(tdq);
 1405 }
 1406 
 1407 /*
 1408  * This routine determines time constants after stathz and hz are setup.
 1409  */
 1410 /* ARGSUSED */
 1411 static void
 1412 sched_initticks(void *dummy)
 1413 {
 1414         int incr;
 1415 
 1416         realstathz = stathz ? stathz : hz;
 1417         sched_slice = realstathz / SCHED_SLICE_DEFAULT_DIVISOR;
 1418         sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
 1419         hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
 1420             realstathz);
 1421 
 1422         /*
 1423          * tickincr is shifted out by 10 to avoid rounding errors due to
 1424          * hz not being evenly divisible by stathz on all platforms.
 1425          */
 1426         incr = (hz << SCHED_TICK_SHIFT) / realstathz;
 1427         /*
 1428          * This does not work for values of stathz that are more than
 1429          * 1 << SCHED_TICK_SHIFT * hz.  In practice this does not happen.
 1430          */
 1431         if (incr == 0)
 1432                 incr = 1;
 1433         tickincr = incr;
 1434 #ifdef SMP
 1435         /*
 1436          * Set the default balance interval now that we know
 1437          * what realstathz is.
 1438          */
 1439         balance_interval = realstathz;
 1440         affinity = SCHED_AFFINITY_DEFAULT;
 1441 #endif
 1442         if (sched_idlespinthresh < 0)
 1443                 sched_idlespinthresh = 2 * max(10000, 6 * hz) / realstathz;
 1444 }
 1445 
 1446 
 1447 /*
 1448  * This is the core of the interactivity algorithm.  Determines a score based
 1449  * on past behavior.  It is the ratio of sleep time to run time scaled to
 1450  * a [0, 100] integer.  This is the voluntary sleep time of a process, which
 1451  * differs from the cpu usage because it does not account for time spent
 1452  * waiting on a run-queue.  Would be prettier if we had floating point.
 1453  */
 1454 static int
 1455 sched_interact_score(struct thread *td)
 1456 {
 1457         struct td_sched *ts;
 1458         int div;
 1459 
 1460         ts = td->td_sched;
 1461         /*
 1462          * The score is only needed if this is likely to be an interactive
 1463          * task.  Don't go through the expense of computing it if there's
 1464          * no chance.
 1465          */
 1466         if (sched_interact <= SCHED_INTERACT_HALF &&
 1467                 ts->ts_runtime >= ts->ts_slptime)
 1468                         return (SCHED_INTERACT_HALF);
 1469 
 1470         if (ts->ts_runtime > ts->ts_slptime) {
 1471                 div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF);
 1472                 return (SCHED_INTERACT_HALF +
 1473                     (SCHED_INTERACT_HALF - (ts->ts_slptime / div)));
 1474         }
 1475         if (ts->ts_slptime > ts->ts_runtime) {
 1476                 div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF);
 1477                 return (ts->ts_runtime / div);
 1478         }
 1479         /* runtime == slptime */
 1480         if (ts->ts_runtime)
 1481                 return (SCHED_INTERACT_HALF);
 1482 
 1483         /*
 1484          * This can happen if slptime and runtime are 0.
 1485          */
 1486         return (0);
 1487 
 1488 }
 1489 
 1490 /*
 1491  * Scale the scheduling priority according to the "interactivity" of this
 1492  * process.
 1493  */
 1494 static void
 1495 sched_priority(struct thread *td)
 1496 {
 1497         int score;
 1498         int pri;
 1499 
 1500         if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
 1501                 return;
 1502         /*
 1503          * If the score is interactive we place the thread in the realtime
 1504          * queue with a priority that is less than kernel and interrupt
 1505          * priorities.  These threads are not subject to nice restrictions.
 1506          *
 1507          * Scores greater than this are placed on the normal timeshare queue
 1508          * where the priority is partially decided by the most recent cpu
 1509          * utilization and the rest is decided by nice value.
 1510          *
 1511          * The nice value of the process has a linear effect on the calculated
 1512          * score.  Negative nice values make it easier for a thread to be
 1513          * considered interactive.
 1514          */
 1515         score = imax(0, sched_interact_score(td) + td->td_proc->p_nice);
 1516         if (score < sched_interact) {
 1517                 pri = PRI_MIN_INTERACT;
 1518                 pri += ((PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) /
 1519                     sched_interact) * score;
 1520                 KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT,
 1521                     ("sched_priority: invalid interactive priority %d score %d",
 1522                     pri, score));
 1523         } else {
 1524                 pri = SCHED_PRI_MIN;
 1525                 if (td->td_sched->ts_ticks)
 1526                         pri += min(SCHED_PRI_TICKS(td->td_sched),
 1527                             SCHED_PRI_RANGE - 1);
 1528                 pri += SCHED_PRI_NICE(td->td_proc->p_nice);
 1529                 KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH,
 1530                     ("sched_priority: invalid priority %d: nice %d, " 
 1531                     "ticks %d ftick %d ltick %d tick pri %d",
 1532                     pri, td->td_proc->p_nice, td->td_sched->ts_ticks,
 1533                     td->td_sched->ts_ftick, td->td_sched->ts_ltick,
 1534                     SCHED_PRI_TICKS(td->td_sched)));
 1535         }
 1536         sched_user_prio(td, pri);
 1537 
 1538         return;
 1539 }
 1540 
 1541 /*
 1542  * This routine enforces a maximum limit on the amount of scheduling history
 1543  * kept.  It is called after either the slptime or runtime is adjusted.  This
 1544  * function is ugly due to integer math.
 1545  */
 1546 static void
 1547 sched_interact_update(struct thread *td)
 1548 {
 1549         struct td_sched *ts;
 1550         u_int sum;
 1551 
 1552         ts = td->td_sched;
 1553         sum = ts->ts_runtime + ts->ts_slptime;
 1554         if (sum < SCHED_SLP_RUN_MAX)
 1555                 return;
 1556         /*
 1557          * This only happens from two places:
 1558          * 1) We have added an unusual amount of run time from fork_exit.
 1559          * 2) We have added an unusual amount of sleep time from sched_sleep().
 1560          */
 1561         if (sum > SCHED_SLP_RUN_MAX * 2) {
 1562                 if (ts->ts_runtime > ts->ts_slptime) {
 1563                         ts->ts_runtime = SCHED_SLP_RUN_MAX;
 1564                         ts->ts_slptime = 1;
 1565                 } else {
 1566                         ts->ts_slptime = SCHED_SLP_RUN_MAX;
 1567                         ts->ts_runtime = 1;
 1568                 }
 1569                 return;
 1570         }
 1571         /*
 1572          * If we have exceeded by more than 1/5th then the algorithm below
 1573          * will not bring us back into range.  Dividing by two here forces
 1574          * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX]
 1575          */
 1576         if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) {
 1577                 ts->ts_runtime /= 2;
 1578                 ts->ts_slptime /= 2;
 1579                 return;
 1580         }
 1581         ts->ts_runtime = (ts->ts_runtime / 5) * 4;
 1582         ts->ts_slptime = (ts->ts_slptime / 5) * 4;
 1583 }
 1584 
 1585 /*
 1586  * Scale back the interactivity history when a child thread is created.  The
 1587  * history is inherited from the parent but the thread may behave totally
 1588  * differently.  For example, a shell spawning a compiler process.  We want
 1589  * to learn that the compiler is behaving badly very quickly.
 1590  */
 1591 static void
 1592 sched_interact_fork(struct thread *td)
 1593 {
 1594         int ratio;
 1595         int sum;
 1596 
 1597         sum = td->td_sched->ts_runtime + td->td_sched->ts_slptime;
 1598         if (sum > SCHED_SLP_RUN_FORK) {
 1599                 ratio = sum / SCHED_SLP_RUN_FORK;
 1600                 td->td_sched->ts_runtime /= ratio;
 1601                 td->td_sched->ts_slptime /= ratio;
 1602         }
 1603 }
 1604 
 1605 /*
 1606  * Called from proc0_init() to setup the scheduler fields.
 1607  */
 1608 void
 1609 schedinit(void)
 1610 {
 1611 
 1612         /*
 1613          * Set up the scheduler specific parts of proc0.
 1614          */
 1615         proc0.p_sched = NULL; /* XXX */
 1616         thread0.td_sched = &td_sched0;
 1617         td_sched0.ts_ltick = ticks;
 1618         td_sched0.ts_ftick = ticks;
 1619         td_sched0.ts_slice = 0;
 1620 }
 1621 
 1622 /*
 1623  * This is only somewhat accurate since given many processes of the same
 1624  * priority they will switch when their slices run out, which will be
 1625  * at most sched_slice stathz ticks.
 1626  */
 1627 int
 1628 sched_rr_interval(void)
 1629 {
 1630 
 1631         /* Convert sched_slice from stathz to hz. */
 1632         return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz));
 1633 }
 1634 
 1635 /*
 1636  * Update the percent cpu tracking information when it is requested or
 1637  * the total history exceeds the maximum.  We keep a sliding history of
 1638  * tick counts that slowly decays.  This is less precise than the 4BSD
 1639  * mechanism since it happens with less regular and frequent events.
 1640  */
 1641 static void
 1642 sched_pctcpu_update(struct td_sched *ts, int run)
 1643 {
 1644         int t = ticks;
 1645 
 1646         if (t - ts->ts_ltick >= SCHED_TICK_TARG) {
 1647                 ts->ts_ticks = 0;
 1648                 ts->ts_ftick = t - SCHED_TICK_TARG;
 1649         } else if (t - ts->ts_ftick >= SCHED_TICK_MAX) {
 1650                 ts->ts_ticks = (ts->ts_ticks / (ts->ts_ltick - ts->ts_ftick)) *
 1651                     (ts->ts_ltick - (t - SCHED_TICK_TARG));
 1652                 ts->ts_ftick = t - SCHED_TICK_TARG;
 1653         }
 1654         if (run)
 1655                 ts->ts_ticks += (t - ts->ts_ltick) << SCHED_TICK_SHIFT;
 1656         ts->ts_ltick = t;
 1657 }
 1658 
 1659 /*
 1660  * Adjust the priority of a thread.  Move it to the appropriate run-queue
 1661  * if necessary.  This is the back-end for several priority related
 1662  * functions.
 1663  */
 1664 static void
 1665 sched_thread_priority(struct thread *td, u_char prio)
 1666 {
 1667         struct td_sched *ts;
 1668         struct tdq *tdq;
 1669         int oldpri;
 1670 
 1671         KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio",
 1672             "prio:%d", td->td_priority, "new prio:%d", prio,
 1673             KTR_ATTR_LINKED, sched_tdname(curthread));
 1674         SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio);
 1675         if (td != curthread && prio < td->td_priority) {
 1676                 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
 1677                     "lend prio", "prio:%d", td->td_priority, "new prio:%d",
 1678                     prio, KTR_ATTR_LINKED, sched_tdname(td));
 1679                 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio, 
 1680                     curthread);
 1681         } 
 1682         ts = td->td_sched;
 1683         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1684         if (td->td_priority == prio)
 1685                 return;
 1686         /*
 1687          * If the priority has been elevated due to priority
 1688          * propagation, we may have to move ourselves to a new
 1689          * queue.  This could be optimized to not re-add in some
 1690          * cases.
 1691          */
 1692         if (TD_ON_RUNQ(td) && prio < td->td_priority) {
 1693                 sched_rem(td);
 1694                 td->td_priority = prio;
 1695                 sched_add(td, SRQ_BORROWING);
 1696                 return;
 1697         }
 1698         /*
 1699          * If the thread is currently running we may have to adjust the lowpri
 1700          * information so other cpus are aware of our current priority.
 1701          */
 1702         if (TD_IS_RUNNING(td)) {
 1703                 tdq = TDQ_CPU(ts->ts_cpu);
 1704                 oldpri = td->td_priority;
 1705                 td->td_priority = prio;
 1706                 if (prio < tdq->tdq_lowpri)
 1707                         tdq->tdq_lowpri = prio;
 1708                 else if (tdq->tdq_lowpri == oldpri)
 1709                         tdq_setlowpri(tdq, td);
 1710                 return;
 1711         }
 1712         td->td_priority = prio;
 1713 }
 1714 
 1715 /*
 1716  * Update a thread's priority when it is lent another thread's
 1717  * priority.
 1718  */
 1719 void
 1720 sched_lend_prio(struct thread *td, u_char prio)
 1721 {
 1722 
 1723         td->td_flags |= TDF_BORROWING;
 1724         sched_thread_priority(td, prio);
 1725 }
 1726 
 1727 /*
 1728  * Restore a thread's priority when priority propagation is
 1729  * over.  The prio argument is the minimum priority the thread
 1730  * needs to have to satisfy other possible priority lending
 1731  * requests.  If the thread's regular priority is less
 1732  * important than prio, the thread will keep a priority boost
 1733  * of prio.
 1734  */
 1735 void
 1736 sched_unlend_prio(struct thread *td, u_char prio)
 1737 {
 1738         u_char base_pri;
 1739 
 1740         if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
 1741             td->td_base_pri <= PRI_MAX_TIMESHARE)
 1742                 base_pri = td->td_user_pri;
 1743         else
 1744                 base_pri = td->td_base_pri;
 1745         if (prio >= base_pri) {
 1746                 td->td_flags &= ~TDF_BORROWING;
 1747                 sched_thread_priority(td, base_pri);
 1748         } else
 1749                 sched_lend_prio(td, prio);
 1750 }
 1751 
 1752 /*
 1753  * Standard entry for setting the priority to an absolute value.
 1754  */
 1755 void
 1756 sched_prio(struct thread *td, u_char prio)
 1757 {
 1758         u_char oldprio;
 1759 
 1760         /* First, update the base priority. */
 1761         td->td_base_pri = prio;
 1762 
 1763         /*
 1764          * If the thread is borrowing another thread's priority, don't
 1765          * ever lower the priority.
 1766          */
 1767         if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
 1768                 return;
 1769 
 1770         /* Change the real priority. */
 1771         oldprio = td->td_priority;
 1772         sched_thread_priority(td, prio);
 1773 
 1774         /*
 1775          * If the thread is on a turnstile, then let the turnstile update
 1776          * its state.
 1777          */
 1778         if (TD_ON_LOCK(td) && oldprio != prio)
 1779                 turnstile_adjust(td, oldprio);
 1780 }
 1781 
 1782 /*
 1783  * Set the base user priority, does not effect current running priority.
 1784  */
 1785 void
 1786 sched_user_prio(struct thread *td, u_char prio)
 1787 {
 1788 
 1789         td->td_base_user_pri = prio;
 1790         if (td->td_lend_user_pri <= prio)
 1791                 return;
 1792         td->td_user_pri = prio;
 1793 }
 1794 
 1795 void
 1796 sched_lend_user_prio(struct thread *td, u_char prio)
 1797 {
 1798 
 1799         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1800         td->td_lend_user_pri = prio;
 1801         td->td_user_pri = min(prio, td->td_base_user_pri);
 1802         if (td->td_priority > td->td_user_pri)
 1803                 sched_prio(td, td->td_user_pri);
 1804         else if (td->td_priority != td->td_user_pri)
 1805                 td->td_flags |= TDF_NEEDRESCHED;
 1806 }
 1807 
 1808 /*
 1809  * Handle migration from sched_switch().  This happens only for
 1810  * cpu binding.
 1811  */
 1812 static struct mtx *
 1813 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags)
 1814 {
 1815         struct tdq *tdn;
 1816 
 1817         tdn = TDQ_CPU(td->td_sched->ts_cpu);
 1818 #ifdef SMP
 1819         tdq_load_rem(tdq, td);
 1820         /*
 1821          * Do the lock dance required to avoid LOR.  We grab an extra
 1822          * spinlock nesting to prevent preemption while we're
 1823          * not holding either run-queue lock.
 1824          */
 1825         spinlock_enter();
 1826         thread_lock_block(td);  /* This releases the lock on tdq. */
 1827 
 1828         /*
 1829          * Acquire both run-queue locks before placing the thread on the new
 1830          * run-queue to avoid deadlocks created by placing a thread with a
 1831          * blocked lock on the run-queue of a remote processor.  The deadlock
 1832          * occurs when a third processor attempts to lock the two queues in
 1833          * question while the target processor is spinning with its own
 1834          * run-queue lock held while waiting for the blocked lock to clear.
 1835          */
 1836         tdq_lock_pair(tdn, tdq);
 1837         tdq_add(tdn, td, flags);
 1838         tdq_notify(tdn, td);
 1839         TDQ_UNLOCK(tdn);
 1840         spinlock_exit();
 1841 #endif
 1842         return (TDQ_LOCKPTR(tdn));
 1843 }
 1844 
 1845 /*
 1846  * Variadic version of thread_lock_unblock() that does not assume td_lock
 1847  * is blocked.
 1848  */
 1849 static inline void
 1850 thread_unblock_switch(struct thread *td, struct mtx *mtx)
 1851 {
 1852         atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock,
 1853             (uintptr_t)mtx);
 1854 }
 1855 
 1856 /*
 1857  * Switch threads.  This function has to handle threads coming in while
 1858  * blocked for some reason, running, or idle.  It also must deal with
 1859  * migrating a thread from one queue to another as running threads may
 1860  * be assigned elsewhere via binding.
 1861  */
 1862 void
 1863 sched_switch(struct thread *td, struct thread *newtd, int flags)
 1864 {
 1865         struct tdq *tdq;
 1866         struct td_sched *ts;
 1867         struct mtx *mtx;
 1868         int srqflag;
 1869         int cpuid, preempted;
 1870 
 1871         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1872         KASSERT(newtd == NULL, ("sched_switch: Unsupported newtd argument"));
 1873 
 1874         cpuid = PCPU_GET(cpuid);
 1875         tdq = TDQ_CPU(cpuid);
 1876         ts = td->td_sched;
 1877         mtx = td->td_lock;
 1878         sched_pctcpu_update(ts, 1);
 1879         ts->ts_rltick = ticks;
 1880         td->td_lastcpu = td->td_oncpu;
 1881         td->td_oncpu = NOCPU;
 1882         preempted = !((td->td_flags & TDF_SLICEEND) ||
 1883             (flags & SWT_RELINQUISH));
 1884         td->td_flags &= ~(TDF_NEEDRESCHED | TDF_SLICEEND);
 1885         td->td_owepreempt = 0;
 1886         if (!TD_IS_IDLETHREAD(td))
 1887                 tdq->tdq_switchcnt++;
 1888         /*
 1889          * The lock pointer in an idle thread should never change.  Reset it
 1890          * to CAN_RUN as well.
 1891          */
 1892         if (TD_IS_IDLETHREAD(td)) {
 1893                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1894                 TD_SET_CAN_RUN(td);
 1895         } else if (TD_IS_RUNNING(td)) {
 1896                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1897                 srqflag = preempted ?
 1898                     SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
 1899                     SRQ_OURSELF|SRQ_YIELDING;
 1900 #ifdef SMP
 1901                 if (THREAD_CAN_MIGRATE(td) && !THREAD_CAN_SCHED(td, ts->ts_cpu))
 1902                         ts->ts_cpu = sched_pickcpu(td, 0);
 1903 #endif
 1904                 if (ts->ts_cpu == cpuid)
 1905                         tdq_runq_add(tdq, td, srqflag);
 1906                 else {
 1907                         KASSERT(THREAD_CAN_MIGRATE(td) ||
 1908                             (ts->ts_flags & TSF_BOUND) != 0,
 1909                             ("Thread %p shouldn't migrate", td));
 1910                         mtx = sched_switch_migrate(tdq, td, srqflag);
 1911                 }
 1912         } else {
 1913                 /* This thread must be going to sleep. */
 1914                 TDQ_LOCK(tdq);
 1915                 mtx = thread_lock_block(td);
 1916                 tdq_load_rem(tdq, td);
 1917         }
 1918         /*
 1919          * We enter here with the thread blocked and assigned to the
 1920          * appropriate cpu run-queue or sleep-queue and with the current
 1921          * thread-queue locked.
 1922          */
 1923         TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
 1924         newtd = choosethread();
 1925         /*
 1926          * Call the MD code to switch contexts if necessary.
 1927          */
 1928         if (td != newtd) {
 1929 #ifdef  HWPMC_HOOKS
 1930                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 1931                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
 1932 #endif
 1933                 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc);
 1934                 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
 1935                 TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
 1936                 sched_pctcpu_update(newtd->td_sched, 0);
 1937 
 1938 #ifdef KDTRACE_HOOKS
 1939                 /*
 1940                  * If DTrace has set the active vtime enum to anything
 1941                  * other than INACTIVE (0), then it should have set the
 1942                  * function to call.
 1943                  */
 1944                 if (dtrace_vtime_active)
 1945                         (*dtrace_vtime_switch_func)(newtd);
 1946 #endif
 1947 
 1948                 cpu_switch(td, newtd, mtx);
 1949                 /*
 1950                  * We may return from cpu_switch on a different cpu.  However,
 1951                  * we always return with td_lock pointing to the current cpu's
 1952                  * run queue lock.
 1953                  */
 1954                 cpuid = PCPU_GET(cpuid);
 1955                 tdq = TDQ_CPU(cpuid);
 1956                 lock_profile_obtain_lock_success(
 1957                     &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
 1958 
 1959                 SDT_PROBE0(sched, , , on__cpu);
 1960 #ifdef  HWPMC_HOOKS
 1961                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 1962                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
 1963 #endif
 1964         } else {
 1965                 thread_unblock_switch(td, mtx);
 1966                 SDT_PROBE0(sched, , , remain__cpu);
 1967         }
 1968         /*
 1969          * Assert that all went well and return.
 1970          */
 1971         TDQ_LOCK_ASSERT(tdq, MA_OWNED|MA_NOTRECURSED);
 1972         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1973         td->td_oncpu = cpuid;
 1974 }
 1975 
 1976 /*
 1977  * Adjust thread priorities as a result of a nice request.
 1978  */
 1979 void
 1980 sched_nice(struct proc *p, int nice)
 1981 {
 1982         struct thread *td;
 1983 
 1984         PROC_LOCK_ASSERT(p, MA_OWNED);
 1985 
 1986         p->p_nice = nice;
 1987         FOREACH_THREAD_IN_PROC(p, td) {
 1988                 thread_lock(td);
 1989                 sched_priority(td);
 1990                 sched_prio(td, td->td_base_user_pri);
 1991                 thread_unlock(td);
 1992         }
 1993 }
 1994 
 1995 /*
 1996  * Record the sleep time for the interactivity scorer.
 1997  */
 1998 void
 1999 sched_sleep(struct thread *td, int prio)
 2000 {
 2001 
 2002         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2003 
 2004         td->td_slptick = ticks;
 2005         if (TD_IS_SUSPENDED(td) || prio >= PSOCK)
 2006                 td->td_flags |= TDF_CANSWAP;
 2007         if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
 2008                 return;
 2009         if (static_boost == 1 && prio)
 2010                 sched_prio(td, prio);
 2011         else if (static_boost && td->td_priority > static_boost)
 2012                 sched_prio(td, static_boost);
 2013 }
 2014 
 2015 /*
 2016  * Schedule a thread to resume execution and record how long it voluntarily
 2017  * slept.  We also update the pctcpu, interactivity, and priority.
 2018  */
 2019 void
 2020 sched_wakeup(struct thread *td)
 2021 {
 2022         struct td_sched *ts;
 2023         int slptick;
 2024 
 2025         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2026         ts = td->td_sched;
 2027         td->td_flags &= ~TDF_CANSWAP;
 2028         /*
 2029          * If we slept for more than a tick update our interactivity and
 2030          * priority.
 2031          */
 2032         slptick = td->td_slptick;
 2033         td->td_slptick = 0;
 2034         if (slptick && slptick != ticks) {
 2035                 ts->ts_slptime += (ticks - slptick) << SCHED_TICK_SHIFT;
 2036                 sched_interact_update(td);
 2037                 sched_pctcpu_update(ts, 0);
 2038         }
 2039         /*
 2040          * Reset the slice value since we slept and advanced the round-robin.
 2041          */
 2042         ts->ts_slice = 0;
 2043         sched_add(td, SRQ_BORING);
 2044 }
 2045 
 2046 /*
 2047  * Penalize the parent for creating a new child and initialize the child's
 2048  * priority.
 2049  */
 2050 void
 2051 sched_fork(struct thread *td, struct thread *child)
 2052 {
 2053         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2054         sched_pctcpu_update(td->td_sched, 1);
 2055         sched_fork_thread(td, child);
 2056         /*
 2057          * Penalize the parent and child for forking.
 2058          */
 2059         sched_interact_fork(child);
 2060         sched_priority(child);
 2061         td->td_sched->ts_runtime += tickincr;
 2062         sched_interact_update(td);
 2063         sched_priority(td);
 2064 }
 2065 
 2066 /*
 2067  * Fork a new thread, may be within the same process.
 2068  */
 2069 void
 2070 sched_fork_thread(struct thread *td, struct thread *child)
 2071 {
 2072         struct td_sched *ts;
 2073         struct td_sched *ts2;
 2074         struct tdq *tdq;
 2075 
 2076         tdq = TDQ_SELF();
 2077         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2078         /*
 2079          * Initialize child.
 2080          */
 2081         ts = td->td_sched;
 2082         ts2 = child->td_sched;
 2083         child->td_lock = TDQ_LOCKPTR(tdq);
 2084         child->td_cpuset = cpuset_ref(td->td_cpuset);
 2085         ts2->ts_cpu = ts->ts_cpu;
 2086         ts2->ts_flags = 0;
 2087         /*
 2088          * Grab our parents cpu estimation information.
 2089          */
 2090         ts2->ts_ticks = ts->ts_ticks;
 2091         ts2->ts_ltick = ts->ts_ltick;
 2092         ts2->ts_ftick = ts->ts_ftick;
 2093         /*
 2094          * Do not inherit any borrowed priority from the parent.
 2095          */
 2096         child->td_priority = child->td_base_pri;
 2097         /*
 2098          * And update interactivity score.
 2099          */
 2100         ts2->ts_slptime = ts->ts_slptime;
 2101         ts2->ts_runtime = ts->ts_runtime;
 2102         /* Attempt to quickly learn interactivity. */
 2103         ts2->ts_slice = tdq_slice(tdq) - sched_slice_min;
 2104 #ifdef KTR
 2105         bzero(ts2->ts_name, sizeof(ts2->ts_name));
 2106 #endif
 2107 }
 2108 
 2109 /*
 2110  * Adjust the priority class of a thread.
 2111  */
 2112 void
 2113 sched_class(struct thread *td, int class)
 2114 {
 2115 
 2116         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2117         if (td->td_pri_class == class)
 2118                 return;
 2119         td->td_pri_class = class;
 2120 }
 2121 
 2122 /*
 2123  * Return some of the child's priority and interactivity to the parent.
 2124  */
 2125 void
 2126 sched_exit(struct proc *p, struct thread *child)
 2127 {
 2128         struct thread *td;
 2129 
 2130         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit",
 2131             "prio:%d", child->td_priority);
 2132         PROC_LOCK_ASSERT(p, MA_OWNED);
 2133         td = FIRST_THREAD_IN_PROC(p);
 2134         sched_exit_thread(td, child);
 2135 }
 2136 
 2137 /*
 2138  * Penalize another thread for the time spent on this one.  This helps to
 2139  * worsen the priority and interactivity of processes which schedule batch
 2140  * jobs such as make.  This has little effect on the make process itself but
 2141  * causes new processes spawned by it to receive worse scores immediately.
 2142  */
 2143 void
 2144 sched_exit_thread(struct thread *td, struct thread *child)
 2145 {
 2146 
 2147         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit",
 2148             "prio:%d", child->td_priority);
 2149         /*
 2150          * Give the child's runtime to the parent without returning the
 2151          * sleep time as a penalty to the parent.  This causes shells that
 2152          * launch expensive things to mark their children as expensive.
 2153          */
 2154         thread_lock(td);
 2155         td->td_sched->ts_runtime += child->td_sched->ts_runtime;
 2156         sched_interact_update(td);
 2157         sched_priority(td);
 2158         thread_unlock(td);
 2159 }
 2160 
 2161 void
 2162 sched_preempt(struct thread *td)
 2163 {
 2164         struct tdq *tdq;
 2165 
 2166         SDT_PROBE2(sched, , , surrender, td, td->td_proc);
 2167 
 2168         thread_lock(td);
 2169         tdq = TDQ_SELF();
 2170         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2171         tdq->tdq_ipipending = 0;
 2172         if (td->td_priority > tdq->tdq_lowpri) {
 2173                 int flags;
 2174 
 2175                 flags = SW_INVOL | SW_PREEMPT;
 2176                 if (td->td_critnest > 1)
 2177                         td->td_owepreempt = 1;
 2178                 else if (TD_IS_IDLETHREAD(td))
 2179                         mi_switch(flags | SWT_REMOTEWAKEIDLE, NULL);
 2180                 else
 2181                         mi_switch(flags | SWT_REMOTEPREEMPT, NULL);
 2182         }
 2183         thread_unlock(td);
 2184 }
 2185 
 2186 /*
 2187  * Fix priorities on return to user-space.  Priorities may be elevated due
 2188  * to static priorities in msleep() or similar.
 2189  */
 2190 void
 2191 sched_userret(struct thread *td)
 2192 {
 2193         /*
 2194          * XXX we cheat slightly on the locking here to avoid locking in  
 2195          * the usual case.  Setting td_priority here is essentially an
 2196          * incomplete workaround for not setting it properly elsewhere.
 2197          * Now that some interrupt handlers are threads, not setting it
 2198          * properly elsewhere can clobber it in the window between setting
 2199          * it here and returning to user mode, so don't waste time setting
 2200          * it perfectly here.
 2201          */
 2202         KASSERT((td->td_flags & TDF_BORROWING) == 0,
 2203             ("thread with borrowed priority returning to userland"));
 2204         if (td->td_priority != td->td_user_pri) {
 2205                 thread_lock(td);
 2206                 td->td_priority = td->td_user_pri;
 2207                 td->td_base_pri = td->td_user_pri;
 2208                 tdq_setlowpri(TDQ_SELF(), td);
 2209                 thread_unlock(td);
 2210         }
 2211 }
 2212 
 2213 /*
 2214  * Handle a stathz tick.  This is really only relevant for timeshare
 2215  * threads.
 2216  */
 2217 void
 2218 sched_clock(struct thread *td)
 2219 {
 2220         struct tdq *tdq;
 2221         struct td_sched *ts;
 2222 
 2223         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2224         tdq = TDQ_SELF();
 2225 #ifdef SMP
 2226         /*
 2227          * We run the long term load balancer infrequently on the first cpu.
 2228          */
 2229         if (balance_tdq == tdq) {
 2230                 if (balance_ticks && --balance_ticks == 0)
 2231                         sched_balance();
 2232         }
 2233 #endif
 2234         /*
 2235          * Save the old switch count so we have a record of the last ticks
 2236          * activity.   Initialize the new switch count based on our load.
 2237          * If there is some activity seed it to reflect that.
 2238          */
 2239         tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt;
 2240         tdq->tdq_switchcnt = tdq->tdq_load;
 2241         /*
 2242          * Advance the insert index once for each tick to ensure that all
 2243          * threads get a chance to run.
 2244          */
 2245         if (tdq->tdq_idx == tdq->tdq_ridx) {
 2246                 tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS;
 2247                 if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx]))
 2248                         tdq->tdq_ridx = tdq->tdq_idx;
 2249         }
 2250         ts = td->td_sched;
 2251         sched_pctcpu_update(ts, 1);
 2252         if (td->td_pri_class & PRI_FIFO_BIT)
 2253                 return;
 2254         if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) {
 2255                 /*
 2256                  * We used a tick; charge it to the thread so
 2257                  * that we can compute our interactivity.
 2258                  */
 2259                 td->td_sched->ts_runtime += tickincr;
 2260                 sched_interact_update(td);
 2261                 sched_priority(td);
 2262         }
 2263 
 2264         /*
 2265          * Force a context switch if the current thread has used up a full
 2266          * time slice (default is 100ms).
 2267          */
 2268         if (!TD_IS_IDLETHREAD(td) && ++ts->ts_slice >= tdq_slice(tdq)) {
 2269                 ts->ts_slice = 0;
 2270                 td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND;
 2271         }
 2272 }
 2273 
 2274 /*
 2275  * Called once per hz tick.
 2276  */
 2277 void
 2278 sched_tick(int cnt)
 2279 {
 2280 
 2281 }
 2282 
 2283 /*
 2284  * Return whether the current CPU has runnable tasks.  Used for in-kernel
 2285  * cooperative idle threads.
 2286  */
 2287 int
 2288 sched_runnable(void)
 2289 {
 2290         struct tdq *tdq;
 2291         int load;
 2292 
 2293         load = 1;
 2294 
 2295         tdq = TDQ_SELF();
 2296         if ((curthread->td_flags & TDF_IDLETD) != 0) {
 2297                 if (tdq->tdq_load > 0)
 2298                         goto out;
 2299         } else
 2300                 if (tdq->tdq_load - 1 > 0)
 2301                         goto out;
 2302         load = 0;
 2303 out:
 2304         return (load);
 2305 }
 2306 
 2307 /*
 2308  * Choose the highest priority thread to run.  The thread is removed from
 2309  * the run-queue while running however the load remains.  For SMP we set
 2310  * the tdq in the global idle bitmask if it idles here.
 2311  */
 2312 struct thread *
 2313 sched_choose(void)
 2314 {
 2315         struct thread *td;
 2316         struct tdq *tdq;
 2317 
 2318         tdq = TDQ_SELF();
 2319         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2320         td = tdq_choose(tdq);
 2321         if (td) {
 2322                 tdq_runq_rem(tdq, td);
 2323                 tdq->tdq_lowpri = td->td_priority;
 2324                 return (td);
 2325         }
 2326         tdq->tdq_lowpri = PRI_MAX_IDLE;
 2327         return (PCPU_GET(idlethread));
 2328 }
 2329 
 2330 /*
 2331  * Set owepreempt if necessary.  Preemption never happens directly in ULE,
 2332  * we always request it once we exit a critical section.
 2333  */
 2334 static inline void
 2335 sched_setpreempt(struct thread *td)
 2336 {
 2337         struct thread *ctd;
 2338         int cpri;
 2339         int pri;
 2340 
 2341         THREAD_LOCK_ASSERT(curthread, MA_OWNED);
 2342 
 2343         ctd = curthread;
 2344         pri = td->td_priority;
 2345         cpri = ctd->td_priority;
 2346         if (pri < cpri)
 2347                 ctd->td_flags |= TDF_NEEDRESCHED;
 2348         if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
 2349                 return;
 2350         if (!sched_shouldpreempt(pri, cpri, 0))
 2351                 return;
 2352         ctd->td_owepreempt = 1;
 2353 }
 2354 
 2355 /*
 2356  * Add a thread to a thread queue.  Select the appropriate runq and add the
 2357  * thread to it.  This is the internal function called when the tdq is
 2358  * predetermined.
 2359  */
 2360 void
 2361 tdq_add(struct tdq *tdq, struct thread *td, int flags)
 2362 {
 2363 
 2364         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2365         KASSERT((td->td_inhibitors == 0),
 2366             ("sched_add: trying to run inhibited thread"));
 2367         KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
 2368             ("sched_add: bad thread state"));
 2369         KASSERT(td->td_flags & TDF_INMEM,
 2370             ("sched_add: thread swapped out"));
 2371 
 2372         if (td->td_priority < tdq->tdq_lowpri)
 2373                 tdq->tdq_lowpri = td->td_priority;
 2374         tdq_runq_add(tdq, td, flags);
 2375         tdq_load_add(tdq, td);
 2376 }
 2377 
 2378 /*
 2379  * Select the target thread queue and add a thread to it.  Request
 2380  * preemption or IPI a remote processor if required.
 2381  */
 2382 void
 2383 sched_add(struct thread *td, int flags)
 2384 {
 2385         struct tdq *tdq;
 2386 #ifdef SMP
 2387         int cpu;
 2388 #endif
 2389 
 2390         KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
 2391             "prio:%d", td->td_priority, KTR_ATTR_LINKED,
 2392             sched_tdname(curthread));
 2393         KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
 2394             KTR_ATTR_LINKED, sched_tdname(td));
 2395         SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL, 
 2396             flags & SRQ_PREEMPTED);
 2397         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2398         /*
 2399          * Recalculate the priority before we select the target cpu or
 2400          * run-queue.
 2401          */
 2402         if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
 2403                 sched_priority(td);
 2404 #ifdef SMP
 2405         /*
 2406          * Pick the destination cpu and if it isn't ours transfer to the
 2407          * target cpu.
 2408          */
 2409         cpu = sched_pickcpu(td, flags);
 2410         tdq = sched_setcpu(td, cpu, flags);
 2411         tdq_add(tdq, td, flags);
 2412         if (cpu != PCPU_GET(cpuid)) {
 2413                 tdq_notify(tdq, td);
 2414                 return;
 2415         }
 2416 #else
 2417         tdq = TDQ_SELF();
 2418         TDQ_LOCK(tdq);
 2419         /*
 2420          * Now that the thread is moving to the run-queue, set the lock
 2421          * to the scheduler's lock.
 2422          */
 2423         thread_lock_set(td, TDQ_LOCKPTR(tdq));
 2424         tdq_add(tdq, td, flags);
 2425 #endif
 2426         if (!(flags & SRQ_YIELDING))
 2427                 sched_setpreempt(td);
 2428 }
 2429 
 2430 /*
 2431  * Remove a thread from a run-queue without running it.  This is used
 2432  * when we're stealing a thread from a remote queue.  Otherwise all threads
 2433  * exit by calling sched_exit_thread() and sched_throw() themselves.
 2434  */
 2435 void
 2436 sched_rem(struct thread *td)
 2437 {
 2438         struct tdq *tdq;
 2439 
 2440         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
 2441             "prio:%d", td->td_priority);
 2442         SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL);
 2443         tdq = TDQ_CPU(td->td_sched->ts_cpu);
 2444         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2445         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2446         KASSERT(TD_ON_RUNQ(td),
 2447             ("sched_rem: thread not on run queue"));
 2448         tdq_runq_rem(tdq, td);
 2449         tdq_load_rem(tdq, td);
 2450         TD_SET_CAN_RUN(td);
 2451         if (td->td_priority == tdq->tdq_lowpri)
 2452                 tdq_setlowpri(tdq, NULL);
 2453 }
 2454 
 2455 /*
 2456  * Fetch cpu utilization information.  Updates on demand.
 2457  */
 2458 fixpt_t
 2459 sched_pctcpu(struct thread *td)
 2460 {
 2461         fixpt_t pctcpu;
 2462         struct td_sched *ts;
 2463 
 2464         pctcpu = 0;
 2465         ts = td->td_sched;
 2466         if (ts == NULL)
 2467                 return (0);
 2468 
 2469         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2470         sched_pctcpu_update(ts, TD_IS_RUNNING(td));
 2471         if (ts->ts_ticks) {
 2472                 int rtick;
 2473 
 2474                 /* How many rtick per second ? */
 2475                 rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
 2476                 pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
 2477         }
 2478 
 2479         return (pctcpu);
 2480 }
 2481 
 2482 /*
 2483  * Enforce affinity settings for a thread.  Called after adjustments to
 2484  * cpumask.
 2485  */
 2486 void
 2487 sched_affinity(struct thread *td)
 2488 {
 2489 #ifdef SMP
 2490         struct td_sched *ts;
 2491 
 2492         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2493         ts = td->td_sched;
 2494         if (THREAD_CAN_SCHED(td, ts->ts_cpu))
 2495                 return;
 2496         if (TD_ON_RUNQ(td)) {
 2497                 sched_rem(td);
 2498                 sched_add(td, SRQ_BORING);
 2499                 return;
 2500         }
 2501         if (!TD_IS_RUNNING(td))
 2502                 return;
 2503         /*
 2504          * Force a switch before returning to userspace.  If the
 2505          * target thread is not running locally send an ipi to force
 2506          * the issue.
 2507          */
 2508         td->td_flags |= TDF_NEEDRESCHED;
 2509         if (td != curthread)
 2510                 ipi_cpu(ts->ts_cpu, IPI_PREEMPT);
 2511 #endif
 2512 }
 2513 
 2514 /*
 2515  * Bind a thread to a target cpu.
 2516  */
 2517 void
 2518 sched_bind(struct thread *td, int cpu)
 2519 {
 2520         struct td_sched *ts;
 2521 
 2522         THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
 2523         KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
 2524         ts = td->td_sched;
 2525         if (ts->ts_flags & TSF_BOUND)
 2526                 sched_unbind(td);
 2527         KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td));
 2528         ts->ts_flags |= TSF_BOUND;
 2529         sched_pin();
 2530         if (PCPU_GET(cpuid) == cpu)
 2531                 return;
 2532         ts->ts_cpu = cpu;
 2533         /* When we return from mi_switch we'll be on the correct cpu. */
 2534         mi_switch(SW_VOL, NULL);
 2535 }
 2536 
 2537 /*
 2538  * Release a bound thread.
 2539  */
 2540 void
 2541 sched_unbind(struct thread *td)
 2542 {
 2543         struct td_sched *ts;
 2544 
 2545         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2546         KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
 2547         ts = td->td_sched;
 2548         if ((ts->ts_flags & TSF_BOUND) == 0)
 2549                 return;
 2550         ts->ts_flags &= ~TSF_BOUND;
 2551         sched_unpin();
 2552 }
 2553 
 2554 int
 2555 sched_is_bound(struct thread *td)
 2556 {
 2557         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2558         return (td->td_sched->ts_flags & TSF_BOUND);
 2559 }
 2560 
 2561 /*
 2562  * Basic yield call.
 2563  */
 2564 void
 2565 sched_relinquish(struct thread *td)
 2566 {
 2567         thread_lock(td);
 2568         mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
 2569         thread_unlock(td);
 2570 }
 2571 
 2572 /*
 2573  * Return the total system load.
 2574  */
 2575 int
 2576 sched_load(void)
 2577 {
 2578 #ifdef SMP
 2579         int total;
 2580         int i;
 2581 
 2582         total = 0;
 2583         CPU_FOREACH(i)
 2584                 total += TDQ_CPU(i)->tdq_sysload;
 2585         return (total);
 2586 #else
 2587         return (TDQ_SELF()->tdq_sysload);
 2588 #endif
 2589 }
 2590 
 2591 int
 2592 sched_sizeof_proc(void)
 2593 {
 2594         return (sizeof(struct proc));
 2595 }
 2596 
 2597 int
 2598 sched_sizeof_thread(void)
 2599 {
 2600         return (sizeof(struct thread) + sizeof(struct td_sched));
 2601 }
 2602 
 2603 #ifdef SMP
 2604 #define TDQ_IDLESPIN(tdq)                                               \
 2605     ((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0)
 2606 #else
 2607 #define TDQ_IDLESPIN(tdq)       1
 2608 #endif
 2609 
 2610 /*
 2611  * The actual idle process.
 2612  */
 2613 void
 2614 sched_idletd(void *dummy)
 2615 {
 2616         struct thread *td;
 2617         struct tdq *tdq;
 2618         int oldswitchcnt, switchcnt;
 2619         int i;
 2620 
 2621         mtx_assert(&Giant, MA_NOTOWNED);
 2622         td = curthread;
 2623         tdq = TDQ_SELF();
 2624         THREAD_NO_SLEEPING();
 2625         oldswitchcnt = -1;
 2626         for (;;) {
 2627                 if (tdq->tdq_load) {
 2628                         thread_lock(td);
 2629                         mi_switch(SW_VOL | SWT_IDLE, NULL);
 2630                         thread_unlock(td);
 2631                 }
 2632                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2633 #ifdef SMP
 2634                 if (switchcnt != oldswitchcnt) {
 2635                         oldswitchcnt = switchcnt;
 2636                         if (tdq_idled(tdq) == 0)
 2637                                 continue;
 2638                 }
 2639                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2640 #else
 2641                 oldswitchcnt = switchcnt;
 2642 #endif
 2643                 /*
 2644                  * If we're switching very frequently, spin while checking
 2645                  * for load rather than entering a low power state that 
 2646                  * may require an IPI.  However, don't do any busy
 2647                  * loops while on SMT machines as this simply steals
 2648                  * cycles from cores doing useful work.
 2649                  */
 2650                 if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) {
 2651                         for (i = 0; i < sched_idlespins; i++) {
 2652                                 if (tdq->tdq_load)
 2653                                         break;
 2654                                 cpu_spinwait();
 2655                         }
 2656                 }
 2657 
 2658                 /* If there was context switch during spin, restart it. */
 2659                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2660                 if (tdq->tdq_load != 0 || switchcnt != oldswitchcnt)
 2661                         continue;
 2662 
 2663                 /* Run main MD idle handler. */
 2664                 tdq->tdq_cpu_idle = 1;
 2665                 /*
 2666                  * Make sure that tdq_cpu_idle update is globally visible
 2667                  * before cpu_idle() read tdq_load.  The order is important
 2668                  * to avoid race with tdq_notify.
 2669                  */
 2670                 atomic_thread_fence_seq_cst();
 2671                 cpu_idle(switchcnt * 4 > sched_idlespinthresh);
 2672                 tdq->tdq_cpu_idle = 0;
 2673 
 2674                 /*
 2675                  * Account thread-less hardware interrupts and
 2676                  * other wakeup reasons equal to context switches.
 2677                  */
 2678                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2679                 if (switchcnt != oldswitchcnt)
 2680                         continue;
 2681                 tdq->tdq_switchcnt++;
 2682                 oldswitchcnt++;
 2683         }
 2684 }
 2685 
 2686 /*
 2687  * A CPU is entering for the first time or a thread is exiting.
 2688  */
 2689 void
 2690 sched_throw(struct thread *td)
 2691 {
 2692         struct thread *newtd;
 2693         struct tdq *tdq;
 2694 
 2695         tdq = TDQ_SELF();
 2696         if (td == NULL) {
 2697                 /* Correct spinlock nesting and acquire the correct lock. */
 2698                 TDQ_LOCK(tdq);
 2699                 spinlock_exit();
 2700                 PCPU_SET(switchtime, cpu_ticks());
 2701                 PCPU_SET(switchticks, ticks);
 2702         } else {
 2703                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2704                 tdq_load_rem(tdq, td);
 2705                 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
 2706         }
 2707         KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
 2708         newtd = choosethread();
 2709         TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
 2710         cpu_throw(td, newtd);           /* doesn't return */
 2711 }
 2712 
 2713 /*
 2714  * This is called from fork_exit().  Just acquire the correct locks and
 2715  * let fork do the rest of the work.
 2716  */
 2717 void
 2718 sched_fork_exit(struct thread *td)
 2719 {
 2720         struct tdq *tdq;
 2721         int cpuid;
 2722 
 2723         /*
 2724          * Finish setting up thread glue so that it begins execution in a
 2725          * non-nested critical section with the scheduler lock held.
 2726          */
 2727         cpuid = PCPU_GET(cpuid);
 2728         tdq = TDQ_CPU(cpuid);
 2729         if (TD_IS_IDLETHREAD(td))
 2730                 td->td_lock = TDQ_LOCKPTR(tdq);
 2731         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2732         td->td_oncpu = cpuid;
 2733         TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
 2734         lock_profile_obtain_lock_success(
 2735             &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
 2736 }
 2737 
 2738 /*
 2739  * Create on first use to catch odd startup conditons.
 2740  */
 2741 char *
 2742 sched_tdname(struct thread *td)
 2743 {
 2744 #ifdef KTR
 2745         struct td_sched *ts;
 2746 
 2747         ts = td->td_sched;
 2748         if (ts->ts_name[0] == '\0')
 2749                 snprintf(ts->ts_name, sizeof(ts->ts_name),
 2750                     "%s tid %d", td->td_name, td->td_tid);
 2751         return (ts->ts_name);
 2752 #else
 2753         return (td->td_name);
 2754 #endif
 2755 }
 2756 
 2757 #ifdef KTR
 2758 void
 2759 sched_clear_tdname(struct thread *td)
 2760 {
 2761         struct td_sched *ts;
 2762 
 2763         ts = td->td_sched;
 2764         ts->ts_name[0] = '\0';
 2765 }
 2766 #endif
 2767 
 2768 #ifdef SMP
 2769 
 2770 /*
 2771  * Build the CPU topology dump string. Is recursively called to collect
 2772  * the topology tree.
 2773  */
 2774 static int
 2775 sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg,
 2776     int indent)
 2777 {
 2778         char cpusetbuf[CPUSETBUFSIZ];
 2779         int i, first;
 2780 
 2781         sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent,
 2782             "", 1 + indent / 2, cg->cg_level);
 2783         sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"%s\">", indent, "",
 2784             cg->cg_count, cpusetobj_strprint(cpusetbuf, &cg->cg_mask));
 2785         first = TRUE;
 2786         for (i = 0; i < MAXCPU; i++) {
 2787                 if (CPU_ISSET(i, &cg->cg_mask)) {
 2788                         if (!first)
 2789                                 sbuf_printf(sb, ", ");
 2790                         else
 2791                                 first = FALSE;
 2792                         sbuf_printf(sb, "%d", i);
 2793                 }
 2794         }
 2795         sbuf_printf(sb, "</cpu>\n");
 2796 
 2797         if (cg->cg_flags != 0) {
 2798                 sbuf_printf(sb, "%*s <flags>", indent, "");
 2799                 if ((cg->cg_flags & CG_FLAG_HTT) != 0)
 2800                         sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>");
 2801                 if ((cg->cg_flags & CG_FLAG_THREAD) != 0)
 2802                         sbuf_printf(sb, "<flag name=\"THREAD\">THREAD group</flag>");
 2803                 if ((cg->cg_flags & CG_FLAG_SMT) != 0)
 2804                         sbuf_printf(sb, "<flag name=\"SMT\">SMT group</flag>");
 2805                 sbuf_printf(sb, "</flags>\n");
 2806         }
 2807 
 2808         if (cg->cg_children > 0) {
 2809                 sbuf_printf(sb, "%*s <children>\n", indent, "");
 2810                 for (i = 0; i < cg->cg_children; i++)
 2811                         sysctl_kern_sched_topology_spec_internal(sb, 
 2812                             &cg->cg_child[i], indent+2);
 2813                 sbuf_printf(sb, "%*s </children>\n", indent, "");
 2814         }
 2815         sbuf_printf(sb, "%*s</group>\n", indent, "");
 2816         return (0);
 2817 }
 2818 
 2819 /*
 2820  * Sysctl handler for retrieving topology dump. It's a wrapper for
 2821  * the recursive sysctl_kern_smp_topology_spec_internal().
 2822  */
 2823 static int
 2824 sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS)
 2825 {
 2826         struct sbuf *topo;
 2827         int err;
 2828 
 2829         KASSERT(cpu_top != NULL, ("cpu_top isn't initialized"));
 2830 
 2831         topo = sbuf_new_for_sysctl(NULL, NULL, 512, req);
 2832         if (topo == NULL)
 2833                 return (ENOMEM);
 2834 
 2835         sbuf_printf(topo, "<groups>\n");
 2836         err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1);
 2837         sbuf_printf(topo, "</groups>\n");
 2838 
 2839         if (err == 0) {
 2840                 err = sbuf_finish(topo);
 2841         }
 2842         sbuf_delete(topo);
 2843         return (err);
 2844 }
 2845 
 2846 #endif
 2847 
 2848 static int
 2849 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
 2850 {
 2851         int error, new_val, period;
 2852 
 2853         period = 1000000 / realstathz;
 2854         new_val = period * sched_slice;
 2855         error = sysctl_handle_int(oidp, &new_val, 0, req);
 2856         if (error != 0 || req->newptr == NULL)
 2857                 return (error);
 2858         if (new_val <= 0)
 2859                 return (EINVAL);
 2860         sched_slice = imax(1, (new_val + period / 2) / period);
 2861         sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
 2862         hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
 2863             realstathz);
 2864         return (0);
 2865 }
 2866 
 2867 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW, 0, "Scheduler");
 2868 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0,
 2869     "Scheduler name");
 2870 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW,
 2871     NULL, 0, sysctl_kern_quantum, "I",
 2872     "Quantum for timeshare threads in microseconds");
 2873 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
 2874     "Quantum for timeshare threads in stathz ticks");
 2875 SYSCTL_INT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0,
 2876     "Interactivity score threshold");
 2877 SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW,
 2878     &preempt_thresh, 0,
 2879     "Maximal (lowest) priority for preemption");
 2880 SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost, 0,
 2881     "Assign static kernel priorities to sleeping threads");
 2882 SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins, 0,
 2883     "Number of times idle thread will spin waiting for new work");
 2884 SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW,
 2885     &sched_idlespinthresh, 0,
 2886     "Threshold before we will permit idle thread spinning");
 2887 #ifdef SMP
 2888 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0,
 2889     "Number of hz ticks to keep thread affinity for");
 2890 SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0,
 2891     "Enables the long-term load balancer");
 2892 SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW,
 2893     &balance_interval, 0,
 2894     "Average period in stathz ticks to run the long-term balancer");
 2895 SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0,
 2896     "Attempts to steal work from other cores before idling");
 2897 SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0,
 2898     "Minimum load on remote CPU before we'll steal");
 2899 SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING |
 2900     CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A",
 2901     "XML dump of detected CPU topology");
 2902 #endif
 2903 
 2904 /* ps compat.  All cpu percentages from ULE are weighted. */
 2905 static int ccpu = 0;
 2906 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");

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