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: releng/8.0/sys/kern/sched_ule.c 198246 2009-10-19 19:40:05Z jhb $");
   40 
   41 #include "opt_hwpmc_hooks.h"
   42 #include "opt_kdtrace.h"
   43 #include "opt_sched.h"
   44 
   45 #include <sys/param.h>
   46 #include <sys/systm.h>
   47 #include <sys/kdb.h>
   48 #include <sys/kernel.h>
   49 #include <sys/ktr.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/smp.h>
   57 #include <sys/sx.h>
   58 #include <sys/sysctl.h>
   59 #include <sys/sysproto.h>
   60 #include <sys/turnstile.h>
   61 #include <sys/umtx.h>
   62 #include <sys/vmmeter.h>
   63 #include <sys/cpuset.h>
   64 #include <sys/sbuf.h>
   65 #ifdef KTRACE
   66 #include <sys/uio.h>
   67 #include <sys/ktrace.h>
   68 #endif
   69 
   70 #ifdef HWPMC_HOOKS
   71 #include <sys/pmckern.h>
   72 #endif
   73 
   74 #ifdef KDTRACE_HOOKS
   75 #include <sys/dtrace_bsd.h>
   76 int                             dtrace_vtime_active;
   77 dtrace_vtime_switch_func_t      dtrace_vtime_switch_func;
   78 #endif
   79 
   80 #include <machine/cpu.h>
   81 #include <machine/smp.h>
   82 
   83 #if defined(__sparc64__) || defined(__mips__)
   84 #error "This architecture is not currently compatible with ULE"
   85 #endif
   86 
   87 #define KTR_ULE 0
   88 
   89 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
   90 #define TDQ_NAME_LEN    (sizeof("sched lock ") + sizeof(__XSTRING(MAXCPU)))
   91 #define TDQ_LOADNAME_LEN        (PCPU_NAME_LEN + sizeof(" load"))
   92 
   93 /*
   94  * Thread scheduler specific section.  All fields are protected
   95  * by the thread lock.
   96  */
   97 struct td_sched {       
   98         struct runq     *ts_runq;       /* Run-queue we're queued on. */
   99         short           ts_flags;       /* TSF_* flags. */
  100         u_char          ts_cpu;         /* CPU that we have affinity for. */
  101         int             ts_rltick;      /* Real last tick, for affinity. */
  102         int             ts_slice;       /* Ticks of slice remaining. */
  103         u_int           ts_slptime;     /* Number of ticks we vol. slept */
  104         u_int           ts_runtime;     /* Number of ticks we were running */
  105         int             ts_ltick;       /* Last tick that we were running on */
  106         int             ts_ftick;       /* First tick that we were running on */
  107         int             ts_ticks;       /* Tick count */
  108 #ifdef KTR
  109         char            ts_name[TS_NAME_LEN];
  110 #endif
  111 };
  112 /* flags kept in ts_flags */
  113 #define TSF_BOUND       0x0001          /* Thread can not migrate. */
  114 #define TSF_XFERABLE    0x0002          /* Thread was added as transferable. */
  115 
  116 static struct td_sched td_sched0;
  117 
  118 #define THREAD_CAN_MIGRATE(td)  ((td)->td_pinned == 0)
  119 #define THREAD_CAN_SCHED(td, cpu)       \
  120     CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
  121 
  122 /*
  123  * Cpu percentage computation macros and defines.
  124  *
  125  * SCHED_TICK_SECS:     Number of seconds to average the cpu usage across.
  126  * SCHED_TICK_TARG:     Number of hz ticks to average the cpu usage across.
  127  * SCHED_TICK_MAX:      Maximum number of ticks before scaling back.
  128  * SCHED_TICK_SHIFT:    Shift factor to avoid rounding away results.
  129  * SCHED_TICK_HZ:       Compute the number of hz ticks for a given ticks count.
  130  * SCHED_TICK_TOTAL:    Gives the amount of time we've been recording ticks.
  131  */
  132 #define SCHED_TICK_SECS         10
  133 #define SCHED_TICK_TARG         (hz * SCHED_TICK_SECS)
  134 #define SCHED_TICK_MAX          (SCHED_TICK_TARG + hz)
  135 #define SCHED_TICK_SHIFT        10
  136 #define SCHED_TICK_HZ(ts)       ((ts)->ts_ticks >> SCHED_TICK_SHIFT)
  137 #define SCHED_TICK_TOTAL(ts)    (max((ts)->ts_ltick - (ts)->ts_ftick, hz))
  138 
  139 /*
  140  * These macros determine priorities for non-interactive threads.  They are
  141  * assigned a priority based on their recent cpu utilization as expressed
  142  * by the ratio of ticks to the tick total.  NHALF priorities at the start
  143  * and end of the MIN to MAX timeshare range are only reachable with negative
  144  * or positive nice respectively.
  145  *
  146  * PRI_RANGE:   Priority range for utilization dependent priorities.
  147  * PRI_NRESV:   Number of nice values.
  148  * PRI_TICKS:   Compute a priority in PRI_RANGE from the ticks count and total.
  149  * PRI_NICE:    Determines the part of the priority inherited from nice.
  150  */
  151 #define SCHED_PRI_NRESV         (PRIO_MAX - PRIO_MIN)
  152 #define SCHED_PRI_NHALF         (SCHED_PRI_NRESV / 2)
  153 #define SCHED_PRI_MIN           (PRI_MIN_TIMESHARE + SCHED_PRI_NHALF)
  154 #define SCHED_PRI_MAX           (PRI_MAX_TIMESHARE - SCHED_PRI_NHALF)
  155 #define SCHED_PRI_RANGE         (SCHED_PRI_MAX - SCHED_PRI_MIN)
  156 #define SCHED_PRI_TICKS(ts)                                             \
  157     (SCHED_TICK_HZ((ts)) /                                              \
  158     (roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE))
  159 #define SCHED_PRI_NICE(nice)    (nice)
  160 
  161 /*
  162  * These determine the interactivity of a process.  Interactivity differs from
  163  * cpu utilization in that it expresses the voluntary time slept vs time ran
  164  * while cpu utilization includes all time not running.  This more accurately
  165  * models the intent of the thread.
  166  *
  167  * SLP_RUN_MAX: Maximum amount of sleep time + run time we'll accumulate
  168  *              before throttling back.
  169  * SLP_RUN_FORK:        Maximum slp+run time to inherit at fork time.
  170  * INTERACT_MAX:        Maximum interactivity value.  Smaller is better.
  171  * INTERACT_THRESH:     Threshhold for placement on the current runq.
  172  */
  173 #define SCHED_SLP_RUN_MAX       ((hz * 5) << SCHED_TICK_SHIFT)
  174 #define SCHED_SLP_RUN_FORK      ((hz / 2) << SCHED_TICK_SHIFT)
  175 #define SCHED_INTERACT_MAX      (100)
  176 #define SCHED_INTERACT_HALF     (SCHED_INTERACT_MAX / 2)
  177 #define SCHED_INTERACT_THRESH   (30)
  178 
  179 /*
  180  * tickincr:            Converts a stathz tick into a hz domain scaled by
  181  *                      the shift factor.  Without the shift the error rate
  182  *                      due to rounding would be unacceptably high.
  183  * realstathz:          stathz is sometimes 0 and run off of hz.
  184  * sched_slice:         Runtime of each thread before rescheduling.
  185  * preempt_thresh:      Priority threshold for preemption and remote IPIs.
  186  */
  187 static int sched_interact = SCHED_INTERACT_THRESH;
  188 static int realstathz;
  189 static int tickincr;
  190 static int sched_slice = 1;
  191 #ifdef PREEMPTION
  192 #ifdef FULL_PREEMPTION
  193 static int preempt_thresh = PRI_MAX_IDLE;
  194 #else
  195 static int preempt_thresh = PRI_MIN_KERN;
  196 #endif
  197 #else 
  198 static int preempt_thresh = 0;
  199 #endif
  200 static int static_boost = PRI_MIN_TIMESHARE;
  201 static int sched_idlespins = 10000;
  202 static int sched_idlespinthresh = 4;
  203 
  204 /*
  205  * tdq - per processor runqs and statistics.  All fields are protected by the
  206  * tdq_lock.  The load and lowpri may be accessed without to avoid excess
  207  * locking in sched_pickcpu();
  208  */
  209 struct tdq {
  210         /* Ordered to improve efficiency of cpu_search() and switch(). */
  211         struct mtx      tdq_lock;               /* run queue lock. */
  212         struct cpu_group *tdq_cg;               /* Pointer to cpu topology. */
  213         volatile int    tdq_load;               /* Aggregate load. */
  214         int             tdq_sysload;            /* For loadavg, !ITHD load. */
  215         int             tdq_transferable;       /* Transferable thread count. */
  216         short           tdq_switchcnt;          /* Switches this tick. */
  217         short           tdq_oldswitchcnt;       /* Switches last tick. */
  218         u_char          tdq_lowpri;             /* Lowest priority thread. */
  219         u_char          tdq_ipipending;         /* IPI pending. */
  220         u_char          tdq_idx;                /* Current insert index. */
  221         u_char          tdq_ridx;               /* Current removal index. */
  222         struct runq     tdq_realtime;           /* real-time run queue. */
  223         struct runq     tdq_timeshare;          /* timeshare run queue. */
  224         struct runq     tdq_idle;               /* Queue of IDLE threads. */
  225         char            tdq_name[TDQ_NAME_LEN];
  226 #ifdef KTR
  227         char            tdq_loadname[TDQ_LOADNAME_LEN];
  228 #endif
  229 } __aligned(64);
  230 
  231 /* Idle thread states and config. */
  232 #define TDQ_RUNNING     1
  233 #define TDQ_IDLE        2
  234 
  235 #ifdef SMP
  236 struct cpu_group *cpu_top;              /* CPU topology */
  237 
  238 #define SCHED_AFFINITY_DEFAULT  (max(1, hz / 1000))
  239 #define SCHED_AFFINITY(ts, t)   ((ts)->ts_rltick > ticks - ((t) * affinity))
  240 
  241 /*
  242  * Run-time tunables.
  243  */
  244 static int rebalance = 1;
  245 static int balance_interval = 128;      /* Default set in sched_initticks(). */
  246 static int affinity;
  247 static int steal_htt = 1;
  248 static int steal_idle = 1;
  249 static int steal_thresh = 2;
  250 
  251 /*
  252  * One thread queue per processor.
  253  */
  254 static struct tdq       tdq_cpu[MAXCPU];
  255 static struct tdq       *balance_tdq;
  256 static int balance_ticks;
  257 
  258 #define TDQ_SELF()      (&tdq_cpu[PCPU_GET(cpuid)])
  259 #define TDQ_CPU(x)      (&tdq_cpu[(x)])
  260 #define TDQ_ID(x)       ((int)((x) - tdq_cpu))
  261 #else   /* !SMP */
  262 static struct tdq       tdq_cpu;
  263 
  264 #define TDQ_ID(x)       (0)
  265 #define TDQ_SELF()      (&tdq_cpu)
  266 #define TDQ_CPU(x)      (&tdq_cpu)
  267 #endif
  268 
  269 #define TDQ_LOCK_ASSERT(t, type)        mtx_assert(TDQ_LOCKPTR((t)), (type))
  270 #define TDQ_LOCK(t)             mtx_lock_spin(TDQ_LOCKPTR((t)))
  271 #define TDQ_LOCK_FLAGS(t, f)    mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f))
  272 #define TDQ_UNLOCK(t)           mtx_unlock_spin(TDQ_LOCKPTR((t)))
  273 #define TDQ_LOCKPTR(t)          (&(t)->tdq_lock)
  274 
  275 static void sched_priority(struct thread *);
  276 static void sched_thread_priority(struct thread *, u_char);
  277 static int sched_interact_score(struct thread *);
  278 static void sched_interact_update(struct thread *);
  279 static void sched_interact_fork(struct thread *);
  280 static void sched_pctcpu_update(struct td_sched *);
  281 
  282 /* Operations on per processor queues */
  283 static struct thread *tdq_choose(struct tdq *);
  284 static void tdq_setup(struct tdq *);
  285 static void tdq_load_add(struct tdq *, struct thread *);
  286 static void tdq_load_rem(struct tdq *, struct thread *);
  287 static __inline void tdq_runq_add(struct tdq *, struct thread *, int);
  288 static __inline void tdq_runq_rem(struct tdq *, struct thread *);
  289 static inline int sched_shouldpreempt(int, int, int);
  290 void tdq_print(int cpu);
  291 static void runq_print(struct runq *rq);
  292 static void tdq_add(struct tdq *, struct thread *, int);
  293 #ifdef SMP
  294 static int tdq_move(struct tdq *, struct tdq *);
  295 static int tdq_idled(struct tdq *);
  296 static void tdq_notify(struct tdq *, struct thread *);
  297 static struct thread *tdq_steal(struct tdq *, int);
  298 static struct thread *runq_steal(struct runq *, int);
  299 static int sched_pickcpu(struct thread *, int);
  300 static void sched_balance(void);
  301 static int sched_balance_pair(struct tdq *, struct tdq *);
  302 static inline struct tdq *sched_setcpu(struct thread *, int, int);
  303 static inline struct mtx *thread_block_switch(struct thread *);
  304 static inline void thread_unblock_switch(struct thread *, struct mtx *);
  305 static struct mtx *sched_switch_migrate(struct tdq *, struct thread *, int);
  306 static int sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS);
  307 static int sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, 
  308     struct cpu_group *cg, int indent);
  309 #endif
  310 
  311 static void sched_setup(void *dummy);
  312 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
  313 
  314 static void sched_initticks(void *dummy);
  315 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
  316     NULL);
  317 
  318 /*
  319  * Print the threads waiting on a run-queue.
  320  */
  321 static void
  322 runq_print(struct runq *rq)
  323 {
  324         struct rqhead *rqh;
  325         struct thread *td;
  326         int pri;
  327         int j;
  328         int i;
  329 
  330         for (i = 0; i < RQB_LEN; i++) {
  331                 printf("\t\trunq bits %d 0x%zx\n",
  332                     i, rq->rq_status.rqb_bits[i]);
  333                 for (j = 0; j < RQB_BPW; j++)
  334                         if (rq->rq_status.rqb_bits[i] & (1ul << j)) {
  335                                 pri = j + (i << RQB_L2BPW);
  336                                 rqh = &rq->rq_queues[pri];
  337                                 TAILQ_FOREACH(td, rqh, td_runq) {
  338                                         printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
  339                                             td, td->td_name, td->td_priority,
  340                                             td->td_rqindex, pri);
  341                                 }
  342                         }
  343         }
  344 }
  345 
  346 /*
  347  * Print the status of a per-cpu thread queue.  Should be a ddb show cmd.
  348  */
  349 void
  350 tdq_print(int cpu)
  351 {
  352         struct tdq *tdq;
  353 
  354         tdq = TDQ_CPU(cpu);
  355 
  356         printf("tdq %d:\n", TDQ_ID(tdq));
  357         printf("\tlock            %p\n", TDQ_LOCKPTR(tdq));
  358         printf("\tLock name:      %s\n", tdq->tdq_name);
  359         printf("\tload:           %d\n", tdq->tdq_load);
  360         printf("\tswitch cnt:     %d\n", tdq->tdq_switchcnt);
  361         printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt);
  362         printf("\ttimeshare idx:  %d\n", tdq->tdq_idx);
  363         printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
  364         printf("\tload transferable: %d\n", tdq->tdq_transferable);
  365         printf("\tlowest priority:   %d\n", tdq->tdq_lowpri);
  366         printf("\trealtime runq:\n");
  367         runq_print(&tdq->tdq_realtime);
  368         printf("\ttimeshare runq:\n");
  369         runq_print(&tdq->tdq_timeshare);
  370         printf("\tidle runq:\n");
  371         runq_print(&tdq->tdq_idle);
  372 }
  373 
  374 static inline int
  375 sched_shouldpreempt(int pri, int cpri, int remote)
  376 {
  377         /*
  378          * If the new priority is not better than the current priority there is
  379          * nothing to do.
  380          */
  381         if (pri >= cpri)
  382                 return (0);
  383         /*
  384          * Always preempt idle.
  385          */
  386         if (cpri >= PRI_MIN_IDLE)
  387                 return (1);
  388         /*
  389          * If preemption is disabled don't preempt others.
  390          */
  391         if (preempt_thresh == 0)
  392                 return (0);
  393         /*
  394          * Preempt if we exceed the threshold.
  395          */
  396         if (pri <= preempt_thresh)
  397                 return (1);
  398         /*
  399          * If we're realtime or better and there is timeshare or worse running
  400          * preempt only remote processors.
  401          */
  402         if (remote && pri <= PRI_MAX_REALTIME && cpri > PRI_MAX_REALTIME)
  403                 return (1);
  404         return (0);
  405 }
  406 
  407 #define TS_RQ_PPQ       (((PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE) + 1) / RQ_NQS)
  408 /*
  409  * Add a thread to the actual run-queue.  Keeps transferable counts up to
  410  * date with what is actually on the run-queue.  Selects the correct
  411  * queue position for timeshare threads.
  412  */
  413 static __inline void
  414 tdq_runq_add(struct tdq *tdq, struct thread *td, int flags)
  415 {
  416         struct td_sched *ts;
  417         u_char pri;
  418 
  419         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  420         THREAD_LOCK_ASSERT(td, MA_OWNED);
  421 
  422         pri = td->td_priority;
  423         ts = td->td_sched;
  424         TD_SET_RUNQ(td);
  425         if (THREAD_CAN_MIGRATE(td)) {
  426                 tdq->tdq_transferable++;
  427                 ts->ts_flags |= TSF_XFERABLE;
  428         }
  429         if (pri <= PRI_MAX_REALTIME) {
  430                 ts->ts_runq = &tdq->tdq_realtime;
  431         } else if (pri <= PRI_MAX_TIMESHARE) {
  432                 ts->ts_runq = &tdq->tdq_timeshare;
  433                 KASSERT(pri <= PRI_MAX_TIMESHARE && pri >= PRI_MIN_TIMESHARE,
  434                         ("Invalid priority %d on timeshare runq", pri));
  435                 /*
  436                  * This queue contains only priorities between MIN and MAX
  437                  * realtime.  Use the whole queue to represent these values.
  438                  */
  439                 if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) {
  440                         pri = (pri - PRI_MIN_TIMESHARE) / TS_RQ_PPQ;
  441                         pri = (pri + tdq->tdq_idx) % RQ_NQS;
  442                         /*
  443                          * This effectively shortens the queue by one so we
  444                          * can have a one slot difference between idx and
  445                          * ridx while we wait for threads to drain.
  446                          */
  447                         if (tdq->tdq_ridx != tdq->tdq_idx &&
  448                             pri == tdq->tdq_ridx)
  449                                 pri = (unsigned char)(pri - 1) % RQ_NQS;
  450                 } else
  451                         pri = tdq->tdq_ridx;
  452                 runq_add_pri(ts->ts_runq, td, pri, flags);
  453                 return;
  454         } else
  455                 ts->ts_runq = &tdq->tdq_idle;
  456         runq_add(ts->ts_runq, td, flags);
  457 }
  458 
  459 /* 
  460  * Remove a thread from a run-queue.  This typically happens when a thread
  461  * is selected to run.  Running threads are not on the queue and the
  462  * transferable count does not reflect them.
  463  */
  464 static __inline void
  465 tdq_runq_rem(struct tdq *tdq, struct thread *td)
  466 {
  467         struct td_sched *ts;
  468 
  469         ts = td->td_sched;
  470         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  471         KASSERT(ts->ts_runq != NULL,
  472             ("tdq_runq_remove: thread %p null ts_runq", td));
  473         if (ts->ts_flags & TSF_XFERABLE) {
  474                 tdq->tdq_transferable--;
  475                 ts->ts_flags &= ~TSF_XFERABLE;
  476         }
  477         if (ts->ts_runq == &tdq->tdq_timeshare) {
  478                 if (tdq->tdq_idx != tdq->tdq_ridx)
  479                         runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx);
  480                 else
  481                         runq_remove_idx(ts->ts_runq, td, NULL);
  482         } else
  483                 runq_remove(ts->ts_runq, td);
  484 }
  485 
  486 /*
  487  * Load is maintained for all threads RUNNING and ON_RUNQ.  Add the load
  488  * for this thread to the referenced thread queue.
  489  */
  490 static void
  491 tdq_load_add(struct tdq *tdq, struct thread *td)
  492 {
  493 
  494         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  495         THREAD_LOCK_ASSERT(td, MA_OWNED);
  496 
  497         tdq->tdq_load++;
  498         if ((td->td_proc->p_flag & P_NOLOAD) == 0)
  499                 tdq->tdq_sysload++;
  500         KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
  501 }
  502 
  503 /*
  504  * Remove the load from a thread that is transitioning to a sleep state or
  505  * exiting.
  506  */
  507 static void
  508 tdq_load_rem(struct tdq *tdq, struct thread *td)
  509 {
  510 
  511         THREAD_LOCK_ASSERT(td, MA_OWNED);
  512         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  513         KASSERT(tdq->tdq_load != 0,
  514             ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
  515 
  516         tdq->tdq_load--;
  517         if ((td->td_proc->p_flag & P_NOLOAD) == 0)
  518                 tdq->tdq_sysload--;
  519         KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
  520 }
  521 
  522 /*
  523  * Set lowpri to its exact value by searching the run-queue and
  524  * evaluating curthread.  curthread may be passed as an optimization.
  525  */
  526 static void
  527 tdq_setlowpri(struct tdq *tdq, struct thread *ctd)
  528 {
  529         struct thread *td;
  530 
  531         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  532         if (ctd == NULL)
  533                 ctd = pcpu_find(TDQ_ID(tdq))->pc_curthread;
  534         td = tdq_choose(tdq);
  535         if (td == NULL || td->td_priority > ctd->td_priority)
  536                 tdq->tdq_lowpri = ctd->td_priority;
  537         else
  538                 tdq->tdq_lowpri = td->td_priority;
  539 }
  540 
  541 #ifdef SMP
  542 struct cpu_search {
  543         cpuset_t cs_mask;
  544         u_int   cs_load;
  545         u_int   cs_cpu;
  546         int     cs_limit;       /* Min priority for low min load for high. */
  547 };
  548 
  549 #define CPU_SEARCH_LOWEST       0x1
  550 #define CPU_SEARCH_HIGHEST      0x2
  551 #define CPU_SEARCH_BOTH         (CPU_SEARCH_LOWEST|CPU_SEARCH_HIGHEST)
  552 
  553 #define CPUSET_FOREACH(cpu, mask)                               \
  554         for ((cpu) = 0; (cpu) <= mp_maxid; (cpu)++)             \
  555                 if ((mask) & 1 << (cpu))
  556 
  557 static __inline int cpu_search(struct cpu_group *cg, struct cpu_search *low,
  558     struct cpu_search *high, const int match);
  559 int cpu_search_lowest(struct cpu_group *cg, struct cpu_search *low);
  560 int cpu_search_highest(struct cpu_group *cg, struct cpu_search *high);
  561 int cpu_search_both(struct cpu_group *cg, struct cpu_search *low,
  562     struct cpu_search *high);
  563 
  564 /*
  565  * This routine compares according to the match argument and should be
  566  * reduced in actual instantiations via constant propagation and dead code
  567  * elimination.
  568  */ 
  569 static __inline int
  570 cpu_compare(int cpu, struct cpu_search *low, struct cpu_search *high,
  571     const int match)
  572 {
  573         struct tdq *tdq;
  574 
  575         tdq = TDQ_CPU(cpu);
  576         if (match & CPU_SEARCH_LOWEST)
  577                 if (CPU_ISSET(cpu, &low->cs_mask) &&
  578                     tdq->tdq_load < low->cs_load &&
  579                     tdq->tdq_lowpri > low->cs_limit) {
  580                         low->cs_cpu = cpu;
  581                         low->cs_load = tdq->tdq_load;
  582                 }
  583         if (match & CPU_SEARCH_HIGHEST)
  584                 if (CPU_ISSET(cpu, &high->cs_mask) &&
  585                     tdq->tdq_load >= high->cs_limit && 
  586                     tdq->tdq_load > high->cs_load &&
  587                     tdq->tdq_transferable) {
  588                         high->cs_cpu = cpu;
  589                         high->cs_load = tdq->tdq_load;
  590                 }
  591         return (tdq->tdq_load);
  592 }
  593 
  594 /*
  595  * Search the tree of cpu_groups for the lowest or highest loaded cpu
  596  * according to the match argument.  This routine actually compares the
  597  * load on all paths through the tree and finds the least loaded cpu on
  598  * the least loaded path, which may differ from the least loaded cpu in
  599  * the system.  This balances work among caches and busses.
  600  *
  601  * This inline is instantiated in three forms below using constants for the
  602  * match argument.  It is reduced to the minimum set for each case.  It is
  603  * also recursive to the depth of the tree.
  604  */
  605 static __inline int
  606 cpu_search(struct cpu_group *cg, struct cpu_search *low,
  607     struct cpu_search *high, const int match)
  608 {
  609         int total;
  610 
  611         total = 0;
  612         if (cg->cg_children) {
  613                 struct cpu_search lgroup;
  614                 struct cpu_search hgroup;
  615                 struct cpu_group *child;
  616                 u_int lload;
  617                 int hload;
  618                 int load;
  619                 int i;
  620 
  621                 lload = -1;
  622                 hload = -1;
  623                 for (i = 0; i < cg->cg_children; i++) {
  624                         child = &cg->cg_child[i];
  625                         if (match & CPU_SEARCH_LOWEST) {
  626                                 lgroup = *low;
  627                                 lgroup.cs_load = -1;
  628                         }
  629                         if (match & CPU_SEARCH_HIGHEST) {
  630                                 hgroup = *high;
  631                                 lgroup.cs_load = 0;
  632                         }
  633                         switch (match) {
  634                         case CPU_SEARCH_LOWEST:
  635                                 load = cpu_search_lowest(child, &lgroup);
  636                                 break;
  637                         case CPU_SEARCH_HIGHEST:
  638                                 load = cpu_search_highest(child, &hgroup);
  639                                 break;
  640                         case CPU_SEARCH_BOTH:
  641                                 load = cpu_search_both(child, &lgroup, &hgroup);
  642                                 break;
  643                         }
  644                         total += load;
  645                         if (match & CPU_SEARCH_LOWEST)
  646                                 if (load < lload || low->cs_cpu == -1) {
  647                                         *low = lgroup;
  648                                         lload = load;
  649                                 }
  650                         if (match & CPU_SEARCH_HIGHEST) 
  651                                 if (load > hload || high->cs_cpu == -1) {
  652                                         hload = load;
  653                                         *high = hgroup;
  654                                 }
  655                 }
  656         } else {
  657                 int cpu;
  658 
  659                 CPUSET_FOREACH(cpu, cg->cg_mask)
  660                         total += cpu_compare(cpu, low, high, match);
  661         }
  662         return (total);
  663 }
  664 
  665 /*
  666  * cpu_search instantiations must pass constants to maintain the inline
  667  * optimization.
  668  */
  669 int
  670 cpu_search_lowest(struct cpu_group *cg, struct cpu_search *low)
  671 {
  672         return cpu_search(cg, low, NULL, CPU_SEARCH_LOWEST);
  673 }
  674 
  675 int
  676 cpu_search_highest(struct cpu_group *cg, struct cpu_search *high)
  677 {
  678         return cpu_search(cg, NULL, high, CPU_SEARCH_HIGHEST);
  679 }
  680 
  681 int
  682 cpu_search_both(struct cpu_group *cg, struct cpu_search *low,
  683     struct cpu_search *high)
  684 {
  685         return cpu_search(cg, low, high, CPU_SEARCH_BOTH);
  686 }
  687 
  688 /*
  689  * Find the cpu with the least load via the least loaded path that has a
  690  * lowpri greater than pri  pri.  A pri of -1 indicates any priority is
  691  * acceptable.
  692  */
  693 static inline int
  694 sched_lowest(struct cpu_group *cg, cpuset_t mask, int pri)
  695 {
  696         struct cpu_search low;
  697 
  698         low.cs_cpu = -1;
  699         low.cs_load = -1;
  700         low.cs_mask = mask;
  701         low.cs_limit = pri;
  702         cpu_search_lowest(cg, &low);
  703         return low.cs_cpu;
  704 }
  705 
  706 /*
  707  * Find the cpu with the highest load via the highest loaded path.
  708  */
  709 static inline int
  710 sched_highest(struct cpu_group *cg, cpuset_t mask, int minload)
  711 {
  712         struct cpu_search high;
  713 
  714         high.cs_cpu = -1;
  715         high.cs_load = 0;
  716         high.cs_mask = mask;
  717         high.cs_limit = minload;
  718         cpu_search_highest(cg, &high);
  719         return high.cs_cpu;
  720 }
  721 
  722 /*
  723  * Simultaneously find the highest and lowest loaded cpu reachable via
  724  * cg.
  725  */
  726 static inline void 
  727 sched_both(struct cpu_group *cg, cpuset_t mask, int *lowcpu, int *highcpu)
  728 {
  729         struct cpu_search high;
  730         struct cpu_search low;
  731 
  732         low.cs_cpu = -1;
  733         low.cs_limit = -1;
  734         low.cs_load = -1;
  735         low.cs_mask = mask;
  736         high.cs_load = 0;
  737         high.cs_cpu = -1;
  738         high.cs_limit = -1;
  739         high.cs_mask = mask;
  740         cpu_search_both(cg, &low, &high);
  741         *lowcpu = low.cs_cpu;
  742         *highcpu = high.cs_cpu;
  743         return;
  744 }
  745 
  746 static void
  747 sched_balance_group(struct cpu_group *cg)
  748 {
  749         cpuset_t mask;
  750         int high;
  751         int low;
  752         int i;
  753 
  754         CPU_FILL(&mask);
  755         for (;;) {
  756                 sched_both(cg, mask, &low, &high);
  757                 if (low == high || low == -1 || high == -1)
  758                         break;
  759                 if (sched_balance_pair(TDQ_CPU(high), TDQ_CPU(low)))
  760                         break;
  761                 /*
  762                  * If we failed to move any threads determine which cpu
  763                  * to kick out of the set and try again.
  764                  */
  765                 if (TDQ_CPU(high)->tdq_transferable == 0)
  766                         CPU_CLR(high, &mask);
  767                 else
  768                         CPU_CLR(low, &mask);
  769         }
  770 
  771         for (i = 0; i < cg->cg_children; i++)
  772                 sched_balance_group(&cg->cg_child[i]);
  773 }
  774 
  775 static void
  776 sched_balance()
  777 {
  778         struct tdq *tdq;
  779 
  780         /*
  781          * Select a random time between .5 * balance_interval and
  782          * 1.5 * balance_interval.
  783          */
  784         balance_ticks = max(balance_interval / 2, 1);
  785         balance_ticks += random() % balance_interval;
  786         if (smp_started == 0 || rebalance == 0)
  787                 return;
  788         tdq = TDQ_SELF();
  789         TDQ_UNLOCK(tdq);
  790         sched_balance_group(cpu_top);
  791         TDQ_LOCK(tdq);
  792 }
  793 
  794 /*
  795  * Lock two thread queues using their address to maintain lock order.
  796  */
  797 static void
  798 tdq_lock_pair(struct tdq *one, struct tdq *two)
  799 {
  800         if (one < two) {
  801                 TDQ_LOCK(one);
  802                 TDQ_LOCK_FLAGS(two, MTX_DUPOK);
  803         } else {
  804                 TDQ_LOCK(two);
  805                 TDQ_LOCK_FLAGS(one, MTX_DUPOK);
  806         }
  807 }
  808 
  809 /*
  810  * Unlock two thread queues.  Order is not important here.
  811  */
  812 static void
  813 tdq_unlock_pair(struct tdq *one, struct tdq *two)
  814 {
  815         TDQ_UNLOCK(one);
  816         TDQ_UNLOCK(two);
  817 }
  818 
  819 /*
  820  * Transfer load between two imbalanced thread queues.
  821  */
  822 static int
  823 sched_balance_pair(struct tdq *high, struct tdq *low)
  824 {
  825         int transferable;
  826         int high_load;
  827         int low_load;
  828         int moved;
  829         int move;
  830         int diff;
  831         int i;
  832 
  833         tdq_lock_pair(high, low);
  834         transferable = high->tdq_transferable;
  835         high_load = high->tdq_load;
  836         low_load = low->tdq_load;
  837         moved = 0;
  838         /*
  839          * Determine what the imbalance is and then adjust that to how many
  840          * threads we actually have to give up (transferable).
  841          */
  842         if (transferable != 0) {
  843                 diff = high_load - low_load;
  844                 move = diff / 2;
  845                 if (diff & 0x1)
  846                         move++;
  847                 move = min(move, transferable);
  848                 for (i = 0; i < move; i++)
  849                         moved += tdq_move(high, low);
  850                 /*
  851                  * IPI the target cpu to force it to reschedule with the new
  852                  * workload.
  853                  */
  854                 ipi_selected(1 << TDQ_ID(low), IPI_PREEMPT);
  855         }
  856         tdq_unlock_pair(high, low);
  857         return (moved);
  858 }
  859 
  860 /*
  861  * Move a thread from one thread queue to another.
  862  */
  863 static int
  864 tdq_move(struct tdq *from, struct tdq *to)
  865 {
  866         struct td_sched *ts;
  867         struct thread *td;
  868         struct tdq *tdq;
  869         int cpu;
  870 
  871         TDQ_LOCK_ASSERT(from, MA_OWNED);
  872         TDQ_LOCK_ASSERT(to, MA_OWNED);
  873 
  874         tdq = from;
  875         cpu = TDQ_ID(to);
  876         td = tdq_steal(tdq, cpu);
  877         if (td == NULL)
  878                 return (0);
  879         ts = td->td_sched;
  880         /*
  881          * Although the run queue is locked the thread may be blocked.  Lock
  882          * it to clear this and acquire the run-queue lock.
  883          */
  884         thread_lock(td);
  885         /* Drop recursive lock on from acquired via thread_lock(). */
  886         TDQ_UNLOCK(from);
  887         sched_rem(td);
  888         ts->ts_cpu = cpu;
  889         td->td_lock = TDQ_LOCKPTR(to);
  890         tdq_add(to, td, SRQ_YIELDING);
  891         return (1);
  892 }
  893 
  894 /*
  895  * This tdq has idled.  Try to steal a thread from another cpu and switch
  896  * to it.
  897  */
  898 static int
  899 tdq_idled(struct tdq *tdq)
  900 {
  901         struct cpu_group *cg;
  902         struct tdq *steal;
  903         cpuset_t mask;
  904         int thresh;
  905         int cpu;
  906 
  907         if (smp_started == 0 || steal_idle == 0)
  908                 return (1);
  909         CPU_FILL(&mask);
  910         CPU_CLR(PCPU_GET(cpuid), &mask);
  911         /* We don't want to be preempted while we're iterating. */
  912         spinlock_enter();
  913         for (cg = tdq->tdq_cg; cg != NULL; ) {
  914                 if ((cg->cg_flags & CG_FLAG_THREAD) == 0)
  915                         thresh = steal_thresh;
  916                 else
  917                         thresh = 1;
  918                 cpu = sched_highest(cg, mask, thresh);
  919                 if (cpu == -1) {
  920                         cg = cg->cg_parent;
  921                         continue;
  922                 }
  923                 steal = TDQ_CPU(cpu);
  924                 CPU_CLR(cpu, &mask);
  925                 tdq_lock_pair(tdq, steal);
  926                 if (steal->tdq_load < thresh || steal->tdq_transferable == 0) {
  927                         tdq_unlock_pair(tdq, steal);
  928                         continue;
  929                 }
  930                 /*
  931                  * If a thread was added while interrupts were disabled don't
  932                  * steal one here.  If we fail to acquire one due to affinity
  933                  * restrictions loop again with this cpu removed from the
  934                  * set.
  935                  */
  936                 if (tdq->tdq_load == 0 && tdq_move(steal, tdq) == 0) {
  937                         tdq_unlock_pair(tdq, steal);
  938                         continue;
  939                 }
  940                 spinlock_exit();
  941                 TDQ_UNLOCK(steal);
  942                 mi_switch(SW_VOL | SWT_IDLE, NULL);
  943                 thread_unlock(curthread);
  944 
  945                 return (0);
  946         }
  947         spinlock_exit();
  948         return (1);
  949 }
  950 
  951 /*
  952  * Notify a remote cpu of new work.  Sends an IPI if criteria are met.
  953  */
  954 static void
  955 tdq_notify(struct tdq *tdq, struct thread *td)
  956 {
  957         struct thread *ctd;
  958         int pri;
  959         int cpu;
  960 
  961         if (tdq->tdq_ipipending)
  962                 return;
  963         cpu = td->td_sched->ts_cpu;
  964         pri = td->td_priority;
  965         ctd = pcpu_find(cpu)->pc_curthread;
  966         if (!sched_shouldpreempt(pri, ctd->td_priority, 1))
  967                 return;
  968         if (TD_IS_IDLETHREAD(ctd)) {
  969                 /*
  970                  * If the MD code has an idle wakeup routine try that before
  971                  * falling back to IPI.
  972                  */
  973                 if (cpu_idle_wakeup(cpu))
  974                         return;
  975         }
  976         tdq->tdq_ipipending = 1;
  977         ipi_selected(1 << cpu, IPI_PREEMPT);
  978 }
  979 
  980 /*
  981  * Steals load from a timeshare queue.  Honors the rotating queue head
  982  * index.
  983  */
  984 static struct thread *
  985 runq_steal_from(struct runq *rq, int cpu, u_char start)
  986 {
  987         struct rqbits *rqb;
  988         struct rqhead *rqh;
  989         struct thread *td;
  990         int first;
  991         int bit;
  992         int pri;
  993         int i;
  994 
  995         rqb = &rq->rq_status;
  996         bit = start & (RQB_BPW -1);
  997         pri = 0;
  998         first = 0;
  999 again:
 1000         for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
 1001                 if (rqb->rqb_bits[i] == 0)
 1002                         continue;
 1003                 if (bit != 0) {
 1004                         for (pri = bit; pri < RQB_BPW; pri++)
 1005                                 if (rqb->rqb_bits[i] & (1ul << pri))
 1006                                         break;
 1007                         if (pri >= RQB_BPW)
 1008                                 continue;
 1009                 } else
 1010                         pri = RQB_FFS(rqb->rqb_bits[i]);
 1011                 pri += (i << RQB_L2BPW);
 1012                 rqh = &rq->rq_queues[pri];
 1013                 TAILQ_FOREACH(td, rqh, td_runq) {
 1014                         if (first && THREAD_CAN_MIGRATE(td) &&
 1015                             THREAD_CAN_SCHED(td, cpu))
 1016                                 return (td);
 1017                         first = 1;
 1018                 }
 1019         }
 1020         if (start != 0) {
 1021                 start = 0;
 1022                 goto again;
 1023         }
 1024 
 1025         return (NULL);
 1026 }
 1027 
 1028 /*
 1029  * Steals load from a standard linear queue.
 1030  */
 1031 static struct thread *
 1032 runq_steal(struct runq *rq, int cpu)
 1033 {
 1034         struct rqhead *rqh;
 1035         struct rqbits *rqb;
 1036         struct thread *td;
 1037         int word;
 1038         int bit;
 1039 
 1040         rqb = &rq->rq_status;
 1041         for (word = 0; word < RQB_LEN; word++) {
 1042                 if (rqb->rqb_bits[word] == 0)
 1043                         continue;
 1044                 for (bit = 0; bit < RQB_BPW; bit++) {
 1045                         if ((rqb->rqb_bits[word] & (1ul << bit)) == 0)
 1046                                 continue;
 1047                         rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)];
 1048                         TAILQ_FOREACH(td, rqh, td_runq)
 1049                                 if (THREAD_CAN_MIGRATE(td) &&
 1050                                     THREAD_CAN_SCHED(td, cpu))
 1051                                         return (td);
 1052                 }
 1053         }
 1054         return (NULL);
 1055 }
 1056 
 1057 /*
 1058  * Attempt to steal a thread in priority order from a thread queue.
 1059  */
 1060 static struct thread *
 1061 tdq_steal(struct tdq *tdq, int cpu)
 1062 {
 1063         struct thread *td;
 1064 
 1065         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 1066         if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL)
 1067                 return (td);
 1068         if ((td = runq_steal_from(&tdq->tdq_timeshare,
 1069             cpu, tdq->tdq_ridx)) != NULL)
 1070                 return (td);
 1071         return (runq_steal(&tdq->tdq_idle, cpu));
 1072 }
 1073 
 1074 /*
 1075  * Sets the thread lock and ts_cpu to match the requested cpu.  Unlocks the
 1076  * current lock and returns with the assigned queue locked.
 1077  */
 1078 static inline struct tdq *
 1079 sched_setcpu(struct thread *td, int cpu, int flags)
 1080 {
 1081 
 1082         struct tdq *tdq;
 1083 
 1084         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1085         tdq = TDQ_CPU(cpu);
 1086         td->td_sched->ts_cpu = cpu;
 1087         /*
 1088          * If the lock matches just return the queue.
 1089          */
 1090         if (td->td_lock == TDQ_LOCKPTR(tdq))
 1091                 return (tdq);
 1092 #ifdef notyet
 1093         /*
 1094          * If the thread isn't running its lockptr is a
 1095          * turnstile or a sleepqueue.  We can just lock_set without
 1096          * blocking.
 1097          */
 1098         if (TD_CAN_RUN(td)) {
 1099                 TDQ_LOCK(tdq);
 1100                 thread_lock_set(td, TDQ_LOCKPTR(tdq));
 1101                 return (tdq);
 1102         }
 1103 #endif
 1104         /*
 1105          * The hard case, migration, we need to block the thread first to
 1106          * prevent order reversals with other cpus locks.
 1107          */
 1108         thread_lock_block(td);
 1109         TDQ_LOCK(tdq);
 1110         thread_lock_unblock(td, TDQ_LOCKPTR(tdq));
 1111         return (tdq);
 1112 }
 1113 
 1114 SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding");
 1115 SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity");
 1116 SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity");
 1117 SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load");
 1118 SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu");
 1119 SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration");
 1120 
 1121 static int
 1122 sched_pickcpu(struct thread *td, int flags)
 1123 {
 1124         struct cpu_group *cg;
 1125         struct td_sched *ts;
 1126         struct tdq *tdq;
 1127         cpuset_t mask;
 1128         int self;
 1129         int pri;
 1130         int cpu;
 1131 
 1132         self = PCPU_GET(cpuid);
 1133         ts = td->td_sched;
 1134         if (smp_started == 0)
 1135                 return (self);
 1136         /*
 1137          * Don't migrate a running thread from sched_switch().
 1138          */
 1139         if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td))
 1140                 return (ts->ts_cpu);
 1141         /*
 1142          * Prefer to run interrupt threads on the processors that generate
 1143          * the interrupt.
 1144          */
 1145         if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) &&
 1146             curthread->td_intr_nesting_level && ts->ts_cpu != self) {
 1147                 SCHED_STAT_INC(pickcpu_intrbind);
 1148                 ts->ts_cpu = self;
 1149         }
 1150         /*
 1151          * If the thread can run on the last cpu and the affinity has not
 1152          * expired or it is idle run it there.
 1153          */
 1154         pri = td->td_priority;
 1155         tdq = TDQ_CPU(ts->ts_cpu);
 1156         if (THREAD_CAN_SCHED(td, ts->ts_cpu)) {
 1157                 if (tdq->tdq_lowpri > PRI_MIN_IDLE) {
 1158                         SCHED_STAT_INC(pickcpu_idle_affinity);
 1159                         return (ts->ts_cpu);
 1160                 }
 1161                 if (SCHED_AFFINITY(ts, CG_SHARE_L2) && tdq->tdq_lowpri > pri) {
 1162                         SCHED_STAT_INC(pickcpu_affinity);
 1163                         return (ts->ts_cpu);
 1164                 }
 1165         }
 1166         /*
 1167          * Search for the highest level in the tree that still has affinity.
 1168          */
 1169         cg = NULL;
 1170         for (cg = tdq->tdq_cg; cg != NULL; cg = cg->cg_parent)
 1171                 if (SCHED_AFFINITY(ts, cg->cg_level))
 1172                         break;
 1173         cpu = -1;
 1174         mask = td->td_cpuset->cs_mask;
 1175         if (cg)
 1176                 cpu = sched_lowest(cg, mask, pri);
 1177         if (cpu == -1)
 1178                 cpu = sched_lowest(cpu_top, mask, -1);
 1179         /*
 1180          * Compare the lowest loaded cpu to current cpu.
 1181          */
 1182         if (THREAD_CAN_SCHED(td, self) && TDQ_CPU(self)->tdq_lowpri > pri &&
 1183             TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE) {
 1184                 SCHED_STAT_INC(pickcpu_local);
 1185                 cpu = self;
 1186         } else
 1187                 SCHED_STAT_INC(pickcpu_lowest);
 1188         if (cpu != ts->ts_cpu)
 1189                 SCHED_STAT_INC(pickcpu_migration);
 1190         KASSERT(cpu != -1, ("sched_pickcpu: Failed to find a cpu."));
 1191         return (cpu);
 1192 }
 1193 #endif
 1194 
 1195 /*
 1196  * Pick the highest priority task we have and return it.
 1197  */
 1198 static struct thread *
 1199 tdq_choose(struct tdq *tdq)
 1200 {
 1201         struct thread *td;
 1202 
 1203         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 1204         td = runq_choose(&tdq->tdq_realtime);
 1205         if (td != NULL)
 1206                 return (td);
 1207         td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
 1208         if (td != NULL) {
 1209                 KASSERT(td->td_priority >= PRI_MIN_TIMESHARE,
 1210                     ("tdq_choose: Invalid priority on timeshare queue %d",
 1211                     td->td_priority));
 1212                 return (td);
 1213         }
 1214         td = runq_choose(&tdq->tdq_idle);
 1215         if (td != NULL) {
 1216                 KASSERT(td->td_priority >= PRI_MIN_IDLE,
 1217                     ("tdq_choose: Invalid priority on idle queue %d",
 1218                     td->td_priority));
 1219                 return (td);
 1220         }
 1221 
 1222         return (NULL);
 1223 }
 1224 
 1225 /*
 1226  * Initialize a thread queue.
 1227  */
 1228 static void
 1229 tdq_setup(struct tdq *tdq)
 1230 {
 1231 
 1232         if (bootverbose)
 1233                 printf("ULE: setup cpu %d\n", TDQ_ID(tdq));
 1234         runq_init(&tdq->tdq_realtime);
 1235         runq_init(&tdq->tdq_timeshare);
 1236         runq_init(&tdq->tdq_idle);
 1237         snprintf(tdq->tdq_name, sizeof(tdq->tdq_name),
 1238             "sched lock %d", (int)TDQ_ID(tdq));
 1239         mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock",
 1240             MTX_SPIN | MTX_RECURSE);
 1241 #ifdef KTR
 1242         snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname),
 1243             "CPU %d load", (int)TDQ_ID(tdq));
 1244 #endif
 1245 }
 1246 
 1247 #ifdef SMP
 1248 static void
 1249 sched_setup_smp(void)
 1250 {
 1251         struct tdq *tdq;
 1252         int i;
 1253 
 1254         cpu_top = smp_topo();
 1255         for (i = 0; i < MAXCPU; i++) {
 1256                 if (CPU_ABSENT(i))
 1257                         continue;
 1258                 tdq = TDQ_CPU(i);
 1259                 tdq_setup(tdq);
 1260                 tdq->tdq_cg = smp_topo_find(cpu_top, i);
 1261                 if (tdq->tdq_cg == NULL)
 1262                         panic("Can't find cpu group for %d\n", i);
 1263         }
 1264         balance_tdq = TDQ_SELF();
 1265         sched_balance();
 1266 }
 1267 #endif
 1268 
 1269 /*
 1270  * Setup the thread queues and initialize the topology based on MD
 1271  * information.
 1272  */
 1273 static void
 1274 sched_setup(void *dummy)
 1275 {
 1276         struct tdq *tdq;
 1277 
 1278         tdq = TDQ_SELF();
 1279 #ifdef SMP
 1280         sched_setup_smp();
 1281 #else
 1282         tdq_setup(tdq);
 1283 #endif
 1284         /*
 1285          * To avoid divide-by-zero, we set realstathz a dummy value
 1286          * in case which sched_clock() called before sched_initticks().
 1287          */
 1288         realstathz = hz;
 1289         sched_slice = (realstathz/10);  /* ~100ms */
 1290         tickincr = 1 << SCHED_TICK_SHIFT;
 1291 
 1292         /* Add thread0's load since it's running. */
 1293         TDQ_LOCK(tdq);
 1294         thread0.td_lock = TDQ_LOCKPTR(TDQ_SELF());
 1295         tdq_load_add(tdq, &thread0);
 1296         tdq->tdq_lowpri = thread0.td_priority;
 1297         TDQ_UNLOCK(tdq);
 1298 }
 1299 
 1300 /*
 1301  * This routine determines the tickincr after stathz and hz are setup.
 1302  */
 1303 /* ARGSUSED */
 1304 static void
 1305 sched_initticks(void *dummy)
 1306 {
 1307         int incr;
 1308 
 1309         realstathz = stathz ? stathz : hz;
 1310         sched_slice = (realstathz/10);  /* ~100ms */
 1311 
 1312         /*
 1313          * tickincr is shifted out by 10 to avoid rounding errors due to
 1314          * hz not being evenly divisible by stathz on all platforms.
 1315          */
 1316         incr = (hz << SCHED_TICK_SHIFT) / realstathz;
 1317         /*
 1318          * This does not work for values of stathz that are more than
 1319          * 1 << SCHED_TICK_SHIFT * hz.  In practice this does not happen.
 1320          */
 1321         if (incr == 0)
 1322                 incr = 1;
 1323         tickincr = incr;
 1324 #ifdef SMP
 1325         /*
 1326          * Set the default balance interval now that we know
 1327          * what realstathz is.
 1328          */
 1329         balance_interval = realstathz;
 1330         /*
 1331          * Set steal thresh to roughly log2(mp_ncpu) but no greater than 4. 
 1332          * This prevents excess thrashing on large machines and excess idle 
 1333          * on smaller machines.
 1334          */
 1335         steal_thresh = min(fls(mp_ncpus) - 1, 3);
 1336         affinity = SCHED_AFFINITY_DEFAULT;
 1337 #endif
 1338 }
 1339 
 1340 
 1341 /*
 1342  * This is the core of the interactivity algorithm.  Determines a score based
 1343  * on past behavior.  It is the ratio of sleep time to run time scaled to
 1344  * a [0, 100] integer.  This is the voluntary sleep time of a process, which
 1345  * differs from the cpu usage because it does not account for time spent
 1346  * waiting on a run-queue.  Would be prettier if we had floating point.
 1347  */
 1348 static int
 1349 sched_interact_score(struct thread *td)
 1350 {
 1351         struct td_sched *ts;
 1352         int div;
 1353 
 1354         ts = td->td_sched;
 1355         /*
 1356          * The score is only needed if this is likely to be an interactive
 1357          * task.  Don't go through the expense of computing it if there's
 1358          * no chance.
 1359          */
 1360         if (sched_interact <= SCHED_INTERACT_HALF &&
 1361                 ts->ts_runtime >= ts->ts_slptime)
 1362                         return (SCHED_INTERACT_HALF);
 1363 
 1364         if (ts->ts_runtime > ts->ts_slptime) {
 1365                 div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF);
 1366                 return (SCHED_INTERACT_HALF +
 1367                     (SCHED_INTERACT_HALF - (ts->ts_slptime / div)));
 1368         }
 1369         if (ts->ts_slptime > ts->ts_runtime) {
 1370                 div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF);
 1371                 return (ts->ts_runtime / div);
 1372         }
 1373         /* runtime == slptime */
 1374         if (ts->ts_runtime)
 1375                 return (SCHED_INTERACT_HALF);
 1376 
 1377         /*
 1378          * This can happen if slptime and runtime are 0.
 1379          */
 1380         return (0);
 1381 
 1382 }
 1383 
 1384 /*
 1385  * Scale the scheduling priority according to the "interactivity" of this
 1386  * process.
 1387  */
 1388 static void
 1389 sched_priority(struct thread *td)
 1390 {
 1391         int score;
 1392         int pri;
 1393 
 1394         if (td->td_pri_class != PRI_TIMESHARE)
 1395                 return;
 1396         /*
 1397          * If the score is interactive we place the thread in the realtime
 1398          * queue with a priority that is less than kernel and interrupt
 1399          * priorities.  These threads are not subject to nice restrictions.
 1400          *
 1401          * Scores greater than this are placed on the normal timeshare queue
 1402          * where the priority is partially decided by the most recent cpu
 1403          * utilization and the rest is decided by nice value.
 1404          *
 1405          * The nice value of the process has a linear effect on the calculated
 1406          * score.  Negative nice values make it easier for a thread to be
 1407          * considered interactive.
 1408          */
 1409         score = imax(0, sched_interact_score(td) + td->td_proc->p_nice);
 1410         if (score < sched_interact) {
 1411                 pri = PRI_MIN_REALTIME;
 1412                 pri += ((PRI_MAX_REALTIME - PRI_MIN_REALTIME) / sched_interact)
 1413                     * score;
 1414                 KASSERT(pri >= PRI_MIN_REALTIME && pri <= PRI_MAX_REALTIME,
 1415                     ("sched_priority: invalid interactive priority %d score %d",
 1416                     pri, score));
 1417         } else {
 1418                 pri = SCHED_PRI_MIN;
 1419                 if (td->td_sched->ts_ticks)
 1420                         pri += SCHED_PRI_TICKS(td->td_sched);
 1421                 pri += SCHED_PRI_NICE(td->td_proc->p_nice);
 1422                 KASSERT(pri >= PRI_MIN_TIMESHARE && pri <= PRI_MAX_TIMESHARE,
 1423                     ("sched_priority: invalid priority %d: nice %d, " 
 1424                     "ticks %d ftick %d ltick %d tick pri %d",
 1425                     pri, td->td_proc->p_nice, td->td_sched->ts_ticks,
 1426                     td->td_sched->ts_ftick, td->td_sched->ts_ltick,
 1427                     SCHED_PRI_TICKS(td->td_sched)));
 1428         }
 1429         sched_user_prio(td, pri);
 1430 
 1431         return;
 1432 }
 1433 
 1434 /*
 1435  * This routine enforces a maximum limit on the amount of scheduling history
 1436  * kept.  It is called after either the slptime or runtime is adjusted.  This
 1437  * function is ugly due to integer math.
 1438  */
 1439 static void
 1440 sched_interact_update(struct thread *td)
 1441 {
 1442         struct td_sched *ts;
 1443         u_int sum;
 1444 
 1445         ts = td->td_sched;
 1446         sum = ts->ts_runtime + ts->ts_slptime;
 1447         if (sum < SCHED_SLP_RUN_MAX)
 1448                 return;
 1449         /*
 1450          * This only happens from two places:
 1451          * 1) We have added an unusual amount of run time from fork_exit.
 1452          * 2) We have added an unusual amount of sleep time from sched_sleep().
 1453          */
 1454         if (sum > SCHED_SLP_RUN_MAX * 2) {
 1455                 if (ts->ts_runtime > ts->ts_slptime) {
 1456                         ts->ts_runtime = SCHED_SLP_RUN_MAX;
 1457                         ts->ts_slptime = 1;
 1458                 } else {
 1459                         ts->ts_slptime = SCHED_SLP_RUN_MAX;
 1460                         ts->ts_runtime = 1;
 1461                 }
 1462                 return;
 1463         }
 1464         /*
 1465          * If we have exceeded by more than 1/5th then the algorithm below
 1466          * will not bring us back into range.  Dividing by two here forces
 1467          * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX]
 1468          */
 1469         if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) {
 1470                 ts->ts_runtime /= 2;
 1471                 ts->ts_slptime /= 2;
 1472                 return;
 1473         }
 1474         ts->ts_runtime = (ts->ts_runtime / 5) * 4;
 1475         ts->ts_slptime = (ts->ts_slptime / 5) * 4;
 1476 }
 1477 
 1478 /*
 1479  * Scale back the interactivity history when a child thread is created.  The
 1480  * history is inherited from the parent but the thread may behave totally
 1481  * differently.  For example, a shell spawning a compiler process.  We want
 1482  * to learn that the compiler is behaving badly very quickly.
 1483  */
 1484 static void
 1485 sched_interact_fork(struct thread *td)
 1486 {
 1487         int ratio;
 1488         int sum;
 1489 
 1490         sum = td->td_sched->ts_runtime + td->td_sched->ts_slptime;
 1491         if (sum > SCHED_SLP_RUN_FORK) {
 1492                 ratio = sum / SCHED_SLP_RUN_FORK;
 1493                 td->td_sched->ts_runtime /= ratio;
 1494                 td->td_sched->ts_slptime /= ratio;
 1495         }
 1496 }
 1497 
 1498 /*
 1499  * Called from proc0_init() to setup the scheduler fields.
 1500  */
 1501 void
 1502 schedinit(void)
 1503 {
 1504 
 1505         /*
 1506          * Set up the scheduler specific parts of proc0.
 1507          */
 1508         proc0.p_sched = NULL; /* XXX */
 1509         thread0.td_sched = &td_sched0;
 1510         td_sched0.ts_ltick = ticks;
 1511         td_sched0.ts_ftick = ticks;
 1512         td_sched0.ts_slice = sched_slice;
 1513 }
 1514 
 1515 /*
 1516  * This is only somewhat accurate since given many processes of the same
 1517  * priority they will switch when their slices run out, which will be
 1518  * at most sched_slice stathz ticks.
 1519  */
 1520 int
 1521 sched_rr_interval(void)
 1522 {
 1523 
 1524         /* Convert sched_slice to hz */
 1525         return (hz/(realstathz/sched_slice));
 1526 }
 1527 
 1528 /*
 1529  * Update the percent cpu tracking information when it is requested or
 1530  * the total history exceeds the maximum.  We keep a sliding history of
 1531  * tick counts that slowly decays.  This is less precise than the 4BSD
 1532  * mechanism since it happens with less regular and frequent events.
 1533  */
 1534 static void
 1535 sched_pctcpu_update(struct td_sched *ts)
 1536 {
 1537 
 1538         if (ts->ts_ticks == 0)
 1539                 return;
 1540         if (ticks - (hz / 10) < ts->ts_ltick &&
 1541             SCHED_TICK_TOTAL(ts) < SCHED_TICK_MAX)
 1542                 return;
 1543         /*
 1544          * Adjust counters and watermark for pctcpu calc.
 1545          */
 1546         if (ts->ts_ltick > ticks - SCHED_TICK_TARG)
 1547                 ts->ts_ticks = (ts->ts_ticks / (ticks - ts->ts_ftick)) *
 1548                             SCHED_TICK_TARG;
 1549         else
 1550                 ts->ts_ticks = 0;
 1551         ts->ts_ltick = ticks;
 1552         ts->ts_ftick = ts->ts_ltick - SCHED_TICK_TARG;
 1553 }
 1554 
 1555 /*
 1556  * Adjust the priority of a thread.  Move it to the appropriate run-queue
 1557  * if necessary.  This is the back-end for several priority related
 1558  * functions.
 1559  */
 1560 static void
 1561 sched_thread_priority(struct thread *td, u_char prio)
 1562 {
 1563         struct td_sched *ts;
 1564         struct tdq *tdq;
 1565         int oldpri;
 1566 
 1567         KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio",
 1568             "prio:%d", td->td_priority, "new prio:%d", prio,
 1569             KTR_ATTR_LINKED, sched_tdname(curthread));
 1570         if (td != curthread && prio > td->td_priority) {
 1571                 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
 1572                     "lend prio", "prio:%d", td->td_priority, "new prio:%d",
 1573                     prio, KTR_ATTR_LINKED, sched_tdname(td));
 1574         } 
 1575         ts = td->td_sched;
 1576         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1577         if (td->td_priority == prio)
 1578                 return;
 1579         /*
 1580          * If the priority has been elevated due to priority
 1581          * propagation, we may have to move ourselves to a new
 1582          * queue.  This could be optimized to not re-add in some
 1583          * cases.
 1584          */
 1585         if (TD_ON_RUNQ(td) && prio < td->td_priority) {
 1586                 sched_rem(td);
 1587                 td->td_priority = prio;
 1588                 sched_add(td, SRQ_BORROWING);
 1589                 return;
 1590         }
 1591         /*
 1592          * If the thread is currently running we may have to adjust the lowpri
 1593          * information so other cpus are aware of our current priority.
 1594          */
 1595         if (TD_IS_RUNNING(td)) {
 1596                 tdq = TDQ_CPU(ts->ts_cpu);
 1597                 oldpri = td->td_priority;
 1598                 td->td_priority = prio;
 1599                 if (prio < tdq->tdq_lowpri)
 1600                         tdq->tdq_lowpri = prio;
 1601                 else if (tdq->tdq_lowpri == oldpri)
 1602                         tdq_setlowpri(tdq, td);
 1603                 return;
 1604         }
 1605         td->td_priority = prio;
 1606 }
 1607 
 1608 /*
 1609  * Update a thread's priority when it is lent another thread's
 1610  * priority.
 1611  */
 1612 void
 1613 sched_lend_prio(struct thread *td, u_char prio)
 1614 {
 1615 
 1616         td->td_flags |= TDF_BORROWING;
 1617         sched_thread_priority(td, prio);
 1618 }
 1619 
 1620 /*
 1621  * Restore a thread's priority when priority propagation is
 1622  * over.  The prio argument is the minimum priority the thread
 1623  * needs to have to satisfy other possible priority lending
 1624  * requests.  If the thread's regular priority is less
 1625  * important than prio, the thread will keep a priority boost
 1626  * of prio.
 1627  */
 1628 void
 1629 sched_unlend_prio(struct thread *td, u_char prio)
 1630 {
 1631         u_char base_pri;
 1632 
 1633         if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
 1634             td->td_base_pri <= PRI_MAX_TIMESHARE)
 1635                 base_pri = td->td_user_pri;
 1636         else
 1637                 base_pri = td->td_base_pri;
 1638         if (prio >= base_pri) {
 1639                 td->td_flags &= ~TDF_BORROWING;
 1640                 sched_thread_priority(td, base_pri);
 1641         } else
 1642                 sched_lend_prio(td, prio);
 1643 }
 1644 
 1645 /*
 1646  * Standard entry for setting the priority to an absolute value.
 1647  */
 1648 void
 1649 sched_prio(struct thread *td, u_char prio)
 1650 {
 1651         u_char oldprio;
 1652 
 1653         /* First, update the base priority. */
 1654         td->td_base_pri = prio;
 1655 
 1656         /*
 1657          * If the thread is borrowing another thread's priority, don't
 1658          * ever lower the priority.
 1659          */
 1660         if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
 1661                 return;
 1662 
 1663         /* Change the real priority. */
 1664         oldprio = td->td_priority;
 1665         sched_thread_priority(td, prio);
 1666 
 1667         /*
 1668          * If the thread is on a turnstile, then let the turnstile update
 1669          * its state.
 1670          */
 1671         if (TD_ON_LOCK(td) && oldprio != prio)
 1672                 turnstile_adjust(td, oldprio);
 1673 }
 1674 
 1675 /*
 1676  * Set the base user priority, does not effect current running priority.
 1677  */
 1678 void
 1679 sched_user_prio(struct thread *td, u_char prio)
 1680 {
 1681         u_char oldprio;
 1682 
 1683         td->td_base_user_pri = prio;
 1684         if (td->td_flags & TDF_UBORROWING && td->td_user_pri <= prio)
 1685                 return;
 1686         oldprio = td->td_user_pri;
 1687         td->td_user_pri = prio;
 1688 }
 1689 
 1690 void
 1691 sched_lend_user_prio(struct thread *td, u_char prio)
 1692 {
 1693         u_char oldprio;
 1694 
 1695         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1696         td->td_flags |= TDF_UBORROWING;
 1697         oldprio = td->td_user_pri;
 1698         td->td_user_pri = prio;
 1699 }
 1700 
 1701 void
 1702 sched_unlend_user_prio(struct thread *td, u_char prio)
 1703 {
 1704         u_char base_pri;
 1705 
 1706         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1707         base_pri = td->td_base_user_pri;
 1708         if (prio >= base_pri) {
 1709                 td->td_flags &= ~TDF_UBORROWING;
 1710                 sched_user_prio(td, base_pri);
 1711         } else {
 1712                 sched_lend_user_prio(td, prio);
 1713         }
 1714 }
 1715 
 1716 /*
 1717  * Block a thread for switching.  Similar to thread_block() but does not
 1718  * bump the spin count.
 1719  */
 1720 static inline struct mtx *
 1721 thread_block_switch(struct thread *td)
 1722 {
 1723         struct mtx *lock;
 1724 
 1725         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1726         lock = td->td_lock;
 1727         td->td_lock = &blocked_lock;
 1728         mtx_unlock_spin(lock);
 1729 
 1730         return (lock);
 1731 }
 1732 
 1733 /*
 1734  * Handle migration from sched_switch().  This happens only for
 1735  * cpu binding.
 1736  */
 1737 static struct mtx *
 1738 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags)
 1739 {
 1740         struct tdq *tdn;
 1741 
 1742         tdn = TDQ_CPU(td->td_sched->ts_cpu);
 1743 #ifdef SMP
 1744         tdq_load_rem(tdq, td);
 1745         /*
 1746          * Do the lock dance required to avoid LOR.  We grab an extra
 1747          * spinlock nesting to prevent preemption while we're
 1748          * not holding either run-queue lock.
 1749          */
 1750         spinlock_enter();
 1751         thread_block_switch(td);        /* This releases the lock on tdq. */
 1752 
 1753         /*
 1754          * Acquire both run-queue locks before placing the thread on the new
 1755          * run-queue to avoid deadlocks created by placing a thread with a
 1756          * blocked lock on the run-queue of a remote processor.  The deadlock
 1757          * occurs when a third processor attempts to lock the two queues in
 1758          * question while the target processor is spinning with its own
 1759          * run-queue lock held while waiting for the blocked lock to clear.
 1760          */
 1761         tdq_lock_pair(tdn, tdq);
 1762         tdq_add(tdn, td, flags);
 1763         tdq_notify(tdn, td);
 1764         TDQ_UNLOCK(tdn);
 1765         spinlock_exit();
 1766 #endif
 1767         return (TDQ_LOCKPTR(tdn));
 1768 }
 1769 
 1770 /*
 1771  * Release a thread that was blocked with thread_block_switch().
 1772  */
 1773 static inline void
 1774 thread_unblock_switch(struct thread *td, struct mtx *mtx)
 1775 {
 1776         atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock,
 1777             (uintptr_t)mtx);
 1778 }
 1779 
 1780 /*
 1781  * Switch threads.  This function has to handle threads coming in while
 1782  * blocked for some reason, running, or idle.  It also must deal with
 1783  * migrating a thread from one queue to another as running threads may
 1784  * be assigned elsewhere via binding.
 1785  */
 1786 void
 1787 sched_switch(struct thread *td, struct thread *newtd, int flags)
 1788 {
 1789         struct tdq *tdq;
 1790         struct td_sched *ts;
 1791         struct mtx *mtx;
 1792         int srqflag;
 1793         int cpuid;
 1794 
 1795         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1796         KASSERT(newtd == NULL, ("sched_switch: Unsupported newtd argument"));
 1797 
 1798         cpuid = PCPU_GET(cpuid);
 1799         tdq = TDQ_CPU(cpuid);
 1800         ts = td->td_sched;
 1801         mtx = td->td_lock;
 1802         ts->ts_rltick = ticks;
 1803         td->td_lastcpu = td->td_oncpu;
 1804         td->td_oncpu = NOCPU;
 1805         td->td_flags &= ~TDF_NEEDRESCHED;
 1806         td->td_owepreempt = 0;
 1807         tdq->tdq_switchcnt++;
 1808         /*
 1809          * The lock pointer in an idle thread should never change.  Reset it
 1810          * to CAN_RUN as well.
 1811          */
 1812         if (TD_IS_IDLETHREAD(td)) {
 1813                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1814                 TD_SET_CAN_RUN(td);
 1815         } else if (TD_IS_RUNNING(td)) {
 1816                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1817                 srqflag = (flags & SW_PREEMPT) ?
 1818                     SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
 1819                     SRQ_OURSELF|SRQ_YIELDING;
 1820                 if (ts->ts_cpu == cpuid)
 1821                         tdq_runq_add(tdq, td, srqflag);
 1822                 else
 1823                         mtx = sched_switch_migrate(tdq, td, srqflag);
 1824         } else {
 1825                 /* This thread must be going to sleep. */
 1826                 TDQ_LOCK(tdq);
 1827                 mtx = thread_block_switch(td);
 1828                 tdq_load_rem(tdq, td);
 1829         }
 1830         /*
 1831          * We enter here with the thread blocked and assigned to the
 1832          * appropriate cpu run-queue or sleep-queue and with the current
 1833          * thread-queue locked.
 1834          */
 1835         TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
 1836         newtd = choosethread();
 1837         /*
 1838          * Call the MD code to switch contexts if necessary.
 1839          */
 1840         if (td != newtd) {
 1841 #ifdef  HWPMC_HOOKS
 1842                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 1843                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
 1844 #endif
 1845                 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
 1846                 TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
 1847 
 1848 #ifdef KDTRACE_HOOKS
 1849                 /*
 1850                  * If DTrace has set the active vtime enum to anything
 1851                  * other than INACTIVE (0), then it should have set the
 1852                  * function to call.
 1853                  */
 1854                 if (dtrace_vtime_active)
 1855                         (*dtrace_vtime_switch_func)(newtd);
 1856 #endif
 1857 
 1858                 cpu_switch(td, newtd, mtx);
 1859                 /*
 1860                  * We may return from cpu_switch on a different cpu.  However,
 1861                  * we always return with td_lock pointing to the current cpu's
 1862                  * run queue lock.
 1863                  */
 1864                 cpuid = PCPU_GET(cpuid);
 1865                 tdq = TDQ_CPU(cpuid);
 1866                 lock_profile_obtain_lock_success(
 1867                     &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
 1868 #ifdef  HWPMC_HOOKS
 1869                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 1870                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
 1871 #endif
 1872         } else
 1873                 thread_unblock_switch(td, mtx);
 1874         /*
 1875          * Assert that all went well and return.
 1876          */
 1877         TDQ_LOCK_ASSERT(tdq, MA_OWNED|MA_NOTRECURSED);
 1878         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1879         td->td_oncpu = cpuid;
 1880 }
 1881 
 1882 /*
 1883  * Adjust thread priorities as a result of a nice request.
 1884  */
 1885 void
 1886 sched_nice(struct proc *p, int nice)
 1887 {
 1888         struct thread *td;
 1889 
 1890         PROC_LOCK_ASSERT(p, MA_OWNED);
 1891 
 1892         p->p_nice = nice;
 1893         FOREACH_THREAD_IN_PROC(p, td) {
 1894                 thread_lock(td);
 1895                 sched_priority(td);
 1896                 sched_prio(td, td->td_base_user_pri);
 1897                 thread_unlock(td);
 1898         }
 1899 }
 1900 
 1901 /*
 1902  * Record the sleep time for the interactivity scorer.
 1903  */
 1904 void
 1905 sched_sleep(struct thread *td, int prio)
 1906 {
 1907 
 1908         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1909 
 1910         td->td_slptick = ticks;
 1911         if (TD_IS_SUSPENDED(td) || prio <= PSOCK)
 1912                 td->td_flags |= TDF_CANSWAP;
 1913         if (static_boost == 1 && prio)
 1914                 sched_prio(td, prio);
 1915         else if (static_boost && td->td_priority > static_boost)
 1916                 sched_prio(td, static_boost);
 1917 }
 1918 
 1919 /*
 1920  * Schedule a thread to resume execution and record how long it voluntarily
 1921  * slept.  We also update the pctcpu, interactivity, and priority.
 1922  */
 1923 void
 1924 sched_wakeup(struct thread *td)
 1925 {
 1926         struct td_sched *ts;
 1927         int slptick;
 1928 
 1929         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1930         ts = td->td_sched;
 1931         td->td_flags &= ~TDF_CANSWAP;
 1932         /*
 1933          * If we slept for more than a tick update our interactivity and
 1934          * priority.
 1935          */
 1936         slptick = td->td_slptick;
 1937         td->td_slptick = 0;
 1938         if (slptick && slptick != ticks) {
 1939                 u_int hzticks;
 1940 
 1941                 hzticks = (ticks - slptick) << SCHED_TICK_SHIFT;
 1942                 ts->ts_slptime += hzticks;
 1943                 sched_interact_update(td);
 1944                 sched_pctcpu_update(ts);
 1945         }
 1946         /* Reset the slice value after we sleep. */
 1947         ts->ts_slice = sched_slice;
 1948         sched_add(td, SRQ_BORING);
 1949 }
 1950 
 1951 /*
 1952  * Penalize the parent for creating a new child and initialize the child's
 1953  * priority.
 1954  */
 1955 void
 1956 sched_fork(struct thread *td, struct thread *child)
 1957 {
 1958         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1959         sched_fork_thread(td, child);
 1960         /*
 1961          * Penalize the parent and child for forking.
 1962          */
 1963         sched_interact_fork(child);
 1964         sched_priority(child);
 1965         td->td_sched->ts_runtime += tickincr;
 1966         sched_interact_update(td);
 1967         sched_priority(td);
 1968 }
 1969 
 1970 /*
 1971  * Fork a new thread, may be within the same process.
 1972  */
 1973 void
 1974 sched_fork_thread(struct thread *td, struct thread *child)
 1975 {
 1976         struct td_sched *ts;
 1977         struct td_sched *ts2;
 1978 
 1979         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1980         /*
 1981          * Initialize child.
 1982          */
 1983         ts = td->td_sched;
 1984         ts2 = child->td_sched;
 1985         child->td_lock = TDQ_LOCKPTR(TDQ_SELF());
 1986         child->td_cpuset = cpuset_ref(td->td_cpuset);
 1987         ts2->ts_cpu = ts->ts_cpu;
 1988         ts2->ts_flags = 0;
 1989         /*
 1990          * Grab our parents cpu estimation information and priority.
 1991          */
 1992         ts2->ts_ticks = ts->ts_ticks;
 1993         ts2->ts_ltick = ts->ts_ltick;
 1994         ts2->ts_ftick = ts->ts_ftick;
 1995         child->td_user_pri = td->td_user_pri;
 1996         child->td_base_user_pri = td->td_base_user_pri;
 1997         /*
 1998          * And update interactivity score.
 1999          */
 2000         ts2->ts_slptime = ts->ts_slptime;
 2001         ts2->ts_runtime = ts->ts_runtime;
 2002         ts2->ts_slice = 1;      /* Attempt to quickly learn interactivity. */
 2003 #ifdef KTR
 2004         bzero(ts2->ts_name, sizeof(ts2->ts_name));
 2005 #endif
 2006 }
 2007 
 2008 /*
 2009  * Adjust the priority class of a thread.
 2010  */
 2011 void
 2012 sched_class(struct thread *td, int class)
 2013 {
 2014 
 2015         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2016         if (td->td_pri_class == class)
 2017                 return;
 2018         td->td_pri_class = class;
 2019 }
 2020 
 2021 /*
 2022  * Return some of the child's priority and interactivity to the parent.
 2023  */
 2024 void
 2025 sched_exit(struct proc *p, struct thread *child)
 2026 {
 2027         struct thread *td;
 2028 
 2029         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit",
 2030             "prio:td", child->td_priority);
 2031         PROC_LOCK_ASSERT(p, MA_OWNED);
 2032         td = FIRST_THREAD_IN_PROC(p);
 2033         sched_exit_thread(td, child);
 2034 }
 2035 
 2036 /*
 2037  * Penalize another thread for the time spent on this one.  This helps to
 2038  * worsen the priority and interactivity of processes which schedule batch
 2039  * jobs such as make.  This has little effect on the make process itself but
 2040  * causes new processes spawned by it to receive worse scores immediately.
 2041  */
 2042 void
 2043 sched_exit_thread(struct thread *td, struct thread *child)
 2044 {
 2045 
 2046         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit",
 2047             "prio:td", child->td_priority);
 2048         /*
 2049          * Give the child's runtime to the parent without returning the
 2050          * sleep time as a penalty to the parent.  This causes shells that
 2051          * launch expensive things to mark their children as expensive.
 2052          */
 2053         thread_lock(td);
 2054         td->td_sched->ts_runtime += child->td_sched->ts_runtime;
 2055         sched_interact_update(td);
 2056         sched_priority(td);
 2057         thread_unlock(td);
 2058 }
 2059 
 2060 void
 2061 sched_preempt(struct thread *td)
 2062 {
 2063         struct tdq *tdq;
 2064 
 2065         thread_lock(td);
 2066         tdq = TDQ_SELF();
 2067         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2068         tdq->tdq_ipipending = 0;
 2069         if (td->td_priority > tdq->tdq_lowpri) {
 2070                 int flags;
 2071 
 2072                 flags = SW_INVOL | SW_PREEMPT;
 2073                 if (td->td_critnest > 1)
 2074                         td->td_owepreempt = 1;
 2075                 else if (TD_IS_IDLETHREAD(td))
 2076                         mi_switch(flags | SWT_REMOTEWAKEIDLE, NULL);
 2077                 else
 2078                         mi_switch(flags | SWT_REMOTEPREEMPT, NULL);
 2079         }
 2080         thread_unlock(td);
 2081 }
 2082 
 2083 /*
 2084  * Fix priorities on return to user-space.  Priorities may be elevated due
 2085  * to static priorities in msleep() or similar.
 2086  */
 2087 void
 2088 sched_userret(struct thread *td)
 2089 {
 2090         /*
 2091          * XXX we cheat slightly on the locking here to avoid locking in  
 2092          * the usual case.  Setting td_priority here is essentially an
 2093          * incomplete workaround for not setting it properly elsewhere.
 2094          * Now that some interrupt handlers are threads, not setting it
 2095          * properly elsewhere can clobber it in the window between setting
 2096          * it here and returning to user mode, so don't waste time setting
 2097          * it perfectly here.
 2098          */
 2099         KASSERT((td->td_flags & TDF_BORROWING) == 0,
 2100             ("thread with borrowed priority returning to userland"));
 2101         if (td->td_priority != td->td_user_pri) {
 2102                 thread_lock(td);
 2103                 td->td_priority = td->td_user_pri;
 2104                 td->td_base_pri = td->td_user_pri;
 2105                 tdq_setlowpri(TDQ_SELF(), td);
 2106                 thread_unlock(td);
 2107         }
 2108 }
 2109 
 2110 /*
 2111  * Handle a stathz tick.  This is really only relevant for timeshare
 2112  * threads.
 2113  */
 2114 void
 2115 sched_clock(struct thread *td)
 2116 {
 2117         struct tdq *tdq;
 2118         struct td_sched *ts;
 2119 
 2120         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2121         tdq = TDQ_SELF();
 2122 #ifdef SMP
 2123         /*
 2124          * We run the long term load balancer infrequently on the first cpu.
 2125          */
 2126         if (balance_tdq == tdq) {
 2127                 if (balance_ticks && --balance_ticks == 0)
 2128                         sched_balance();
 2129         }
 2130 #endif
 2131         /*
 2132          * Save the old switch count so we have a record of the last ticks
 2133          * activity.   Initialize the new switch count based on our load.
 2134          * If there is some activity seed it to reflect that.
 2135          */
 2136         tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt;
 2137         tdq->tdq_switchcnt = tdq->tdq_load;
 2138         /*
 2139          * Advance the insert index once for each tick to ensure that all
 2140          * threads get a chance to run.
 2141          */
 2142         if (tdq->tdq_idx == tdq->tdq_ridx) {
 2143                 tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS;
 2144                 if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx]))
 2145                         tdq->tdq_ridx = tdq->tdq_idx;
 2146         }
 2147         ts = td->td_sched;
 2148         if (td->td_pri_class & PRI_FIFO_BIT)
 2149                 return;
 2150         if (td->td_pri_class == PRI_TIMESHARE) {
 2151                 /*
 2152                  * We used a tick; charge it to the thread so
 2153                  * that we can compute our interactivity.
 2154                  */
 2155                 td->td_sched->ts_runtime += tickincr;
 2156                 sched_interact_update(td);
 2157                 sched_priority(td);
 2158         }
 2159         /*
 2160          * We used up one time slice.
 2161          */
 2162         if (--ts->ts_slice > 0)
 2163                 return;
 2164         /*
 2165          * We're out of time, force a requeue at userret().
 2166          */
 2167         ts->ts_slice = sched_slice;
 2168         td->td_flags |= TDF_NEEDRESCHED;
 2169 }
 2170 
 2171 /*
 2172  * Called once per hz tick.  Used for cpu utilization information.  This
 2173  * is easier than trying to scale based on stathz.
 2174  */
 2175 void
 2176 sched_tick(void)
 2177 {
 2178         struct td_sched *ts;
 2179 
 2180         ts = curthread->td_sched;
 2181         /*
 2182          * Ticks is updated asynchronously on a single cpu.  Check here to
 2183          * avoid incrementing ts_ticks multiple times in a single tick.
 2184          */
 2185         if (ts->ts_ltick == ticks)
 2186                 return;
 2187         /* Adjust ticks for pctcpu */
 2188         ts->ts_ticks += 1 << SCHED_TICK_SHIFT;
 2189         ts->ts_ltick = ticks;
 2190         /*
 2191          * Update if we've exceeded our desired tick threshhold by over one
 2192          * second.
 2193          */
 2194         if (ts->ts_ftick + SCHED_TICK_MAX < ts->ts_ltick)
 2195                 sched_pctcpu_update(ts);
 2196 }
 2197 
 2198 /*
 2199  * Return whether the current CPU has runnable tasks.  Used for in-kernel
 2200  * cooperative idle threads.
 2201  */
 2202 int
 2203 sched_runnable(void)
 2204 {
 2205         struct tdq *tdq;
 2206         int load;
 2207 
 2208         load = 1;
 2209 
 2210         tdq = TDQ_SELF();
 2211         if ((curthread->td_flags & TDF_IDLETD) != 0) {
 2212                 if (tdq->tdq_load > 0)
 2213                         goto out;
 2214         } else
 2215                 if (tdq->tdq_load - 1 > 0)
 2216                         goto out;
 2217         load = 0;
 2218 out:
 2219         return (load);
 2220 }
 2221 
 2222 /*
 2223  * Choose the highest priority thread to run.  The thread is removed from
 2224  * the run-queue while running however the load remains.  For SMP we set
 2225  * the tdq in the global idle bitmask if it idles here.
 2226  */
 2227 struct thread *
 2228 sched_choose(void)
 2229 {
 2230         struct thread *td;
 2231         struct tdq *tdq;
 2232 
 2233         tdq = TDQ_SELF();
 2234         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2235         td = tdq_choose(tdq);
 2236         if (td) {
 2237                 td->td_sched->ts_ltick = ticks;
 2238                 tdq_runq_rem(tdq, td);
 2239                 tdq->tdq_lowpri = td->td_priority;
 2240                 return (td);
 2241         }
 2242         tdq->tdq_lowpri = PRI_MAX_IDLE;
 2243         return (PCPU_GET(idlethread));
 2244 }
 2245 
 2246 /*
 2247  * Set owepreempt if necessary.  Preemption never happens directly in ULE,
 2248  * we always request it once we exit a critical section.
 2249  */
 2250 static inline void
 2251 sched_setpreempt(struct thread *td)
 2252 {
 2253         struct thread *ctd;
 2254         int cpri;
 2255         int pri;
 2256 
 2257         THREAD_LOCK_ASSERT(curthread, MA_OWNED);
 2258 
 2259         ctd = curthread;
 2260         pri = td->td_priority;
 2261         cpri = ctd->td_priority;
 2262         if (pri < cpri)
 2263                 ctd->td_flags |= TDF_NEEDRESCHED;
 2264         if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
 2265                 return;
 2266         if (!sched_shouldpreempt(pri, cpri, 0))
 2267                 return;
 2268         ctd->td_owepreempt = 1;
 2269 }
 2270 
 2271 /*
 2272  * Add a thread to a thread queue.  Select the appropriate runq and add the
 2273  * thread to it.  This is the internal function called when the tdq is
 2274  * predetermined.
 2275  */
 2276 void
 2277 tdq_add(struct tdq *tdq, struct thread *td, int flags)
 2278 {
 2279 
 2280         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2281         KASSERT((td->td_inhibitors == 0),
 2282             ("sched_add: trying to run inhibited thread"));
 2283         KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
 2284             ("sched_add: bad thread state"));
 2285         KASSERT(td->td_flags & TDF_INMEM,
 2286             ("sched_add: thread swapped out"));
 2287 
 2288         if (td->td_priority < tdq->tdq_lowpri)
 2289                 tdq->tdq_lowpri = td->td_priority;
 2290         tdq_runq_add(tdq, td, flags);
 2291         tdq_load_add(tdq, td);
 2292 }
 2293 
 2294 /*
 2295  * Select the target thread queue and add a thread to it.  Request
 2296  * preemption or IPI a remote processor if required.
 2297  */
 2298 void
 2299 sched_add(struct thread *td, int flags)
 2300 {
 2301         struct tdq *tdq;
 2302 #ifdef SMP
 2303         int cpu;
 2304 #endif
 2305 
 2306         KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
 2307             "prio:%d", td->td_priority, KTR_ATTR_LINKED,
 2308             sched_tdname(curthread));
 2309         KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
 2310             KTR_ATTR_LINKED, sched_tdname(td));
 2311         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2312         /*
 2313          * Recalculate the priority before we select the target cpu or
 2314          * run-queue.
 2315          */
 2316         if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
 2317                 sched_priority(td);
 2318 #ifdef SMP
 2319         /*
 2320          * Pick the destination cpu and if it isn't ours transfer to the
 2321          * target cpu.
 2322          */
 2323         cpu = sched_pickcpu(td, flags);
 2324         tdq = sched_setcpu(td, cpu, flags);
 2325         tdq_add(tdq, td, flags);
 2326         if (cpu != PCPU_GET(cpuid)) {
 2327                 tdq_notify(tdq, td);
 2328                 return;
 2329         }
 2330 #else
 2331         tdq = TDQ_SELF();
 2332         TDQ_LOCK(tdq);
 2333         /*
 2334          * Now that the thread is moving to the run-queue, set the lock
 2335          * to the scheduler's lock.
 2336          */
 2337         thread_lock_set(td, TDQ_LOCKPTR(tdq));
 2338         tdq_add(tdq, td, flags);
 2339 #endif
 2340         if (!(flags & SRQ_YIELDING))
 2341                 sched_setpreempt(td);
 2342 }
 2343 
 2344 /*
 2345  * Remove a thread from a run-queue without running it.  This is used
 2346  * when we're stealing a thread from a remote queue.  Otherwise all threads
 2347  * exit by calling sched_exit_thread() and sched_throw() themselves.
 2348  */
 2349 void
 2350 sched_rem(struct thread *td)
 2351 {
 2352         struct tdq *tdq;
 2353 
 2354         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
 2355             "prio:%d", td->td_priority);
 2356         tdq = TDQ_CPU(td->td_sched->ts_cpu);
 2357         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2358         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2359         KASSERT(TD_ON_RUNQ(td),
 2360             ("sched_rem: thread not on run queue"));
 2361         tdq_runq_rem(tdq, td);
 2362         tdq_load_rem(tdq, td);
 2363         TD_SET_CAN_RUN(td);
 2364         if (td->td_priority == tdq->tdq_lowpri)
 2365                 tdq_setlowpri(tdq, NULL);
 2366 }
 2367 
 2368 /*
 2369  * Fetch cpu utilization information.  Updates on demand.
 2370  */
 2371 fixpt_t
 2372 sched_pctcpu(struct thread *td)
 2373 {
 2374         fixpt_t pctcpu;
 2375         struct td_sched *ts;
 2376 
 2377         pctcpu = 0;
 2378         ts = td->td_sched;
 2379         if (ts == NULL)
 2380                 return (0);
 2381 
 2382         thread_lock(td);
 2383         if (ts->ts_ticks) {
 2384                 int rtick;
 2385 
 2386                 sched_pctcpu_update(ts);
 2387                 /* How many rtick per second ? */
 2388                 rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
 2389                 pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
 2390         }
 2391         thread_unlock(td);
 2392 
 2393         return (pctcpu);
 2394 }
 2395 
 2396 /*
 2397  * Enforce affinity settings for a thread.  Called after adjustments to
 2398  * cpumask.
 2399  */
 2400 void
 2401 sched_affinity(struct thread *td)
 2402 {
 2403 #ifdef SMP
 2404         struct td_sched *ts;
 2405         int cpu;
 2406 
 2407         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2408         ts = td->td_sched;
 2409         if (THREAD_CAN_SCHED(td, ts->ts_cpu))
 2410                 return;
 2411         if (TD_ON_RUNQ(td)) {
 2412                 sched_rem(td);
 2413                 sched_add(td, SRQ_BORING);
 2414                 return;
 2415         }
 2416         if (!TD_IS_RUNNING(td))
 2417                 return;
 2418         td->td_flags |= TDF_NEEDRESCHED;
 2419         if (!THREAD_CAN_MIGRATE(td))
 2420                 return;
 2421         /*
 2422          * Assign the new cpu and force a switch before returning to
 2423          * userspace.  If the target thread is not running locally send
 2424          * an ipi to force the issue.
 2425          */
 2426         cpu = ts->ts_cpu;
 2427         ts->ts_cpu = sched_pickcpu(td, 0);
 2428         if (cpu != PCPU_GET(cpuid))
 2429                 ipi_selected(1 << cpu, IPI_PREEMPT);
 2430 #endif
 2431 }
 2432 
 2433 /*
 2434  * Bind a thread to a target cpu.
 2435  */
 2436 void
 2437 sched_bind(struct thread *td, int cpu)
 2438 {
 2439         struct td_sched *ts;
 2440 
 2441         THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
 2442         ts = td->td_sched;
 2443         if (ts->ts_flags & TSF_BOUND)
 2444                 sched_unbind(td);
 2445         ts->ts_flags |= TSF_BOUND;
 2446         sched_pin();
 2447         if (PCPU_GET(cpuid) == cpu)
 2448                 return;
 2449         ts->ts_cpu = cpu;
 2450         /* When we return from mi_switch we'll be on the correct cpu. */
 2451         mi_switch(SW_VOL, NULL);
 2452 }
 2453 
 2454 /*
 2455  * Release a bound thread.
 2456  */
 2457 void
 2458 sched_unbind(struct thread *td)
 2459 {
 2460         struct td_sched *ts;
 2461 
 2462         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2463         ts = td->td_sched;
 2464         if ((ts->ts_flags & TSF_BOUND) == 0)
 2465                 return;
 2466         ts->ts_flags &= ~TSF_BOUND;
 2467         sched_unpin();
 2468 }
 2469 
 2470 int
 2471 sched_is_bound(struct thread *td)
 2472 {
 2473         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2474         return (td->td_sched->ts_flags & TSF_BOUND);
 2475 }
 2476 
 2477 /*
 2478  * Basic yield call.
 2479  */
 2480 void
 2481 sched_relinquish(struct thread *td)
 2482 {
 2483         thread_lock(td);
 2484         mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
 2485         thread_unlock(td);
 2486 }
 2487 
 2488 /*
 2489  * Return the total system load.
 2490  */
 2491 int
 2492 sched_load(void)
 2493 {
 2494 #ifdef SMP
 2495         int total;
 2496         int i;
 2497 
 2498         total = 0;
 2499         for (i = 0; i <= mp_maxid; i++)
 2500                 total += TDQ_CPU(i)->tdq_sysload;
 2501         return (total);
 2502 #else
 2503         return (TDQ_SELF()->tdq_sysload);
 2504 #endif
 2505 }
 2506 
 2507 int
 2508 sched_sizeof_proc(void)
 2509 {
 2510         return (sizeof(struct proc));
 2511 }
 2512 
 2513 int
 2514 sched_sizeof_thread(void)
 2515 {
 2516         return (sizeof(struct thread) + sizeof(struct td_sched));
 2517 }
 2518 
 2519 #ifdef SMP
 2520 #define TDQ_IDLESPIN(tdq)                                               \
 2521     ((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0)
 2522 #else
 2523 #define TDQ_IDLESPIN(tdq)       1
 2524 #endif
 2525 
 2526 /*
 2527  * The actual idle process.
 2528  */
 2529 void
 2530 sched_idletd(void *dummy)
 2531 {
 2532         struct thread *td;
 2533         struct tdq *tdq;
 2534         int switchcnt;
 2535         int i;
 2536 
 2537         mtx_assert(&Giant, MA_NOTOWNED);
 2538         td = curthread;
 2539         tdq = TDQ_SELF();
 2540         for (;;) {
 2541 #ifdef SMP
 2542                 if (tdq_idled(tdq) == 0)
 2543                         continue;
 2544 #endif
 2545                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2546                 /*
 2547                  * If we're switching very frequently, spin while checking
 2548                  * for load rather than entering a low power state that 
 2549                  * may require an IPI.  However, don't do any busy
 2550                  * loops while on SMT machines as this simply steals
 2551                  * cycles from cores doing useful work.
 2552                  */
 2553                 if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) {
 2554                         for (i = 0; i < sched_idlespins; i++) {
 2555                                 if (tdq->tdq_load)
 2556                                         break;
 2557                                 cpu_spinwait();
 2558                         }
 2559                 }
 2560                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2561                 if (tdq->tdq_load == 0)
 2562                         cpu_idle(switchcnt > 1);
 2563                 if (tdq->tdq_load) {
 2564                         thread_lock(td);
 2565                         mi_switch(SW_VOL | SWT_IDLE, NULL);
 2566                         thread_unlock(td);
 2567                 }
 2568         }
 2569 }
 2570 
 2571 /*
 2572  * A CPU is entering for the first time or a thread is exiting.
 2573  */
 2574 void
 2575 sched_throw(struct thread *td)
 2576 {
 2577         struct thread *newtd;
 2578         struct tdq *tdq;
 2579 
 2580         tdq = TDQ_SELF();
 2581         if (td == NULL) {
 2582                 /* Correct spinlock nesting and acquire the correct lock. */
 2583                 TDQ_LOCK(tdq);
 2584                 spinlock_exit();
 2585         } else {
 2586                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2587                 tdq_load_rem(tdq, td);
 2588                 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
 2589         }
 2590         KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
 2591         newtd = choosethread();
 2592         TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
 2593         PCPU_SET(switchtime, cpu_ticks());
 2594         PCPU_SET(switchticks, ticks);
 2595         cpu_throw(td, newtd);           /* doesn't return */
 2596 }
 2597 
 2598 /*
 2599  * This is called from fork_exit().  Just acquire the correct locks and
 2600  * let fork do the rest of the work.
 2601  */
 2602 void
 2603 sched_fork_exit(struct thread *td)
 2604 {
 2605         struct td_sched *ts;
 2606         struct tdq *tdq;
 2607         int cpuid;
 2608 
 2609         /*
 2610          * Finish setting up thread glue so that it begins execution in a
 2611          * non-nested critical section with the scheduler lock held.
 2612          */
 2613         cpuid = PCPU_GET(cpuid);
 2614         tdq = TDQ_CPU(cpuid);
 2615         ts = td->td_sched;
 2616         if (TD_IS_IDLETHREAD(td))
 2617                 td->td_lock = TDQ_LOCKPTR(tdq);
 2618         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2619         td->td_oncpu = cpuid;
 2620         TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
 2621         lock_profile_obtain_lock_success(
 2622             &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
 2623 }
 2624 
 2625 /*
 2626  * Create on first use to catch odd startup conditons.
 2627  */
 2628 char *
 2629 sched_tdname(struct thread *td)
 2630 {
 2631 #ifdef KTR
 2632         struct td_sched *ts;
 2633 
 2634         ts = td->td_sched;
 2635         if (ts->ts_name[0] == '\0')
 2636                 snprintf(ts->ts_name, sizeof(ts->ts_name),
 2637                     "%s tid %d", td->td_name, td->td_tid);
 2638         return (ts->ts_name);
 2639 #else
 2640         return (td->td_name);
 2641 #endif
 2642 }
 2643 
 2644 #ifdef SMP
 2645 
 2646 /*
 2647  * Build the CPU topology dump string. Is recursively called to collect
 2648  * the topology tree.
 2649  */
 2650 static int
 2651 sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg,
 2652     int indent)
 2653 {
 2654         int i, first;
 2655 
 2656         sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent,
 2657             "", indent, cg->cg_level);
 2658         sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"0x%x\">", indent, "",
 2659             cg->cg_count, cg->cg_mask);
 2660         first = TRUE;
 2661         for (i = 0; i < MAXCPU; i++) {
 2662                 if ((cg->cg_mask & (1 << i)) != 0) {
 2663                         if (!first)
 2664                                 sbuf_printf(sb, ", ");
 2665                         else
 2666                                 first = FALSE;
 2667                         sbuf_printf(sb, "%d", i);
 2668                 }
 2669         }
 2670         sbuf_printf(sb, "</cpu>\n");
 2671 
 2672         sbuf_printf(sb, "%*s <flags>", indent, "");
 2673         if (cg->cg_flags != 0) {
 2674                 if ((cg->cg_flags & CG_FLAG_HTT) != 0)
 2675                         sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>\n");
 2676                 if ((cg->cg_flags & CG_FLAG_SMT) != 0)
 2677                         sbuf_printf(sb, "<flag name=\"THREAD\">SMT group</flag>\n");
 2678         }
 2679         sbuf_printf(sb, "</flags>\n");
 2680 
 2681         if (cg->cg_children > 0) {
 2682                 sbuf_printf(sb, "%*s <children>\n", indent, "");
 2683                 for (i = 0; i < cg->cg_children; i++)
 2684                         sysctl_kern_sched_topology_spec_internal(sb, 
 2685                             &cg->cg_child[i], indent+2);
 2686                 sbuf_printf(sb, "%*s </children>\n", indent, "");
 2687         }
 2688         sbuf_printf(sb, "%*s</group>\n", indent, "");
 2689         return (0);
 2690 }
 2691 
 2692 /*
 2693  * Sysctl handler for retrieving topology dump. It's a wrapper for
 2694  * the recursive sysctl_kern_smp_topology_spec_internal().
 2695  */
 2696 static int
 2697 sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS)
 2698 {
 2699         struct sbuf *topo;
 2700         int err;
 2701 
 2702         KASSERT(cpu_top != NULL, ("cpu_top isn't initialized"));
 2703 
 2704         topo = sbuf_new(NULL, NULL, 500, SBUF_AUTOEXTEND);
 2705         if (topo == NULL)
 2706                 return (ENOMEM);
 2707 
 2708         sbuf_printf(topo, "<groups>\n");
 2709         err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1);
 2710         sbuf_printf(topo, "</groups>\n");
 2711 
 2712         if (err == 0) {
 2713                 sbuf_finish(topo);
 2714                 err = SYSCTL_OUT(req, sbuf_data(topo), sbuf_len(topo));
 2715         }
 2716         sbuf_delete(topo);
 2717         return (err);
 2718 }
 2719 #endif
 2720 
 2721 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW, 0, "Scheduler");
 2722 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0,
 2723     "Scheduler name");
 2724 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
 2725     "Slice size for timeshare threads");
 2726 SYSCTL_INT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0,
 2727      "Interactivity score threshold");
 2728 SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW, &preempt_thresh,
 2729      0,"Min priority for preemption, lower priorities have greater precedence");
 2730 SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost,
 2731      0,"Controls whether static kernel priorities are assigned to sleeping threads.");
 2732 SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins,
 2733      0,"Number of times idle will spin waiting for new work.");
 2734 SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW, &sched_idlespinthresh,
 2735      0,"Threshold before we will permit idle spinning.");
 2736 #ifdef SMP
 2737 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0,
 2738     "Number of hz ticks to keep thread affinity for");
 2739 SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0,
 2740     "Enables the long-term load balancer");
 2741 SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW,
 2742     &balance_interval, 0,
 2743     "Average frequency in stathz ticks to run the long-term balancer");
 2744 SYSCTL_INT(_kern_sched, OID_AUTO, steal_htt, CTLFLAG_RW, &steal_htt, 0,
 2745     "Steals work from another hyper-threaded core on idle");
 2746 SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0,
 2747     "Attempts to steal work from other cores before idling");
 2748 SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0,
 2749     "Minimum load on remote cpu before we'll steal");
 2750 
 2751 /* Retrieve SMP topology */
 2752 SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING |
 2753     CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A", 
 2754     "XML dump of detected CPU topology");
 2755 #endif
 2756 
 2757 /* ps compat.  All cpu percentages from ULE are weighted. */
 2758 static int ccpu = 0;
 2759 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");

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