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


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

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    1 /*-
    2  * Copyright (c) 2002-2007, Jeffrey Roberson <jeff@freebsd.org>
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice unmodified, this list of conditions, and the following
   10  *    disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  *
   15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   25  */
   26 
   27 /*
   28  * This file implements the ULE scheduler.  ULE supports independent CPU
   29  * run queues and fine grain locking.  It has superior interactive
   30  * performance under load even on uni-processor systems.
   31  *
   32  * etymology:
   33  *   ULE is the last three letters in schedule.  It owes its name to a
   34  * generic user created for a scheduling system by Paul Mikesell at
   35  * Isilon Systems and a general lack of creativity on the part of the author.
   36  */
   37 
   38 #include <sys/cdefs.h>
   39 __FBSDID("$FreeBSD: releng/8.3/sys/kern/sched_ule.c 230178 2012-01-15 22:47:49Z avg $");
   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__)
   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_incrtick;    /* Last tick that we incremented on */
  107         int             ts_ftick;       /* First tick that we were running on */
  108         int             ts_ticks;       /* Tick count */
  109 #ifdef KTR
  110         char            ts_name[TS_NAME_LEN];
  111 #endif
  112 };
  113 /* flags kept in ts_flags */
  114 #define TSF_BOUND       0x0001          /* Thread can not migrate. */
  115 #define TSF_XFERABLE    0x0002          /* Thread was added as transferable. */
  116 
  117 static struct td_sched td_sched0;
  118 
  119 #define THREAD_CAN_MIGRATE(td)  ((td)->td_pinned == 0)
  120 #define THREAD_CAN_SCHED(td, cpu)       \
  121     CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
  122 
  123 /*
  124  * Priority ranges used for interactive and non-interactive timeshare
  125  * threads.  Interactive threads use realtime priorities.
  126  */
  127 #define PRI_MIN_INTERACT        PRI_MIN_REALTIME
  128 #define PRI_MAX_INTERACT        PRI_MAX_REALTIME
  129 #define PRI_MIN_BATCH           PRI_MIN_TIMESHARE
  130 #define PRI_MAX_BATCH           PRI_MAX_TIMESHARE
  131 
  132 /*
  133  * Cpu percentage computation macros and defines.
  134  *
  135  * SCHED_TICK_SECS:     Number of seconds to average the cpu usage across.
  136  * SCHED_TICK_TARG:     Number of hz ticks to average the cpu usage across.
  137  * SCHED_TICK_MAX:      Maximum number of ticks before scaling back.
  138  * SCHED_TICK_SHIFT:    Shift factor to avoid rounding away results.
  139  * SCHED_TICK_HZ:       Compute the number of hz ticks for a given ticks count.
  140  * SCHED_TICK_TOTAL:    Gives the amount of time we've been recording ticks.
  141  */
  142 #define SCHED_TICK_SECS         10
  143 #define SCHED_TICK_TARG         (hz * SCHED_TICK_SECS)
  144 #define SCHED_TICK_MAX          (SCHED_TICK_TARG + hz)
  145 #define SCHED_TICK_SHIFT        10
  146 #define SCHED_TICK_HZ(ts)       ((ts)->ts_ticks >> SCHED_TICK_SHIFT)
  147 #define SCHED_TICK_TOTAL(ts)    (max((ts)->ts_ltick - (ts)->ts_ftick, hz))
  148 
  149 /*
  150  * These macros determine priorities for non-interactive threads.  They are
  151  * assigned a priority based on their recent cpu utilization as expressed
  152  * by the ratio of ticks to the tick total.  NHALF priorities at the start
  153  * and end of the MIN to MAX timeshare range are only reachable with negative
  154  * or positive nice respectively.
  155  *
  156  * PRI_RANGE:   Priority range for utilization dependent priorities.
  157  * PRI_NRESV:   Number of nice values.
  158  * PRI_TICKS:   Compute a priority in PRI_RANGE from the ticks count and total.
  159  * PRI_NICE:    Determines the part of the priority inherited from nice.
  160  */
  161 #define SCHED_PRI_NRESV         (PRIO_MAX - PRIO_MIN)
  162 #define SCHED_PRI_NHALF         (SCHED_PRI_NRESV / 2)
  163 #define SCHED_PRI_MIN           (PRI_MIN_BATCH + SCHED_PRI_NHALF)
  164 #define SCHED_PRI_MAX           (PRI_MAX_BATCH - SCHED_PRI_NHALF)
  165 #define SCHED_PRI_RANGE         (SCHED_PRI_MAX - SCHED_PRI_MIN + 1)
  166 #define SCHED_PRI_TICKS(ts)                                             \
  167     (SCHED_TICK_HZ((ts)) /                                              \
  168     (roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE))
  169 #define SCHED_PRI_NICE(nice)    (nice)
  170 
  171 /*
  172  * These determine the interactivity of a process.  Interactivity differs from
  173  * cpu utilization in that it expresses the voluntary time slept vs time ran
  174  * while cpu utilization includes all time not running.  This more accurately
  175  * models the intent of the thread.
  176  *
  177  * SLP_RUN_MAX: Maximum amount of sleep time + run time we'll accumulate
  178  *              before throttling back.
  179  * SLP_RUN_FORK:        Maximum slp+run time to inherit at fork time.
  180  * INTERACT_MAX:        Maximum interactivity value.  Smaller is better.
  181  * INTERACT_THRESH:     Threshold for placement on the current runq.
  182  */
  183 #define SCHED_SLP_RUN_MAX       ((hz * 5) << SCHED_TICK_SHIFT)
  184 #define SCHED_SLP_RUN_FORK      ((hz / 2) << SCHED_TICK_SHIFT)
  185 #define SCHED_INTERACT_MAX      (100)
  186 #define SCHED_INTERACT_HALF     (SCHED_INTERACT_MAX / 2)
  187 #define SCHED_INTERACT_THRESH   (30)
  188 
  189 /*
  190  * tickincr:            Converts a stathz tick into a hz domain scaled by
  191  *                      the shift factor.  Without the shift the error rate
  192  *                      due to rounding would be unacceptably high.
  193  * realstathz:          stathz is sometimes 0 and run off of hz.
  194  * sched_slice:         Runtime of each thread before rescheduling.
  195  * preempt_thresh:      Priority threshold for preemption and remote IPIs.
  196  */
  197 static int sched_interact = SCHED_INTERACT_THRESH;
  198 static int realstathz;
  199 static int tickincr;
  200 static int sched_slice = 1;
  201 #ifdef PREEMPTION
  202 #ifdef FULL_PREEMPTION
  203 static int preempt_thresh = PRI_MAX_IDLE;
  204 #else
  205 static int preempt_thresh = PRI_MIN_KERN;
  206 #endif
  207 #else 
  208 static int preempt_thresh = 0;
  209 #endif
  210 static int static_boost = PRI_MIN_BATCH;
  211 static int sched_idlespins = 10000;
  212 static int sched_idlespinthresh = 4;
  213 
  214 /*
  215  * tdq - per processor runqs and statistics.  All fields are protected by the
  216  * tdq_lock.  The load and lowpri may be accessed without to avoid excess
  217  * locking in sched_pickcpu();
  218  */
  219 struct tdq {
  220         /* Ordered to improve efficiency of cpu_search() and switch(). */
  221         struct mtx      tdq_lock;               /* run queue lock. */
  222         struct cpu_group *tdq_cg;               /* Pointer to cpu topology. */
  223         volatile int    tdq_load;               /* Aggregate load. */
  224         int             tdq_sysload;            /* For loadavg, !ITHD load. */
  225         int             tdq_transferable;       /* Transferable thread count. */
  226         short           tdq_switchcnt;          /* Switches this tick. */
  227         short           tdq_oldswitchcnt;       /* Switches last tick. */
  228         u_char          tdq_lowpri;             /* Lowest priority thread. */
  229         u_char          tdq_ipipending;         /* IPI pending. */
  230         u_char          tdq_idx;                /* Current insert index. */
  231         u_char          tdq_ridx;               /* Current removal index. */
  232         struct runq     tdq_realtime;           /* real-time run queue. */
  233         struct runq     tdq_timeshare;          /* timeshare run queue. */
  234         struct runq     tdq_idle;               /* Queue of IDLE threads. */
  235         char            tdq_name[TDQ_NAME_LEN];
  236 #ifdef KTR
  237         char            tdq_loadname[TDQ_LOADNAME_LEN];
  238 #endif
  239 } __aligned(64);
  240 
  241 /* Idle thread states and config. */
  242 #define TDQ_RUNNING     1
  243 #define TDQ_IDLE        2
  244 
  245 #ifdef SMP
  246 struct cpu_group *cpu_top;              /* CPU topology */
  247 
  248 #define SCHED_AFFINITY_DEFAULT  (max(1, hz / 1000))
  249 #define SCHED_AFFINITY(ts, t)   ((ts)->ts_rltick > ticks - ((t) * affinity))
  250 
  251 /*
  252  * Run-time tunables.
  253  */
  254 static int rebalance = 1;
  255 static int balance_interval = 128;      /* Default set in sched_initticks(). */
  256 static int affinity;
  257 static int steal_htt = 1;
  258 static int steal_idle = 1;
  259 static int steal_thresh = 2;
  260 
  261 /*
  262  * One thread queue per processor.
  263  */
  264 static struct tdq       tdq_cpu[MAXCPU];
  265 static struct tdq       *balance_tdq;
  266 static int balance_ticks;
  267 
  268 #define TDQ_SELF()      (&tdq_cpu[PCPU_GET(cpuid)])
  269 #define TDQ_CPU(x)      (&tdq_cpu[(x)])
  270 #define TDQ_ID(x)       ((int)((x) - tdq_cpu))
  271 #else   /* !SMP */
  272 static struct tdq       tdq_cpu;
  273 
  274 #define TDQ_ID(x)       (0)
  275 #define TDQ_SELF()      (&tdq_cpu)
  276 #define TDQ_CPU(x)      (&tdq_cpu)
  277 #endif
  278 
  279 #define TDQ_LOCK_ASSERT(t, type)        mtx_assert(TDQ_LOCKPTR((t)), (type))
  280 #define TDQ_LOCK(t)             mtx_lock_spin(TDQ_LOCKPTR((t)))
  281 #define TDQ_LOCK_FLAGS(t, f)    mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f))
  282 #define TDQ_UNLOCK(t)           mtx_unlock_spin(TDQ_LOCKPTR((t)))
  283 #define TDQ_LOCKPTR(t)          (&(t)->tdq_lock)
  284 
  285 static void sched_priority(struct thread *);
  286 static void sched_thread_priority(struct thread *, u_char);
  287 static int sched_interact_score(struct thread *);
  288 static void sched_interact_update(struct thread *);
  289 static void sched_interact_fork(struct thread *);
  290 static void sched_pctcpu_update(struct td_sched *);
  291 
  292 /* Operations on per processor queues */
  293 static struct thread *tdq_choose(struct tdq *);
  294 static void tdq_setup(struct tdq *);
  295 static void tdq_load_add(struct tdq *, struct thread *);
  296 static void tdq_load_rem(struct tdq *, struct thread *);
  297 static __inline void tdq_runq_add(struct tdq *, struct thread *, int);
  298 static __inline void tdq_runq_rem(struct tdq *, struct thread *);
  299 static inline int sched_shouldpreempt(int, int, int);
  300 void tdq_print(int cpu);
  301 static void runq_print(struct runq *rq);
  302 static void tdq_add(struct tdq *, struct thread *, int);
  303 #ifdef SMP
  304 static int tdq_move(struct tdq *, struct tdq *);
  305 static int tdq_idled(struct tdq *);
  306 static void tdq_notify(struct tdq *, struct thread *);
  307 static struct thread *tdq_steal(struct tdq *, int);
  308 static struct thread *runq_steal(struct runq *, int);
  309 static int sched_pickcpu(struct thread *, int);
  310 static void sched_balance(void);
  311 static int sched_balance_pair(struct tdq *, struct tdq *);
  312 static inline struct tdq *sched_setcpu(struct thread *, int, int);
  313 static inline void thread_unblock_switch(struct thread *, struct mtx *);
  314 static struct mtx *sched_switch_migrate(struct tdq *, struct thread *, int);
  315 static int sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS);
  316 static int sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, 
  317     struct cpu_group *cg, int indent);
  318 #endif
  319 
  320 static void sched_setup(void *dummy);
  321 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
  322 
  323 static void sched_initticks(void *dummy);
  324 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
  325     NULL);
  326 
  327 /*
  328  * Print the threads waiting on a run-queue.
  329  */
  330 static void
  331 runq_print(struct runq *rq)
  332 {
  333         struct rqhead *rqh;
  334         struct thread *td;
  335         int pri;
  336         int j;
  337         int i;
  338 
  339         for (i = 0; i < RQB_LEN; i++) {
  340                 printf("\t\trunq bits %d 0x%zx\n",
  341                     i, rq->rq_status.rqb_bits[i]);
  342                 for (j = 0; j < RQB_BPW; j++)
  343                         if (rq->rq_status.rqb_bits[i] & (1ul << j)) {
  344                                 pri = j + (i << RQB_L2BPW);
  345                                 rqh = &rq->rq_queues[pri];
  346                                 TAILQ_FOREACH(td, rqh, td_runq) {
  347                                         printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
  348                                             td, td->td_name, td->td_priority,
  349                                             td->td_rqindex, pri);
  350                                 }
  351                         }
  352         }
  353 }
  354 
  355 /*
  356  * Print the status of a per-cpu thread queue.  Should be a ddb show cmd.
  357  */
  358 void
  359 tdq_print(int cpu)
  360 {
  361         struct tdq *tdq;
  362 
  363         tdq = TDQ_CPU(cpu);
  364 
  365         printf("tdq %d:\n", TDQ_ID(tdq));
  366         printf("\tlock            %p\n", TDQ_LOCKPTR(tdq));
  367         printf("\tLock name:      %s\n", tdq->tdq_name);
  368         printf("\tload:           %d\n", tdq->tdq_load);
  369         printf("\tswitch cnt:     %d\n", tdq->tdq_switchcnt);
  370         printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt);
  371         printf("\ttimeshare idx:  %d\n", tdq->tdq_idx);
  372         printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
  373         printf("\tload transferable: %d\n", tdq->tdq_transferable);
  374         printf("\tlowest priority:   %d\n", tdq->tdq_lowpri);
  375         printf("\trealtime runq:\n");
  376         runq_print(&tdq->tdq_realtime);
  377         printf("\ttimeshare runq:\n");
  378         runq_print(&tdq->tdq_timeshare);
  379         printf("\tidle runq:\n");
  380         runq_print(&tdq->tdq_idle);
  381 }
  382 
  383 static inline int
  384 sched_shouldpreempt(int pri, int cpri, int remote)
  385 {
  386         /*
  387          * If the new priority is not better than the current priority there is
  388          * nothing to do.
  389          */
  390         if (pri >= cpri)
  391                 return (0);
  392         /*
  393          * Always preempt idle.
  394          */
  395         if (cpri >= PRI_MIN_IDLE)
  396                 return (1);
  397         /*
  398          * If preemption is disabled don't preempt others.
  399          */
  400         if (preempt_thresh == 0)
  401                 return (0);
  402         /*
  403          * Preempt if we exceed the threshold.
  404          */
  405         if (pri <= preempt_thresh)
  406                 return (1);
  407         /*
  408          * If we're interactive or better and there is non-interactive
  409          * or worse running preempt only remote processors.
  410          */
  411         if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT)
  412                 return (1);
  413         return (0);
  414 }
  415 
  416 /*
  417  * Add a thread to the actual run-queue.  Keeps transferable counts up to
  418  * date with what is actually on the run-queue.  Selects the correct
  419  * queue position for timeshare threads.
  420  */
  421 static __inline void
  422 tdq_runq_add(struct tdq *tdq, struct thread *td, int flags)
  423 {
  424         struct td_sched *ts;
  425         u_char pri;
  426 
  427         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  428         THREAD_LOCK_ASSERT(td, MA_OWNED);
  429 
  430         pri = td->td_priority;
  431         ts = td->td_sched;
  432         TD_SET_RUNQ(td);
  433         if (THREAD_CAN_MIGRATE(td)) {
  434                 tdq->tdq_transferable++;
  435                 ts->ts_flags |= TSF_XFERABLE;
  436         }
  437         if (pri < PRI_MIN_BATCH) {
  438                 ts->ts_runq = &tdq->tdq_realtime;
  439         } else if (pri <= PRI_MAX_BATCH) {
  440                 ts->ts_runq = &tdq->tdq_timeshare;
  441                 KASSERT(pri <= PRI_MAX_BATCH && pri >= PRI_MIN_BATCH,
  442                         ("Invalid priority %d on timeshare runq", pri));
  443                 /*
  444                  * This queue contains only priorities between MIN and MAX
  445                  * realtime.  Use the whole queue to represent these values.
  446                  */
  447                 if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) {
  448                         pri = RQ_NQS * (pri - PRI_MIN_BATCH) /
  449                             (PRI_MAX_BATCH - PRI_MIN_BATCH + 1);
  450                         pri = (pri + tdq->tdq_idx) % RQ_NQS;
  451                         /*
  452                          * This effectively shortens the queue by one so we
  453                          * can have a one slot difference between idx and
  454                          * ridx while we wait for threads to drain.
  455                          */
  456                         if (tdq->tdq_ridx != tdq->tdq_idx &&
  457                             pri == tdq->tdq_ridx)
  458                                 pri = (unsigned char)(pri - 1) % RQ_NQS;
  459                 } else
  460                         pri = tdq->tdq_ridx;
  461                 runq_add_pri(ts->ts_runq, td, pri, flags);
  462                 return;
  463         } else
  464                 ts->ts_runq = &tdq->tdq_idle;
  465         runq_add(ts->ts_runq, td, flags);
  466 }
  467 
  468 /* 
  469  * Remove a thread from a run-queue.  This typically happens when a thread
  470  * is selected to run.  Running threads are not on the queue and the
  471  * transferable count does not reflect them.
  472  */
  473 static __inline void
  474 tdq_runq_rem(struct tdq *tdq, struct thread *td)
  475 {
  476         struct td_sched *ts;
  477 
  478         ts = td->td_sched;
  479         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  480         KASSERT(ts->ts_runq != NULL,
  481             ("tdq_runq_remove: thread %p null ts_runq", td));
  482         if (ts->ts_flags & TSF_XFERABLE) {
  483                 tdq->tdq_transferable--;
  484                 ts->ts_flags &= ~TSF_XFERABLE;
  485         }
  486         if (ts->ts_runq == &tdq->tdq_timeshare) {
  487                 if (tdq->tdq_idx != tdq->tdq_ridx)
  488                         runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx);
  489                 else
  490                         runq_remove_idx(ts->ts_runq, td, NULL);
  491         } else
  492                 runq_remove(ts->ts_runq, td);
  493 }
  494 
  495 /*
  496  * Load is maintained for all threads RUNNING and ON_RUNQ.  Add the load
  497  * for this thread to the referenced thread queue.
  498  */
  499 static void
  500 tdq_load_add(struct tdq *tdq, struct thread *td)
  501 {
  502 
  503         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  504         THREAD_LOCK_ASSERT(td, MA_OWNED);
  505 
  506         tdq->tdq_load++;
  507         if ((td->td_flags & TDF_NOLOAD) == 0)
  508                 tdq->tdq_sysload++;
  509         KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
  510 }
  511 
  512 /*
  513  * Remove the load from a thread that is transitioning to a sleep state or
  514  * exiting.
  515  */
  516 static void
  517 tdq_load_rem(struct tdq *tdq, struct thread *td)
  518 {
  519 
  520         THREAD_LOCK_ASSERT(td, MA_OWNED);
  521         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  522         KASSERT(tdq->tdq_load != 0,
  523             ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
  524 
  525         tdq->tdq_load--;
  526         if ((td->td_flags & TDF_NOLOAD) == 0)
  527                 tdq->tdq_sysload--;
  528         KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
  529 }
  530 
  531 /*
  532  * Set lowpri to its exact value by searching the run-queue and
  533  * evaluating curthread.  curthread may be passed as an optimization.
  534  */
  535 static void
  536 tdq_setlowpri(struct tdq *tdq, struct thread *ctd)
  537 {
  538         struct thread *td;
  539 
  540         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
  541         if (ctd == NULL)
  542                 ctd = pcpu_find(TDQ_ID(tdq))->pc_curthread;
  543         td = tdq_choose(tdq);
  544         if (td == NULL || td->td_priority > ctd->td_priority)
  545                 tdq->tdq_lowpri = ctd->td_priority;
  546         else
  547                 tdq->tdq_lowpri = td->td_priority;
  548 }
  549 
  550 #ifdef SMP
  551 struct cpu_search {
  552         cpuset_t cs_mask;
  553         u_int   cs_load;
  554         u_int   cs_cpu;
  555         int     cs_limit;       /* Min priority for low min load for high. */
  556 };
  557 
  558 #define CPU_SEARCH_LOWEST       0x1
  559 #define CPU_SEARCH_HIGHEST      0x2
  560 #define CPU_SEARCH_BOTH         (CPU_SEARCH_LOWEST|CPU_SEARCH_HIGHEST)
  561 
  562 #define CPUSET_FOREACH(cpu, mask)                               \
  563         for ((cpu) = 0; (cpu) <= mp_maxid; (cpu)++)             \
  564                 if ((mask) & 1 << (cpu))
  565 
  566 static __inline int cpu_search(struct cpu_group *cg, struct cpu_search *low,
  567     struct cpu_search *high, const int match);
  568 int cpu_search_lowest(struct cpu_group *cg, struct cpu_search *low);
  569 int cpu_search_highest(struct cpu_group *cg, struct cpu_search *high);
  570 int cpu_search_both(struct cpu_group *cg, struct cpu_search *low,
  571     struct cpu_search *high);
  572 
  573 /*
  574  * This routine compares according to the match argument and should be
  575  * reduced in actual instantiations via constant propagation and dead code
  576  * elimination.
  577  */ 
  578 static __inline int
  579 cpu_compare(int cpu, struct cpu_search *low, struct cpu_search *high,
  580     const int match)
  581 {
  582         struct tdq *tdq;
  583 
  584         tdq = TDQ_CPU(cpu);
  585         if (match & CPU_SEARCH_LOWEST)
  586                 if (CPU_ISSET(cpu, &low->cs_mask) &&
  587                     tdq->tdq_load < low->cs_load &&
  588                     tdq->tdq_lowpri > low->cs_limit) {
  589                         low->cs_cpu = cpu;
  590                         low->cs_load = tdq->tdq_load;
  591                 }
  592         if (match & CPU_SEARCH_HIGHEST)
  593                 if (CPU_ISSET(cpu, &high->cs_mask) &&
  594                     tdq->tdq_load >= high->cs_limit && 
  595                     tdq->tdq_load > high->cs_load &&
  596                     tdq->tdq_transferable) {
  597                         high->cs_cpu = cpu;
  598                         high->cs_load = tdq->tdq_load;
  599                 }
  600         return (tdq->tdq_load);
  601 }
  602 
  603 /*
  604  * Search the tree of cpu_groups for the lowest or highest loaded cpu
  605  * according to the match argument.  This routine actually compares the
  606  * load on all paths through the tree and finds the least loaded cpu on
  607  * the least loaded path, which may differ from the least loaded cpu in
  608  * the system.  This balances work among caches and busses.
  609  *
  610  * This inline is instantiated in three forms below using constants for the
  611  * match argument.  It is reduced to the minimum set for each case.  It is
  612  * also recursive to the depth of the tree.
  613  */
  614 static __inline int
  615 cpu_search(struct cpu_group *cg, struct cpu_search *low,
  616     struct cpu_search *high, const int match)
  617 {
  618         int total;
  619 
  620         total = 0;
  621         if (cg->cg_children) {
  622                 struct cpu_search lgroup;
  623                 struct cpu_search hgroup;
  624                 struct cpu_group *child;
  625                 u_int lload;
  626                 int hload;
  627                 int load;
  628                 int i;
  629 
  630                 lload = -1;
  631                 hload = -1;
  632                 for (i = 0; i < cg->cg_children; i++) {
  633                         child = &cg->cg_child[i];
  634                         if (match & CPU_SEARCH_LOWEST) {
  635                                 lgroup = *low;
  636                                 lgroup.cs_load = -1;
  637                         }
  638                         if (match & CPU_SEARCH_HIGHEST) {
  639                                 hgroup = *high;
  640                                 lgroup.cs_load = 0;
  641                         }
  642                         switch (match) {
  643                         case CPU_SEARCH_LOWEST:
  644                                 load = cpu_search_lowest(child, &lgroup);
  645                                 break;
  646                         case CPU_SEARCH_HIGHEST:
  647                                 load = cpu_search_highest(child, &hgroup);
  648                                 break;
  649                         case CPU_SEARCH_BOTH:
  650                                 load = cpu_search_both(child, &lgroup, &hgroup);
  651                                 break;
  652                         }
  653                         total += load;
  654                         if (match & CPU_SEARCH_LOWEST)
  655                                 if (load < lload || low->cs_cpu == -1) {
  656                                         *low = lgroup;
  657                                         lload = load;
  658                                 }
  659                         if (match & CPU_SEARCH_HIGHEST) 
  660                                 if (load > hload || high->cs_cpu == -1) {
  661                                         hload = load;
  662                                         *high = hgroup;
  663                                 }
  664                 }
  665         } else {
  666                 int cpu;
  667 
  668                 CPUSET_FOREACH(cpu, cg->cg_mask)
  669                         total += cpu_compare(cpu, low, high, match);
  670         }
  671         return (total);
  672 }
  673 
  674 /*
  675  * cpu_search instantiations must pass constants to maintain the inline
  676  * optimization.
  677  */
  678 int
  679 cpu_search_lowest(struct cpu_group *cg, struct cpu_search *low)
  680 {
  681         return cpu_search(cg, low, NULL, CPU_SEARCH_LOWEST);
  682 }
  683 
  684 int
  685 cpu_search_highest(struct cpu_group *cg, struct cpu_search *high)
  686 {
  687         return cpu_search(cg, NULL, high, CPU_SEARCH_HIGHEST);
  688 }
  689 
  690 int
  691 cpu_search_both(struct cpu_group *cg, struct cpu_search *low,
  692     struct cpu_search *high)
  693 {
  694         return cpu_search(cg, low, high, CPU_SEARCH_BOTH);
  695 }
  696 
  697 /*
  698  * Find the cpu with the least load via the least loaded path that has a
  699  * lowpri greater than pri  pri.  A pri of -1 indicates any priority is
  700  * acceptable.
  701  */
  702 static inline int
  703 sched_lowest(struct cpu_group *cg, cpuset_t mask, int pri)
  704 {
  705         struct cpu_search low;
  706 
  707         low.cs_cpu = -1;
  708         low.cs_load = -1;
  709         low.cs_mask = mask;
  710         low.cs_limit = pri;
  711         cpu_search_lowest(cg, &low);
  712         return low.cs_cpu;
  713 }
  714 
  715 /*
  716  * Find the cpu with the highest load via the highest loaded path.
  717  */
  718 static inline int
  719 sched_highest(struct cpu_group *cg, cpuset_t mask, int minload)
  720 {
  721         struct cpu_search high;
  722 
  723         high.cs_cpu = -1;
  724         high.cs_load = 0;
  725         high.cs_mask = mask;
  726         high.cs_limit = minload;
  727         cpu_search_highest(cg, &high);
  728         return high.cs_cpu;
  729 }
  730 
  731 /*
  732  * Simultaneously find the highest and lowest loaded cpu reachable via
  733  * cg.
  734  */
  735 static inline void 
  736 sched_both(struct cpu_group *cg, cpuset_t mask, int *lowcpu, int *highcpu)
  737 {
  738         struct cpu_search high;
  739         struct cpu_search low;
  740 
  741         low.cs_cpu = -1;
  742         low.cs_limit = -1;
  743         low.cs_load = -1;
  744         low.cs_mask = mask;
  745         high.cs_load = 0;
  746         high.cs_cpu = -1;
  747         high.cs_limit = -1;
  748         high.cs_mask = mask;
  749         cpu_search_both(cg, &low, &high);
  750         *lowcpu = low.cs_cpu;
  751         *highcpu = high.cs_cpu;
  752         return;
  753 }
  754 
  755 static void
  756 sched_balance_group(struct cpu_group *cg)
  757 {
  758         cpuset_t mask;
  759         int high;
  760         int low;
  761         int i;
  762 
  763         CPU_FILL(&mask);
  764         for (;;) {
  765                 sched_both(cg, mask, &low, &high);
  766                 if (low == high || low == -1 || high == -1)
  767                         break;
  768                 if (sched_balance_pair(TDQ_CPU(high), TDQ_CPU(low)))
  769                         break;
  770                 /*
  771                  * If we failed to move any threads determine which cpu
  772                  * to kick out of the set and try again.
  773                  */
  774                 if (TDQ_CPU(high)->tdq_transferable == 0)
  775                         CPU_CLR(high, &mask);
  776                 else
  777                         CPU_CLR(low, &mask);
  778         }
  779 
  780         for (i = 0; i < cg->cg_children; i++)
  781                 sched_balance_group(&cg->cg_child[i]);
  782 }
  783 
  784 static void
  785 sched_balance(void)
  786 {
  787         struct tdq *tdq;
  788 
  789         /*
  790          * Select a random time between .5 * balance_interval and
  791          * 1.5 * balance_interval.
  792          */
  793         balance_ticks = max(balance_interval / 2, 1);
  794         balance_ticks += random() % balance_interval;
  795         if (smp_started == 0 || rebalance == 0)
  796                 return;
  797         tdq = TDQ_SELF();
  798         TDQ_UNLOCK(tdq);
  799         sched_balance_group(cpu_top);
  800         TDQ_LOCK(tdq);
  801 }
  802 
  803 /*
  804  * Lock two thread queues using their address to maintain lock order.
  805  */
  806 static void
  807 tdq_lock_pair(struct tdq *one, struct tdq *two)
  808 {
  809         if (one < two) {
  810                 TDQ_LOCK(one);
  811                 TDQ_LOCK_FLAGS(two, MTX_DUPOK);
  812         } else {
  813                 TDQ_LOCK(two);
  814                 TDQ_LOCK_FLAGS(one, MTX_DUPOK);
  815         }
  816 }
  817 
  818 /*
  819  * Unlock two thread queues.  Order is not important here.
  820  */
  821 static void
  822 tdq_unlock_pair(struct tdq *one, struct tdq *two)
  823 {
  824         TDQ_UNLOCK(one);
  825         TDQ_UNLOCK(two);
  826 }
  827 
  828 /*
  829  * Transfer load between two imbalanced thread queues.
  830  */
  831 static int
  832 sched_balance_pair(struct tdq *high, struct tdq *low)
  833 {
  834         int transferable;
  835         int high_load;
  836         int low_load;
  837         int moved;
  838         int move;
  839         int diff;
  840         int i;
  841 
  842         tdq_lock_pair(high, low);
  843         transferable = high->tdq_transferable;
  844         high_load = high->tdq_load;
  845         low_load = low->tdq_load;
  846         moved = 0;
  847         /*
  848          * Determine what the imbalance is and then adjust that to how many
  849          * threads we actually have to give up (transferable).
  850          */
  851         if (transferable != 0) {
  852                 diff = high_load - low_load;
  853                 move = diff / 2;
  854                 if (diff & 0x1)
  855                         move++;
  856                 move = min(move, transferable);
  857                 for (i = 0; i < move; i++)
  858                         moved += tdq_move(high, low);
  859                 /*
  860                  * IPI the target cpu to force it to reschedule with the new
  861                  * workload.
  862                  */
  863                 ipi_cpu(TDQ_ID(low), IPI_PREEMPT);
  864         }
  865         tdq_unlock_pair(high, low);
  866         return (moved);
  867 }
  868 
  869 /*
  870  * Move a thread from one thread queue to another.
  871  */
  872 static int
  873 tdq_move(struct tdq *from, struct tdq *to)
  874 {
  875         struct td_sched *ts;
  876         struct thread *td;
  877         struct tdq *tdq;
  878         int cpu;
  879 
  880         TDQ_LOCK_ASSERT(from, MA_OWNED);
  881         TDQ_LOCK_ASSERT(to, MA_OWNED);
  882 
  883         tdq = from;
  884         cpu = TDQ_ID(to);
  885         td = tdq_steal(tdq, cpu);
  886         if (td == NULL)
  887                 return (0);
  888         ts = td->td_sched;
  889         /*
  890          * Although the run queue is locked the thread may be blocked.  Lock
  891          * it to clear this and acquire the run-queue lock.
  892          */
  893         thread_lock(td);
  894         /* Drop recursive lock on from acquired via thread_lock(). */
  895         TDQ_UNLOCK(from);
  896         sched_rem(td);
  897         ts->ts_cpu = cpu;
  898         td->td_lock = TDQ_LOCKPTR(to);
  899         tdq_add(to, td, SRQ_YIELDING);
  900         return (1);
  901 }
  902 
  903 /*
  904  * This tdq has idled.  Try to steal a thread from another cpu and switch
  905  * to it.
  906  */
  907 static int
  908 tdq_idled(struct tdq *tdq)
  909 {
  910         struct cpu_group *cg;
  911         struct tdq *steal;
  912         cpuset_t mask;
  913         int thresh;
  914         int cpu;
  915 
  916         if (smp_started == 0 || steal_idle == 0)
  917                 return (1);
  918         CPU_FILL(&mask);
  919         CPU_CLR(PCPU_GET(cpuid), &mask);
  920         /* We don't want to be preempted while we're iterating. */
  921         spinlock_enter();
  922         for (cg = tdq->tdq_cg; cg != NULL; ) {
  923                 if ((cg->cg_flags & CG_FLAG_THREAD) == 0)
  924                         thresh = steal_thresh;
  925                 else
  926                         thresh = 1;
  927                 cpu = sched_highest(cg, mask, thresh);
  928                 if (cpu == -1) {
  929                         cg = cg->cg_parent;
  930                         continue;
  931                 }
  932                 steal = TDQ_CPU(cpu);
  933                 CPU_CLR(cpu, &mask);
  934                 tdq_lock_pair(tdq, steal);
  935                 if (steal->tdq_load < thresh || steal->tdq_transferable == 0) {
  936                         tdq_unlock_pair(tdq, steal);
  937                         continue;
  938                 }
  939                 /*
  940                  * If a thread was added while interrupts were disabled don't
  941                  * steal one here.  If we fail to acquire one due to affinity
  942                  * restrictions loop again with this cpu removed from the
  943                  * set.
  944                  */
  945                 if (tdq->tdq_load == 0 && tdq_move(steal, tdq) == 0) {
  946                         tdq_unlock_pair(tdq, steal);
  947                         continue;
  948                 }
  949                 spinlock_exit();
  950                 TDQ_UNLOCK(steal);
  951                 mi_switch(SW_VOL | SWT_IDLE, NULL);
  952                 thread_unlock(curthread);
  953 
  954                 return (0);
  955         }
  956         spinlock_exit();
  957         return (1);
  958 }
  959 
  960 /*
  961  * Notify a remote cpu of new work.  Sends an IPI if criteria are met.
  962  */
  963 static void
  964 tdq_notify(struct tdq *tdq, struct thread *td)
  965 {
  966         struct thread *ctd;
  967         int pri;
  968         int cpu;
  969 
  970         if (tdq->tdq_ipipending)
  971                 return;
  972         cpu = td->td_sched->ts_cpu;
  973         pri = td->td_priority;
  974         ctd = pcpu_find(cpu)->pc_curthread;
  975         if (!sched_shouldpreempt(pri, ctd->td_priority, 1))
  976                 return;
  977         if (TD_IS_IDLETHREAD(ctd)) {
  978                 /*
  979                  * If the MD code has an idle wakeup routine try that before
  980                  * falling back to IPI.
  981                  */
  982                 if (cpu_idle_wakeup(cpu))
  983                         return;
  984         }
  985         tdq->tdq_ipipending = 1;
  986         ipi_cpu(cpu, IPI_PREEMPT);
  987 }
  988 
  989 /*
  990  * Steals load from a timeshare queue.  Honors the rotating queue head
  991  * index.
  992  */
  993 static struct thread *
  994 runq_steal_from(struct runq *rq, int cpu, u_char start)
  995 {
  996         struct rqbits *rqb;
  997         struct rqhead *rqh;
  998         struct thread *td;
  999         int first;
 1000         int bit;
 1001         int pri;
 1002         int i;
 1003 
 1004         rqb = &rq->rq_status;
 1005         bit = start & (RQB_BPW -1);
 1006         pri = 0;
 1007         first = 0;
 1008 again:
 1009         for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
 1010                 if (rqb->rqb_bits[i] == 0)
 1011                         continue;
 1012                 if (bit != 0) {
 1013                         for (pri = bit; pri < RQB_BPW; pri++)
 1014                                 if (rqb->rqb_bits[i] & (1ul << pri))
 1015                                         break;
 1016                         if (pri >= RQB_BPW)
 1017                                 continue;
 1018                 } else
 1019                         pri = RQB_FFS(rqb->rqb_bits[i]);
 1020                 pri += (i << RQB_L2BPW);
 1021                 rqh = &rq->rq_queues[pri];
 1022                 TAILQ_FOREACH(td, rqh, td_runq) {
 1023                         if (first && THREAD_CAN_MIGRATE(td) &&
 1024                             THREAD_CAN_SCHED(td, cpu))
 1025                                 return (td);
 1026                         first = 1;
 1027                 }
 1028         }
 1029         if (start != 0) {
 1030                 start = 0;
 1031                 goto again;
 1032         }
 1033 
 1034         return (NULL);
 1035 }
 1036 
 1037 /*
 1038  * Steals load from a standard linear queue.
 1039  */
 1040 static struct thread *
 1041 runq_steal(struct runq *rq, int cpu)
 1042 {
 1043         struct rqhead *rqh;
 1044         struct rqbits *rqb;
 1045         struct thread *td;
 1046         int word;
 1047         int bit;
 1048 
 1049         rqb = &rq->rq_status;
 1050         for (word = 0; word < RQB_LEN; word++) {
 1051                 if (rqb->rqb_bits[word] == 0)
 1052                         continue;
 1053                 for (bit = 0; bit < RQB_BPW; bit++) {
 1054                         if ((rqb->rqb_bits[word] & (1ul << bit)) == 0)
 1055                                 continue;
 1056                         rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)];
 1057                         TAILQ_FOREACH(td, rqh, td_runq)
 1058                                 if (THREAD_CAN_MIGRATE(td) &&
 1059                                     THREAD_CAN_SCHED(td, cpu))
 1060                                         return (td);
 1061                 }
 1062         }
 1063         return (NULL);
 1064 }
 1065 
 1066 /*
 1067  * Attempt to steal a thread in priority order from a thread queue.
 1068  */
 1069 static struct thread *
 1070 tdq_steal(struct tdq *tdq, int cpu)
 1071 {
 1072         struct thread *td;
 1073 
 1074         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 1075         if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL)
 1076                 return (td);
 1077         if ((td = runq_steal_from(&tdq->tdq_timeshare,
 1078             cpu, tdq->tdq_ridx)) != NULL)
 1079                 return (td);
 1080         return (runq_steal(&tdq->tdq_idle, cpu));
 1081 }
 1082 
 1083 /*
 1084  * Sets the thread lock and ts_cpu to match the requested cpu.  Unlocks the
 1085  * current lock and returns with the assigned queue locked.
 1086  */
 1087 static inline struct tdq *
 1088 sched_setcpu(struct thread *td, int cpu, int flags)
 1089 {
 1090 
 1091         struct tdq *tdq;
 1092 
 1093         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1094         tdq = TDQ_CPU(cpu);
 1095         td->td_sched->ts_cpu = cpu;
 1096         /*
 1097          * If the lock matches just return the queue.
 1098          */
 1099         if (td->td_lock == TDQ_LOCKPTR(tdq))
 1100                 return (tdq);
 1101 #ifdef notyet
 1102         /*
 1103          * If the thread isn't running its lockptr is a
 1104          * turnstile or a sleepqueue.  We can just lock_set without
 1105          * blocking.
 1106          */
 1107         if (TD_CAN_RUN(td)) {
 1108                 TDQ_LOCK(tdq);
 1109                 thread_lock_set(td, TDQ_LOCKPTR(tdq));
 1110                 return (tdq);
 1111         }
 1112 #endif
 1113         /*
 1114          * The hard case, migration, we need to block the thread first to
 1115          * prevent order reversals with other cpus locks.
 1116          */
 1117         spinlock_enter();
 1118         thread_lock_block(td);
 1119         TDQ_LOCK(tdq);
 1120         thread_lock_unblock(td, TDQ_LOCKPTR(tdq));
 1121         spinlock_exit();
 1122         return (tdq);
 1123 }
 1124 
 1125 SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding");
 1126 SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity");
 1127 SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity");
 1128 SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load");
 1129 SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu");
 1130 SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration");
 1131 
 1132 static int
 1133 sched_pickcpu(struct thread *td, int flags)
 1134 {
 1135         struct cpu_group *cg;
 1136         struct td_sched *ts;
 1137         struct tdq *tdq;
 1138         cpuset_t mask;
 1139         int self;
 1140         int pri;
 1141         int cpu;
 1142 
 1143         self = PCPU_GET(cpuid);
 1144         ts = td->td_sched;
 1145         if (smp_started == 0)
 1146                 return (self);
 1147         /*
 1148          * Don't migrate a running thread from sched_switch().
 1149          */
 1150         if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td))
 1151                 return (ts->ts_cpu);
 1152         /*
 1153          * Prefer to run interrupt threads on the processors that generate
 1154          * the interrupt.
 1155          */
 1156         if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) &&
 1157             curthread->td_intr_nesting_level && ts->ts_cpu != self) {
 1158                 SCHED_STAT_INC(pickcpu_intrbind);
 1159                 ts->ts_cpu = self;
 1160         }
 1161         /*
 1162          * If the thread can run on the last cpu and the affinity has not
 1163          * expired or it is idle run it there.
 1164          */
 1165         pri = td->td_priority;
 1166         tdq = TDQ_CPU(ts->ts_cpu);
 1167         if (THREAD_CAN_SCHED(td, ts->ts_cpu)) {
 1168                 if (tdq->tdq_lowpri > PRI_MIN_IDLE) {
 1169                         SCHED_STAT_INC(pickcpu_idle_affinity);
 1170                         return (ts->ts_cpu);
 1171                 }
 1172                 if (SCHED_AFFINITY(ts, CG_SHARE_L2) && tdq->tdq_lowpri > pri) {
 1173                         SCHED_STAT_INC(pickcpu_affinity);
 1174                         return (ts->ts_cpu);
 1175                 }
 1176         }
 1177         /*
 1178          * Search for the highest level in the tree that still has affinity.
 1179          */
 1180         cg = NULL;
 1181         for (cg = tdq->tdq_cg; cg != NULL; cg = cg->cg_parent)
 1182                 if (SCHED_AFFINITY(ts, cg->cg_level))
 1183                         break;
 1184         cpu = -1;
 1185         mask = td->td_cpuset->cs_mask;
 1186         if (cg)
 1187                 cpu = sched_lowest(cg, mask, pri);
 1188         if (cpu == -1)
 1189                 cpu = sched_lowest(cpu_top, mask, -1);
 1190         /*
 1191          * Compare the lowest loaded cpu to current cpu.
 1192          */
 1193         if (THREAD_CAN_SCHED(td, self) && TDQ_CPU(self)->tdq_lowpri > pri &&
 1194             TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE) {
 1195                 SCHED_STAT_INC(pickcpu_local);
 1196                 cpu = self;
 1197         } else
 1198                 SCHED_STAT_INC(pickcpu_lowest);
 1199         if (cpu != ts->ts_cpu)
 1200                 SCHED_STAT_INC(pickcpu_migration);
 1201         KASSERT(cpu != -1, ("sched_pickcpu: Failed to find a cpu."));
 1202         return (cpu);
 1203 }
 1204 #endif
 1205 
 1206 /*
 1207  * Pick the highest priority task we have and return it.
 1208  */
 1209 static struct thread *
 1210 tdq_choose(struct tdq *tdq)
 1211 {
 1212         struct thread *td;
 1213 
 1214         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 1215         td = runq_choose(&tdq->tdq_realtime);
 1216         if (td != NULL)
 1217                 return (td);
 1218         td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
 1219         if (td != NULL) {
 1220                 KASSERT(td->td_priority >= PRI_MIN_BATCH,
 1221                     ("tdq_choose: Invalid priority on timeshare queue %d",
 1222                     td->td_priority));
 1223                 return (td);
 1224         }
 1225         td = runq_choose(&tdq->tdq_idle);
 1226         if (td != NULL) {
 1227                 KASSERT(td->td_priority >= PRI_MIN_IDLE,
 1228                     ("tdq_choose: Invalid priority on idle queue %d",
 1229                     td->td_priority));
 1230                 return (td);
 1231         }
 1232 
 1233         return (NULL);
 1234 }
 1235 
 1236 /*
 1237  * Initialize a thread queue.
 1238  */
 1239 static void
 1240 tdq_setup(struct tdq *tdq)
 1241 {
 1242 
 1243         if (bootverbose)
 1244                 printf("ULE: setup cpu %d\n", TDQ_ID(tdq));
 1245         runq_init(&tdq->tdq_realtime);
 1246         runq_init(&tdq->tdq_timeshare);
 1247         runq_init(&tdq->tdq_idle);
 1248         snprintf(tdq->tdq_name, sizeof(tdq->tdq_name),
 1249             "sched lock %d", (int)TDQ_ID(tdq));
 1250         mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock",
 1251             MTX_SPIN | MTX_RECURSE);
 1252 #ifdef KTR
 1253         snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname),
 1254             "CPU %d load", (int)TDQ_ID(tdq));
 1255 #endif
 1256 }
 1257 
 1258 #ifdef SMP
 1259 static void
 1260 sched_setup_smp(void)
 1261 {
 1262         struct tdq *tdq;
 1263         int i;
 1264 
 1265         cpu_top = smp_topo();
 1266         CPU_FOREACH(i) {
 1267                 tdq = TDQ_CPU(i);
 1268                 tdq_setup(tdq);
 1269                 tdq->tdq_cg = smp_topo_find(cpu_top, i);
 1270                 if (tdq->tdq_cg == NULL)
 1271                         panic("Can't find cpu group for %d\n", i);
 1272         }
 1273         balance_tdq = TDQ_SELF();
 1274         sched_balance();
 1275 }
 1276 #endif
 1277 
 1278 /*
 1279  * Setup the thread queues and initialize the topology based on MD
 1280  * information.
 1281  */
 1282 static void
 1283 sched_setup(void *dummy)
 1284 {
 1285         struct tdq *tdq;
 1286 
 1287         tdq = TDQ_SELF();
 1288 #ifdef SMP
 1289         sched_setup_smp();
 1290 #else
 1291         tdq_setup(tdq);
 1292 #endif
 1293         /*
 1294          * To avoid divide-by-zero, we set realstathz a dummy value
 1295          * in case which sched_clock() called before sched_initticks().
 1296          */
 1297         realstathz = hz;
 1298         sched_slice = (realstathz/10);  /* ~100ms */
 1299         tickincr = 1 << SCHED_TICK_SHIFT;
 1300 
 1301         /* Add thread0's load since it's running. */
 1302         TDQ_LOCK(tdq);
 1303         thread0.td_lock = TDQ_LOCKPTR(TDQ_SELF());
 1304         tdq_load_add(tdq, &thread0);
 1305         tdq->tdq_lowpri = thread0.td_priority;
 1306         TDQ_UNLOCK(tdq);
 1307 }
 1308 
 1309 /*
 1310  * This routine determines the tickincr after stathz and hz are setup.
 1311  */
 1312 /* ARGSUSED */
 1313 static void
 1314 sched_initticks(void *dummy)
 1315 {
 1316         int incr;
 1317 
 1318         realstathz = stathz ? stathz : hz;
 1319         sched_slice = (realstathz/10);  /* ~100ms */
 1320 
 1321         /*
 1322          * tickincr is shifted out by 10 to avoid rounding errors due to
 1323          * hz not being evenly divisible by stathz on all platforms.
 1324          */
 1325         incr = (hz << SCHED_TICK_SHIFT) / realstathz;
 1326         /*
 1327          * This does not work for values of stathz that are more than
 1328          * 1 << SCHED_TICK_SHIFT * hz.  In practice this does not happen.
 1329          */
 1330         if (incr == 0)
 1331                 incr = 1;
 1332         tickincr = incr;
 1333 #ifdef SMP
 1334         /*
 1335          * Set the default balance interval now that we know
 1336          * what realstathz is.
 1337          */
 1338         balance_interval = realstathz;
 1339         /*
 1340          * Set steal thresh to roughly log2(mp_ncpu) but no greater than 4. 
 1341          * This prevents excess thrashing on large machines and excess idle 
 1342          * on smaller machines.
 1343          */
 1344         steal_thresh = min(fls(mp_ncpus) - 1, 3);
 1345         affinity = SCHED_AFFINITY_DEFAULT;
 1346 #endif
 1347 }
 1348 
 1349 
 1350 /*
 1351  * This is the core of the interactivity algorithm.  Determines a score based
 1352  * on past behavior.  It is the ratio of sleep time to run time scaled to
 1353  * a [0, 100] integer.  This is the voluntary sleep time of a process, which
 1354  * differs from the cpu usage because it does not account for time spent
 1355  * waiting on a run-queue.  Would be prettier if we had floating point.
 1356  */
 1357 static int
 1358 sched_interact_score(struct thread *td)
 1359 {
 1360         struct td_sched *ts;
 1361         int div;
 1362 
 1363         ts = td->td_sched;
 1364         /*
 1365          * The score is only needed if this is likely to be an interactive
 1366          * task.  Don't go through the expense of computing it if there's
 1367          * no chance.
 1368          */
 1369         if (sched_interact <= SCHED_INTERACT_HALF &&
 1370                 ts->ts_runtime >= ts->ts_slptime)
 1371                         return (SCHED_INTERACT_HALF);
 1372 
 1373         if (ts->ts_runtime > ts->ts_slptime) {
 1374                 div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF);
 1375                 return (SCHED_INTERACT_HALF +
 1376                     (SCHED_INTERACT_HALF - (ts->ts_slptime / div)));
 1377         }
 1378         if (ts->ts_slptime > ts->ts_runtime) {
 1379                 div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF);
 1380                 return (ts->ts_runtime / div);
 1381         }
 1382         /* runtime == slptime */
 1383         if (ts->ts_runtime)
 1384                 return (SCHED_INTERACT_HALF);
 1385 
 1386         /*
 1387          * This can happen if slptime and runtime are 0.
 1388          */
 1389         return (0);
 1390 
 1391 }
 1392 
 1393 /*
 1394  * Scale the scheduling priority according to the "interactivity" of this
 1395  * process.
 1396  */
 1397 static void
 1398 sched_priority(struct thread *td)
 1399 {
 1400         int score;
 1401         int pri;
 1402 
 1403         if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
 1404                 return;
 1405         /*
 1406          * If the score is interactive we place the thread in the realtime
 1407          * queue with a priority that is less than kernel and interrupt
 1408          * priorities.  These threads are not subject to nice restrictions.
 1409          *
 1410          * Scores greater than this are placed on the normal timeshare queue
 1411          * where the priority is partially decided by the most recent cpu
 1412          * utilization and the rest is decided by nice value.
 1413          *
 1414          * The nice value of the process has a linear effect on the calculated
 1415          * score.  Negative nice values make it easier for a thread to be
 1416          * considered interactive.
 1417          */
 1418         score = imax(0, sched_interact_score(td) + td->td_proc->p_nice);
 1419         if (score < sched_interact) {
 1420                 pri = PRI_MIN_INTERACT;
 1421                 pri += ((PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) /
 1422                     sched_interact) * score;
 1423                 KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT,
 1424                     ("sched_priority: invalid interactive priority %d score %d",
 1425                     pri, score));
 1426         } else {
 1427                 pri = SCHED_PRI_MIN;
 1428                 if (td->td_sched->ts_ticks)
 1429                         pri += min(SCHED_PRI_TICKS(td->td_sched),
 1430                             SCHED_PRI_RANGE);
 1431                 pri += SCHED_PRI_NICE(td->td_proc->p_nice);
 1432                 KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH,
 1433                     ("sched_priority: invalid priority %d: nice %d, " 
 1434                     "ticks %d ftick %d ltick %d tick pri %d",
 1435                     pri, td->td_proc->p_nice, td->td_sched->ts_ticks,
 1436                     td->td_sched->ts_ftick, td->td_sched->ts_ltick,
 1437                     SCHED_PRI_TICKS(td->td_sched)));
 1438         }
 1439         sched_user_prio(td, pri);
 1440 
 1441         return;
 1442 }
 1443 
 1444 /*
 1445  * This routine enforces a maximum limit on the amount of scheduling history
 1446  * kept.  It is called after either the slptime or runtime is adjusted.  This
 1447  * function is ugly due to integer math.
 1448  */
 1449 static void
 1450 sched_interact_update(struct thread *td)
 1451 {
 1452         struct td_sched *ts;
 1453         u_int sum;
 1454 
 1455         ts = td->td_sched;
 1456         sum = ts->ts_runtime + ts->ts_slptime;
 1457         if (sum < SCHED_SLP_RUN_MAX)
 1458                 return;
 1459         /*
 1460          * This only happens from two places:
 1461          * 1) We have added an unusual amount of run time from fork_exit.
 1462          * 2) We have added an unusual amount of sleep time from sched_sleep().
 1463          */
 1464         if (sum > SCHED_SLP_RUN_MAX * 2) {
 1465                 if (ts->ts_runtime > ts->ts_slptime) {
 1466                         ts->ts_runtime = SCHED_SLP_RUN_MAX;
 1467                         ts->ts_slptime = 1;
 1468                 } else {
 1469                         ts->ts_slptime = SCHED_SLP_RUN_MAX;
 1470                         ts->ts_runtime = 1;
 1471                 }
 1472                 return;
 1473         }
 1474         /*
 1475          * If we have exceeded by more than 1/5th then the algorithm below
 1476          * will not bring us back into range.  Dividing by two here forces
 1477          * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX]
 1478          */
 1479         if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) {
 1480                 ts->ts_runtime /= 2;
 1481                 ts->ts_slptime /= 2;
 1482                 return;
 1483         }
 1484         ts->ts_runtime = (ts->ts_runtime / 5) * 4;
 1485         ts->ts_slptime = (ts->ts_slptime / 5) * 4;
 1486 }
 1487 
 1488 /*
 1489  * Scale back the interactivity history when a child thread is created.  The
 1490  * history is inherited from the parent but the thread may behave totally
 1491  * differently.  For example, a shell spawning a compiler process.  We want
 1492  * to learn that the compiler is behaving badly very quickly.
 1493  */
 1494 static void
 1495 sched_interact_fork(struct thread *td)
 1496 {
 1497         int ratio;
 1498         int sum;
 1499 
 1500         sum = td->td_sched->ts_runtime + td->td_sched->ts_slptime;
 1501         if (sum > SCHED_SLP_RUN_FORK) {
 1502                 ratio = sum / SCHED_SLP_RUN_FORK;
 1503                 td->td_sched->ts_runtime /= ratio;
 1504                 td->td_sched->ts_slptime /= ratio;
 1505         }
 1506 }
 1507 
 1508 /*
 1509  * Called from proc0_init() to setup the scheduler fields.
 1510  */
 1511 void
 1512 schedinit(void)
 1513 {
 1514 
 1515         /*
 1516          * Set up the scheduler specific parts of proc0.
 1517          */
 1518         proc0.p_sched = NULL; /* XXX */
 1519         thread0.td_sched = &td_sched0;
 1520         td_sched0.ts_ltick = ticks;
 1521         td_sched0.ts_ftick = ticks;
 1522         td_sched0.ts_slice = sched_slice;
 1523 }
 1524 
 1525 /*
 1526  * This is only somewhat accurate since given many processes of the same
 1527  * priority they will switch when their slices run out, which will be
 1528  * at most sched_slice stathz ticks.
 1529  */
 1530 int
 1531 sched_rr_interval(void)
 1532 {
 1533 
 1534         /* Convert sched_slice to hz */
 1535         return (hz/(realstathz/sched_slice));
 1536 }
 1537 
 1538 /*
 1539  * Update the percent cpu tracking information when it is requested or
 1540  * the total history exceeds the maximum.  We keep a sliding history of
 1541  * tick counts that slowly decays.  This is less precise than the 4BSD
 1542  * mechanism since it happens with less regular and frequent events.
 1543  */
 1544 static void
 1545 sched_pctcpu_update(struct td_sched *ts)
 1546 {
 1547 
 1548         if (ts->ts_ticks == 0)
 1549                 return;
 1550         if (ticks - (hz / 10) < ts->ts_ltick &&
 1551             SCHED_TICK_TOTAL(ts) < SCHED_TICK_MAX)
 1552                 return;
 1553         /*
 1554          * Adjust counters and watermark for pctcpu calc.
 1555          */
 1556         if (ts->ts_ltick > ticks - SCHED_TICK_TARG)
 1557                 ts->ts_ticks = (ts->ts_ticks / (ticks - ts->ts_ftick)) *
 1558                             SCHED_TICK_TARG;
 1559         else
 1560                 ts->ts_ticks = 0;
 1561         ts->ts_ltick = ticks;
 1562         ts->ts_ftick = ts->ts_ltick - SCHED_TICK_TARG;
 1563 }
 1564 
 1565 /*
 1566  * Adjust the priority of a thread.  Move it to the appropriate run-queue
 1567  * if necessary.  This is the back-end for several priority related
 1568  * functions.
 1569  */
 1570 static void
 1571 sched_thread_priority(struct thread *td, u_char prio)
 1572 {
 1573         struct td_sched *ts;
 1574         struct tdq *tdq;
 1575         int oldpri;
 1576 
 1577         KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio",
 1578             "prio:%d", td->td_priority, "new prio:%d", prio,
 1579             KTR_ATTR_LINKED, sched_tdname(curthread));
 1580         if (td != curthread && prio > td->td_priority) {
 1581                 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
 1582                     "lend prio", "prio:%d", td->td_priority, "new prio:%d",
 1583                     prio, KTR_ATTR_LINKED, sched_tdname(td));
 1584         } 
 1585         ts = td->td_sched;
 1586         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1587         if (td->td_priority == prio)
 1588                 return;
 1589         /*
 1590          * If the priority has been elevated due to priority
 1591          * propagation, we may have to move ourselves to a new
 1592          * queue.  This could be optimized to not re-add in some
 1593          * cases.
 1594          */
 1595         if (TD_ON_RUNQ(td) && prio < td->td_priority) {
 1596                 sched_rem(td);
 1597                 td->td_priority = prio;
 1598                 sched_add(td, SRQ_BORROWING);
 1599                 return;
 1600         }
 1601         /*
 1602          * If the thread is currently running we may have to adjust the lowpri
 1603          * information so other cpus are aware of our current priority.
 1604          */
 1605         if (TD_IS_RUNNING(td)) {
 1606                 tdq = TDQ_CPU(ts->ts_cpu);
 1607                 oldpri = td->td_priority;
 1608                 td->td_priority = prio;
 1609                 if (prio < tdq->tdq_lowpri)
 1610                         tdq->tdq_lowpri = prio;
 1611                 else if (tdq->tdq_lowpri == oldpri)
 1612                         tdq_setlowpri(tdq, td);
 1613                 return;
 1614         }
 1615         td->td_priority = prio;
 1616 }
 1617 
 1618 /*
 1619  * Update a thread's priority when it is lent another thread's
 1620  * priority.
 1621  */
 1622 void
 1623 sched_lend_prio(struct thread *td, u_char prio)
 1624 {
 1625 
 1626         td->td_flags |= TDF_BORROWING;
 1627         sched_thread_priority(td, prio);
 1628 }
 1629 
 1630 /*
 1631  * Restore a thread's priority when priority propagation is
 1632  * over.  The prio argument is the minimum priority the thread
 1633  * needs to have to satisfy other possible priority lending
 1634  * requests.  If the thread's regular priority is less
 1635  * important than prio, the thread will keep a priority boost
 1636  * of prio.
 1637  */
 1638 void
 1639 sched_unlend_prio(struct thread *td, u_char prio)
 1640 {
 1641         u_char base_pri;
 1642 
 1643         if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
 1644             td->td_base_pri <= PRI_MAX_TIMESHARE)
 1645                 base_pri = td->td_user_pri;
 1646         else
 1647                 base_pri = td->td_base_pri;
 1648         if (prio >= base_pri) {
 1649                 td->td_flags &= ~TDF_BORROWING;
 1650                 sched_thread_priority(td, base_pri);
 1651         } else
 1652                 sched_lend_prio(td, prio);
 1653 }
 1654 
 1655 /*
 1656  * Standard entry for setting the priority to an absolute value.
 1657  */
 1658 void
 1659 sched_prio(struct thread *td, u_char prio)
 1660 {
 1661         u_char oldprio;
 1662 
 1663         /* First, update the base priority. */
 1664         td->td_base_pri = prio;
 1665 
 1666         /*
 1667          * If the thread is borrowing another thread's priority, don't
 1668          * ever lower the priority.
 1669          */
 1670         if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
 1671                 return;
 1672 
 1673         /* Change the real priority. */
 1674         oldprio = td->td_priority;
 1675         sched_thread_priority(td, prio);
 1676 
 1677         /*
 1678          * If the thread is on a turnstile, then let the turnstile update
 1679          * its state.
 1680          */
 1681         if (TD_ON_LOCK(td) && oldprio != prio)
 1682                 turnstile_adjust(td, oldprio);
 1683 }
 1684 
 1685 /*
 1686  * Set the base user priority, does not effect current running priority.
 1687  */
 1688 void
 1689 sched_user_prio(struct thread *td, u_char prio)
 1690 {
 1691         u_char oldprio;
 1692 
 1693         td->td_base_user_pri = prio;
 1694         if (td->td_flags & TDF_UBORROWING && td->td_user_pri <= prio)
 1695                 return;
 1696         oldprio = td->td_user_pri;
 1697         td->td_user_pri = prio;
 1698 }
 1699 
 1700 void
 1701 sched_lend_user_prio(struct thread *td, u_char prio)
 1702 {
 1703         u_char oldprio;
 1704 
 1705         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1706         td->td_flags |= TDF_UBORROWING;
 1707         oldprio = td->td_user_pri;
 1708         td->td_user_pri = prio;
 1709 }
 1710 
 1711 void
 1712 sched_unlend_user_prio(struct thread *td, u_char prio)
 1713 {
 1714         u_char base_pri;
 1715 
 1716         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1717         base_pri = td->td_base_user_pri;
 1718         if (prio >= base_pri) {
 1719                 td->td_flags &= ~TDF_UBORROWING;
 1720                 sched_user_prio(td, base_pri);
 1721         } else {
 1722                 sched_lend_user_prio(td, prio);
 1723         }
 1724 }
 1725 
 1726 /*
 1727  * Handle migration from sched_switch().  This happens only for
 1728  * cpu binding.
 1729  */
 1730 static struct mtx *
 1731 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags)
 1732 {
 1733         struct tdq *tdn;
 1734 
 1735         tdn = TDQ_CPU(td->td_sched->ts_cpu);
 1736 #ifdef SMP
 1737         tdq_load_rem(tdq, td);
 1738         /*
 1739          * Do the lock dance required to avoid LOR.  We grab an extra
 1740          * spinlock nesting to prevent preemption while we're
 1741          * not holding either run-queue lock.
 1742          */
 1743         spinlock_enter();
 1744         thread_lock_block(td);  /* This releases the lock on tdq. */
 1745 
 1746         /*
 1747          * Acquire both run-queue locks before placing the thread on the new
 1748          * run-queue to avoid deadlocks created by placing a thread with a
 1749          * blocked lock on the run-queue of a remote processor.  The deadlock
 1750          * occurs when a third processor attempts to lock the two queues in
 1751          * question while the target processor is spinning with its own
 1752          * run-queue lock held while waiting for the blocked lock to clear.
 1753          */
 1754         tdq_lock_pair(tdn, tdq);
 1755         tdq_add(tdn, td, flags);
 1756         tdq_notify(tdn, td);
 1757         TDQ_UNLOCK(tdn);
 1758         spinlock_exit();
 1759 #endif
 1760         return (TDQ_LOCKPTR(tdn));
 1761 }
 1762 
 1763 /*
 1764  * Variadic version of thread_lock_unblock() that does not assume td_lock
 1765  * is blocked.
 1766  */
 1767 static inline void
 1768 thread_unblock_switch(struct thread *td, struct mtx *mtx)
 1769 {
 1770         atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock,
 1771             (uintptr_t)mtx);
 1772 }
 1773 
 1774 /*
 1775  * Switch threads.  This function has to handle threads coming in while
 1776  * blocked for some reason, running, or idle.  It also must deal with
 1777  * migrating a thread from one queue to another as running threads may
 1778  * be assigned elsewhere via binding.
 1779  */
 1780 void
 1781 sched_switch(struct thread *td, struct thread *newtd, int flags)
 1782 {
 1783         struct tdq *tdq;
 1784         struct td_sched *ts;
 1785         struct mtx *mtx;
 1786         int srqflag;
 1787         int cpuid;
 1788 
 1789         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1790         KASSERT(newtd == NULL, ("sched_switch: Unsupported newtd argument"));
 1791 
 1792         cpuid = PCPU_GET(cpuid);
 1793         tdq = TDQ_CPU(cpuid);
 1794         ts = td->td_sched;
 1795         mtx = td->td_lock;
 1796         ts->ts_rltick = ticks;
 1797         td->td_lastcpu = td->td_oncpu;
 1798         td->td_oncpu = NOCPU;
 1799         if (!(flags & SW_PREEMPT))
 1800                 td->td_flags &= ~TDF_NEEDRESCHED;
 1801         td->td_owepreempt = 0;
 1802         tdq->tdq_switchcnt++;
 1803         /*
 1804          * The lock pointer in an idle thread should never change.  Reset it
 1805          * to CAN_RUN as well.
 1806          */
 1807         if (TD_IS_IDLETHREAD(td)) {
 1808                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1809                 TD_SET_CAN_RUN(td);
 1810         } else if (TD_IS_RUNNING(td)) {
 1811                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1812                 srqflag = (flags & SW_PREEMPT) ?
 1813                     SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
 1814                     SRQ_OURSELF|SRQ_YIELDING;
 1815 #ifdef SMP
 1816                 if (THREAD_CAN_MIGRATE(td) && !THREAD_CAN_SCHED(td, ts->ts_cpu))
 1817                         ts->ts_cpu = sched_pickcpu(td, 0);
 1818 #endif
 1819                 if (ts->ts_cpu == cpuid)
 1820                         tdq_runq_add(tdq, td, srqflag);
 1821                 else {
 1822                         KASSERT(THREAD_CAN_MIGRATE(td) ||
 1823                             (ts->ts_flags & TSF_BOUND) != 0,
 1824                             ("Thread %p shouldn't migrate", td));
 1825                         mtx = sched_switch_migrate(tdq, td, srqflag);
 1826                 }
 1827         } else {
 1828                 /* This thread must be going to sleep. */
 1829                 TDQ_LOCK(tdq);
 1830                 mtx = thread_lock_block(td);
 1831                 tdq_load_rem(tdq, td);
 1832         }
 1833         /*
 1834          * We enter here with the thread blocked and assigned to the
 1835          * appropriate cpu run-queue or sleep-queue and with the current
 1836          * thread-queue locked.
 1837          */
 1838         TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
 1839         newtd = choosethread();
 1840         /*
 1841          * Call the MD code to switch contexts if necessary.
 1842          */
 1843         if (td != newtd) {
 1844 #ifdef  HWPMC_HOOKS
 1845                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 1846                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
 1847 #endif
 1848                 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
 1849                 TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
 1850 
 1851 #ifdef KDTRACE_HOOKS
 1852                 /*
 1853                  * If DTrace has set the active vtime enum to anything
 1854                  * other than INACTIVE (0), then it should have set the
 1855                  * function to call.
 1856                  */
 1857                 if (dtrace_vtime_active)
 1858                         (*dtrace_vtime_switch_func)(newtd);
 1859 #endif
 1860 
 1861                 cpu_switch(td, newtd, mtx);
 1862                 /*
 1863                  * We may return from cpu_switch on a different cpu.  However,
 1864                  * we always return with td_lock pointing to the current cpu's
 1865                  * run queue lock.
 1866                  */
 1867                 cpuid = PCPU_GET(cpuid);
 1868                 tdq = TDQ_CPU(cpuid);
 1869                 lock_profile_obtain_lock_success(
 1870                     &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
 1871 #ifdef  HWPMC_HOOKS
 1872                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 1873                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
 1874 #endif
 1875         } else
 1876                 thread_unblock_switch(td, mtx);
 1877         /*
 1878          * Assert that all went well and return.
 1879          */
 1880         TDQ_LOCK_ASSERT(tdq, MA_OWNED|MA_NOTRECURSED);
 1881         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 1882         td->td_oncpu = cpuid;
 1883 }
 1884 
 1885 /*
 1886  * Adjust thread priorities as a result of a nice request.
 1887  */
 1888 void
 1889 sched_nice(struct proc *p, int nice)
 1890 {
 1891         struct thread *td;
 1892 
 1893         PROC_LOCK_ASSERT(p, MA_OWNED);
 1894 
 1895         p->p_nice = nice;
 1896         FOREACH_THREAD_IN_PROC(p, td) {
 1897                 thread_lock(td);
 1898                 sched_priority(td);
 1899                 sched_prio(td, td->td_base_user_pri);
 1900                 thread_unlock(td);
 1901         }
 1902 }
 1903 
 1904 /*
 1905  * Record the sleep time for the interactivity scorer.
 1906  */
 1907 void
 1908 sched_sleep(struct thread *td, int prio)
 1909 {
 1910 
 1911         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1912 
 1913         td->td_slptick = ticks;
 1914         if (TD_IS_SUSPENDED(td) || prio >= PSOCK)
 1915                 td->td_flags |= TDF_CANSWAP;
 1916         if (static_boost == 1 && prio)
 1917                 sched_prio(td, prio);
 1918         else if (static_boost && td->td_priority > static_boost)
 1919                 sched_prio(td, static_boost);
 1920 }
 1921 
 1922 /*
 1923  * Schedule a thread to resume execution and record how long it voluntarily
 1924  * slept.  We also update the pctcpu, interactivity, and priority.
 1925  */
 1926 void
 1927 sched_wakeup(struct thread *td)
 1928 {
 1929         struct td_sched *ts;
 1930         int slptick;
 1931 
 1932         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1933         ts = td->td_sched;
 1934         td->td_flags &= ~TDF_CANSWAP;
 1935         /*
 1936          * If we slept for more than a tick update our interactivity and
 1937          * priority.
 1938          */
 1939         slptick = td->td_slptick;
 1940         td->td_slptick = 0;
 1941         if (slptick && slptick != ticks) {
 1942                 u_int hzticks;
 1943 
 1944                 hzticks = (ticks - slptick) << SCHED_TICK_SHIFT;
 1945                 ts->ts_slptime += hzticks;
 1946                 sched_interact_update(td);
 1947                 sched_pctcpu_update(ts);
 1948         }
 1949         /* Reset the slice value after we sleep. */
 1950         ts->ts_slice = sched_slice;
 1951         sched_add(td, SRQ_BORING);
 1952 }
 1953 
 1954 /*
 1955  * Penalize the parent for creating a new child and initialize the child's
 1956  * priority.
 1957  */
 1958 void
 1959 sched_fork(struct thread *td, struct thread *child)
 1960 {
 1961         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1962         sched_fork_thread(td, child);
 1963         /*
 1964          * Penalize the parent and child for forking.
 1965          */
 1966         sched_interact_fork(child);
 1967         sched_priority(child);
 1968         td->td_sched->ts_runtime += tickincr;
 1969         sched_interact_update(td);
 1970         sched_priority(td);
 1971 }
 1972 
 1973 /*
 1974  * Fork a new thread, may be within the same process.
 1975  */
 1976 void
 1977 sched_fork_thread(struct thread *td, struct thread *child)
 1978 {
 1979         struct td_sched *ts;
 1980         struct td_sched *ts2;
 1981 
 1982         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1983         /*
 1984          * Initialize child.
 1985          */
 1986         ts = td->td_sched;
 1987         ts2 = child->td_sched;
 1988         child->td_lock = TDQ_LOCKPTR(TDQ_SELF());
 1989         child->td_cpuset = cpuset_ref(td->td_cpuset);
 1990         ts2->ts_cpu = ts->ts_cpu;
 1991         ts2->ts_flags = 0;
 1992         /*
 1993          * Grab our parents cpu estimation information.
 1994          */
 1995         ts2->ts_ticks = ts->ts_ticks;
 1996         ts2->ts_ltick = ts->ts_ltick;
 1997         ts2->ts_incrtick = ts->ts_incrtick;
 1998         ts2->ts_ftick = ts->ts_ftick;
 1999         /*
 2000          * Do not inherit any borrowed priority from the parent.
 2001          */
 2002         child->td_priority = child->td_base_pri;
 2003         /*
 2004          * And update interactivity score.
 2005          */
 2006         ts2->ts_slptime = ts->ts_slptime;
 2007         ts2->ts_runtime = ts->ts_runtime;
 2008         ts2->ts_slice = 1;      /* Attempt to quickly learn interactivity. */
 2009 #ifdef KTR
 2010         bzero(ts2->ts_name, sizeof(ts2->ts_name));
 2011 #endif
 2012 }
 2013 
 2014 /*
 2015  * Adjust the priority class of a thread.
 2016  */
 2017 void
 2018 sched_class(struct thread *td, int class)
 2019 {
 2020 
 2021         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2022         if (td->td_pri_class == class)
 2023                 return;
 2024         td->td_pri_class = class;
 2025 }
 2026 
 2027 /*
 2028  * Return some of the child's priority and interactivity to the parent.
 2029  */
 2030 void
 2031 sched_exit(struct proc *p, struct thread *child)
 2032 {
 2033         struct thread *td;
 2034 
 2035         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit",
 2036             "prio:%d", child->td_priority);
 2037         PROC_LOCK_ASSERT(p, MA_OWNED);
 2038         td = FIRST_THREAD_IN_PROC(p);
 2039         sched_exit_thread(td, child);
 2040 }
 2041 
 2042 /*
 2043  * Penalize another thread for the time spent on this one.  This helps to
 2044  * worsen the priority and interactivity of processes which schedule batch
 2045  * jobs such as make.  This has little effect on the make process itself but
 2046  * causes new processes spawned by it to receive worse scores immediately.
 2047  */
 2048 void
 2049 sched_exit_thread(struct thread *td, struct thread *child)
 2050 {
 2051 
 2052         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit",
 2053             "prio:%d", child->td_priority);
 2054         /*
 2055          * Give the child's runtime to the parent without returning the
 2056          * sleep time as a penalty to the parent.  This causes shells that
 2057          * launch expensive things to mark their children as expensive.
 2058          */
 2059         thread_lock(td);
 2060         td->td_sched->ts_runtime += child->td_sched->ts_runtime;
 2061         sched_interact_update(td);
 2062         sched_priority(td);
 2063         thread_unlock(td);
 2064 }
 2065 
 2066 void
 2067 sched_preempt(struct thread *td)
 2068 {
 2069         struct tdq *tdq;
 2070 
 2071         thread_lock(td);
 2072         tdq = TDQ_SELF();
 2073         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2074         tdq->tdq_ipipending = 0;
 2075         if (td->td_priority > tdq->tdq_lowpri) {
 2076                 int flags;
 2077 
 2078                 flags = SW_INVOL | SW_PREEMPT;
 2079                 if (td->td_critnest > 1)
 2080                         td->td_owepreempt = 1;
 2081                 else if (TD_IS_IDLETHREAD(td))
 2082                         mi_switch(flags | SWT_REMOTEWAKEIDLE, NULL);
 2083                 else
 2084                         mi_switch(flags | SWT_REMOTEPREEMPT, NULL);
 2085         }
 2086         thread_unlock(td);
 2087 }
 2088 
 2089 /*
 2090  * Fix priorities on return to user-space.  Priorities may be elevated due
 2091  * to static priorities in msleep() or similar.
 2092  */
 2093 void
 2094 sched_userret(struct thread *td)
 2095 {
 2096         /*
 2097          * XXX we cheat slightly on the locking here to avoid locking in  
 2098          * the usual case.  Setting td_priority here is essentially an
 2099          * incomplete workaround for not setting it properly elsewhere.
 2100          * Now that some interrupt handlers are threads, not setting it
 2101          * properly elsewhere can clobber it in the window between setting
 2102          * it here and returning to user mode, so don't waste time setting
 2103          * it perfectly here.
 2104          */
 2105         KASSERT((td->td_flags & TDF_BORROWING) == 0,
 2106             ("thread with borrowed priority returning to userland"));
 2107         if (td->td_priority != td->td_user_pri) {
 2108                 thread_lock(td);
 2109                 td->td_priority = td->td_user_pri;
 2110                 td->td_base_pri = td->td_user_pri;
 2111                 tdq_setlowpri(TDQ_SELF(), td);
 2112                 thread_unlock(td);
 2113         }
 2114 }
 2115 
 2116 /*
 2117  * Handle a stathz tick.  This is really only relevant for timeshare
 2118  * threads.
 2119  */
 2120 void
 2121 sched_clock(struct thread *td)
 2122 {
 2123         struct tdq *tdq;
 2124         struct td_sched *ts;
 2125 
 2126         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2127         tdq = TDQ_SELF();
 2128 #ifdef SMP
 2129         /*
 2130          * We run the long term load balancer infrequently on the first cpu.
 2131          */
 2132         if (balance_tdq == tdq) {
 2133                 if (balance_ticks && --balance_ticks == 0)
 2134                         sched_balance();
 2135         }
 2136 #endif
 2137         /*
 2138          * Save the old switch count so we have a record of the last ticks
 2139          * activity.   Initialize the new switch count based on our load.
 2140          * If there is some activity seed it to reflect that.
 2141          */
 2142         tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt;
 2143         tdq->tdq_switchcnt = tdq->tdq_load;
 2144         /*
 2145          * Advance the insert index once for each tick to ensure that all
 2146          * threads get a chance to run.
 2147          */
 2148         if (tdq->tdq_idx == tdq->tdq_ridx) {
 2149                 tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS;
 2150                 if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx]))
 2151                         tdq->tdq_ridx = tdq->tdq_idx;
 2152         }
 2153         ts = td->td_sched;
 2154         if (td->td_pri_class & PRI_FIFO_BIT)
 2155                 return;
 2156         if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) {
 2157                 /*
 2158                  * We used a tick; charge it to the thread so
 2159                  * that we can compute our interactivity.
 2160                  */
 2161                 td->td_sched->ts_runtime += tickincr;
 2162                 sched_interact_update(td);
 2163                 sched_priority(td);
 2164         }
 2165         /*
 2166          * We used up one time slice.
 2167          */
 2168         if (--ts->ts_slice > 0)
 2169                 return;
 2170         /*
 2171          * We're out of time, force a requeue at userret().
 2172          */
 2173         ts->ts_slice = sched_slice;
 2174         td->td_flags |= TDF_NEEDRESCHED;
 2175 }
 2176 
 2177 /*
 2178  * Called once per hz tick.  Used for cpu utilization information.  This
 2179  * is easier than trying to scale based on stathz.
 2180  */
 2181 void
 2182 sched_tick(void)
 2183 {
 2184         struct td_sched *ts;
 2185 
 2186         ts = curthread->td_sched;
 2187         /*
 2188          * Ticks is updated asynchronously on a single cpu.  Check here to
 2189          * avoid incrementing ts_ticks multiple times in a single tick.
 2190          */
 2191         if (ts->ts_incrtick == ticks)
 2192                 return;
 2193         /* Adjust ticks for pctcpu */
 2194         ts->ts_ticks += 1 << SCHED_TICK_SHIFT;
 2195         ts->ts_ltick = ticks;
 2196         ts->ts_incrtick = ticks;
 2197         /*
 2198          * Update if we've exceeded our desired tick threshold by over one
 2199          * second.
 2200          */
 2201         if (ts->ts_ftick + SCHED_TICK_MAX < ts->ts_ltick)
 2202                 sched_pctcpu_update(ts);
 2203 }
 2204 
 2205 /*
 2206  * Return whether the current CPU has runnable tasks.  Used for in-kernel
 2207  * cooperative idle threads.
 2208  */
 2209 int
 2210 sched_runnable(void)
 2211 {
 2212         struct tdq *tdq;
 2213         int load;
 2214 
 2215         load = 1;
 2216 
 2217         tdq = TDQ_SELF();
 2218         if ((curthread->td_flags & TDF_IDLETD) != 0) {
 2219                 if (tdq->tdq_load > 0)
 2220                         goto out;
 2221         } else
 2222                 if (tdq->tdq_load - 1 > 0)
 2223                         goto out;
 2224         load = 0;
 2225 out:
 2226         return (load);
 2227 }
 2228 
 2229 /*
 2230  * Choose the highest priority thread to run.  The thread is removed from
 2231  * the run-queue while running however the load remains.  For SMP we set
 2232  * the tdq in the global idle bitmask if it idles here.
 2233  */
 2234 struct thread *
 2235 sched_choose(void)
 2236 {
 2237         struct thread *td;
 2238         struct tdq *tdq;
 2239 
 2240         tdq = TDQ_SELF();
 2241         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2242         td = tdq_choose(tdq);
 2243         if (td) {
 2244                 td->td_sched->ts_ltick = ticks;
 2245                 tdq_runq_rem(tdq, td);
 2246                 tdq->tdq_lowpri = td->td_priority;
 2247                 return (td);
 2248         }
 2249         tdq->tdq_lowpri = PRI_MAX_IDLE;
 2250         return (PCPU_GET(idlethread));
 2251 }
 2252 
 2253 /*
 2254  * Set owepreempt if necessary.  Preemption never happens directly in ULE,
 2255  * we always request it once we exit a critical section.
 2256  */
 2257 static inline void
 2258 sched_setpreempt(struct thread *td)
 2259 {
 2260         struct thread *ctd;
 2261         int cpri;
 2262         int pri;
 2263 
 2264         THREAD_LOCK_ASSERT(curthread, MA_OWNED);
 2265 
 2266         ctd = curthread;
 2267         pri = td->td_priority;
 2268         cpri = ctd->td_priority;
 2269         if (pri < cpri)
 2270                 ctd->td_flags |= TDF_NEEDRESCHED;
 2271         if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
 2272                 return;
 2273         if (!sched_shouldpreempt(pri, cpri, 0))
 2274                 return;
 2275         ctd->td_owepreempt = 1;
 2276 }
 2277 
 2278 /*
 2279  * Add a thread to a thread queue.  Select the appropriate runq and add the
 2280  * thread to it.  This is the internal function called when the tdq is
 2281  * predetermined.
 2282  */
 2283 void
 2284 tdq_add(struct tdq *tdq, struct thread *td, int flags)
 2285 {
 2286 
 2287         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2288         KASSERT((td->td_inhibitors == 0),
 2289             ("sched_add: trying to run inhibited thread"));
 2290         KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
 2291             ("sched_add: bad thread state"));
 2292         KASSERT(td->td_flags & TDF_INMEM,
 2293             ("sched_add: thread swapped out"));
 2294 
 2295         if (td->td_priority < tdq->tdq_lowpri)
 2296                 tdq->tdq_lowpri = td->td_priority;
 2297         tdq_runq_add(tdq, td, flags);
 2298         tdq_load_add(tdq, td);
 2299 }
 2300 
 2301 /*
 2302  * Select the target thread queue and add a thread to it.  Request
 2303  * preemption or IPI a remote processor if required.
 2304  */
 2305 void
 2306 sched_add(struct thread *td, int flags)
 2307 {
 2308         struct tdq *tdq;
 2309 #ifdef SMP
 2310         int cpu;
 2311 #endif
 2312 
 2313         KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
 2314             "prio:%d", td->td_priority, KTR_ATTR_LINKED,
 2315             sched_tdname(curthread));
 2316         KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
 2317             KTR_ATTR_LINKED, sched_tdname(td));
 2318         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2319         /*
 2320          * Recalculate the priority before we select the target cpu or
 2321          * run-queue.
 2322          */
 2323         if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
 2324                 sched_priority(td);
 2325 #ifdef SMP
 2326         /*
 2327          * Pick the destination cpu and if it isn't ours transfer to the
 2328          * target cpu.
 2329          */
 2330         cpu = sched_pickcpu(td, flags);
 2331         tdq = sched_setcpu(td, cpu, flags);
 2332         tdq_add(tdq, td, flags);
 2333         if (cpu != PCPU_GET(cpuid)) {
 2334                 tdq_notify(tdq, td);
 2335                 return;
 2336         }
 2337 #else
 2338         tdq = TDQ_SELF();
 2339         TDQ_LOCK(tdq);
 2340         /*
 2341          * Now that the thread is moving to the run-queue, set the lock
 2342          * to the scheduler's lock.
 2343          */
 2344         thread_lock_set(td, TDQ_LOCKPTR(tdq));
 2345         tdq_add(tdq, td, flags);
 2346 #endif
 2347         if (!(flags & SRQ_YIELDING))
 2348                 sched_setpreempt(td);
 2349 }
 2350 
 2351 /*
 2352  * Remove a thread from a run-queue without running it.  This is used
 2353  * when we're stealing a thread from a remote queue.  Otherwise all threads
 2354  * exit by calling sched_exit_thread() and sched_throw() themselves.
 2355  */
 2356 void
 2357 sched_rem(struct thread *td)
 2358 {
 2359         struct tdq *tdq;
 2360 
 2361         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
 2362             "prio:%d", td->td_priority);
 2363         tdq = TDQ_CPU(td->td_sched->ts_cpu);
 2364         TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 2365         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2366         KASSERT(TD_ON_RUNQ(td),
 2367             ("sched_rem: thread not on run queue"));
 2368         tdq_runq_rem(tdq, td);
 2369         tdq_load_rem(tdq, td);
 2370         TD_SET_CAN_RUN(td);
 2371         if (td->td_priority == tdq->tdq_lowpri)
 2372                 tdq_setlowpri(tdq, NULL);
 2373 }
 2374 
 2375 /*
 2376  * Fetch cpu utilization information.  Updates on demand.
 2377  */
 2378 fixpt_t
 2379 sched_pctcpu(struct thread *td)
 2380 {
 2381         fixpt_t pctcpu;
 2382         struct td_sched *ts;
 2383 
 2384         pctcpu = 0;
 2385         ts = td->td_sched;
 2386         if (ts == NULL)
 2387                 return (0);
 2388 
 2389         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2390         if (ts->ts_ticks) {
 2391                 int rtick;
 2392 
 2393                 sched_pctcpu_update(ts);
 2394                 /* How many rtick per second ? */
 2395                 rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
 2396                 pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
 2397         }
 2398 
 2399         return (pctcpu);
 2400 }
 2401 
 2402 /*
 2403  * Enforce affinity settings for a thread.  Called after adjustments to
 2404  * cpumask.
 2405  */
 2406 void
 2407 sched_affinity(struct thread *td)
 2408 {
 2409 #ifdef SMP
 2410         struct td_sched *ts;
 2411 
 2412         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2413         ts = td->td_sched;
 2414         if (THREAD_CAN_SCHED(td, ts->ts_cpu))
 2415                 return;
 2416         if (TD_ON_RUNQ(td)) {
 2417                 sched_rem(td);
 2418                 sched_add(td, SRQ_BORING);
 2419                 return;
 2420         }
 2421         if (!TD_IS_RUNNING(td))
 2422                 return;
 2423         /*
 2424          * Force a switch before returning to userspace.  If the
 2425          * target thread is not running locally send an ipi to force
 2426          * the issue.
 2427          */
 2428         td->td_flags |= TDF_NEEDRESCHED;
 2429         if (td != curthread)
 2430                 ipi_cpu(ts->ts_cpu, IPI_PREEMPT);
 2431 #endif
 2432 }
 2433 
 2434 /*
 2435  * Bind a thread to a target cpu.
 2436  */
 2437 void
 2438 sched_bind(struct thread *td, int cpu)
 2439 {
 2440         struct td_sched *ts;
 2441 
 2442         THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
 2443         KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
 2444         ts = td->td_sched;
 2445         if (ts->ts_flags & TSF_BOUND)
 2446                 sched_unbind(td);
 2447         KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td));
 2448         ts->ts_flags |= TSF_BOUND;
 2449         sched_pin();
 2450         if (PCPU_GET(cpuid) == cpu)
 2451                 return;
 2452         ts->ts_cpu = cpu;
 2453         /* When we return from mi_switch we'll be on the correct cpu. */
 2454         mi_switch(SW_VOL, NULL);
 2455 }
 2456 
 2457 /*
 2458  * Release a bound thread.
 2459  */
 2460 void
 2461 sched_unbind(struct thread *td)
 2462 {
 2463         struct td_sched *ts;
 2464 
 2465         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2466         KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
 2467         ts = td->td_sched;
 2468         if ((ts->ts_flags & TSF_BOUND) == 0)
 2469                 return;
 2470         ts->ts_flags &= ~TSF_BOUND;
 2471         sched_unpin();
 2472 }
 2473 
 2474 int
 2475 sched_is_bound(struct thread *td)
 2476 {
 2477         THREAD_LOCK_ASSERT(td, MA_OWNED);
 2478         return (td->td_sched->ts_flags & TSF_BOUND);
 2479 }
 2480 
 2481 /*
 2482  * Basic yield call.
 2483  */
 2484 void
 2485 sched_relinquish(struct thread *td)
 2486 {
 2487         thread_lock(td);
 2488         mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
 2489         thread_unlock(td);
 2490 }
 2491 
 2492 /*
 2493  * Return the total system load.
 2494  */
 2495 int
 2496 sched_load(void)
 2497 {
 2498 #ifdef SMP
 2499         int total;
 2500         int i;
 2501 
 2502         total = 0;
 2503         CPU_FOREACH(i)
 2504                 total += TDQ_CPU(i)->tdq_sysload;
 2505         return (total);
 2506 #else
 2507         return (TDQ_SELF()->tdq_sysload);
 2508 #endif
 2509 }
 2510 
 2511 int
 2512 sched_sizeof_proc(void)
 2513 {
 2514         return (sizeof(struct proc));
 2515 }
 2516 
 2517 int
 2518 sched_sizeof_thread(void)
 2519 {
 2520         return (sizeof(struct thread) + sizeof(struct td_sched));
 2521 }
 2522 
 2523 #ifdef SMP
 2524 #define TDQ_IDLESPIN(tdq)                                               \
 2525     ((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0)
 2526 #else
 2527 #define TDQ_IDLESPIN(tdq)       1
 2528 #endif
 2529 
 2530 /*
 2531  * The actual idle process.
 2532  */
 2533 void
 2534 sched_idletd(void *dummy)
 2535 {
 2536         struct thread *td;
 2537         struct tdq *tdq;
 2538         int switchcnt;
 2539         int i;
 2540 
 2541         mtx_assert(&Giant, MA_NOTOWNED);
 2542         td = curthread;
 2543         tdq = TDQ_SELF();
 2544         for (;;) {
 2545 #ifdef SMP
 2546                 if (tdq_idled(tdq) == 0)
 2547                         continue;
 2548 #endif
 2549                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2550                 /*
 2551                  * If we're switching very frequently, spin while checking
 2552                  * for load rather than entering a low power state that 
 2553                  * may require an IPI.  However, don't do any busy
 2554                  * loops while on SMT machines as this simply steals
 2555                  * cycles from cores doing useful work.
 2556                  */
 2557                 if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) {
 2558                         for (i = 0; i < sched_idlespins; i++) {
 2559                                 if (tdq->tdq_load)
 2560                                         break;
 2561                                 cpu_spinwait();
 2562                         }
 2563                 }
 2564                 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
 2565                 if (tdq->tdq_load == 0)
 2566                         cpu_idle(switchcnt > 1);
 2567                 if (tdq->tdq_load) {
 2568                         thread_lock(td);
 2569                         mi_switch(SW_VOL | SWT_IDLE, NULL);
 2570                         thread_unlock(td);
 2571                 }
 2572         }
 2573 }
 2574 
 2575 /*
 2576  * A CPU is entering for the first time or a thread is exiting.
 2577  */
 2578 void
 2579 sched_throw(struct thread *td)
 2580 {
 2581         struct thread *newtd;
 2582         struct tdq *tdq;
 2583 
 2584         tdq = TDQ_SELF();
 2585         if (td == NULL) {
 2586                 /* Correct spinlock nesting and acquire the correct lock. */
 2587                 TDQ_LOCK(tdq);
 2588                 spinlock_exit();
 2589                 PCPU_SET(switchtime, cpu_ticks());
 2590                 PCPU_SET(switchticks, ticks);
 2591         } else {
 2592                 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2593                 tdq_load_rem(tdq, td);
 2594                 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
 2595         }
 2596         KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
 2597         newtd = choosethread();
 2598         TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
 2599         cpu_throw(td, newtd);           /* doesn't return */
 2600 }
 2601 
 2602 /*
 2603  * This is called from fork_exit().  Just acquire the correct locks and
 2604  * let fork do the rest of the work.
 2605  */
 2606 void
 2607 sched_fork_exit(struct thread *td)
 2608 {
 2609         struct td_sched *ts;
 2610         struct tdq *tdq;
 2611         int cpuid;
 2612 
 2613         /*
 2614          * Finish setting up thread glue so that it begins execution in a
 2615          * non-nested critical section with the scheduler lock held.
 2616          */
 2617         cpuid = PCPU_GET(cpuid);
 2618         tdq = TDQ_CPU(cpuid);
 2619         ts = td->td_sched;
 2620         if (TD_IS_IDLETHREAD(td))
 2621                 td->td_lock = TDQ_LOCKPTR(tdq);
 2622         MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 2623         td->td_oncpu = cpuid;
 2624         TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
 2625         lock_profile_obtain_lock_success(
 2626             &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
 2627 }
 2628 
 2629 /*
 2630  * Create on first use to catch odd startup conditons.
 2631  */
 2632 char *
 2633 sched_tdname(struct thread *td)
 2634 {
 2635 #ifdef KTR
 2636         struct td_sched *ts;
 2637 
 2638         ts = td->td_sched;
 2639         if (ts->ts_name[0] == '\0')
 2640                 snprintf(ts->ts_name, sizeof(ts->ts_name),
 2641                     "%s tid %d", td->td_name, td->td_tid);
 2642         return (ts->ts_name);
 2643 #else
 2644         return (td->td_name);
 2645 #endif
 2646 }
 2647 
 2648 #ifdef SMP
 2649 
 2650 /*
 2651  * Build the CPU topology dump string. Is recursively called to collect
 2652  * the topology tree.
 2653  */
 2654 static int
 2655 sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg,
 2656     int indent)
 2657 {
 2658         int i, first;
 2659 
 2660         sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent,
 2661             "", 1 + indent / 2, cg->cg_level);
 2662         sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"0x%x\">", indent, "",
 2663             cg->cg_count, cg->cg_mask);
 2664         first = TRUE;
 2665         for (i = 0; i < MAXCPU; i++) {
 2666                 if ((cg->cg_mask & (1 << i)) != 0) {
 2667                         if (!first)
 2668                                 sbuf_printf(sb, ", ");
 2669                         else
 2670                                 first = FALSE;
 2671                         sbuf_printf(sb, "%d", i);
 2672                 }
 2673         }
 2674         sbuf_printf(sb, "</cpu>\n");
 2675 
 2676         if (cg->cg_flags != 0) {
 2677                 sbuf_printf(sb, "%*s <flags>", indent, "");
 2678                 if ((cg->cg_flags & CG_FLAG_HTT) != 0)
 2679                         sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>");
 2680                 if ((cg->cg_flags & CG_FLAG_THREAD) != 0)
 2681                         sbuf_printf(sb, "<flag name=\"THREAD\">THREAD group</flag>");
 2682                 if ((cg->cg_flags & CG_FLAG_SMT) != 0)
 2683                         sbuf_printf(sb, "<flag name=\"SMT\">SMT group</flag>");
 2684                 sbuf_printf(sb, "</flags>\n");
 2685         }
 2686 
 2687         if (cg->cg_children > 0) {
 2688                 sbuf_printf(sb, "%*s <children>\n", indent, "");
 2689                 for (i = 0; i < cg->cg_children; i++)
 2690                         sysctl_kern_sched_topology_spec_internal(sb, 
 2691                             &cg->cg_child[i], indent+2);
 2692                 sbuf_printf(sb, "%*s </children>\n", indent, "");
 2693         }
 2694         sbuf_printf(sb, "%*s</group>\n", indent, "");
 2695         return (0);
 2696 }
 2697 
 2698 /*
 2699  * Sysctl handler for retrieving topology dump. It's a wrapper for
 2700  * the recursive sysctl_kern_smp_topology_spec_internal().
 2701  */
 2702 static int
 2703 sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS)
 2704 {
 2705         struct sbuf *topo;
 2706         int err;
 2707 
 2708         KASSERT(cpu_top != NULL, ("cpu_top isn't initialized"));
 2709 
 2710         topo = sbuf_new(NULL, NULL, 500, SBUF_AUTOEXTEND);
 2711         if (topo == NULL)
 2712                 return (ENOMEM);
 2713 
 2714         sbuf_printf(topo, "<groups>\n");
 2715         err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1);
 2716         sbuf_printf(topo, "</groups>\n");
 2717 
 2718         if (err == 0) {
 2719                 sbuf_finish(topo);
 2720                 err = SYSCTL_OUT(req, sbuf_data(topo), sbuf_len(topo));
 2721         }
 2722         sbuf_delete(topo);
 2723         return (err);
 2724 }
 2725 #endif
 2726 
 2727 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW, 0, "Scheduler");
 2728 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0,
 2729     "Scheduler name");
 2730 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
 2731     "Slice size for timeshare threads");
 2732 SYSCTL_INT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0,
 2733      "Interactivity score threshold");
 2734 SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW, &preempt_thresh,
 2735      0,"Min priority for preemption, lower priorities have greater precedence");
 2736 SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost,
 2737      0,"Controls whether static kernel priorities are assigned to sleeping threads.");
 2738 SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins,
 2739      0,"Number of times idle will spin waiting for new work.");
 2740 SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW, &sched_idlespinthresh,
 2741      0,"Threshold before we will permit idle spinning.");
 2742 #ifdef SMP
 2743 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0,
 2744     "Number of hz ticks to keep thread affinity for");
 2745 SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0,
 2746     "Enables the long-term load balancer");
 2747 SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW,
 2748     &balance_interval, 0,
 2749     "Average frequency in stathz ticks to run the long-term balancer");
 2750 SYSCTL_INT(_kern_sched, OID_AUTO, steal_htt, CTLFLAG_RW, &steal_htt, 0,
 2751     "Steals work from another hyper-threaded core on idle");
 2752 SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0,
 2753     "Attempts to steal work from other cores before idling");
 2754 SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0,
 2755     "Minimum load on remote cpu before we'll steal");
 2756 
 2757 /* Retrieve SMP topology */
 2758 SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING |
 2759     CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A", 
 2760     "XML dump of detected CPU topology");
 2761 #endif
 2762 
 2763 /* ps compat.  All cpu percentages from ULE are weighted. */
 2764 static int ccpu = 0;
 2765 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");

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