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 279383 2015-02-27 23:14:08Z imp $");
   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 #ifdef SMP
  360 /*
  361  * We need some randomness. Implement the classic Linear Congruential
  362  * generator X_{n+1}=(aX_n+c) mod m. These values are optimized for
  363  * m = 2^32, a = 69069 and c = 5. We only return the upper 16 bits
  364  * of the random state (in the low bits of our answer) to return
  365  * the maximum randomness.
  366  */
  367 static uint32_t
  368 sched_random(void) 
  369 {
  370         uint32_t *rndptr;
  371 
  372         rndptr = DPCPU_PTR(randomval);
  373         *rndptr = *rndptr * 69069 + 5;
  374 
  375         return (*rndptr >> 16);
  376 } 
  377 #endif
  378 
  379 /*
  380  * Print the threads waiting on a run-queue.
  381  */
  382 static void
  383 runq_print(struct runq *rq)
  384 {
  385         struct rqhead *rqh;
  386         struct thread *td;
  387         int pri;
  388         int j;
  389         int i;
  390 
  391         for (i = 0; i < RQB_LEN; i++) {
  392                 printf("\t\trunq bits %d 0x%zx\n",
  393                     i, rq->rq_status.rqb_bits[i]);
  394                 for (j = 0; j < RQB_BPW; j++)
  395                         if (rq->rq_status.rqb_bits[i] & (1ul << j)) {
  396                                 pri = j + (i << RQB_L2BPW);
  397                                 rqh = &rq->rq_queues[pri];
  398                                 TAILQ_FOREACH(td, rqh, td_runq) {
  399                                         printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
  400                                             td, td->td_name, td->td_priority,
  401                                             td->td_rqindex, pri);
  402                                 }
  403                         }
  404         }
  405 }
  406 
  407 /*
  408  * Print the status of a per-cpu thread queue.  Should be a ddb show cmd.
  409  */
  410 void
  411 tdq_print(int cpu)
  412 {
  413         struct tdq *tdq;
  414 
  415         tdq = TDQ_CPU(cpu);
  416 
  417         printf("tdq %d:\n", TDQ_ID(tdq));
  418         printf("\tlock            %p\n", TDQ_LOCKPTR(tdq));
  419         printf("\tLock name:      %s\n", tdq->tdq_name);
  420         printf("\tload:           %d\n", tdq->tdq_load);
  421         printf("\tswitch cnt:     %d\n", tdq->tdq_switchcnt);
  422         printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt);
  423         printf("\ttimeshare idx:  %d\n", tdq->tdq_idx);
  424         printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
  425         printf("\tload transferable: %d\n", tdq->tdq_transferable);
  426         printf("\tlowest priority:   %d\n", tdq->tdq_lowpri);
  427         printf("\trealtime runq:\n");
  428         runq_print(&tdq->tdq_realtime);
  429         printf("\ttimeshare runq:\n");
  430         runq_print(&tdq->tdq_timeshare);
  431         printf("\tidle runq:\n");
  432         runq_print(&tdq->tdq_idle);
  433 }
  434 
  435 static inline int
  436 sched_shouldpreempt(int pri, int cpri, int remote)
  437 {
  438         /*
  439          * If the new priority is not better than the current priority there is
  440          * nothing to do.
  441          */
  442         if (pri >= cpri)
  443                 return (0);
  444         /*
  445          * Always preempt idle.
  446          */
  447         if (cpri >= PRI_MIN_IDLE)
  448                 return (1);
  449         /*
  450          * If preemption is disabled don't preempt others.
  451          */
  452         if (preempt_thresh == 0)
  453                 return (0);
  454         /*
  455          * Preempt if we exceed the threshold.
  456          */
  457         if (pri <= preempt_thresh)
  458                 return (1);
  459         /*
  460          * If we're interactive or better and there is non-interactive
  461          * or worse running preempt only remote processors.
  462          */
  463         if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT)
  464                 return (1);
  465         return (0);
  466 }
  467 
  468 /*
  469  * Add a thread to the actual run-queue.  Keeps transferable counts up to
  470  * date with what is actually on the run-queue.  Selects the correct
  471  * queue position for timeshare threads.
  472  */
  473 static __inline void
  474 tdq_runq_add(struct tdq *tdq, struct thread *td, int flags)
  475 {
  476         struct td_sched *ts;
  477         u_char pri;
  478 
  479         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  480         THREAD_LOCK_ASSERT(td, MA_OWNED);
  481 
  482         pri = td->td_priority;
  483         ts = td->td_sched;
  484         TD_SET_RUNQ(td);
  485         if (THREAD_CAN_MIGRATE(td)) {
  486                 tdq->tdq_transferable++;
  487                 ts->ts_flags |= TSF_XFERABLE;
  488         }
  489         if (pri < PRI_MIN_BATCH) {
  490                 ts->ts_runq = &tdq->tdq_realtime;
  491         } else if (pri <= PRI_MAX_BATCH) {
  492                 ts->ts_runq = &tdq->tdq_timeshare;
  493                 KASSERT(pri <= PRI_MAX_BATCH && pri >= PRI_MIN_BATCH,
  494                         ("Invalid priority %d on timeshare runq", pri));
  495                 /*
  496                  * This queue contains only priorities between MIN and MAX
  497                  * realtime.  Use the whole queue to represent these values.
  498                  */
  499                 if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) {
  500                         pri = RQ_NQS * (pri - PRI_MIN_BATCH) / PRI_BATCH_RANGE;
  501                         pri = (pri + tdq->tdq_idx) % RQ_NQS;
  502                         /*
  503                          * This effectively shortens the queue by one so we
  504                          * can have a one slot difference between idx and
  505                          * ridx while we wait for threads to drain.
  506                          */
  507                         if (tdq->tdq_ridx != tdq->tdq_idx &&
  508                             pri == tdq->tdq_ridx)
  509                                 pri = (unsigned char)(pri - 1) % RQ_NQS;
  510                 } else
  511                         pri = tdq->tdq_ridx;
  512                 runq_add_pri(ts->ts_runq, td, pri, flags);
  513                 return;
  514         } else
  515                 ts->ts_runq = &tdq->tdq_idle;
  516         runq_add(ts->ts_runq, td, flags);
  517 }
  518 
  519 /* 
  520  * Remove a thread from a run-queue.  This typically happens when a thread
  521  * is selected to run.  Running threads are not on the queue and the
  522  * transferable count does not reflect them.
  523  */
  524 static __inline void
  525 tdq_runq_rem(struct tdq *tdq, struct thread *td)
  526 {
  527         struct td_sched *ts;
  528 
  529         ts = td->td_sched;
  530         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  531         KASSERT(ts->ts_runq != NULL,
  532             ("tdq_runq_remove: thread %p null ts_runq", td));
  533         if (ts->ts_flags & TSF_XFERABLE) {
  534                 tdq->tdq_transferable--;
  535                 ts->ts_flags &= ~TSF_XFERABLE;
  536         }
  537         if (ts->ts_runq == &tdq->tdq_timeshare) {
  538                 if (tdq->tdq_idx != tdq->tdq_ridx)
  539                         runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx);
  540                 else
  541                         runq_remove_idx(ts->ts_runq, td, NULL);
  542         } else
  543                 runq_remove(ts->ts_runq, td);
  544 }
  545 
  546 /*
  547  * Load is maintained for all threads RUNNING and ON_RUNQ.  Add the load
  548  * for this thread to the referenced thread queue.
  549  */
  550 static void
  551 tdq_load_add(struct tdq *tdq, struct thread *td)
  552 {
  553 
  554         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  555         THREAD_LOCK_ASSERT(td, MA_OWNED);
  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  * Remove the load from a thread that is transitioning to a sleep state or
  566  * exiting.
  567  */
  568 static void
  569 tdq_load_rem(struct tdq *tdq, struct thread *td)
  570 {
  571 
  572         THREAD_LOCK_ASSERT(td, MA_OWNED);
  573         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  574         KASSERT(tdq->tdq_load != 0,
  575             ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
  576 
  577         tdq->tdq_load--;
  578         if ((td->td_flags & TDF_NOLOAD) == 0)
  579                 tdq->tdq_sysload--;
  580         KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
  581         SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
  582 }
  583 
  584 /*
  585  * Bound timeshare latency by decreasing slice size as load increases.  We
  586  * consider the maximum latency as the sum of the threads waiting to run
  587  * aside from curthread and target no more than sched_slice latency but
  588  * no less than sched_slice_min runtime.
  589  */
  590 static inline int
  591 tdq_slice(struct tdq *tdq)
  592 {
  593         int load;
  594 
  595         /*
  596          * It is safe to use sys_load here because this is called from
  597          * contexts where timeshare threads are running and so there
  598          * cannot be higher priority load in the system.
  599          */
  600         load = tdq->tdq_sysload - 1;
  601         if (load >= SCHED_SLICE_MIN_DIVISOR)
  602                 return (sched_slice_min);
  603         if (load <= 1)
  604                 return (sched_slice);
  605         return (sched_slice / load);
  606 }
  607 
  608 /*
  609  * Set lowpri to its exact value by searching the run-queue and
  610  * evaluating curthread.  curthread may be passed as an optimization.
  611  */
  612 static void
  613 tdq_setlowpri(struct tdq *tdq, struct thread *ctd)
  614 {
  615         struct thread *td;
  616 
  617         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  618         if (ctd == NULL)
  619                 ctd = pcpu_find(TDQ_ID(tdq))->pc_curthread;
  620         td = tdq_choose(tdq);
  621         if (td == NULL || td->td_priority > ctd->td_priority)
  622                 tdq->tdq_lowpri = ctd->td_priority;
  623         else
  624                 tdq->tdq_lowpri = td->td_priority;
  625 }
  626 
  627 #ifdef SMP
  628 struct cpu_search {
  629         cpuset_t cs_mask;
  630         u_int   cs_prefer;
  631         int     cs_pri;         /* Min priority for low. */
  632         int     cs_limit;       /* Max load for low, min load for high. */
  633         int     cs_cpu;
  634         int     cs_load;
  635 };
  636 
  637 #define CPU_SEARCH_LOWEST       0x1
  638 #define CPU_SEARCH_HIGHEST      0x2
  639 #define CPU_SEARCH_BOTH         (CPU_SEARCH_LOWEST|CPU_SEARCH_HIGHEST)
  640 
  641 #define CPUSET_FOREACH(cpu, mask)                               \
  642         for ((cpu) = 0; (cpu) <= mp_maxid; (cpu)++)             \
  643                 if (CPU_ISSET(cpu, &mask))
  644 
  645 static __always_inline int cpu_search(const struct cpu_group *cg,
  646     struct cpu_search *low, struct cpu_search *high, const int match);
  647 int __noinline cpu_search_lowest(const struct cpu_group *cg,
  648     struct cpu_search *low);
  649 int __noinline cpu_search_highest(const struct cpu_group *cg,
  650     struct cpu_search *high);
  651 int __noinline cpu_search_both(const struct cpu_group *cg,
  652     struct cpu_search *low, struct cpu_search *high);
  653 
  654 /*
  655  * Search the tree of cpu_groups for the lowest or highest loaded cpu
  656  * according to the match argument.  This routine actually compares the
  657  * load on all paths through the tree and finds the least loaded cpu on
  658  * the least loaded path, which may differ from the least loaded cpu in
  659  * the system.  This balances work among caches and busses.
  660  *
  661  * This inline is instantiated in three forms below using constants for the
  662  * match argument.  It is reduced to the minimum set for each case.  It is
  663  * also recursive to the depth of the tree.
  664  */
  665 static __always_inline int
  666 cpu_search(const struct cpu_group *cg, struct cpu_search *low,
  667     struct cpu_search *high, const int match)
  668 {
  669         struct cpu_search lgroup;
  670         struct cpu_search hgroup;
  671         cpuset_t cpumask;
  672         struct cpu_group *child;
  673         struct tdq *tdq;
  674         int cpu, i, hload, lload, load, total, rnd;
  675 
  676         total = 0;
  677         cpumask = cg->cg_mask;
  678         if (match & CPU_SEARCH_LOWEST) {
  679                 lload = INT_MAX;
  680                 lgroup = *low;
  681         }
  682         if (match & CPU_SEARCH_HIGHEST) {
  683                 hload = INT_MIN;
  684                 hgroup = *high;
  685         }
  686 
  687         /* Iterate through the child CPU groups and then remaining CPUs. */
  688         for (i = cg->cg_children, cpu = mp_maxid; ; ) {
  689                 if (i == 0) {
  690 #ifdef HAVE_INLINE_FFSL
  691                         cpu = CPU_FFS(&cpumask) - 1;
  692 #else
  693                         while (cpu >= 0 && !CPU_ISSET(cpu, &cpumask))
  694                                 cpu--;
  695 #endif
  696                         if (cpu < 0)
  697                                 break;
  698                         child = NULL;
  699                 } else
  700                         child = &cg->cg_child[i - 1];
  701 
  702                 if (match & CPU_SEARCH_LOWEST)
  703                         lgroup.cs_cpu = -1;
  704                 if (match & CPU_SEARCH_HIGHEST)
  705                         hgroup.cs_cpu = -1;
  706                 if (child) {                    /* Handle child CPU group. */
  707                         CPU_NAND(&cpumask, &child->cg_mask);
  708                         switch (match) {
  709                         case CPU_SEARCH_LOWEST:
  710                                 load = cpu_search_lowest(child, &lgroup);
  711                                 break;
  712                         case CPU_SEARCH_HIGHEST:
  713                                 load = cpu_search_highest(child, &hgroup);
  714                                 break;
  715                         case CPU_SEARCH_BOTH:
  716                                 load = cpu_search_both(child, &lgroup, &hgroup);
  717                                 break;
  718                         }
  719                 } else {                        /* Handle child CPU. */
  720                         CPU_CLR(cpu, &cpumask);
  721                         tdq = TDQ_CPU(cpu);
  722                         load = tdq->tdq_load * 256;
  723                         rnd = sched_random() % 32;
  724                         if (match & CPU_SEARCH_LOWEST) {
  725                                 if (cpu == low->cs_prefer)
  726                                         load -= 64;
  727                                 /* If that CPU is allowed and get data. */
  728                                 if (tdq->tdq_lowpri > lgroup.cs_pri &&
  729                                     tdq->tdq_load <= lgroup.cs_limit &&
  730                                     CPU_ISSET(cpu, &lgroup.cs_mask)) {
  731                                         lgroup.cs_cpu = cpu;
  732                                         lgroup.cs_load = load - rnd;
  733                                 }
  734                         }
  735                         if (match & CPU_SEARCH_HIGHEST)
  736                                 if (tdq->tdq_load >= hgroup.cs_limit &&
  737                                     tdq->tdq_transferable &&
  738                                     CPU_ISSET(cpu, &hgroup.cs_mask)) {
  739                                         hgroup.cs_cpu = cpu;
  740                                         hgroup.cs_load = load - rnd;
  741                                 }
  742                 }
  743                 total += load;
  744 
  745                 /* We have info about child item. Compare it. */
  746                 if (match & CPU_SEARCH_LOWEST) {
  747                         if (lgroup.cs_cpu >= 0 &&
  748                             (load < lload ||
  749                              (load == lload && lgroup.cs_load < low->cs_load))) {
  750                                 lload = load;
  751                                 low->cs_cpu = lgroup.cs_cpu;
  752                                 low->cs_load = lgroup.cs_load;
  753                         }
  754                 }
  755                 if (match & CPU_SEARCH_HIGHEST)
  756                         if (hgroup.cs_cpu >= 0 &&
  757                             (load > hload ||
  758                              (load == hload && hgroup.cs_load > high->cs_load))) {
  759                                 hload = load;
  760                                 high->cs_cpu = hgroup.cs_cpu;
  761                                 high->cs_load = hgroup.cs_load;
  762                         }
  763                 if (child) {
  764                         i--;
  765                         if (i == 0 && CPU_EMPTY(&cpumask))
  766                                 break;
  767                 }
  768 #ifndef HAVE_INLINE_FFSL
  769                 else
  770                         cpu--;
  771 #endif
  772         }
  773         return (total);
  774 }
  775 
  776 /*
  777  * cpu_search instantiations must pass constants to maintain the inline
  778  * optimization.
  779  */
  780 int
  781 cpu_search_lowest(const struct cpu_group *cg, struct cpu_search *low)
  782 {
  783         return cpu_search(cg, low, NULL, CPU_SEARCH_LOWEST);
  784 }
  785 
  786 int
  787 cpu_search_highest(const struct cpu_group *cg, struct cpu_search *high)
  788 {
  789         return cpu_search(cg, NULL, high, CPU_SEARCH_HIGHEST);
  790 }
  791 
  792 int
  793 cpu_search_both(const struct cpu_group *cg, struct cpu_search *low,
  794     struct cpu_search *high)
  795 {
  796         return cpu_search(cg, low, high, CPU_SEARCH_BOTH);
  797 }
  798 
  799 /*
  800  * Find the cpu with the least load via the least loaded path that has a
  801  * lowpri greater than pri  pri.  A pri of -1 indicates any priority is
  802  * acceptable.
  803  */
  804 static inline int
  805 sched_lowest(const struct cpu_group *cg, cpuset_t mask, int pri, int maxload,
  806     int prefer)
  807 {
  808         struct cpu_search low;
  809 
  810         low.cs_cpu = -1;
  811         low.cs_prefer = prefer;
  812         low.cs_mask = mask;
  813         low.cs_pri = pri;
  814         low.cs_limit = maxload;
  815         cpu_search_lowest(cg, &low);
  816         return low.cs_cpu;
  817 }
  818 
  819 /*
  820  * Find the cpu with the highest load via the highest loaded path.
  821  */
  822 static inline int
  823 sched_highest(const struct cpu_group *cg, cpuset_t mask, int minload)
  824 {
  825         struct cpu_search high;
  826 
  827         high.cs_cpu = -1;
  828         high.cs_mask = mask;
  829         high.cs_limit = minload;
  830         cpu_search_highest(cg, &high);
  831         return high.cs_cpu;
  832 }
  833 
  834 static void
  835 sched_balance_group(struct cpu_group *cg)
  836 {
  837         cpuset_t hmask, lmask;
  838         int high, low, anylow;
  839 
  840         CPU_FILL(&hmask);
  841         for (;;) {
  842                 high = sched_highest(cg, hmask, 1);
  843                 /* Stop if there is no more CPU with transferrable threads. */
  844                 if (high == -1)
  845                         break;
  846                 CPU_CLR(high, &hmask);
  847                 CPU_COPY(&hmask, &lmask);
  848                 /* Stop if there is no more CPU left for low. */
  849                 if (CPU_EMPTY(&lmask))
  850                         break;
  851                 anylow = 1;
  852 nextlow:
  853                 low = sched_lowest(cg, lmask, -1,
  854                     TDQ_CPU(high)->tdq_load - 1, high);
  855                 /* Stop if we looked well and found no less loaded CPU. */
  856                 if (anylow && low == -1)
  857                         break;
  858                 /* Go to next high if we found no less loaded CPU. */
  859                 if (low == -1)
  860                         continue;
  861                 /* Transfer thread from high to low. */
  862                 if (sched_balance_pair(TDQ_CPU(high), TDQ_CPU(low))) {
  863                         /* CPU that got thread can no longer be a donor. */
  864                         CPU_CLR(low, &hmask);
  865                 } else {
  866                         /*
  867                          * If failed, then there is no threads on high
  868                          * that can run on this low. Drop low from low
  869                          * mask and look for different one.
  870                          */
  871                         CPU_CLR(low, &lmask);
  872                         anylow = 0;
  873                         goto nextlow;
  874                 }
  875         }
  876 }
  877 
  878 static void
  879 sched_balance(void)
  880 {
  881         struct tdq *tdq;
  882 
  883         if (smp_started == 0 || rebalance == 0)
  884                 return;
  885 
  886         balance_ticks = max(balance_interval / 2, 1) +
  887             (sched_random() % balance_interval);
  888         tdq = TDQ_SELF();
  889         TDQ_UNLOCK(tdq);
  890         sched_balance_group(cpu_top);
  891         TDQ_LOCK(tdq);
  892 }
  893 
  894 /*
  895  * Lock two thread queues using their address to maintain lock order.
  896  */
  897 static void
  898 tdq_lock_pair(struct tdq *one, struct tdq *two)
  899 {
  900         if (one < two) {
  901                 TDQ_LOCK(one);
  902                 TDQ_LOCK_FLAGS(two, MTX_DUPOK);
  903         } else {
  904                 TDQ_LOCK(two);
  905                 TDQ_LOCK_FLAGS(one, MTX_DUPOK);
  906         }
  907 }
  908 
  909 /*
  910  * Unlock two thread queues.  Order is not important here.
  911  */
  912 static void
  913 tdq_unlock_pair(struct tdq *one, struct tdq *two)
  914 {
  915         TDQ_UNLOCK(one);
  916         TDQ_UNLOCK(two);
  917 }
  918 
  919 /*
  920  * Transfer load between two imbalanced thread queues.
  921  */
  922 static int
  923 sched_balance_pair(struct tdq *high, struct tdq *low)
  924 {
  925         int moved;
  926         int cpu;
  927 
  928         tdq_lock_pair(high, low);
  929         moved = 0;
  930         /*
  931          * Determine what the imbalance is and then adjust that to how many
  932          * threads we actually have to give up (transferable).
  933          */
  934         if (high->tdq_transferable != 0 && high->tdq_load > low->tdq_load &&
  935             (moved = tdq_move(high, low)) > 0) {
  936                 /*
  937                  * In case the target isn't the current cpu IPI it to force a
  938                  * reschedule with the new workload.
  939                  */
  940                 cpu = TDQ_ID(low);
  941                 if (cpu != PCPU_GET(cpuid))
  942                         ipi_cpu(cpu, IPI_PREEMPT);
  943         }
  944         tdq_unlock_pair(high, low);
  945         return (moved);
  946 }
  947 
  948 /*
  949  * Move a thread from one thread queue to another.
  950  */
  951 static int
  952 tdq_move(struct tdq *from, struct tdq *to)
  953 {
  954         struct td_sched *ts;
  955         struct thread *td;
  956         struct tdq *tdq;
  957         int cpu;
  958 
  959         TDQ_LOCK_ASSERT(from, MA_OWNED);
  960         TDQ_LOCK_ASSERT(to, MA_OWNED);
  961 
  962         tdq = from;
  963         cpu = TDQ_ID(to);
  964         td = tdq_steal(tdq, cpu);
  965         if (td == NULL)
  966                 return (0);
  967         ts = td->td_sched;
  968         /*
  969          * Although the run queue is locked the thread may be blocked.  Lock
  970          * it to clear this and acquire the run-queue lock.
  971          */
  972         thread_lock(td);
  973         /* Drop recursive lock on from acquired via thread_lock(). */
  974         TDQ_UNLOCK(from);
  975         sched_rem(td);
  976         ts->ts_cpu = cpu;
  977         td->td_lock = TDQ_LOCKPTR(to);
  978         tdq_add(to, td, SRQ_YIELDING);
  979         return (1);
  980 }
  981 
  982 /*
  983  * This tdq has idled.  Try to steal a thread from another cpu and switch
  984  * to it.
  985  */
  986 static int
  987 tdq_idled(struct tdq *tdq)
  988 {
  989         struct cpu_group *cg;
  990         struct tdq *steal;
  991         cpuset_t mask;
  992         int thresh;
  993         int cpu;
  994 
  995         if (smp_started == 0 || steal_idle == 0)
  996                 return (1);
  997         CPU_FILL(&mask);
  998         CPU_CLR(PCPU_GET(cpuid), &mask);
  999         /* We don't want to be preempted while we're iterating. */
 1000         spinlock_enter();
 1001         for (cg = tdq->tdq_cg; cg != NULL; ) {
 1002                 if ((cg->cg_flags & CG_FLAG_THREAD) == 0)
 1003                         thresh = steal_thresh;
 1004                 else
 1005                         thresh = 1;
 1006                 cpu = sched_highest(cg, mask, thresh);
 1007                 if (cpu == -1) {
 1008                         cg = cg->cg_parent;
 1009                         continue;
 1010                 }
 1011                 steal = TDQ_CPU(cpu);
 1012                 CPU_CLR(cpu, &mask);
 1013                 tdq_lock_pair(tdq, steal);
 1014                 if (steal->tdq_load < thresh || steal->tdq_transferable == 0) {
 1015                         tdq_unlock_pair(tdq, steal);
 1016                         continue;
 1017                 }
 1018                 /*
 1019                  * If a thread was added while interrupts were disabled don't
 1020                  * steal one here.  If we fail to acquire one due to affinity
 1021                  * restrictions loop again with this cpu removed from the
 1022                  * set.
 1023                  */
 1024                 if (tdq->tdq_load == 0 && tdq_move(steal, tdq) == 0) {
 1025                         tdq_unlock_pair(tdq, steal);
 1026                         continue;
 1027                 }
 1028                 spinlock_exit();
 1029                 TDQ_UNLOCK(steal);
 1030                 mi_switch(SW_VOL | SWT_IDLE, NULL);
 1031                 thread_unlock(curthread);
 1032 
 1033                 return (0);
 1034         }
 1035         spinlock_exit();
 1036         return (1);
 1037 }
 1038 
 1039 /*
 1040  * Notify a remote cpu of new work.  Sends an IPI if criteria are met.
 1041  */
 1042 static void
 1043 tdq_notify(struct tdq *tdq, struct thread *td)
 1044 {
 1045         struct thread *ctd;
 1046         int pri;
 1047         int cpu;
 1048 
 1049         if (tdq->tdq_ipipending)
 1050                 return;
 1051         cpu = td->td_sched->ts_cpu;
 1052         pri = td->td_priority;
 1053         ctd = pcpu_find(cpu)->pc_curthread;
 1054         if (!sched_shouldpreempt(pri, ctd->td_priority, 1))
 1055                 return;
 1056 
 1057         /*
 1058          * Make sure that our caller's earlier update to tdq_load is
 1059          * globally visible before we read tdq_cpu_idle.  Idle thread
 1060          * accesses both of them without locks, and the order is important.
 1061          */
 1062         mb();
 1063 
 1064         if (TD_IS_IDLETHREAD(ctd)) {
 1065                 /*
 1066                  * If the MD code has an idle wakeup routine try that before
 1067                  * falling back to IPI.
 1068                  */
 1069                 if (!tdq->tdq_cpu_idle || cpu_idle_wakeup(cpu))
 1070                         return;
 1071         }
 1072         tdq->tdq_ipipending = 1;
 1073         ipi_cpu(cpu, IPI_PREEMPT);
 1074 }
 1075 
 1076 /*
 1077  * Steals load from a timeshare queue.  Honors the rotating queue head
 1078  * index.
 1079  */
 1080 static struct thread *
 1081 runq_steal_from(struct runq *rq, int cpu, u_char start)
 1082 {
 1083         struct rqbits *rqb;
 1084         struct rqhead *rqh;
 1085         struct thread *td, *first;
 1086         int bit;
 1087         int i;
 1088 
 1089         rqb = &rq->rq_status;
 1090         bit = start & (RQB_BPW -1);
 1091         first = NULL;
 1092 again:
 1093         for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
 1094                 if (rqb->rqb_bits[i] == 0)
 1095                         continue;
 1096                 if (bit == 0)
 1097                         bit = RQB_FFS(rqb->rqb_bits[i]);
 1098                 for (; bit < RQB_BPW; bit++) {
 1099                         if ((rqb->rqb_bits[i] & (1ul << bit)) == 0)
 1100                                 continue;
 1101                         rqh = &rq->rq_queues[bit + (i << RQB_L2BPW)];
 1102                         TAILQ_FOREACH(td, rqh, td_runq) {
 1103                                 if (first && THREAD_CAN_MIGRATE(td) &&
 1104                                     THREAD_CAN_SCHED(td, cpu))
 1105                                         return (td);
 1106                                 first = td;
 1107                         }
 1108                 }
 1109         }
 1110         if (start != 0) {
 1111                 start = 0;
 1112                 goto again;
 1113         }
 1114 
 1115         if (first && THREAD_CAN_MIGRATE(first) &&
 1116             THREAD_CAN_SCHED(first, cpu))
 1117                 return (first);
 1118         return (NULL);
 1119 }
 1120 
 1121 /*
 1122  * Steals load from a standard linear queue.
 1123  */
 1124 static struct thread *
 1125 runq_steal(struct runq *rq, int cpu)
 1126 {
 1127         struct rqhead *rqh;
 1128         struct rqbits *rqb;
 1129         struct thread *td;
 1130         int word;
 1131         int bit;
 1132 
 1133         rqb = &rq->rq_status;
 1134         for (word = 0; word < RQB_LEN; word++) {
 1135                 if (rqb->rqb_bits[word] == 0)
 1136                         continue;
 1137                 for (bit = 0; bit < RQB_BPW; bit++) {
 1138                         if ((rqb->rqb_bits[word] & (1ul << bit)) == 0)
 1139                                 continue;
 1140                         rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)];
 1141                         TAILQ_FOREACH(td, rqh, td_runq)
 1142                                 if (THREAD_CAN_MIGRATE(td) &&
 1143                                     THREAD_CAN_SCHED(td, cpu))
 1144                                         return (td);
 1145                 }
 1146         }
 1147         return (NULL);
 1148 }
 1149 
 1150 /*
 1151  * Attempt to steal a thread in priority order from a thread queue.
 1152  */
 1153 static struct thread *
 1154 tdq_steal(struct tdq *tdq, int cpu)
 1155 {
 1156         struct thread *td;
 1157 
 1158         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 1159         if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL)
 1160                 return (td);
 1161         if ((td = runq_steal_from(&tdq->tdq_timeshare,
 1162             cpu, tdq->tdq_ridx)) != NULL)
 1163                 return (td);
 1164         return (runq_steal(&tdq->tdq_idle, cpu));
 1165 }
 1166 
 1167 /*
 1168  * Sets the thread lock and ts_cpu to match the requested cpu.  Unlocks the
 1169  * current lock and returns with the assigned queue locked.
 1170  */
 1171 static inline struct tdq *
 1172 sched_setcpu(struct thread *td, int cpu, int flags)
 1173 {
 1174 
 1175         struct tdq *tdq;
 1176 
 1177         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1178         tdq = TDQ_CPU(cpu);
 1179         td->td_sched->ts_cpu = cpu;
 1180         /*
 1181          * If the lock matches just return the queue.
 1182          */
 1183         if (td->td_lock == TDQ_LOCKPTR(tdq))
 1184                 return (tdq);
 1185 #ifdef notyet
 1186         /*
 1187          * If the thread isn't running its lockptr is a
 1188          * turnstile or a sleepqueue.  We can just lock_set without
 1189          * blocking.
 1190          */
 1191         if (TD_CAN_RUN(td)) {
 1192                 TDQ_LOCK(tdq);
 1193                 thread_lock_set(td, TDQ_LOCKPTR(tdq));
 1194                 return (tdq);
 1195         }
 1196 #endif
 1197         /*
 1198          * The hard case, migration, we need to block the thread first to
 1199          * prevent order reversals with other cpus locks.
 1200          */
 1201         spinlock_enter();
 1202         thread_lock_block(td);
 1203         TDQ_LOCK(tdq);
 1204         thread_lock_unblock(td, TDQ_LOCKPTR(tdq));
 1205         spinlock_exit();
 1206         return (tdq);
 1207 }
 1208 
 1209 SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding");
 1210 SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity");
 1211 SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity");
 1212 SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load");
 1213 SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu");
 1214 SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration");
 1215 
 1216 static int
 1217 sched_pickcpu(struct thread *td, int flags)
 1218 {
 1219         struct cpu_group *cg, *ccg;
 1220         struct td_sched *ts;
 1221         struct tdq *tdq;
 1222         cpuset_t mask;
 1223         int cpu, pri, self;
 1224 
 1225         self = PCPU_GET(cpuid);
 1226         ts = td->td_sched;
 1227         if (smp_started == 0)
 1228                 return (self);
 1229         /*
 1230          * Don't migrate a running thread from sched_switch().
 1231          */
 1232         if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td))
 1233                 return (ts->ts_cpu);
 1234         /*
 1235          * Prefer to run interrupt threads on the processors that generate
 1236          * the interrupt.
 1237          */
 1238         pri = td->td_priority;
 1239         if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) &&
 1240             curthread->td_intr_nesting_level && ts->ts_cpu != self) {
 1241                 SCHED_STAT_INC(pickcpu_intrbind);
 1242                 ts->ts_cpu = self;
 1243                 if (TDQ_CPU(self)->tdq_lowpri > pri) {
 1244                         SCHED_STAT_INC(pickcpu_affinity);
 1245                         return (ts->ts_cpu);
 1246                 }
 1247         }
 1248         /*
 1249          * If the thread can run on the last cpu and the affinity has not
 1250          * expired or it is idle run it there.
 1251          */
 1252         tdq = TDQ_CPU(ts->ts_cpu);
 1253         cg = tdq->tdq_cg;
 1254         if (THREAD_CAN_SCHED(td, ts->ts_cpu) &&
 1255             tdq->tdq_lowpri >= PRI_MIN_IDLE &&
 1256             SCHED_AFFINITY(ts, CG_SHARE_L2)) {
 1257                 if (cg->cg_flags & CG_FLAG_THREAD) {
 1258                         CPUSET_FOREACH(cpu, cg->cg_mask) {
 1259                                 if (TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE)
 1260                                         break;
 1261                         }
 1262                 } else
 1263                         cpu = INT_MAX;
 1264                 if (cpu > mp_maxid) {
 1265                         SCHED_STAT_INC(pickcpu_idle_affinity);
 1266                         return (ts->ts_cpu);
 1267                 }
 1268         }
 1269         /*
 1270          * Search for the last level cache CPU group in the tree.
 1271          * Skip caches with expired affinity time and SMT groups.
 1272          * Affinity to higher level caches will be handled less aggressively.
 1273          */
 1274         for (ccg = NULL; cg != NULL; cg = cg->cg_parent) {
 1275                 if (cg->cg_flags & CG_FLAG_THREAD)
 1276                         continue;
 1277                 if (!SCHED_AFFINITY(ts, cg->cg_level))
 1278                         continue;
 1279                 ccg = cg;
 1280         }
 1281         if (ccg != NULL)
 1282                 cg = ccg;
 1283         cpu = -1;
 1284         /* Search the group for the less loaded idle CPU we can run now. */
 1285         mask = td->td_cpuset->cs_mask;
 1286         if (cg != NULL && cg != cpu_top &&
 1287             CPU_CMP(&cg->cg_mask, &cpu_top->cg_mask) != 0)
 1288                 cpu = sched_lowest(cg, mask, max(pri, PRI_MAX_TIMESHARE),
 1289                     INT_MAX, ts->ts_cpu);
 1290         /* Search globally for the less loaded CPU we can run now. */
 1291         if (cpu == -1)
 1292                 cpu = sched_lowest(cpu_top, mask, pri, INT_MAX, ts->ts_cpu);
 1293         /* Search globally for the less loaded CPU. */
 1294         if (cpu == -1)
 1295                 cpu = sched_lowest(cpu_top, mask, -1, INT_MAX, ts->ts_cpu);
 1296         KASSERT(cpu != -1, ("sched_pickcpu: Failed to find a cpu."));
 1297         /*
 1298          * Compare the lowest loaded cpu to current cpu.
 1299          */
 1300         if (THREAD_CAN_SCHED(td, self) && TDQ_CPU(self)->tdq_lowpri > pri &&
 1301             TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE &&
 1302             TDQ_CPU(self)->tdq_load <= TDQ_CPU(cpu)->tdq_load + 1) {
 1303                 SCHED_STAT_INC(pickcpu_local);
 1304                 cpu = self;
 1305         } else
 1306                 SCHED_STAT_INC(pickcpu_lowest);
 1307         if (cpu != ts->ts_cpu)
 1308                 SCHED_STAT_INC(pickcpu_migration);
 1309         return (cpu);
 1310 }
 1311 #endif
 1312 
 1313 /*
 1314  * Pick the highest priority task we have and return it.
 1315  */
 1316 static struct thread *
 1317 tdq_choose(struct tdq *tdq)
 1318 {
 1319         struct thread *td;
 1320 
 1321         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 1322         td = runq_choose(&tdq->tdq_realtime);
 1323         if (td != NULL)
 1324                 return (td);
 1325         td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
 1326         if (td != NULL) {
 1327                 KASSERT(td->td_priority >= PRI_MIN_BATCH,
 1328                     ("tdq_choose: Invalid priority on timeshare queue %d",
 1329                     td->td_priority));
 1330                 return (td);
 1331         }
 1332         td = runq_choose(&tdq->tdq_idle);
 1333         if (td != NULL) {
 1334                 KASSERT(td->td_priority >= PRI_MIN_IDLE,
 1335                     ("tdq_choose: Invalid priority on idle queue %d",
 1336                     td->td_priority));
 1337                 return (td);
 1338         }
 1339 
 1340         return (NULL);
 1341 }
 1342 
 1343 /*
 1344  * Initialize a thread queue.
 1345  */
 1346 static void
 1347 tdq_setup(struct tdq *tdq)
 1348 {
 1349 
 1350         if (bootverbose)
 1351                 printf("ULE: setup cpu %d\n", TDQ_ID(tdq));
 1352         runq_init(&tdq->tdq_realtime);
 1353         runq_init(&tdq->tdq_timeshare);
 1354         runq_init(&tdq->tdq_idle);
 1355         snprintf(tdq->tdq_name, sizeof(tdq->tdq_name),
 1356             "sched lock %d", (int)TDQ_ID(tdq));
 1357         mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock",
 1358             MTX_SPIN | MTX_RECURSE);
 1359 #ifdef KTR
 1360         snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname),
 1361             "CPU %d load", (int)TDQ_ID(tdq));
 1362 #endif
 1363 }
 1364 
 1365 #ifdef SMP
 1366 static void
 1367 sched_setup_smp(void)
 1368 {
 1369         struct tdq *tdq;
 1370         int i;
 1371 
 1372         cpu_top = smp_topo();
 1373         CPU_FOREACH(i) {
 1374                 tdq = TDQ_CPU(i);
 1375                 tdq_setup(tdq);
 1376                 tdq->tdq_cg = smp_topo_find(cpu_top, i);
 1377                 if (tdq->tdq_cg == NULL)
 1378                         panic("Can't find cpu group for %d\n", i);
 1379         }
 1380         balance_tdq = TDQ_SELF();
 1381         sched_balance();
 1382 }
 1383 #endif
 1384 
 1385 /*
 1386  * Setup the thread queues and initialize the topology based on MD
 1387  * information.
 1388  */
 1389 static void
 1390 sched_setup(void *dummy)
 1391 {
 1392         struct tdq *tdq;
 1393 
 1394         tdq = TDQ_SELF();
 1395 #ifdef SMP
 1396         sched_setup_smp();
 1397 #else
 1398         tdq_setup(tdq);
 1399 #endif
 1400 
 1401         /* Add thread0's load since it's running. */
 1402         TDQ_LOCK(tdq);
 1403         thread0.td_lock = TDQ_LOCKPTR(TDQ_SELF());
 1404         tdq_load_add(tdq, &thread0);
 1405         tdq->tdq_lowpri = thread0.td_priority;
 1406         TDQ_UNLOCK(tdq);
 1407 }
 1408 
 1409 /*
 1410  * This routine determines time constants after stathz and hz are setup.
 1411  */
 1412 /* ARGSUSED */
 1413 static void
 1414 sched_initticks(void *dummy)
 1415 {
 1416         int incr;
 1417 
 1418         realstathz = stathz ? stathz : hz;
 1419         sched_slice = realstathz / SCHED_SLICE_DEFAULT_DIVISOR;
 1420         sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
 1421         hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
 1422             realstathz);
 1423 
 1424         /*
 1425          * tickincr is shifted out by 10 to avoid rounding errors due to
 1426          * hz not being evenly divisible by stathz on all platforms.
 1427          */
 1428         incr = (hz << SCHED_TICK_SHIFT) / realstathz;
 1429         /*
 1430          * This does not work for values of stathz that are more than
 1431          * 1 << SCHED_TICK_SHIFT * hz.  In practice this does not happen.
 1432          */
 1433         if (incr == 0)
 1434                 incr = 1;
 1435         tickincr = incr;
 1436 #ifdef SMP
 1437         /*
 1438          * Set the default balance interval now that we know
 1439          * what realstathz is.
 1440          */
 1441         balance_interval = realstathz;
 1442         affinity = SCHED_AFFINITY_DEFAULT;
 1443 #endif
 1444         if (sched_idlespinthresh < 0)
 1445                 sched_idlespinthresh = 2 * max(10000, 6 * hz) / realstathz;
 1446 }
 1447 
 1448 
 1449 /*
 1450  * This is the core of the interactivity algorithm.  Determines a score based
 1451  * on past behavior.  It is the ratio of sleep time to run time scaled to
 1452  * a [0, 100] integer.  This is the voluntary sleep time of a process, which
 1453  * differs from the cpu usage because it does not account for time spent
 1454  * waiting on a run-queue.  Would be prettier if we had floating point.
 1455  */
 1456 static int
 1457 sched_interact_score(struct thread *td)
 1458 {
 1459         struct td_sched *ts;
 1460         int div;
 1461 
 1462         ts = td->td_sched;
 1463         /*
 1464          * The score is only needed if this is likely to be an interactive
 1465          * task.  Don't go through the expense of computing it if there's
 1466          * no chance.
 1467          */
 1468         if (sched_interact <= SCHED_INTERACT_HALF &&
 1469                 ts->ts_runtime >= ts->ts_slptime)
 1470                         return (SCHED_INTERACT_HALF);
 1471 
 1472         if (ts->ts_runtime > ts->ts_slptime) {
 1473                 div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF);
 1474                 return (SCHED_INTERACT_HALF +
 1475                     (SCHED_INTERACT_HALF - (ts->ts_slptime / div)));
 1476         }
 1477         if (ts->ts_slptime > ts->ts_runtime) {
 1478                 div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF);
 1479                 return (ts->ts_runtime / div);
 1480         }
 1481         /* runtime == slptime */
 1482         if (ts->ts_runtime)
 1483                 return (SCHED_INTERACT_HALF);
 1484 
 1485         /*
 1486          * This can happen if slptime and runtime are 0.
 1487          */
 1488         return (0);
 1489 
 1490 }
 1491 
 1492 /*
 1493  * Scale the scheduling priority according to the "interactivity" of this
 1494  * process.
 1495  */
 1496 static void
 1497 sched_priority(struct thread *td)
 1498 {
 1499         int score;
 1500         int pri;
 1501 
 1502         if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
 1503                 return;
 1504         /*
 1505          * If the score is interactive we place the thread in the realtime
 1506          * queue with a priority that is less than kernel and interrupt
 1507          * priorities.  These threads are not subject to nice restrictions.
 1508          *
 1509          * Scores greater than this are placed on the normal timeshare queue
 1510          * where the priority is partially decided by the most recent cpu
 1511          * utilization and the rest is decided by nice value.
 1512          *
 1513          * The nice value of the process has a linear effect on the calculated
 1514          * score.  Negative nice values make it easier for a thread to be
 1515          * considered interactive.
 1516          */
 1517         score = imax(0, sched_interact_score(td) + td->td_proc->p_nice);
 1518         if (score < sched_interact) {
 1519                 pri = PRI_MIN_INTERACT;
 1520                 pri += ((PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) /
 1521                     sched_interact) * score;
 1522                 KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT,
 1523                     ("sched_priority: invalid interactive priority %d score %d",
 1524                     pri, score));
 1525         } else {
 1526                 pri = SCHED_PRI_MIN;
 1527                 if (td->td_sched->ts_ticks)
 1528                         pri += min(SCHED_PRI_TICKS(td->td_sched),
 1529                             SCHED_PRI_RANGE - 1);
 1530                 pri += SCHED_PRI_NICE(td->td_proc->p_nice);
 1531                 KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH,
 1532                     ("sched_priority: invalid priority %d: nice %d, " 
 1533                     "ticks %d ftick %d ltick %d tick pri %d",
 1534                     pri, td->td_proc->p_nice, td->td_sched->ts_ticks,
 1535                     td->td_sched->ts_ftick, td->td_sched->ts_ltick,
 1536                     SCHED_PRI_TICKS(td->td_sched)));
 1537         }
 1538         sched_user_prio(td, pri);
 1539 
 1540         return;
 1541 }
 1542 
 1543 /*
 1544  * This routine enforces a maximum limit on the amount of scheduling history
 1545  * kept.  It is called after either the slptime or runtime is adjusted.  This
 1546  * function is ugly due to integer math.
 1547  */
 1548 static void
 1549 sched_interact_update(struct thread *td)
 1550 {
 1551         struct td_sched *ts;
 1552         u_int sum;
 1553 
 1554         ts = td->td_sched;
 1555         sum = ts->ts_runtime + ts->ts_slptime;
 1556         if (sum < SCHED_SLP_RUN_MAX)
 1557                 return;
 1558         /*
 1559          * This only happens from two places:
 1560          * 1) We have added an unusual amount of run time from fork_exit.
 1561          * 2) We have added an unusual amount of sleep time from sched_sleep().
 1562          */
 1563         if (sum > SCHED_SLP_RUN_MAX * 2) {
 1564                 if (ts->ts_runtime > ts->ts_slptime) {
 1565                         ts->ts_runtime = SCHED_SLP_RUN_MAX;
 1566                         ts->ts_slptime = 1;
 1567                 } else {
 1568                         ts->ts_slptime = SCHED_SLP_RUN_MAX;
 1569                         ts->ts_runtime = 1;
 1570                 }
 1571                 return;
 1572         }
 1573         /*
 1574          * If we have exceeded by more than 1/5th then the algorithm below
 1575          * will not bring us back into range.  Dividing by two here forces
 1576          * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX]
 1577          */
 1578         if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) {
 1579                 ts->ts_runtime /= 2;
 1580                 ts->ts_slptime /= 2;
 1581                 return;
 1582         }
 1583         ts->ts_runtime = (ts->ts_runtime / 5) * 4;
 1584         ts->ts_slptime = (ts->ts_slptime / 5) * 4;
 1585 }
 1586 
 1587 /*
 1588  * Scale back the interactivity history when a child thread is created.  The
 1589  * history is inherited from the parent but the thread may behave totally
 1590  * differently.  For example, a shell spawning a compiler process.  We want
 1591  * to learn that the compiler is behaving badly very quickly.
 1592  */
 1593 static void
 1594 sched_interact_fork(struct thread *td)
 1595 {
 1596         int ratio;
 1597         int sum;
 1598 
 1599         sum = td->td_sched->ts_runtime + td->td_sched->ts_slptime;
 1600         if (sum > SCHED_SLP_RUN_FORK) {
 1601                 ratio = sum / SCHED_SLP_RUN_FORK;
 1602                 td->td_sched->ts_runtime /= ratio;
 1603                 td->td_sched->ts_slptime /= ratio;
 1604         }
 1605 }
 1606 
 1607 /*
 1608  * Called from proc0_init() to setup the scheduler fields.
 1609  */
 1610 void
 1611 schedinit(void)
 1612 {
 1613 
 1614         /*
 1615          * Set up the scheduler specific parts of proc0.
 1616          */
 1617         proc0.p_sched = NULL; /* XXX */
 1618         thread0.td_sched = &td_sched0;
 1619         td_sched0.ts_ltick = ticks;
 1620         td_sched0.ts_ftick = ticks;
 1621         td_sched0.ts_slice = 0;
 1622 }
 1623 
 1624 /*
 1625  * This is only somewhat accurate since given many processes of the same
 1626  * priority they will switch when their slices run out, which will be
 1627  * at most sched_slice stathz ticks.
 1628  */
 1629 int
 1630 sched_rr_interval(void)
 1631 {
 1632 
 1633         /* Convert sched_slice from stathz to hz. */
 1634         return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz));
 1635 }
 1636 
 1637 /*
 1638  * Update the percent cpu tracking information when it is requested or
 1639  * the total history exceeds the maximum.  We keep a sliding history of
 1640  * tick counts that slowly decays.  This is less precise than the 4BSD
 1641  * mechanism since it happens with less regular and frequent events.
 1642  */
 1643 static void
 1644 sched_pctcpu_update(struct td_sched *ts, int run)
 1645 {
 1646         int t = ticks;
 1647 
 1648         if (t - ts->ts_ltick >= SCHED_TICK_TARG) {
 1649                 ts->ts_ticks = 0;
 1650                 ts->ts_ftick = t - SCHED_TICK_TARG;
 1651         } else if (t - ts->ts_ftick >= SCHED_TICK_MAX) {
 1652                 ts->ts_ticks = (ts->ts_ticks / (ts->ts_ltick - ts->ts_ftick)) *
 1653                     (ts->ts_ltick - (t - SCHED_TICK_TARG));
 1654                 ts->ts_ftick = t - SCHED_TICK_TARG;
 1655         }
 1656         if (run)
 1657                 ts->ts_ticks += (t - ts->ts_ltick) << SCHED_TICK_SHIFT;
 1658         ts->ts_ltick = t;
 1659 }
 1660 
 1661 /*
 1662  * Adjust the priority of a thread.  Move it to the appropriate run-queue
 1663  * if necessary.  This is the back-end for several priority related
 1664  * functions.
 1665  */
 1666 static void
 1667 sched_thread_priority(struct thread *td, u_char prio)
 1668 {
 1669         struct td_sched *ts;
 1670         struct tdq *tdq;
 1671         int oldpri;
 1672 
 1673         KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio",
 1674             "prio:%d", td->td_priority, "new prio:%d", prio,
 1675             KTR_ATTR_LINKED, sched_tdname(curthread));
 1676         SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio);
 1677         if (td != curthread && prio < td->td_priority) {
 1678                 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
 1679                     "lend prio", "prio:%d", td->td_priority, "new prio:%d",
 1680                     prio, KTR_ATTR_LINKED, sched_tdname(td));
 1681                 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio, 
 1682                     curthread);
 1683         } 
 1684         ts = td->td_sched;
 1685         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1686         if (td->td_priority == prio)
 1687                 return;
 1688         /*
 1689          * If the priority has been elevated due to priority
 1690          * propagation, we may have to move ourselves to a new
 1691          * queue.  This could be optimized to not re-add in some
 1692          * cases.
 1693          */
 1694         if (TD_ON_RUNQ(td) && prio < td->td_priority) {
 1695                 sched_rem(td);
 1696                 td->td_priority = prio;
 1697                 sched_add(td, SRQ_BORROWING);
 1698                 return;
 1699         }
 1700         /*
 1701          * If the thread is currently running we may have to adjust the lowpri
 1702          * information so other cpus are aware of our current priority.
 1703          */
 1704         if (TD_IS_RUNNING(td)) {
 1705                 tdq = TDQ_CPU(ts->ts_cpu);
 1706                 oldpri = td->td_priority;
 1707                 td->td_priority = prio;
 1708                 if (prio < tdq->tdq_lowpri)
 1709                         tdq->tdq_lowpri = prio;
 1710                 else if (tdq->tdq_lowpri == oldpri)
 1711                         tdq_setlowpri(tdq, td);
 1712                 return;
 1713         }
 1714         td->td_priority = prio;
 1715 }
 1716 
 1717 /*
 1718  * Update a thread's priority when it is lent another thread's
 1719  * priority.
 1720  */
 1721 void
 1722 sched_lend_prio(struct thread *td, u_char prio)
 1723 {
 1724 
 1725         td->td_flags |= TDF_BORROWING;
 1726         sched_thread_priority(td, prio);
 1727 }
 1728 
 1729 /*
 1730  * Restore a thread's priority when priority propagation is
 1731  * over.  The prio argument is the minimum priority the thread
 1732  * needs to have to satisfy other possible priority lending
 1733  * requests.  If the thread's regular priority is less
 1734  * important than prio, the thread will keep a priority boost
 1735  * of prio.
 1736  */
 1737 void
 1738 sched_unlend_prio(struct thread *td, u_char prio)
 1739 {
 1740         u_char base_pri;
 1741 
 1742         if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
 1743             td->td_base_pri <= PRI_MAX_TIMESHARE)
 1744                 base_pri = td->td_user_pri;
 1745         else
 1746                 base_pri = td->td_base_pri;
 1747         if (prio >= base_pri) {
 1748                 td->td_flags &= ~TDF_BORROWING;
 1749                 sched_thread_priority(td, base_pri);
 1750         } else
 1751                 sched_lend_prio(td, prio);
 1752 }
 1753 
 1754 /*
 1755  * Standard entry for setting the priority to an absolute value.
 1756  */
 1757 void
 1758 sched_prio(struct thread *td, u_char prio)
 1759 {
 1760         u_char oldprio;
 1761 
 1762         /* First, update the base priority. */
 1763         td->td_base_pri = prio;
 1764 
 1765         /*
 1766          * If the thread is borrowing another thread's priority, don't
 1767          * ever lower the priority.
 1768          */
 1769         if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
 1770                 return;
 1771 
 1772         /* Change the real priority. */
 1773         oldprio = td->td_priority;
 1774         sched_thread_priority(td, prio);
 1775 
 1776         /*
 1777          * If the thread is on a turnstile, then let the turnstile update
 1778          * its state.
 1779          */
 1780         if (TD_ON_LOCK(td) && oldprio != prio)
 1781                 turnstile_adjust(td, oldprio);
 1782 }
 1783 
 1784 /*
 1785  * Set the base user priority, does not effect current running priority.
 1786  */
 1787 void
 1788 sched_user_prio(struct thread *td, u_char prio)
 1789 {
 1790 
 1791         td->td_base_user_pri = prio;
 1792         if (td->td_lend_user_pri <= prio)
 1793                 return;
 1794         td->td_user_pri = prio;
 1795 }
 1796 
 1797 void
 1798 sched_lend_user_prio(struct thread *td, u_char prio)
 1799 {
 1800 
 1801         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1802         td->td_lend_user_pri = prio;
 1803         td->td_user_pri = min(prio, td->td_base_user_pri);
 1804         if (td->td_priority > td->td_user_pri)
 1805                 sched_prio(td, td->td_user_pri);
 1806         else if (td->td_priority != td->td_user_pri)
 1807                 td->td_flags |= TDF_NEEDRESCHED;
 1808 }
 1809 
 1810 /*
 1811  * Handle migration from sched_switch().  This happens only for
 1812  * cpu binding.
 1813  */
 1814 static struct mtx *
 1815 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags)
 1816 {
 1817         struct tdq *tdn;
 1818 
 1819         tdn = TDQ_CPU(td->td_sched->ts_cpu);
 1820 #ifdef SMP
 1821         tdq_load_rem(tdq, td);
 1822         /*
 1823          * Do the lock dance required to avoid LOR.  We grab an extra
 1824          * spinlock nesting to prevent preemption while we're
 1825          * not holding either run-queue lock.
 1826          */
 1827         spinlock_enter();
 1828         thread_lock_block(td);  /* This releases the lock on tdq. */
 1829 
 1830         /*
 1831          * Acquire both run-queue locks before placing the thread on the new
 1832          * run-queue to avoid deadlocks created by placing a thread with a
 1833          * blocked lock on the run-queue of a remote processor.  The deadlock
 1834          * occurs when a third processor attempts to lock the two queues in
 1835          * question while the target processor is spinning with its own
 1836          * run-queue lock held while waiting for the blocked lock to clear.
 1837          */
 1838         tdq_lock_pair(tdn, tdq);
 1839         tdq_add(tdn, td, flags);
 1840         tdq_notify(tdn, td);
 1841         TDQ_UNLOCK(tdn);
 1842         spinlock_exit();
 1843 #endif
 1844         return (TDQ_LOCKPTR(tdn));
 1845 }
 1846 
 1847 /*
 1848  * Variadic version of thread_lock_unblock() that does not assume td_lock
 1849  * is blocked.
 1850  */
 1851 static inline void
 1852 thread_unblock_switch(struct thread *td, struct mtx *mtx)
 1853 {
 1854         atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock,
 1855             (uintptr_t)mtx);
 1856 }
 1857 
 1858 /*
 1859  * Switch threads.  This function has to handle threads coming in while
 1860  * blocked for some reason, running, or idle.  It also must deal with
 1861  * migrating a thread from one queue to another as running threads may
 1862  * be assigned elsewhere via binding.
 1863  */
 1864 void
 1865 sched_switch(struct thread *td, struct thread *newtd, int flags)
 1866 {
 1867         struct tdq *tdq;
 1868         struct td_sched *ts;
 1869         struct mtx *mtx;
 1870         int srqflag;
 1871         int cpuid, preempted;
 1872 
 1873         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1874         KASSERT(newtd == NULL, ("sched_switch: Unsupported newtd argument"));
 1875 
 1876         cpuid = PCPU_GET(cpuid);
 1877         tdq = TDQ_CPU(cpuid);
 1878         ts = td->td_sched;
 1879         mtx = td->td_lock;
 1880         sched_pctcpu_update(ts, 1);
 1881         ts->ts_rltick = ticks;
 1882         td->td_lastcpu = td->td_oncpu;
 1883         td->td_oncpu = NOCPU;
 1884         preempted = !((td->td_flags & TDF_SLICEEND) ||
 1885             (flags & SWT_RELINQUISH));
 1886         td->td_flags &= ~(TDF_NEEDRESCHED | TDF_SLICEEND);
 1887         td->td_owepreempt = 0;
 1888         if (!TD_IS_IDLETHREAD(td))
 1889                 tdq->tdq_switchcnt++;
 1890         /*
 1891          * The lock pointer in an idle thread should never change.  Reset it
 1892          * to CAN_RUN as well.
 1893          */
 1894         if (TD_IS_IDLETHREAD(td)) {
 1895                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1896                 TD_SET_CAN_RUN(td);
 1897         } else if (TD_IS_RUNNING(td)) {
 1898                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1899                 srqflag = preempted ?
 1900                     SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
 1901                     SRQ_OURSELF|SRQ_YIELDING;
 1902 #ifdef SMP
 1903                 if (THREAD_CAN_MIGRATE(td) && !THREAD_CAN_SCHED(td, ts->ts_cpu))
 1904                         ts->ts_cpu = sched_pickcpu(td, 0);
 1905 #endif
 1906                 if (ts->ts_cpu == cpuid)
 1907                         tdq_runq_add(tdq, td, srqflag);
 1908                 else {
 1909                         KASSERT(THREAD_CAN_MIGRATE(td) ||
 1910                             (ts->ts_flags & TSF_BOUND) != 0,
 1911                             ("Thread %p shouldn't migrate", td));
 1912                         mtx = sched_switch_migrate(tdq, td, srqflag);
 1913                 }
 1914         } else {
 1915                 /* This thread must be going to sleep. */
 1916                 TDQ_LOCK(tdq);
 1917                 mtx = thread_lock_block(td);
 1918                 tdq_load_rem(tdq, td);
 1919         }
 1920         /*
 1921          * We enter here with the thread blocked and assigned to the
 1922          * appropriate cpu run-queue or sleep-queue and with the current
 1923          * thread-queue locked.
 1924          */
 1925         TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
 1926         newtd = choosethread();
 1927         /*
 1928          * Call the MD code to switch contexts if necessary.
 1929          */
 1930         if (td != newtd) {
 1931 #ifdef  HWPMC_HOOKS
 1932                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 1933                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
 1934 #endif
 1935                 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc);
 1936                 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
 1937                 TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
 1938                 sched_pctcpu_update(newtd->td_sched, 0);
 1939 
 1940 #ifdef KDTRACE_HOOKS
 1941                 /*
 1942                  * If DTrace has set the active vtime enum to anything
 1943                  * other than INACTIVE (0), then it should have set the
 1944                  * function to call.
 1945                  */
 1946                 if (dtrace_vtime_active)
 1947                         (*dtrace_vtime_switch_func)(newtd);
 1948 #endif
 1949 
 1950                 cpu_switch(td, newtd, mtx);
 1951                 /*
 1952                  * We may return from cpu_switch on a different cpu.  However,
 1953                  * we always return with td_lock pointing to the current cpu's
 1954                  * run queue lock.
 1955                  */
 1956                 cpuid = PCPU_GET(cpuid);
 1957                 tdq = TDQ_CPU(cpuid);
 1958                 lock_profile_obtain_lock_success(
 1959                     &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
 1960 
 1961                 SDT_PROBE0(sched, , , on__cpu);
 1962 #ifdef  HWPMC_HOOKS
 1963                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 1964                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
 1965 #endif
 1966         } else {
 1967                 thread_unblock_switch(td, mtx);
 1968                 SDT_PROBE0(sched, , , remain__cpu);
 1969         }
 1970         /*
 1971          * Assert that all went well and return.
 1972          */
 1973         TDQ_LOCK_ASSERT(tdq, MA_OWNED|MA_NOTRECURSED);
 1974         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1975         td->td_oncpu = cpuid;
 1976 }
 1977 
 1978 /*
 1979  * Adjust thread priorities as a result of a nice request.
 1980  */
 1981 void
 1982 sched_nice(struct proc *p, int nice)
 1983 {
 1984         struct thread *td;
 1985 
 1986         PROC_LOCK_ASSERT(p, MA_OWNED);
 1987 
 1988         p->p_nice = nice;
 1989         FOREACH_THREAD_IN_PROC(p, td) {
 1990                 thread_lock(td);
 1991                 sched_priority(td);
 1992                 sched_prio(td, td->td_base_user_pri);
 1993                 thread_unlock(td);
 1994         }
 1995 }
 1996 
 1997 /*
 1998  * Record the sleep time for the interactivity scorer.
 1999  */
 2000 void
 2001 sched_sleep(struct thread *td, int prio)
 2002 {
 2003 
 2004         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2005 
 2006         td->td_slptick = ticks;
 2007         if (TD_IS_SUSPENDED(td) || prio >= PSOCK)
 2008                 td->td_flags |= TDF_CANSWAP;
 2009         if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
 2010                 return;
 2011         if (static_boost == 1 && prio)
 2012                 sched_prio(td, prio);
 2013         else if (static_boost && td->td_priority > static_boost)
 2014                 sched_prio(td, static_boost);
 2015 }
 2016 
 2017 /*
 2018  * Schedule a thread to resume execution and record how long it voluntarily
 2019  * slept.  We also update the pctcpu, interactivity, and priority.
 2020  */
 2021 void
 2022 sched_wakeup(struct thread *td)
 2023 {
 2024         struct td_sched *ts;
 2025         int slptick;
 2026 
 2027         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2028         ts = td->td_sched;
 2029         td->td_flags &= ~TDF_CANSWAP;
 2030         /*
 2031          * If we slept for more than a tick update our interactivity and
 2032          * priority.
 2033          */
 2034         slptick = td->td_slptick;
 2035         td->td_slptick = 0;
 2036         if (slptick && slptick != ticks) {
 2037                 ts->ts_slptime += (ticks - slptick) << SCHED_TICK_SHIFT;
 2038                 sched_interact_update(td);
 2039                 sched_pctcpu_update(ts, 0);
 2040         }
 2041         /*
 2042          * Reset the slice value since we slept and advanced the round-robin.
 2043          */
 2044         ts->ts_slice = 0;
 2045         sched_add(td, SRQ_BORING);
 2046 }
 2047 
 2048 /*
 2049  * Penalize the parent for creating a new child and initialize the child's
 2050  * priority.
 2051  */
 2052 void
 2053 sched_fork(struct thread *td, struct thread *child)
 2054 {
 2055         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2056         sched_pctcpu_update(td->td_sched, 1);
 2057         sched_fork_thread(td, child);
 2058         /*
 2059          * Penalize the parent and child for forking.
 2060          */
 2061         sched_interact_fork(child);
 2062         sched_priority(child);
 2063         td->td_sched->ts_runtime += tickincr;
 2064         sched_interact_update(td);
 2065         sched_priority(td);
 2066 }
 2067 
 2068 /*
 2069  * Fork a new thread, may be within the same process.
 2070  */
 2071 void
 2072 sched_fork_thread(struct thread *td, struct thread *child)
 2073 {
 2074         struct td_sched *ts;
 2075         struct td_sched *ts2;
 2076         struct tdq *tdq;
 2077 
 2078         tdq = TDQ_SELF();
 2079         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2080         /*
 2081          * Initialize child.
 2082          */
 2083         ts = td->td_sched;
 2084         ts2 = child->td_sched;
 2085         child->td_lock = TDQ_LOCKPTR(tdq);
 2086         child->td_cpuset = cpuset_ref(td->td_cpuset);
 2087         ts2->ts_cpu = ts->ts_cpu;
 2088         ts2->ts_flags = 0;
 2089         /*
 2090          * Grab our parents cpu estimation information.
 2091          */
 2092         ts2->ts_ticks = ts->ts_ticks;
 2093         ts2->ts_ltick = ts->ts_ltick;
 2094         ts2->ts_ftick = ts->ts_ftick;
 2095         /*
 2096          * Do not inherit any borrowed priority from the parent.
 2097          */
 2098         child->td_priority = child->td_base_pri;
 2099         /*
 2100          * And update interactivity score.
 2101          */
 2102         ts2->ts_slptime = ts->ts_slptime;
 2103         ts2->ts_runtime = ts->ts_runtime;
 2104         /* Attempt to quickly learn interactivity. */
 2105         ts2->ts_slice = tdq_slice(tdq) - sched_slice_min;
 2106 #ifdef KTR
 2107         bzero(ts2->ts_name, sizeof(ts2->ts_name));
 2108 #endif
 2109 }
 2110 
 2111 /*
 2112  * Adjust the priority class of a thread.
 2113  */
 2114 void
 2115 sched_class(struct thread *td, int class)
 2116 {
 2117 
 2118         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2119         if (td->td_pri_class == class)
 2120                 return;
 2121         td->td_pri_class = class;
 2122 }
 2123 
 2124 /*
 2125  * Return some of the child's priority and interactivity to the parent.
 2126  */
 2127 void
 2128 sched_exit(struct proc *p, struct thread *child)
 2129 {
 2130         struct thread *td;
 2131 
 2132         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit",
 2133             "prio:%d", child->td_priority);
 2134         PROC_LOCK_ASSERT(p, MA_OWNED);
 2135         td = FIRST_THREAD_IN_PROC(p);
 2136         sched_exit_thread(td, child);
 2137 }
 2138 
 2139 /*
 2140  * Penalize another thread for the time spent on this one.  This helps to
 2141  * worsen the priority and interactivity of processes which schedule batch
 2142  * jobs such as make.  This has little effect on the make process itself but
 2143  * causes new processes spawned by it to receive worse scores immediately.
 2144  */
 2145 void
 2146 sched_exit_thread(struct thread *td, struct thread *child)
 2147 {
 2148 
 2149         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit",
 2150             "prio:%d", child->td_priority);
 2151         /*
 2152          * Give the child's runtime to the parent without returning the
 2153          * sleep time as a penalty to the parent.  This causes shells that
 2154          * launch expensive things to mark their children as expensive.
 2155          */
 2156         thread_lock(td);
 2157         td->td_sched->ts_runtime += child->td_sched->ts_runtime;
 2158         sched_interact_update(td);
 2159         sched_priority(td);
 2160         thread_unlock(td);
 2161 }
 2162 
 2163 void
 2164 sched_preempt(struct thread *td)
 2165 {
 2166         struct tdq *tdq;
 2167 
 2168         SDT_PROBE2(sched, , , surrender, td, td->td_proc);
 2169 
 2170         thread_lock(td);
 2171         tdq = TDQ_SELF();
 2172         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2173         tdq->tdq_ipipending = 0;
 2174         if (td->td_priority > tdq->tdq_lowpri) {
 2175                 int flags;
 2176 
 2177                 flags = SW_INVOL | SW_PREEMPT;
 2178                 if (td->td_critnest > 1)
 2179                         td->td_owepreempt = 1;
 2180                 else if (TD_IS_IDLETHREAD(td))
 2181                         mi_switch(flags | SWT_REMOTEWAKEIDLE, NULL);
 2182                 else
 2183                         mi_switch(flags | SWT_REMOTEPREEMPT, NULL);
 2184         }
 2185         thread_unlock(td);
 2186 }
 2187 
 2188 /*
 2189  * Fix priorities on return to user-space.  Priorities may be elevated due
 2190  * to static priorities in msleep() or similar.
 2191  */
 2192 void
 2193 sched_userret(struct thread *td)
 2194 {
 2195         /*
 2196          * XXX we cheat slightly on the locking here to avoid locking in  
 2197          * the usual case.  Setting td_priority here is essentially an
 2198          * incomplete workaround for not setting it properly elsewhere.
 2199          * Now that some interrupt handlers are threads, not setting it
 2200          * properly elsewhere can clobber it in the window between setting
 2201          * it here and returning to user mode, so don't waste time setting
 2202          * it perfectly here.
 2203          */
 2204         KASSERT((td->td_flags & TDF_BORROWING) == 0,
 2205             ("thread with borrowed priority returning to userland"));
 2206         if (td->td_priority != td->td_user_pri) {
 2207                 thread_lock(td);
 2208                 td->td_priority = td->td_user_pri;
 2209                 td->td_base_pri = td->td_user_pri;
 2210                 tdq_setlowpri(TDQ_SELF(), td);
 2211                 thread_unlock(td);
 2212         }
 2213 }
 2214 
 2215 /*
 2216  * Handle a stathz tick.  This is really only relevant for timeshare
 2217  * threads.
 2218  */
 2219 void
 2220 sched_clock(struct thread *td)
 2221 {
 2222         struct tdq *tdq;
 2223         struct td_sched *ts;
 2224 
 2225         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2226         tdq = TDQ_SELF();
 2227 #ifdef SMP
 2228         /*
 2229          * We run the long term load balancer infrequently on the first cpu.
 2230          */
 2231         if (balance_tdq == tdq) {
 2232                 if (balance_ticks && --balance_ticks == 0)
 2233                         sched_balance();
 2234         }
 2235 #endif
 2236         /*
 2237          * Save the old switch count so we have a record of the last ticks
 2238          * activity.   Initialize the new switch count based on our load.
 2239          * If there is some activity seed it to reflect that.
 2240          */
 2241         tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt;
 2242         tdq->tdq_switchcnt = tdq->tdq_load;
 2243         /*
 2244          * Advance the insert index once for each tick to ensure that all
 2245          * threads get a chance to run.
 2246          */
 2247         if (tdq->tdq_idx == tdq->tdq_ridx) {
 2248                 tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS;
 2249                 if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx]))
 2250                         tdq->tdq_ridx = tdq->tdq_idx;
 2251         }
 2252         ts = td->td_sched;
 2253         sched_pctcpu_update(ts, 1);
 2254         if (td->td_pri_class & PRI_FIFO_BIT)
 2255                 return;
 2256         if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) {
 2257                 /*
 2258                  * We used a tick; charge it to the thread so
 2259                  * that we can compute our interactivity.
 2260                  */
 2261                 td->td_sched->ts_runtime += tickincr;
 2262                 sched_interact_update(td);
 2263                 sched_priority(td);
 2264         }
 2265 
 2266         /*
 2267          * Force a context switch if the current thread has used up a full
 2268          * time slice (default is 100ms).
 2269          */
 2270         if (!TD_IS_IDLETHREAD(td) && ++ts->ts_slice >= tdq_slice(tdq)) {
 2271                 ts->ts_slice = 0;
 2272                 td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND;
 2273         }
 2274 }
 2275 
 2276 /*
 2277  * Called once per hz tick.
 2278  */
 2279 void
 2280 sched_tick(int cnt)
 2281 {
 2282 
 2283 }
 2284 
 2285 /*
 2286  * Return whether the current CPU has runnable tasks.  Used for in-kernel
 2287  * cooperative idle threads.
 2288  */
 2289 int
 2290 sched_runnable(void)
 2291 {
 2292         struct tdq *tdq;
 2293         int load;
 2294 
 2295         load = 1;
 2296 
 2297         tdq = TDQ_SELF();
 2298         if ((curthread->td_flags & TDF_IDLETD) != 0) {
 2299                 if (tdq->tdq_load > 0)
 2300                         goto out;
 2301         } else
 2302                 if (tdq->tdq_load - 1 > 0)
 2303                         goto out;
 2304         load = 0;
 2305 out:
 2306         return (load);
 2307 }
 2308 
 2309 /*
 2310  * Choose the highest priority thread to run.  The thread is removed from
 2311  * the run-queue while running however the load remains.  For SMP we set
 2312  * the tdq in the global idle bitmask if it idles here.
 2313  */
 2314 struct thread *
 2315 sched_choose(void)
 2316 {
 2317         struct thread *td;
 2318         struct tdq *tdq;
 2319 
 2320         tdq = TDQ_SELF();
 2321         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2322         td = tdq_choose(tdq);
 2323         if (td) {
 2324                 tdq_runq_rem(tdq, td);
 2325                 tdq->tdq_lowpri = td->td_priority;
 2326                 return (td);
 2327         }
 2328         tdq->tdq_lowpri = PRI_MAX_IDLE;
 2329         return (PCPU_GET(idlethread));
 2330 }
 2331 
 2332 /*
 2333  * Set owepreempt if necessary.  Preemption never happens directly in ULE,
 2334  * we always request it once we exit a critical section.
 2335  */
 2336 static inline void
 2337 sched_setpreempt(struct thread *td)
 2338 {
 2339         struct thread *ctd;
 2340         int cpri;
 2341         int pri;
 2342 
 2343         THREAD_LOCK_ASSERT(curthread, MA_OWNED);
 2344 
 2345         ctd = curthread;
 2346         pri = td->td_priority;
 2347         cpri = ctd->td_priority;
 2348         if (pri < cpri)
 2349                 ctd->td_flags |= TDF_NEEDRESCHED;
 2350         if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
 2351                 return;
 2352         if (!sched_shouldpreempt(pri, cpri, 0))
 2353                 return;
 2354         ctd->td_owepreempt = 1;
 2355 }
 2356 
 2357 /*
 2358  * Add a thread to a thread queue.  Select the appropriate runq and add the
 2359  * thread to it.  This is the internal function called when the tdq is
 2360  * predetermined.
 2361  */
 2362 void
 2363 tdq_add(struct tdq *tdq, struct thread *td, int flags)
 2364 {
 2365 
 2366         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2367         KASSERT((td->td_inhibitors == 0),
 2368             ("sched_add: trying to run inhibited thread"));
 2369         KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
 2370             ("sched_add: bad thread state"));
 2371         KASSERT(td->td_flags & TDF_INMEM,
 2372             ("sched_add: thread swapped out"));
 2373 
 2374         if (td->td_priority < tdq->tdq_lowpri)
 2375                 tdq->tdq_lowpri = td->td_priority;
 2376         tdq_runq_add(tdq, td, flags);
 2377         tdq_load_add(tdq, td);
 2378 }
 2379 
 2380 /*
 2381  * Select the target thread queue and add a thread to it.  Request
 2382  * preemption or IPI a remote processor if required.
 2383  */
 2384 void
 2385 sched_add(struct thread *td, int flags)
 2386 {
 2387         struct tdq *tdq;
 2388 #ifdef SMP
 2389         int cpu;
 2390 #endif
 2391 
 2392         KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
 2393             "prio:%d", td->td_priority, KTR_ATTR_LINKED,
 2394             sched_tdname(curthread));
 2395         KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
 2396             KTR_ATTR_LINKED, sched_tdname(td));
 2397         SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL, 
 2398             flags & SRQ_PREEMPTED);
 2399         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2400         /*
 2401          * Recalculate the priority before we select the target cpu or
 2402          * run-queue.
 2403          */
 2404         if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
 2405                 sched_priority(td);
 2406 #ifdef SMP
 2407         /*
 2408          * Pick the destination cpu and if it isn't ours transfer to the
 2409          * target cpu.
 2410          */
 2411         cpu = sched_pickcpu(td, flags);
 2412         tdq = sched_setcpu(td, cpu, flags);
 2413         tdq_add(tdq, td, flags);
 2414         if (cpu != PCPU_GET(cpuid)) {
 2415                 tdq_notify(tdq, td);
 2416                 return;
 2417         }
 2418 #else
 2419         tdq = TDQ_SELF();
 2420         TDQ_LOCK(tdq);
 2421         /*
 2422          * Now that the thread is moving to the run-queue, set the lock
 2423          * to the scheduler's lock.
 2424          */
 2425         thread_lock_set(td, TDQ_LOCKPTR(tdq));
 2426         tdq_add(tdq, td, flags);
 2427 #endif
 2428         if (!(flags & SRQ_YIELDING))
 2429                 sched_setpreempt(td);
 2430 }
 2431 
 2432 /*
 2433  * Remove a thread from a run-queue without running it.  This is used
 2434  * when we're stealing a thread from a remote queue.  Otherwise all threads
 2435  * exit by calling sched_exit_thread() and sched_throw() themselves.
 2436  */
 2437 void
 2438 sched_rem(struct thread *td)
 2439 {
 2440         struct tdq *tdq;
 2441 
 2442         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
 2443             "prio:%d", td->td_priority);
 2444         SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL);
 2445         tdq = TDQ_CPU(td->td_sched->ts_cpu);
 2446         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2447         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2448         KASSERT(TD_ON_RUNQ(td),
 2449             ("sched_rem: thread not on run queue"));
 2450         tdq_runq_rem(tdq, td);
 2451         tdq_load_rem(tdq, td);
 2452         TD_SET_CAN_RUN(td);
 2453         if (td->td_priority == tdq->tdq_lowpri)
 2454                 tdq_setlowpri(tdq, NULL);
 2455 }
 2456 
 2457 /*
 2458  * Fetch cpu utilization information.  Updates on demand.
 2459  */
 2460 fixpt_t
 2461 sched_pctcpu(struct thread *td)
 2462 {
 2463         fixpt_t pctcpu;
 2464         struct td_sched *ts;
 2465 
 2466         pctcpu = 0;
 2467         ts = td->td_sched;
 2468         if (ts == NULL)
 2469                 return (0);
 2470 
 2471         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2472         sched_pctcpu_update(ts, TD_IS_RUNNING(td));
 2473         if (ts->ts_ticks) {
 2474                 int rtick;
 2475 
 2476                 /* How many rtick per second ? */
 2477                 rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
 2478                 pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
 2479         }
 2480 
 2481         return (pctcpu);
 2482 }
 2483 
 2484 /*
 2485  * Enforce affinity settings for a thread.  Called after adjustments to
 2486  * cpumask.
 2487  */
 2488 void
 2489 sched_affinity(struct thread *td)
 2490 {
 2491 #ifdef SMP
 2492         struct td_sched *ts;
 2493 
 2494         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2495         ts = td->td_sched;
 2496         if (THREAD_CAN_SCHED(td, ts->ts_cpu))
 2497                 return;
 2498         if (TD_ON_RUNQ(td)) {
 2499                 sched_rem(td);
 2500                 sched_add(td, SRQ_BORING);
 2501                 return;
 2502         }
 2503         if (!TD_IS_RUNNING(td))
 2504                 return;
 2505         /*
 2506          * Force a switch before returning to userspace.  If the
 2507          * target thread is not running locally send an ipi to force
 2508          * the issue.
 2509          */
 2510         td->td_flags |= TDF_NEEDRESCHED;
 2511         if (td != curthread)
 2512                 ipi_cpu(ts->ts_cpu, IPI_PREEMPT);
 2513 #endif
 2514 }
 2515 
 2516 /*
 2517  * Bind a thread to a target cpu.
 2518  */
 2519 void
 2520 sched_bind(struct thread *td, int cpu)
 2521 {
 2522         struct td_sched *ts;
 2523 
 2524         THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
 2525         KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
 2526         ts = td->td_sched;
 2527         if (ts->ts_flags & TSF_BOUND)
 2528                 sched_unbind(td);
 2529         KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td));
 2530         ts->ts_flags |= TSF_BOUND;
 2531         sched_pin();
 2532         if (PCPU_GET(cpuid) == cpu)
 2533                 return;
 2534         ts->ts_cpu = cpu;
 2535         /* When we return from mi_switch we'll be on the correct cpu. */
 2536         mi_switch(SW_VOL, NULL);
 2537 }
 2538 
 2539 /*
 2540  * Release a bound thread.
 2541  */
 2542 void
 2543 sched_unbind(struct thread *td)
 2544 {
 2545         struct td_sched *ts;
 2546 
 2547         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2548         KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
 2549         ts = td->td_sched;
 2550         if ((ts->ts_flags & TSF_BOUND) == 0)
 2551                 return;
 2552         ts->ts_flags &= ~TSF_BOUND;
 2553         sched_unpin();
 2554 }
 2555 
 2556 int
 2557 sched_is_bound(struct thread *td)
 2558 {
 2559         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2560         return (td->td_sched->ts_flags & TSF_BOUND);
 2561 }
 2562 
 2563 /*
 2564  * Basic yield call.
 2565  */
 2566 void
 2567 sched_relinquish(struct thread *td)
 2568 {
 2569         thread_lock(td);
 2570         mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
 2571         thread_unlock(td);
 2572 }
 2573 
 2574 /*
 2575  * Return the total system load.
 2576  */
 2577 int
 2578 sched_load(void)
 2579 {
 2580 #ifdef SMP
 2581         int total;
 2582         int i;
 2583 
 2584         total = 0;
 2585         CPU_FOREACH(i)
 2586                 total += TDQ_CPU(i)->tdq_sysload;
 2587         return (total);
 2588 #else
 2589         return (TDQ_SELF()->tdq_sysload);
 2590 #endif
 2591 }
 2592 
 2593 int
 2594 sched_sizeof_proc(void)
 2595 {
 2596         return (sizeof(struct proc));
 2597 }
 2598 
 2599 int
 2600 sched_sizeof_thread(void)
 2601 {
 2602         return (sizeof(struct thread) + sizeof(struct td_sched));
 2603 }
 2604 
 2605 #ifdef SMP
 2606 #define TDQ_IDLESPIN(tdq)                                               \
 2607     ((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0)
 2608 #else
 2609 #define TDQ_IDLESPIN(tdq)       1
 2610 #endif
 2611 
 2612 /*
 2613  * The actual idle process.
 2614  */
 2615 void
 2616 sched_idletd(void *dummy)
 2617 {
 2618         struct thread *td;
 2619         struct tdq *tdq;
 2620         int oldswitchcnt, switchcnt;
 2621         int i;
 2622 
 2623         mtx_assert(&Giant, MA_NOTOWNED);
 2624         td = curthread;
 2625         tdq = TDQ_SELF();
 2626         THREAD_NO_SLEEPING();
 2627         oldswitchcnt = -1;
 2628         for (;;) {
 2629                 if (tdq->tdq_load) {
 2630                         thread_lock(td);
 2631                         mi_switch(SW_VOL | SWT_IDLE, NULL);
 2632                         thread_unlock(td);
 2633                 }
 2634                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2635 #ifdef SMP
 2636                 if (switchcnt != oldswitchcnt) {
 2637                         oldswitchcnt = switchcnt;
 2638                         if (tdq_idled(tdq) == 0)
 2639                                 continue;
 2640                 }
 2641                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2642 #else
 2643                 oldswitchcnt = switchcnt;
 2644 #endif
 2645                 /*
 2646                  * If we're switching very frequently, spin while checking
 2647                  * for load rather than entering a low power state that 
 2648                  * may require an IPI.  However, don't do any busy
 2649                  * loops while on SMT machines as this simply steals
 2650                  * cycles from cores doing useful work.
 2651                  */
 2652                 if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) {
 2653                         for (i = 0; i < sched_idlespins; i++) {
 2654                                 if (tdq->tdq_load)
 2655                                         break;
 2656                                 cpu_spinwait();
 2657                         }
 2658                 }
 2659 
 2660                 /* If there was context switch during spin, restart it. */
 2661                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2662                 if (tdq->tdq_load != 0 || switchcnt != oldswitchcnt)
 2663                         continue;
 2664 
 2665                 /* Run main MD idle handler. */
 2666                 tdq->tdq_cpu_idle = 1;
 2667                 /*
 2668                  * Make sure that tdq_cpu_idle update is globally visible
 2669                  * before cpu_idle() read tdq_load.  The order is important
 2670                  * to avoid race with tdq_notify.
 2671                  */
 2672                 mb();
 2673                 cpu_idle(switchcnt * 4 > sched_idlespinthresh);
 2674                 tdq->tdq_cpu_idle = 0;
 2675 
 2676                 /*
 2677                  * Account thread-less hardware interrupts and
 2678                  * other wakeup reasons equal to context switches.
 2679                  */
 2680                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2681                 if (switchcnt != oldswitchcnt)
 2682                         continue;
 2683                 tdq->tdq_switchcnt++;
 2684                 oldswitchcnt++;
 2685         }
 2686 }
 2687 
 2688 /*
 2689  * A CPU is entering for the first time or a thread is exiting.
 2690  */
 2691 void
 2692 sched_throw(struct thread *td)
 2693 {
 2694         struct thread *newtd;
 2695         struct tdq *tdq;
 2696 
 2697         tdq = TDQ_SELF();
 2698         if (td == NULL) {
 2699                 /* Correct spinlock nesting and acquire the correct lock. */
 2700                 TDQ_LOCK(tdq);
 2701                 spinlock_exit();
 2702                 PCPU_SET(switchtime, cpu_ticks());
 2703                 PCPU_SET(switchticks, ticks);
 2704         } else {
 2705                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2706                 tdq_load_rem(tdq, td);
 2707                 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
 2708         }
 2709         KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
 2710         newtd = choosethread();
 2711         TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
 2712         cpu_throw(td, newtd);           /* doesn't return */
 2713 }
 2714 
 2715 /*
 2716  * This is called from fork_exit().  Just acquire the correct locks and
 2717  * let fork do the rest of the work.
 2718  */
 2719 void
 2720 sched_fork_exit(struct thread *td)
 2721 {
 2722         struct tdq *tdq;
 2723         int cpuid;
 2724 
 2725         /*
 2726          * Finish setting up thread glue so that it begins execution in a
 2727          * non-nested critical section with the scheduler lock held.
 2728          */
 2729         cpuid = PCPU_GET(cpuid);
 2730         tdq = TDQ_CPU(cpuid);
 2731         if (TD_IS_IDLETHREAD(td))
 2732                 td->td_lock = TDQ_LOCKPTR(tdq);
 2733         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2734         td->td_oncpu = cpuid;
 2735         TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
 2736         lock_profile_obtain_lock_success(
 2737             &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
 2738 }
 2739 
 2740 /*
 2741  * Create on first use to catch odd startup conditons.
 2742  */
 2743 char *
 2744 sched_tdname(struct thread *td)
 2745 {
 2746 #ifdef KTR
 2747         struct td_sched *ts;
 2748 
 2749         ts = td->td_sched;
 2750         if (ts->ts_name[0] == '\0')
 2751                 snprintf(ts->ts_name, sizeof(ts->ts_name),
 2752                     "%s tid %d", td->td_name, td->td_tid);
 2753         return (ts->ts_name);
 2754 #else
 2755         return (td->td_name);
 2756 #endif
 2757 }
 2758 
 2759 #ifdef KTR
 2760 void
 2761 sched_clear_tdname(struct thread *td)
 2762 {
 2763         struct td_sched *ts;
 2764 
 2765         ts = td->td_sched;
 2766         ts->ts_name[0] = '\0';
 2767 }
 2768 #endif
 2769 
 2770 #ifdef SMP
 2771 
 2772 /*
 2773  * Build the CPU topology dump string. Is recursively called to collect
 2774  * the topology tree.
 2775  */
 2776 static int
 2777 sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg,
 2778     int indent)
 2779 {
 2780         char cpusetbuf[CPUSETBUFSIZ];
 2781         int i, first;
 2782 
 2783         sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent,
 2784             "", 1 + indent / 2, cg->cg_level);
 2785         sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"%s\">", indent, "",
 2786             cg->cg_count, cpusetobj_strprint(cpusetbuf, &cg->cg_mask));
 2787         first = TRUE;
 2788         for (i = 0; i < MAXCPU; i++) {
 2789                 if (CPU_ISSET(i, &cg->cg_mask)) {
 2790                         if (!first)
 2791                                 sbuf_printf(sb, ", ");
 2792                         else
 2793                                 first = FALSE;
 2794                         sbuf_printf(sb, "%d", i);
 2795                 }
 2796         }
 2797         sbuf_printf(sb, "</cpu>\n");
 2798 
 2799         if (cg->cg_flags != 0) {
 2800                 sbuf_printf(sb, "%*s <flags>", indent, "");
 2801                 if ((cg->cg_flags & CG_FLAG_HTT) != 0)
 2802                         sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>");
 2803                 if ((cg->cg_flags & CG_FLAG_THREAD) != 0)
 2804                         sbuf_printf(sb, "<flag name=\"THREAD\">THREAD group</flag>");
 2805                 if ((cg->cg_flags & CG_FLAG_SMT) != 0)
 2806                         sbuf_printf(sb, "<flag name=\"SMT\">SMT group</flag>");
 2807                 sbuf_printf(sb, "</flags>\n");
 2808         }
 2809 
 2810         if (cg->cg_children > 0) {
 2811                 sbuf_printf(sb, "%*s <children>\n", indent, "");
 2812                 for (i = 0; i < cg->cg_children; i++)
 2813                         sysctl_kern_sched_topology_spec_internal(sb, 
 2814                             &cg->cg_child[i], indent+2);
 2815                 sbuf_printf(sb, "%*s </children>\n", indent, "");
 2816         }
 2817         sbuf_printf(sb, "%*s</group>\n", indent, "");
 2818         return (0);
 2819 }
 2820 
 2821 /*
 2822  * Sysctl handler for retrieving topology dump. It's a wrapper for
 2823  * the recursive sysctl_kern_smp_topology_spec_internal().
 2824  */
 2825 static int
 2826 sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS)
 2827 {
 2828         struct sbuf *topo;
 2829         int err;
 2830 
 2831         KASSERT(cpu_top != NULL, ("cpu_top isn't initialized"));
 2832 
 2833         topo = sbuf_new(NULL, NULL, 500, SBUF_AUTOEXTEND);
 2834         if (topo == NULL)
 2835                 return (ENOMEM);
 2836 
 2837         sbuf_printf(topo, "<groups>\n");
 2838         err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1);
 2839         sbuf_printf(topo, "</groups>\n");
 2840 
 2841         if (err == 0) {
 2842                 sbuf_finish(topo);
 2843                 err = SYSCTL_OUT(req, sbuf_data(topo), sbuf_len(topo));
 2844         }
 2845         sbuf_delete(topo);
 2846         return (err);
 2847 }
 2848 
 2849 #endif
 2850 
 2851 static int
 2852 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
 2853 {
 2854         int error, new_val, period;
 2855 
 2856         period = 1000000 / realstathz;
 2857         new_val = period * sched_slice;
 2858         error = sysctl_handle_int(oidp, &new_val, 0, req);
 2859         if (error != 0 || req->newptr == NULL)
 2860                 return (error);
 2861         if (new_val <= 0)
 2862                 return (EINVAL);
 2863         sched_slice = imax(1, (new_val + period / 2) / period);
 2864         sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
 2865         hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
 2866             realstathz);
 2867         return (0);
 2868 }
 2869 
 2870 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW, 0, "Scheduler");
 2871 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0,
 2872     "Scheduler name");
 2873 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW,
 2874     NULL, 0, sysctl_kern_quantum, "I",
 2875     "Quantum for timeshare threads in microseconds");
 2876 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
 2877     "Quantum for timeshare threads in stathz ticks");
 2878 SYSCTL_INT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0,
 2879     "Interactivity score threshold");
 2880 SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW,
 2881     &preempt_thresh, 0,
 2882     "Maximal (lowest) priority for preemption");
 2883 SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost, 0,
 2884     "Assign static kernel priorities to sleeping threads");
 2885 SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins, 0,
 2886     "Number of times idle thread will spin waiting for new work");
 2887 SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW,
 2888     &sched_idlespinthresh, 0,
 2889     "Threshold before we will permit idle thread spinning");
 2890 #ifdef SMP
 2891 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0,
 2892     "Number of hz ticks to keep thread affinity for");
 2893 SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0,
 2894     "Enables the long-term load balancer");
 2895 SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW,
 2896     &balance_interval, 0,
 2897     "Average period in stathz ticks to run the long-term balancer");
 2898 SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0,
 2899     "Attempts to steal work from other cores before idling");
 2900 SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0,
 2901     "Minimum load on remote CPU before we'll steal");
 2902 SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING |
 2903     CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A",
 2904     "XML dump of detected CPU topology");
 2905 #endif
 2906 
 2907 /* ps compat.  All cpu percentages from ULE are weighted. */
 2908 static int ccpu = 0;
 2909 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");

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