2 * Copyright (c) 2012 The DragonFly Project. All rights reserved.
3 * Copyright (c) 1999 Peter Wemm <peter@FreeBSD.org>. All rights reserved.
5 * This code is derived from software contributed to The DragonFly Project
6 * by Matthew Dillon <dillon@backplane.com>,
7 * by Mihai Carabas <mihai.carabas@gmail.com>
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in
18 * the documentation and/or other materials provided with the
20 * 3. Neither the name of The DragonFly Project nor the names of its
21 * contributors may be used to endorse or promote products derived
22 * from this software without specific, prior written permission.
24 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
25 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
26 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
27 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
28 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
29 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
30 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
31 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
32 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
33 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
34 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/kernel.h>
41 #include <sys/queue.h>
43 #include <sys/rtprio.h>
45 #include <sys/sysctl.h>
46 #include <sys/resourcevar.h>
47 #include <sys/spinlock.h>
48 #include <sys/cpu_topology.h>
49 #include <sys/thread2.h>
50 #include <sys/spinlock2.h>
51 #include <sys/mplock2.h>
55 #include <machine/cpu.h>
56 #include <machine/smp.h>
59 * Priorities. Note that with 32 run queues per scheduler each queue
60 * represents four priority levels.
66 #define PRIMASK (MAXPRI - 1)
67 #define PRIBASE_REALTIME 0
68 #define PRIBASE_NORMAL MAXPRI
69 #define PRIBASE_IDLE (MAXPRI * 2)
70 #define PRIBASE_THREAD (MAXPRI * 3)
71 #define PRIBASE_NULL (MAXPRI * 4)
73 #define NQS 32 /* 32 run queues. */
74 #define PPQ (MAXPRI / NQS) /* priorities per queue */
75 #define PPQMASK (PPQ - 1)
78 * NICEPPQ - number of nice units per priority queue
79 * ESTCPUPPQ - number of estcpu units per priority queue
80 * ESTCPUMAX - number of estcpu units
84 #define ESTCPUMAX (ESTCPUPPQ * NQS)
85 #define BATCHMAX (ESTCPUFREQ * 30)
86 #define PRIO_RANGE (PRIO_MAX - PRIO_MIN + 1)
88 #define ESTCPULIM(v) min((v), ESTCPUMAX)
92 #define lwp_priority lwp_usdata.dfly.priority
93 #define lwp_forked lwp_usdata.dfly.forked
94 #define lwp_rqindex lwp_usdata.dfly.rqindex
95 #define lwp_estcpu lwp_usdata.dfly.estcpu
96 #define lwp_estfast lwp_usdata.dfly.estfast
97 #define lwp_uload lwp_usdata.dfly.uload
98 #define lwp_rqtype lwp_usdata.dfly.rqtype
99 #define lwp_qcpu lwp_usdata.dfly.qcpu
100 #define lwp_rrcount lwp_usdata.dfly.rrcount
102 struct usched_dfly_pcpu {
103 struct spinlock spin;
104 struct thread helper_thread;
109 struct lwp *uschedcp;
110 struct rq queues[NQS];
111 struct rq rtqueues[NQS];
112 struct rq idqueues[NQS];
114 u_int32_t rtqueuebits;
115 u_int32_t idqueuebits;
124 typedef struct usched_dfly_pcpu *dfly_pcpu_t;
126 static void dfly_acquire_curproc(struct lwp *lp);
127 static void dfly_release_curproc(struct lwp *lp);
128 static void dfly_select_curproc(globaldata_t gd);
129 static void dfly_setrunqueue(struct lwp *lp);
130 static void dfly_setrunqueue_dd(dfly_pcpu_t rdd, struct lwp *lp);
131 static void dfly_schedulerclock(struct lwp *lp, sysclock_t period,
133 static void dfly_recalculate_estcpu(struct lwp *lp);
134 static void dfly_resetpriority(struct lwp *lp);
135 static void dfly_forking(struct lwp *plp, struct lwp *lp);
136 static void dfly_exiting(struct lwp *lp, struct proc *);
137 static void dfly_uload_update(struct lwp *lp);
138 static void dfly_yield(struct lwp *lp);
140 static void dfly_changeqcpu_locked(struct lwp *lp,
141 dfly_pcpu_t dd, dfly_pcpu_t rdd);
142 static dfly_pcpu_t dfly_choose_best_queue(struct lwp *lp);
143 static dfly_pcpu_t dfly_choose_worst_queue(dfly_pcpu_t dd);
144 static dfly_pcpu_t dfly_choose_queue_simple(dfly_pcpu_t dd, struct lwp *lp);
148 static void dfly_need_user_resched_remote(void *dummy);
150 static struct lwp *dfly_chooseproc_locked(dfly_pcpu_t rdd, dfly_pcpu_t dd,
151 struct lwp *chklp, int worst);
152 static void dfly_remrunqueue_locked(dfly_pcpu_t dd, struct lwp *lp);
153 static void dfly_setrunqueue_locked(dfly_pcpu_t dd, struct lwp *lp);
155 struct usched usched_dfly = {
157 "dfly", "Original DragonFly Scheduler",
158 NULL, /* default registration */
159 NULL, /* default deregistration */
160 dfly_acquire_curproc,
161 dfly_release_curproc,
164 dfly_recalculate_estcpu,
169 NULL, /* setcpumask not supported */
174 * We have NQS (32) run queues per scheduling class. For the normal
175 * class, there are 128 priorities scaled onto these 32 queues. New
176 * processes are added to the last entry in each queue, and processes
177 * are selected for running by taking them from the head and maintaining
178 * a simple FIFO arrangement. Realtime and Idle priority processes have
179 * and explicit 0-31 priority which maps directly onto their class queue
180 * index. When a queue has something in it, the corresponding bit is
181 * set in the queuebits variable, allowing a single read to determine
182 * the state of all 32 queues and then a ffs() to find the first busy
185 static cpumask_t dfly_curprocmask = -1; /* currently running a user process */
186 static cpumask_t dfly_rdyprocmask; /* ready to accept a user process */
188 static volatile int dfly_scancpu;
190 static volatile int dfly_ucount; /* total running on whole system */
191 static struct usched_dfly_pcpu dfly_pcpu[MAXCPU];
192 static struct sysctl_ctx_list usched_dfly_sysctl_ctx;
193 static struct sysctl_oid *usched_dfly_sysctl_tree;
195 /* Debug info exposed through debug.* sysctl */
197 static int usched_dfly_debug = -1;
198 SYSCTL_INT(_debug, OID_AUTO, dfly_scdebug, CTLFLAG_RW,
199 &usched_dfly_debug, 0,
200 "Print debug information for this pid");
202 static int usched_dfly_pid_debug = -1;
203 SYSCTL_INT(_debug, OID_AUTO, dfly_pid_debug, CTLFLAG_RW,
204 &usched_dfly_pid_debug, 0,
205 "Print KTR debug information for this pid");
207 static int usched_dfly_chooser = 0;
208 SYSCTL_INT(_debug, OID_AUTO, dfly_chooser, CTLFLAG_RW,
209 &usched_dfly_chooser, 0,
210 "Print KTR debug information for this pid");
213 * Tunning usched_dfly - configurable through kern.usched_dfly.
215 * weight1 - Tries to keep threads on their current cpu. If you
216 * make this value too large the scheduler will not be
217 * able to load-balance large loads.
219 * weight2 - If non-zero, detects thread pairs undergoing synchronous
220 * communications and tries to move them closer together.
221 * Behavior is adjusted by bit 4 of features (0x10).
223 * WARNING! Weight2 is a ridiculously sensitive parameter,
224 * a small value is recommended.
226 * weight3 - Weighting based on the number of recently runnable threads
227 * on the userland scheduling queue (ignoring their loads).
228 * A nominal value here prevents high-priority (low-load)
229 * threads from accumulating on one cpu core when other
230 * cores are available.
232 * This value should be left fairly small relative to weight1
235 * weight4 - Weighting based on other cpu queues being available
236 * or running processes with higher lwp_priority's.
238 * This allows a thread to migrate to another nearby cpu if it
239 * is unable to run on the current cpu based on the other cpu
240 * being idle or running a lower priority (higher lwp_priority)
241 * thread. This value should be large enough to override weight1
243 * features - These flags can be set or cleared to enable or disable various
246 * 0x01 Enable idle-cpu pulling (default)
247 * 0x02 Enable proactive pushing (default)
248 * 0x04 Enable rebalancing rover (default)
249 * 0x08 Enable more proactive pushing (default)
250 * 0x10 (flip weight2 limit on same cpu) (default)
251 * 0x20 choose best cpu for forked process
252 * 0x40 choose current cpu for forked process
253 * 0x80 choose random cpu for forked process (default)
256 static int usched_dfly_smt = 0;
257 static int usched_dfly_cache_coherent = 0;
258 static int usched_dfly_weight1 = 200; /* keep thread on current cpu */
259 static int usched_dfly_weight2 = 180; /* synchronous peer's current cpu */
260 static int usched_dfly_weight3 = 40; /* number of threads on queue */
261 static int usched_dfly_weight4 = 160; /* availability of idle cores */
262 static int usched_dfly_features = 0x8F; /* allow pulls */
264 static int usched_dfly_fast_resched = 0;/* delta priority / resched */
265 static int usched_dfly_swmask = ~PPQMASK; /* allow pulls */
266 static int usched_dfly_rrinterval = (ESTCPUFREQ + 9) / 10;
267 static int usched_dfly_decay = 8;
269 /* KTR debug printings */
271 KTR_INFO_MASTER(usched);
273 #if !defined(KTR_USCHED_DFLY)
274 #define KTR_USCHED_DFLY KTR_ALL
277 KTR_INFO(KTR_USCHED_DFLY, usched, chooseproc, 0,
278 "USCHED_DFLY(chooseproc: pid %d, old_cpuid %d, curr_cpuid %d)",
279 pid_t pid, int old_cpuid, int curr);
282 * This function is called when the kernel intends to return to userland.
283 * It is responsible for making the thread the current designated userland
284 * thread for this cpu, blocking if necessary.
286 * The kernel will not depress our LWKT priority until after we return,
287 * in case we have to shove over to another cpu.
289 * We must determine our thread's disposition before we switch away. This
290 * is very sensitive code.
292 * WARNING! THIS FUNCTION IS ALLOWED TO CAUSE THE CURRENT THREAD TO MIGRATE
293 * TO ANOTHER CPU! Because most of the kernel assumes that no migration will
294 * occur, this function is called only under very controlled circumstances.
297 dfly_acquire_curproc(struct lwp *lp)
308 * Make sure we aren't sitting on a tsleep queue.
311 crit_enter_quick(td);
312 if (td->td_flags & TDF_TSLEEPQ)
314 dfly_recalculate_estcpu(lp);
317 dd = &dfly_pcpu[gd->gd_cpuid];
320 * Process any pending interrupts/ipi's, then handle reschedule
321 * requests. dfly_release_curproc() will try to assign a new
322 * uschedcp that isn't us and otherwise NULL it out.
325 if ((td->td_mpflags & TDF_MP_BATCH_DEMARC) &&
326 lp->lwp_rrcount >= usched_dfly_rrinterval / 2) {
330 if (user_resched_wanted()) {
331 if (dd->uschedcp == lp)
333 clear_user_resched();
334 dfly_release_curproc(lp);
338 * Loop until we are the current user thread.
340 * NOTE: dd spinlock not held at top of loop.
342 if (dd->uschedcp == lp)
345 while (dd->uschedcp != lp) {
348 spin_lock(&dd->spin);
351 * We are not or are no longer the current lwp and a forced
352 * reschedule was requested. Figure out the best cpu to
353 * run on (our current cpu will be given significant weight).
355 * (if a reschedule was not requested we want to move this
356 * step after the uschedcp tests).
360 (usched_dfly_features & 0x08) &&
361 (rdd = dfly_choose_best_queue(lp)) != dd) {
362 dfly_changeqcpu_locked(lp, dd, rdd);
363 spin_unlock(&dd->spin);
364 lwkt_deschedule(lp->lwp_thread);
365 dfly_setrunqueue_dd(rdd, lp);
368 dd = &dfly_pcpu[gd->gd_cpuid];
374 * Either no reschedule was requested or the best queue was
375 * dd, and no current process has been selected. We can
376 * trivially become the current lwp on the current cpu.
378 if (dd->uschedcp == NULL) {
379 atomic_set_cpumask(&dfly_curprocmask, gd->gd_cpumask);
381 dd->upri = lp->lwp_priority;
382 KKASSERT(lp->lwp_qcpu == dd->cpuid);
383 spin_unlock(&dd->spin);
388 * Can we steal the current designated user thread?
390 * If we do the other thread will stall when it tries to
391 * return to userland, possibly rescheduling elsewhere.
393 * It is important to do a masked test to avoid the edge
394 * case where two near-equal-priority threads are constantly
395 * interrupting each other.
397 * In the exact match case another thread has already gained
398 * uschedcp and lowered its priority, if we steal it the
399 * other thread will stay stuck on the LWKT runq and not
400 * push to another cpu. So don't steal on equal-priority even
401 * though it might appear to be more beneficial due to not
402 * having to switch back to the other thread's context.
404 * usched_dfly_fast_resched requires that two threads be
405 * significantly far apart in priority in order to interrupt.
407 * If better but not sufficiently far apart, the current
408 * uschedcp will be interrupted at the next scheduler clock.
411 (dd->upri & ~PPQMASK) >
412 (lp->lwp_priority & ~PPQMASK) + usched_dfly_fast_resched) {
414 dd->upri = lp->lwp_priority;
415 KKASSERT(lp->lwp_qcpu == dd->cpuid);
416 spin_unlock(&dd->spin);
421 * We are not the current lwp, figure out the best cpu
422 * to run on (our current cpu will be given significant
423 * weight). Loop on cpu change.
425 if ((usched_dfly_features & 0x02) &&
426 force_resched == 0 &&
427 (rdd = dfly_choose_best_queue(lp)) != dd) {
428 dfly_changeqcpu_locked(lp, dd, rdd);
429 spin_unlock(&dd->spin);
430 lwkt_deschedule(lp->lwp_thread);
431 dfly_setrunqueue_dd(rdd, lp);
434 dd = &dfly_pcpu[gd->gd_cpuid];
440 * We cannot become the current lwp, place the lp on the
441 * run-queue of this or another cpu and deschedule ourselves.
443 * When we are reactivated we will have another chance.
445 * Reload after a switch or setrunqueue/switch possibly
446 * moved us to another cpu.
448 spin_unlock(&dd->spin);
449 lwkt_deschedule(lp->lwp_thread);
450 dfly_setrunqueue_dd(dd, lp);
453 dd = &dfly_pcpu[gd->gd_cpuid];
457 * Make sure upri is synchronized, then yield to LWKT threads as
458 * needed before returning. This could result in another reschedule.
463 KKASSERT((lp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
467 * DFLY_RELEASE_CURPROC
469 * This routine detaches the current thread from the userland scheduler,
470 * usually because the thread needs to run or block in the kernel (at
471 * kernel priority) for a while.
473 * This routine is also responsible for selecting a new thread to
474 * make the current thread.
476 * NOTE: This implementation differs from the dummy example in that
477 * dfly_select_curproc() is able to select the current process, whereas
478 * dummy_select_curproc() is not able to select the current process.
479 * This means we have to NULL out uschedcp.
481 * Additionally, note that we may already be on a run queue if releasing
482 * via the lwkt_switch() in dfly_setrunqueue().
485 dfly_release_curproc(struct lwp *lp)
487 globaldata_t gd = mycpu;
488 dfly_pcpu_t dd = &dfly_pcpu[gd->gd_cpuid];
491 * Make sure td_wakefromcpu is defaulted. This will be overwritten
494 if (dd->uschedcp == lp) {
495 KKASSERT((lp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
496 spin_lock(&dd->spin);
497 if (dd->uschedcp == lp) {
498 dd->uschedcp = NULL; /* don't let lp be selected */
499 dd->upri = PRIBASE_NULL;
500 atomic_clear_cpumask(&dfly_curprocmask, gd->gd_cpumask);
501 spin_unlock(&dd->spin);
502 dfly_select_curproc(gd);
504 spin_unlock(&dd->spin);
510 * DFLY_SELECT_CURPROC
512 * Select a new current process for this cpu and clear any pending user
513 * reschedule request. The cpu currently has no current process.
515 * This routine is also responsible for equal-priority round-robining,
516 * typically triggered from dfly_schedulerclock(). In our dummy example
517 * all the 'user' threads are LWKT scheduled all at once and we just
518 * call lwkt_switch().
520 * The calling process is not on the queue and cannot be selected.
524 dfly_select_curproc(globaldata_t gd)
526 dfly_pcpu_t dd = &dfly_pcpu[gd->gd_cpuid];
528 int cpuid = gd->gd_cpuid;
532 spin_lock(&dd->spin);
533 nlp = dfly_chooseproc_locked(dd, dd, dd->uschedcp, 0);
536 atomic_set_cpumask(&dfly_curprocmask, CPUMASK(cpuid));
537 dd->upri = nlp->lwp_priority;
540 dd->rrcount = 0; /* reset round robin */
542 spin_unlock(&dd->spin);
544 lwkt_acquire(nlp->lwp_thread);
546 lwkt_schedule(nlp->lwp_thread);
548 spin_unlock(&dd->spin);
554 * Place the specified lwp on the user scheduler's run queue. This routine
555 * must be called with the thread descheduled. The lwp must be runnable.
556 * It must not be possible for anyone else to explicitly schedule this thread.
558 * The thread may be the current thread as a special case.
561 dfly_setrunqueue(struct lwp *lp)
567 * First validate the process LWKT state.
569 KASSERT(lp->lwp_stat == LSRUN, ("setrunqueue: lwp not LSRUN"));
570 KASSERT((lp->lwp_mpflags & LWP_MP_ONRUNQ) == 0,
571 ("lwp %d/%d already on runq! flag %08x/%08x", lp->lwp_proc->p_pid,
572 lp->lwp_tid, lp->lwp_proc->p_flags, lp->lwp_flags));
573 KKASSERT((lp->lwp_thread->td_flags & TDF_RUNQ) == 0);
576 * NOTE: dd/rdd do not necessarily represent the current cpu.
577 * Instead they may represent the cpu the thread was last
578 * scheduled on or inherited by its parent.
580 dd = &dfly_pcpu[lp->lwp_qcpu];
584 * This process is not supposed to be scheduled anywhere or assigned
585 * as the current process anywhere. Assert the condition.
587 KKASSERT(rdd->uschedcp != lp);
591 * If we are not SMP we do not have a scheduler helper to kick
592 * and must directly activate the process if none are scheduled.
594 * This is really only an issue when bootstrapping init since
595 * the caller in all other cases will be a user process, and
596 * even if released (rdd->uschedcp == NULL), that process will
597 * kickstart the scheduler when it returns to user mode from
600 * NOTE: On SMP we can't just set some other cpu's uschedcp.
602 if (rdd->uschedcp == NULL) {
603 spin_lock(&rdd->spin);
604 if (rdd->uschedcp == NULL) {
605 atomic_set_cpumask(&dfly_curprocmask, 1);
607 rdd->upri = lp->lwp_priority;
608 spin_unlock(&rdd->spin);
609 lwkt_schedule(lp->lwp_thread);
612 spin_unlock(&rdd->spin);
618 * Ok, we have to setrunqueue some target cpu and request a reschedule
621 * We have to choose the best target cpu. It might not be the current
622 * target even if the current cpu has no running user thread (for
623 * example, because the current cpu might be a hyperthread and its
624 * sibling has a thread assigned).
626 * If we just forked it is most optimal to run the child on the same
627 * cpu just in case the parent decides to wait for it (thus getting
628 * off that cpu). As long as there is nothing else runnable on the
629 * cpu, that is. If we did this unconditionally a parent forking
630 * multiple children before waiting (e.g. make -j N) leaves other
631 * cpus idle that could be working.
633 if (lp->lwp_forked) {
635 if (usched_dfly_features & 0x20)
636 rdd = dfly_choose_best_queue(lp);
637 else if (usched_dfly_features & 0x40)
638 rdd = &dfly_pcpu[lp->lwp_qcpu];
639 else if (usched_dfly_features & 0x80)
640 rdd = dfly_choose_queue_simple(rdd, lp);
641 else if (dfly_pcpu[lp->lwp_qcpu].runqcount)
642 rdd = dfly_choose_best_queue(lp);
644 rdd = &dfly_pcpu[lp->lwp_qcpu];
646 rdd = dfly_choose_best_queue(lp);
647 /* rdd = &dfly_pcpu[lp->lwp_qcpu]; */
649 if (lp->lwp_qcpu != rdd->cpuid) {
650 spin_lock(&dd->spin);
651 dfly_changeqcpu_locked(lp, dd, rdd);
652 spin_unlock(&dd->spin);
655 dfly_setrunqueue_dd(rdd, lp);
661 * Change qcpu to rdd->cpuid. The dd the lp is CURRENTLY on must be
662 * spin-locked on-call. rdd does not have to be.
665 dfly_changeqcpu_locked(struct lwp *lp, dfly_pcpu_t dd, dfly_pcpu_t rdd)
667 if (lp->lwp_qcpu != rdd->cpuid) {
668 if (lp->lwp_mpflags & LWP_MP_ULOAD) {
669 atomic_clear_int(&lp->lwp_mpflags, LWP_MP_ULOAD);
670 atomic_add_int(&dd->uload, -lp->lwp_uload);
671 atomic_add_int(&dd->ucount, -1);
672 atomic_add_int(&dfly_ucount, -1);
674 lp->lwp_qcpu = rdd->cpuid;
681 * Place lp on rdd's runqueue. Nothing is locked on call. This function
682 * also performs all necessary ancillary notification actions.
685 dfly_setrunqueue_dd(dfly_pcpu_t rdd, struct lwp *lp)
691 * We might be moving the lp to another cpu's run queue, and once
692 * on the runqueue (even if it is our cpu's), another cpu can rip
695 * TDF_MIGRATING might already be set if this is part of a
696 * remrunqueue+setrunqueue sequence.
698 if ((lp->lwp_thread->td_flags & TDF_MIGRATING) == 0)
699 lwkt_giveaway(lp->lwp_thread);
701 rgd = globaldata_find(rdd->cpuid);
704 * We lose control of the lp the moment we release the spinlock
705 * after having placed it on the queue. i.e. another cpu could pick
706 * it up, or it could exit, or its priority could be further
707 * adjusted, or something like that.
709 * WARNING! rdd can point to a foreign cpu!
711 spin_lock(&rdd->spin);
712 dfly_setrunqueue_locked(rdd, lp);
715 * Potentially interrupt the currently-running thread
717 if ((rdd->upri & ~PPQMASK) <= (lp->lwp_priority & ~PPQMASK)) {
719 * Currently running thread is better or same, do not
722 spin_unlock(&rdd->spin);
723 } else if ((rdd->upri & ~PPQMASK) <= (lp->lwp_priority & ~PPQMASK) +
724 usched_dfly_fast_resched) {
726 * Currently running thread is not better, but not so bad
727 * that we need to interrupt it. Let it run for one more
731 rdd->uschedcp->lwp_rrcount < usched_dfly_rrinterval) {
732 rdd->uschedcp->lwp_rrcount = usched_dfly_rrinterval - 1;
734 spin_unlock(&rdd->spin);
735 } else if (rgd == mycpu) {
737 * We should interrupt the currently running thread, which
738 * is on the current cpu.
740 spin_unlock(&rdd->spin);
741 if (rdd->uschedcp == NULL) {
742 wakeup_mycpu(&rdd->helper_thread); /* XXX */
749 * We should interrupt the currently running thread, which
750 * is on a different cpu.
752 spin_unlock(&rdd->spin);
753 lwkt_send_ipiq(rgd, dfly_need_user_resched_remote, NULL);
757 * Request a reschedule if appropriate.
759 spin_lock(&rdd->spin);
760 dfly_setrunqueue_locked(rdd, lp);
761 spin_unlock(&rdd->spin);
762 if ((rdd->upri & ~PPQMASK) > (lp->lwp_priority & ~PPQMASK)) {
769 * This routine is called from a systimer IPI. It MUST be MP-safe and
770 * the BGL IS NOT HELD ON ENTRY. This routine is called at ESTCPUFREQ on
775 dfly_schedulerclock(struct lwp *lp, sysclock_t period, sysclock_t cpstamp)
777 globaldata_t gd = mycpu;
779 dfly_pcpu_t dd = &dfly_pcpu[gd->gd_cpuid];
783 * Spinlocks also hold a critical section so there should not be
786 KKASSERT(gd->gd_spinlocks == 0);
792 * Do we need to round-robin? We round-robin 10 times a second.
793 * This should only occur for cpu-bound batch processes.
795 if (++lp->lwp_rrcount >= usched_dfly_rrinterval) {
796 lp->lwp_thread->td_wakefromcpu = -1;
801 * Adjust estcpu upward using a real time equivalent calculation,
802 * and recalculate lp's priority.
804 lp->lwp_estcpu = ESTCPULIM(lp->lwp_estcpu + ESTCPUMAX / ESTCPUFREQ + 1);
805 dfly_resetpriority(lp);
808 * Rebalance two cpus every 8 ticks, pulling the worst thread
809 * from the worst cpu's queue into a rotating cpu number.
811 * This mechanic is needed because the push algorithms can
812 * steady-state in an non-optimal configuration. We need to mix it
813 * up a little, even if it means breaking up a paired thread, so
814 * the push algorithms can rebalance the degenerate conditions.
815 * This portion of the algorithm exists to ensure stability at the
816 * selected weightings.
818 * Because we might be breaking up optimal conditions we do not want
819 * to execute this too quickly, hence we only rebalance approximately
820 * ~7-8 times per second. The push's, on the otherhand, are capable
821 * moving threads to other cpus at a much higher rate.
823 * We choose the most heavily loaded thread from the worst queue
824 * in order to ensure that multiple heavy-weight threads on the same
825 * queue get broken up, and also because these threads are the most
826 * likely to be able to remain in place. Hopefully then any pairings,
827 * if applicable, migrate to where these threads are.
830 if ((usched_dfly_features & 0x04) &&
831 ((u_int)sched_ticks & 7) == 0 &&
832 (u_int)sched_ticks / 8 % ncpus == gd->gd_cpuid) {
839 rdd = dfly_choose_worst_queue(dd);
841 spin_lock(&dd->spin);
842 if (spin_trylock(&rdd->spin)) {
843 nlp = dfly_chooseproc_locked(rdd, dd, NULL, 1);
844 spin_unlock(&rdd->spin);
846 spin_unlock(&dd->spin);
848 spin_unlock(&dd->spin);
854 /* dd->spin held if nlp != NULL */
857 * Either schedule it or add it to our queue.
860 (nlp->lwp_priority & ~PPQMASK) < (dd->upri & ~PPQMASK)) {
861 atomic_set_cpumask(&dfly_curprocmask, dd->cpumask);
862 dd->upri = nlp->lwp_priority;
865 dd->rrcount = 0; /* reset round robin */
867 spin_unlock(&dd->spin);
868 lwkt_acquire(nlp->lwp_thread);
869 lwkt_schedule(nlp->lwp_thread);
871 dfly_setrunqueue_locked(dd, nlp);
872 spin_unlock(&dd->spin);
879 * Called from acquire and from kern_synch's one-second timer (one of the
880 * callout helper threads) with a critical section held.
882 * Adjust p_estcpu based on our single-cpu load, p_nice, and compensate for
883 * overall system load.
885 * Note that no recalculation occurs for a process which sleeps and wakes
886 * up in the same tick. That is, a system doing thousands of context
887 * switches per second will still only do serious estcpu calculations
888 * ESTCPUFREQ times per second.
892 dfly_recalculate_estcpu(struct lwp *lp)
894 globaldata_t gd = mycpu;
902 * We have to subtract periodic to get the last schedclock
903 * timeout time, otherwise we would get the upcoming timeout.
904 * Keep in mind that a process can migrate between cpus and
905 * while the scheduler clock should be very close, boundary
906 * conditions could lead to a small negative delta.
908 cpbase = gd->gd_schedclock.time - gd->gd_schedclock.periodic;
910 if (lp->lwp_slptime > 1) {
912 * Too much time has passed, do a coarse correction.
914 lp->lwp_estcpu = lp->lwp_estcpu >> 1;
915 dfly_resetpriority(lp);
916 lp->lwp_cpbase = cpbase;
919 } else if (lp->lwp_cpbase != cpbase) {
921 * Adjust estcpu if we are in a different tick. Don't waste
922 * time if we are in the same tick.
924 * First calculate the number of ticks in the measurement
925 * interval. The ttlticks calculation can wind up 0 due to
926 * a bug in the handling of lwp_slptime (as yet not found),
927 * so make sure we do not get a divide by 0 panic.
929 ttlticks = (cpbase - lp->lwp_cpbase) /
930 gd->gd_schedclock.periodic;
931 if ((ssysclock_t)ttlticks < 0) {
933 lp->lwp_cpbase = cpbase;
937 updatepcpu(lp, lp->lwp_cpticks, ttlticks);
940 * Calculate the percentage of one cpu being used then
941 * compensate for any system load in excess of ncpus.
943 * For example, if we have 8 cores and 16 running cpu-bound
944 * processes then all things being equal each process will
945 * get 50% of one cpu. We need to pump this value back
946 * up to 100% so the estcpu calculation properly adjusts
947 * the process's dynamic priority.
949 * estcpu is scaled by ESTCPUMAX, pctcpu is scaled by FSCALE.
951 estcpu = (lp->lwp_pctcpu * ESTCPUMAX) >> FSHIFT;
952 ucount = dfly_ucount;
953 if (ucount > ncpus) {
954 estcpu += estcpu * (ucount - ncpus) / ncpus;
957 if (usched_dfly_debug == lp->lwp_proc->p_pid) {
958 kprintf("pid %d lwp %p estcpu %3d %3d cp %d/%d",
959 lp->lwp_proc->p_pid, lp,
960 estcpu, lp->lwp_estcpu,
961 lp->lwp_cpticks, ttlticks);
965 * Adjust lp->lwp_esetcpu. The decay factor determines how
966 * quickly lwp_estcpu collapses to its realtime calculation.
967 * A slower collapse gives us a more accurate number over
968 * the long term but can create problems with bursty threads
969 * or threads which become cpu hogs.
971 * To solve this problem, newly started lwps and lwps which
972 * are restarting after having been asleep for a while are
973 * given a much, much faster decay in order to quickly
974 * detect whether they become cpu-bound.
976 * NOTE: p_nice is accounted for in dfly_resetpriority(),
977 * and not here, but we must still ensure that a
978 * cpu-bound nice -20 process does not completely
979 * override a cpu-bound nice +20 process.
981 * NOTE: We must use ESTCPULIM() here to deal with any
984 decay_factor = usched_dfly_decay;
985 if (decay_factor < 1)
987 if (decay_factor > 1024)
990 if (lp->lwp_estfast < usched_dfly_decay) {
992 lp->lwp_estcpu = ESTCPULIM(
993 (lp->lwp_estcpu * lp->lwp_estfast + estcpu) /
994 (lp->lwp_estfast + 1));
996 lp->lwp_estcpu = ESTCPULIM(
997 (lp->lwp_estcpu * decay_factor + estcpu) /
1001 if (usched_dfly_debug == lp->lwp_proc->p_pid)
1002 kprintf(" finalestcpu %d\n", lp->lwp_estcpu);
1003 dfly_resetpriority(lp);
1004 lp->lwp_cpbase += ttlticks * gd->gd_schedclock.periodic;
1005 lp->lwp_cpticks = 0;
1010 * Compute the priority of a process when running in user mode.
1011 * Arrange to reschedule if the resulting priority is better
1012 * than that of the current process.
1014 * This routine may be called with any process.
1016 * This routine is called by fork1() for initial setup with the process
1017 * of the run queue, and also may be called normally with the process on or
1018 * off the run queue.
1021 dfly_resetpriority(struct lwp *lp)
1034 * Lock the scheduler (lp) belongs to. This can be on a different
1035 * cpu. Handle races. This loop breaks out with the appropriate
1039 rcpu = lp->lwp_qcpu;
1041 rdd = &dfly_pcpu[rcpu];
1042 spin_lock(&rdd->spin);
1043 if (rcpu == lp->lwp_qcpu)
1045 spin_unlock(&rdd->spin);
1049 * Calculate the new priority and queue type
1051 newrqtype = lp->lwp_rtprio.type;
1054 case RTP_PRIO_REALTIME:
1056 newpriority = PRIBASE_REALTIME +
1057 (lp->lwp_rtprio.prio & PRIMASK);
1059 case RTP_PRIO_NORMAL:
1063 estcpu = lp->lwp_estcpu;
1066 * p_nice piece Adds (0-40) * 2 0-80
1067 * estcpu Adds 16384 * 4 / 512 0-128
1069 newpriority = (lp->lwp_proc->p_nice - PRIO_MIN) * PPQ / NICEPPQ;
1070 newpriority += estcpu * PPQ / ESTCPUPPQ;
1071 newpriority = newpriority * MAXPRI / (PRIO_RANGE * PPQ /
1072 NICEPPQ + ESTCPUMAX * PPQ / ESTCPUPPQ);
1073 newpriority = PRIBASE_NORMAL + (newpriority & PRIMASK);
1076 newpriority = PRIBASE_IDLE + (lp->lwp_rtprio.prio & PRIMASK);
1078 case RTP_PRIO_THREAD:
1079 newpriority = PRIBASE_THREAD + (lp->lwp_rtprio.prio & PRIMASK);
1082 panic("Bad RTP_PRIO %d", newrqtype);
1087 * The LWKT scheduler doesn't dive usched structures, give it a hint
1088 * on the relative priority of user threads running in the kernel.
1089 * The LWKT scheduler will always ensure that a user thread running
1090 * in the kernel will get cpu some time, regardless of its upri,
1091 * but can decide not to instantly switch from one kernel or user
1092 * mode user thread to a kernel-mode user thread when it has a less
1093 * desireable user priority.
1095 * td_upri has normal sense (higher values are more desireable), so
1098 lp->lwp_thread->td_upri = -(newpriority & usched_dfly_swmask);
1101 * The newpriority incorporates the queue type so do a simple masked
1102 * check to determine if the process has moved to another queue. If
1103 * it has, and it is currently on a run queue, then move it.
1105 * Since uload is ~PPQMASK masked, no modifications are necessary if
1106 * we end up in the same run queue.
1108 if ((lp->lwp_priority ^ newpriority) & ~PPQMASK) {
1109 if (lp->lwp_mpflags & LWP_MP_ONRUNQ) {
1110 dfly_remrunqueue_locked(rdd, lp);
1111 lp->lwp_priority = newpriority;
1112 lp->lwp_rqtype = newrqtype;
1113 lp->lwp_rqindex = (newpriority & PRIMASK) / PPQ;
1114 dfly_setrunqueue_locked(rdd, lp);
1117 lp->lwp_priority = newpriority;
1118 lp->lwp_rqtype = newrqtype;
1119 lp->lwp_rqindex = (newpriority & PRIMASK) / PPQ;
1124 * In the same PPQ, uload cannot change.
1126 lp->lwp_priority = newpriority;
1132 * Adjust effective load.
1134 * Calculate load then scale up or down geometrically based on p_nice.
1135 * Processes niced up (positive) are less important, and processes
1136 * niced downard (negative) are more important. The higher the uload,
1137 * the more important the thread.
1139 /* 0-511, 0-100% cpu */
1140 delta_uload = lp->lwp_estcpu / NQS;
1141 delta_uload -= delta_uload * lp->lwp_proc->p_nice / (PRIO_MAX + 1);
1144 delta_uload -= lp->lwp_uload;
1145 lp->lwp_uload += delta_uload;
1146 if (lp->lwp_mpflags & LWP_MP_ULOAD)
1147 atomic_add_int(&dfly_pcpu[lp->lwp_qcpu].uload, delta_uload);
1150 * Determine if we need to reschedule the target cpu. This only
1151 * occurs if the LWP is already on a scheduler queue, which means
1152 * that idle cpu notification has already occured. At most we
1153 * need only issue a need_user_resched() on the appropriate cpu.
1155 * The LWP may be owned by a CPU different from the current one,
1156 * in which case dd->uschedcp may be modified without an MP lock
1157 * or a spinlock held. The worst that happens is that the code
1158 * below causes a spurious need_user_resched() on the target CPU
1159 * and dd->pri to be wrong for a short period of time, both of
1160 * which are harmless.
1162 * If checkpri is 0 we are adjusting the priority of the current
1163 * process, possibly higher (less desireable), so ignore the upri
1164 * check which will fail in that case.
1167 if ((dfly_rdyprocmask & CPUMASK(rcpu)) &&
1169 (rdd->upri & ~PRIMASK) >
1170 (lp->lwp_priority & ~PRIMASK))) {
1172 if (rcpu == mycpu->gd_cpuid) {
1173 spin_unlock(&rdd->spin);
1174 need_user_resched();
1176 spin_unlock(&rdd->spin);
1177 lwkt_send_ipiq(globaldata_find(rcpu),
1178 dfly_need_user_resched_remote,
1182 spin_unlock(&rdd->spin);
1183 need_user_resched();
1186 spin_unlock(&rdd->spin);
1189 spin_unlock(&rdd->spin);
1196 dfly_yield(struct lwp *lp)
1199 /* FUTURE (or something similar) */
1200 switch(lp->lwp_rqtype) {
1201 case RTP_PRIO_NORMAL:
1202 lp->lwp_estcpu = ESTCPULIM(lp->lwp_estcpu + ESTCPUINCR);
1208 need_user_resched();
1212 * Called from fork1() when a new child process is being created.
1214 * Give the child process an initial estcpu that is more batch then
1215 * its parent and dock the parent for the fork (but do not
1216 * reschedule the parent).
1220 * XXX lwp should be "spawning" instead of "forking"
1223 dfly_forking(struct lwp *plp, struct lwp *lp)
1226 * Put the child 4 queue slots (out of 32) higher than the parent
1227 * (less desireable than the parent).
1229 lp->lwp_estcpu = ESTCPULIM(plp->lwp_estcpu + ESTCPUPPQ * 4);
1231 lp->lwp_estfast = 0;
1234 * Dock the parent a cost for the fork, protecting us from fork
1235 * bombs. If the parent is forking quickly make the child more
1238 plp->lwp_estcpu = ESTCPULIM(plp->lwp_estcpu + ESTCPUPPQ / 16);
1242 * Called when a lwp is being removed from this scheduler, typically
1243 * during lwp_exit(). We have to clean out any ULOAD accounting before
1244 * we can let the lp go. The dd->spin lock is not needed for uload
1247 * Scheduler dequeueing has already occurred, no further action in that
1251 dfly_exiting(struct lwp *lp, struct proc *child_proc)
1253 dfly_pcpu_t dd = &dfly_pcpu[lp->lwp_qcpu];
1255 if (lp->lwp_mpflags & LWP_MP_ULOAD) {
1256 atomic_clear_int(&lp->lwp_mpflags, LWP_MP_ULOAD);
1257 atomic_add_int(&dd->uload, -lp->lwp_uload);
1258 atomic_add_int(&dd->ucount, -1);
1259 atomic_add_int(&dfly_ucount, -1);
1264 * This function cannot block in any way, but spinlocks are ok.
1266 * Update the uload based on the state of the thread (whether it is going
1267 * to sleep or running again). The uload is meant to be a longer-term
1268 * load and not an instantanious load.
1271 dfly_uload_update(struct lwp *lp)
1273 dfly_pcpu_t dd = &dfly_pcpu[lp->lwp_qcpu];
1275 if (lp->lwp_thread->td_flags & TDF_RUNQ) {
1276 if ((lp->lwp_mpflags & LWP_MP_ULOAD) == 0) {
1277 spin_lock(&dd->spin);
1278 if ((lp->lwp_mpflags & LWP_MP_ULOAD) == 0) {
1279 atomic_set_int(&lp->lwp_mpflags,
1281 atomic_add_int(&dd->uload, lp->lwp_uload);
1282 atomic_add_int(&dd->ucount, 1);
1283 atomic_add_int(&dfly_ucount, 1);
1285 spin_unlock(&dd->spin);
1287 } else if (lp->lwp_slptime > 0) {
1288 if (lp->lwp_mpflags & LWP_MP_ULOAD) {
1289 spin_lock(&dd->spin);
1290 if (lp->lwp_mpflags & LWP_MP_ULOAD) {
1291 atomic_clear_int(&lp->lwp_mpflags,
1293 atomic_add_int(&dd->uload, -lp->lwp_uload);
1294 atomic_add_int(&dd->ucount, -1);
1295 atomic_add_int(&dfly_ucount, -1);
1297 spin_unlock(&dd->spin);
1303 * chooseproc() is called when a cpu needs a user process to LWKT schedule,
1304 * it selects a user process and returns it. If chklp is non-NULL and chklp
1305 * has a better or equal priority then the process that would otherwise be
1306 * chosen, NULL is returned.
1308 * Until we fix the RUNQ code the chklp test has to be strict or we may
1309 * bounce between processes trying to acquire the current process designation.
1311 * Must be called with rdd->spin locked. The spinlock is left intact through
1312 * the entire routine. dd->spin does not have to be locked.
1314 * If worst is non-zero this function finds the worst thread instead of the
1315 * best thread (used by the schedulerclock-based rover).
1319 dfly_chooseproc_locked(dfly_pcpu_t rdd, dfly_pcpu_t dd,
1320 struct lwp *chklp, int worst)
1324 u_int32_t *which, *which2;
1330 rtqbits = rdd->rtqueuebits;
1331 tsqbits = rdd->queuebits;
1332 idqbits = rdd->idqueuebits;
1336 pri = bsrl(idqbits);
1337 q = &rdd->idqueues[pri];
1338 which = &rdd->idqueuebits;
1340 } else if (tsqbits) {
1341 pri = bsrl(tsqbits);
1342 q = &rdd->queues[pri];
1343 which = &rdd->queuebits;
1345 } else if (rtqbits) {
1346 pri = bsrl(rtqbits);
1347 q = &rdd->rtqueues[pri];
1348 which = &rdd->rtqueuebits;
1353 lp = TAILQ_LAST(q, rq);
1356 pri = bsfl(rtqbits);
1357 q = &rdd->rtqueues[pri];
1358 which = &rdd->rtqueuebits;
1360 } else if (tsqbits) {
1361 pri = bsfl(tsqbits);
1362 q = &rdd->queues[pri];
1363 which = &rdd->queuebits;
1365 } else if (idqbits) {
1366 pri = bsfl(idqbits);
1367 q = &rdd->idqueues[pri];
1368 which = &rdd->idqueuebits;
1373 lp = TAILQ_FIRST(q);
1375 KASSERT(lp, ("chooseproc: no lwp on busy queue"));
1378 * If the passed lwp <chklp> is reasonably close to the selected
1379 * lwp <lp>, return NULL (indicating that <chklp> should be kept).
1381 * Note that we must error on the side of <chklp> to avoid bouncing
1382 * between threads in the acquire code.
1385 if (chklp->lwp_priority < lp->lwp_priority + PPQ)
1389 KTR_COND_LOG(usched_chooseproc,
1390 lp->lwp_proc->p_pid == usched_dfly_pid_debug,
1391 lp->lwp_proc->p_pid,
1392 lp->lwp_thread->td_gd->gd_cpuid,
1395 KASSERT((lp->lwp_mpflags & LWP_MP_ONRUNQ) != 0, ("not on runq6!"));
1396 atomic_clear_int(&lp->lwp_mpflags, LWP_MP_ONRUNQ);
1397 TAILQ_REMOVE(q, lp, lwp_procq);
1400 *which &= ~(1 << pri);
1403 * If we are choosing a process from rdd with the intent to
1404 * move it to dd, lwp_qcpu must be adjusted while rdd's spinlock
1408 if (lp->lwp_mpflags & LWP_MP_ULOAD) {
1409 atomic_add_int(&rdd->uload, -lp->lwp_uload);
1410 atomic_add_int(&rdd->ucount, -1);
1411 atomic_add_int(&dfly_ucount, -1);
1413 lp->lwp_qcpu = dd->cpuid;
1414 atomic_add_int(&dd->uload, lp->lwp_uload);
1415 atomic_add_int(&dd->ucount, 1);
1416 atomic_add_int(&dfly_ucount, 1);
1417 atomic_set_int(&lp->lwp_mpflags, LWP_MP_ULOAD);
1425 * USED TO PUSH RUNNABLE LWPS TO THE LEAST LOADED CPU.
1427 * Choose a cpu node to schedule lp on, hopefully nearby its current
1430 * We give the current node a modest advantage for obvious reasons.
1432 * We also give the node the thread was woken up FROM a slight advantage
1433 * in order to try to schedule paired threads which synchronize/block waiting
1434 * for each other fairly close to each other. Similarly in a network setting
1435 * this feature will also attempt to place a user process near the kernel
1436 * protocol thread that is feeding it data. THIS IS A CRITICAL PART of the
1437 * algorithm as it heuristically groups synchronizing processes for locality
1438 * of reference in multi-socket systems.
1440 * We check against running processes and give a big advantage if there
1443 * The caller will normally dfly_setrunqueue() lp on the returned queue.
1445 * When the topology is known choose a cpu whos group has, in aggregate,
1446 * has the lowest weighted load.
1450 dfly_choose_best_queue(struct lwp *lp)
1457 dfly_pcpu_t dd = &dfly_pcpu[lp->lwp_qcpu];
1467 * When the topology is unknown choose a random cpu that is hopefully
1470 if (dd->cpunode == NULL)
1471 return (dfly_choose_queue_simple(dd, lp));
1476 if ((wakecpu = lp->lwp_thread->td_wakefromcpu) >= 0)
1477 wakemask = dfly_pcpu[wakecpu].cpumask;
1482 * When the topology is known choose a cpu whos group has, in
1483 * aggregate, has the lowest weighted load.
1485 cpup = root_cpu_node;
1490 * Degenerate case super-root
1492 if (cpup->child_node && cpup->child_no == 1) {
1493 cpup = cpup->child_node;
1500 if (cpup->child_node == NULL) {
1501 rdd = &dfly_pcpu[BSFCPUMASK(cpup->members)];
1506 lowest_load = 0x7FFFFFFF;
1508 for (n = 0; n < cpup->child_no; ++n) {
1510 * Accumulate load information for all cpus
1511 * which are members of this node.
1513 cpun = &cpup->child_node[n];
1514 mask = cpun->members & usched_global_cpumask &
1515 smp_active_mask & lp->lwp_cpumask;
1523 cpuid = BSFCPUMASK(mask);
1524 rdd = &dfly_pcpu[cpuid];
1526 load += rdd->ucount * usched_dfly_weight3;
1528 if (rdd->uschedcp == NULL &&
1529 rdd->runqcount == 0 &&
1530 globaldata_find(cpuid)->gd_tdrunqcount == 0
1532 load -= usched_dfly_weight4;
1535 else if (rdd->upri > lp->lwp_priority + PPQ) {
1536 load -= usched_dfly_weight4 / 2;
1539 mask &= ~CPUMASK(cpuid);
1544 * Compensate if the lp is already accounted for in
1545 * the aggregate uload for this mask set. We want
1546 * to calculate the loads as if lp were not present,
1547 * otherwise the calculation is bogus.
1549 if ((lp->lwp_mpflags & LWP_MP_ULOAD) &&
1550 (dd->cpumask & cpun->members)) {
1551 load -= lp->lwp_uload;
1552 load -= usched_dfly_weight3;
1558 * Advantage the cpu group (lp) is already on.
1560 if (cpun->members & dd->cpumask)
1561 load -= usched_dfly_weight1;
1564 * Advantage the cpu group we want to pair (lp) to,
1565 * but don't let it go to the exact same cpu as
1566 * the wakecpu target.
1568 * We do this by checking whether cpun is a
1569 * terminal node or not. All cpun's at the same
1570 * level will either all be terminal or all not
1573 * If it is and we match we disadvantage the load.
1574 * If it is and we don't match we advantage the load.
1576 * Also note that we are effectively disadvantaging
1577 * all-but-one by the same amount, so it won't effect
1578 * the weight1 factor for the all-but-one nodes.
1580 if (cpun->members & wakemask) {
1581 if (cpun->child_node != NULL) {
1583 load -= usched_dfly_weight2;
1585 if (usched_dfly_features & 0x10)
1586 load += usched_dfly_weight2;
1588 load -= usched_dfly_weight2;
1593 * Calculate the best load
1595 if (cpub == NULL || lowest_load > load ||
1596 (lowest_load == load &&
1597 (cpun->members & dd->cpumask))
1605 if (usched_dfly_chooser)
1606 kprintf("lp %02d->%02d %s\n",
1607 lp->lwp_qcpu, rdd->cpuid, lp->lwp_proc->p_comm);
1612 * USED TO PULL RUNNABLE LWPS FROM THE MOST LOADED CPU.
1614 * Choose the worst queue close to dd's cpu node with a non-empty runq
1615 * that is NOT dd. Also require that the moving of the highest-load thread
1616 * from rdd to dd does not cause the uload's to cross each other.
1618 * This is used by the thread chooser when the current cpu's queues are
1619 * empty to steal a thread from another cpu's queue. We want to offload
1620 * the most heavily-loaded queue.
1624 dfly_choose_worst_queue(dfly_pcpu_t dd)
1642 * When the topology is unknown choose a random cpu that is hopefully
1645 if (dd->cpunode == NULL) {
1650 * When the topology is known choose a cpu whos group has, in
1651 * aggregate, has the lowest weighted load.
1653 cpup = root_cpu_node;
1657 * Degenerate case super-root
1659 if (cpup->child_node && cpup->child_no == 1) {
1660 cpup = cpup->child_node;
1667 if (cpup->child_node == NULL) {
1668 rdd = &dfly_pcpu[BSFCPUMASK(cpup->members)];
1675 for (n = 0; n < cpup->child_no; ++n) {
1677 * Accumulate load information for all cpus
1678 * which are members of this node.
1680 cpun = &cpup->child_node[n];
1681 mask = cpun->members & usched_global_cpumask &
1689 cpuid = BSFCPUMASK(mask);
1690 rdd = &dfly_pcpu[cpuid];
1692 load += rdd->ucount * usched_dfly_weight3;
1693 if (rdd->uschedcp == NULL &&
1694 rdd->runqcount == 0 &&
1695 globaldata_find(cpuid)->gd_tdrunqcount == 0
1697 load -= usched_dfly_weight4;
1700 else if (rdd->upri > dd->upri + PPQ) {
1701 load -= usched_dfly_weight4 / 2;
1704 mask &= ~CPUMASK(cpuid);
1710 * Prefer candidates which are somewhat closer to
1713 if (dd->cpumask & cpun->members)
1714 load += usched_dfly_weight1;
1717 * The best candidate is the one with the worst
1720 if (cpub == NULL || highest_load < load) {
1721 highest_load = load;
1729 * We never return our own node (dd), and only return a remote
1730 * node if it's load is significantly worse than ours (i.e. where
1731 * stealing a thread would be considered reasonable).
1733 * This also helps us avoid breaking paired threads apart which
1734 * can have disastrous effects on performance.
1741 if (rdd->rtqueuebits && hpri < (pri = bsrl(rdd->rtqueuebits)))
1743 if (rdd->queuebits && hpri < (pri = bsrl(rdd->queuebits)))
1745 if (rdd->idqueuebits && hpri < (pri = bsrl(rdd->idqueuebits)))
1748 if (rdd->uload - hpri < dd->uload + hpri)
1756 dfly_choose_queue_simple(dfly_pcpu_t dd, struct lwp *lp)
1764 * Fallback to the original heuristic, select random cpu,
1765 * first checking cpus not currently running a user thread.
1768 cpuid = (dfly_scancpu & 0xFFFF) % ncpus;
1769 mask = ~dfly_curprocmask & dfly_rdyprocmask & lp->lwp_cpumask &
1770 smp_active_mask & usched_global_cpumask;
1773 tmpmask = ~(CPUMASK(cpuid) - 1);
1775 cpuid = BSFCPUMASK(mask & tmpmask);
1777 cpuid = BSFCPUMASK(mask);
1778 rdd = &dfly_pcpu[cpuid];
1780 if ((rdd->upri & ~PPQMASK) >= (lp->lwp_priority & ~PPQMASK))
1782 mask &= ~CPUMASK(cpuid);
1786 * Then cpus which might have a currently running lp
1788 cpuid = (dfly_scancpu & 0xFFFF) % ncpus;
1789 mask = dfly_curprocmask & dfly_rdyprocmask &
1790 lp->lwp_cpumask & smp_active_mask & usched_global_cpumask;
1793 tmpmask = ~(CPUMASK(cpuid) - 1);
1795 cpuid = BSFCPUMASK(mask & tmpmask);
1797 cpuid = BSFCPUMASK(mask);
1798 rdd = &dfly_pcpu[cpuid];
1800 if ((rdd->upri & ~PPQMASK) > (lp->lwp_priority & ~PPQMASK))
1802 mask &= ~CPUMASK(cpuid);
1806 * If we cannot find a suitable cpu we reload from dfly_scancpu
1807 * and round-robin. Other cpus will pickup as they release their
1808 * current lwps or become ready.
1810 * Avoid a degenerate system lockup case if usched_global_cpumask
1811 * is set to 0 or otherwise does not cover lwp_cpumask.
1813 * We only kick the target helper thread in this case, we do not
1814 * set the user resched flag because
1816 cpuid = (dfly_scancpu & 0xFFFF) % ncpus;
1817 if ((CPUMASK(cpuid) & usched_global_cpumask) == 0)
1819 rdd = &dfly_pcpu[cpuid];
1826 dfly_need_user_resched_remote(void *dummy)
1828 globaldata_t gd = mycpu;
1829 dfly_pcpu_t dd = &dfly_pcpu[gd->gd_cpuid];
1832 * Flag reschedule needed
1834 need_user_resched();
1837 * If no user thread is currently running we need to kick the helper
1838 * on our cpu to recover. Otherwise the cpu will never schedule
1841 * We cannot schedule the process ourselves because this is an
1842 * IPI callback and we cannot acquire spinlocks in an IPI callback.
1844 * Call wakeup_mycpu to avoid sending IPIs to other CPUs
1846 if (dd->uschedcp == NULL && (dfly_rdyprocmask & gd->gd_cpumask)) {
1847 atomic_clear_cpumask(&dfly_rdyprocmask, gd->gd_cpumask);
1848 wakeup_mycpu(&dd->helper_thread);
1855 * dfly_remrunqueue_locked() removes a given process from the run queue
1856 * that it is on, clearing the queue busy bit if it becomes empty.
1858 * Note that user process scheduler is different from the LWKT schedule.
1859 * The user process scheduler only manages user processes but it uses LWKT
1860 * underneath, and a user process operating in the kernel will often be
1861 * 'released' from our management.
1863 * uload is NOT adjusted here. It is only adjusted if the lwkt_thread goes
1864 * to sleep or the lwp is moved to a different runq.
1867 dfly_remrunqueue_locked(dfly_pcpu_t rdd, struct lwp *lp)
1873 KKASSERT(rdd->runqcount >= 0);
1875 pri = lp->lwp_rqindex;
1877 switch(lp->lwp_rqtype) {
1878 case RTP_PRIO_NORMAL:
1879 q = &rdd->queues[pri];
1880 which = &rdd->queuebits;
1882 case RTP_PRIO_REALTIME:
1884 q = &rdd->rtqueues[pri];
1885 which = &rdd->rtqueuebits;
1888 q = &rdd->idqueues[pri];
1889 which = &rdd->idqueuebits;
1892 panic("remrunqueue: invalid rtprio type");
1895 KKASSERT(lp->lwp_mpflags & LWP_MP_ONRUNQ);
1896 atomic_clear_int(&lp->lwp_mpflags, LWP_MP_ONRUNQ);
1897 TAILQ_REMOVE(q, lp, lwp_procq);
1899 if (TAILQ_EMPTY(q)) {
1900 KASSERT((*which & (1 << pri)) != 0,
1901 ("remrunqueue: remove from empty queue"));
1902 *which &= ~(1 << pri);
1907 * dfly_setrunqueue_locked()
1909 * Add a process whos rqtype and rqindex had previously been calculated
1910 * onto the appropriate run queue. Determine if the addition requires
1911 * a reschedule on a cpu and return the cpuid or -1.
1913 * NOTE: Lower priorities are better priorities.
1915 * NOTE ON ULOAD: This variable specifies the aggregate load on a cpu, the
1916 * sum of the rough lwp_priority for all running and runnable
1917 * processes. Lower priority processes (higher lwp_priority
1918 * values) actually DO count as more load, not less, because
1919 * these are the programs which require the most care with
1920 * regards to cpu selection.
1923 dfly_setrunqueue_locked(dfly_pcpu_t rdd, struct lwp *lp)
1929 KKASSERT(lp->lwp_qcpu == rdd->cpuid);
1931 if ((lp->lwp_mpflags & LWP_MP_ULOAD) == 0) {
1932 atomic_set_int(&lp->lwp_mpflags, LWP_MP_ULOAD);
1933 atomic_add_int(&dfly_pcpu[lp->lwp_qcpu].uload, lp->lwp_uload);
1934 atomic_add_int(&dfly_pcpu[lp->lwp_qcpu].ucount, 1);
1935 atomic_add_int(&dfly_ucount, 1);
1938 pri = lp->lwp_rqindex;
1940 switch(lp->lwp_rqtype) {
1941 case RTP_PRIO_NORMAL:
1942 q = &rdd->queues[pri];
1943 which = &rdd->queuebits;
1945 case RTP_PRIO_REALTIME:
1947 q = &rdd->rtqueues[pri];
1948 which = &rdd->rtqueuebits;
1951 q = &rdd->idqueues[pri];
1952 which = &rdd->idqueuebits;
1955 panic("remrunqueue: invalid rtprio type");
1960 * Place us on the selected queue. Determine if we should be
1961 * placed at the head of the queue or at the end.
1963 * We are placed at the tail if our round-robin count has expired,
1964 * or is about to expire and the system thinks its a good place to
1965 * round-robin, or there is already a next thread on the queue
1966 * (it might be trying to pick up where it left off and we don't
1967 * want to interfere).
1969 KKASSERT((lp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
1970 atomic_set_int(&lp->lwp_mpflags, LWP_MP_ONRUNQ);
1973 if (lp->lwp_rrcount >= usched_dfly_rrinterval ||
1974 (lp->lwp_rrcount >= usched_dfly_rrinterval / 2 &&
1975 (lp->lwp_thread->td_mpflags & TDF_MP_BATCH_DEMARC)) ||
1978 atomic_clear_int(&lp->lwp_thread->td_mpflags,
1979 TDF_MP_BATCH_DEMARC);
1980 lp->lwp_rrcount = 0;
1981 TAILQ_INSERT_TAIL(q, lp, lwp_procq);
1984 lp->lwp_rrcount = 0;
1985 TAILQ_INSERT_HEAD(q, lp, lwp_procq);
1993 * For SMP systems a user scheduler helper thread is created for each
1994 * cpu and is used to allow one cpu to wakeup another for the purposes of
1995 * scheduling userland threads from setrunqueue().
1997 * UP systems do not need the helper since there is only one cpu.
1999 * We can't use the idle thread for this because we might block.
2000 * Additionally, doing things this way allows us to HLT idle cpus
2004 dfly_helper_thread(void *dummy)
2014 cpuid = gd->gd_cpuid; /* doesn't change */
2015 mask = gd->gd_cpumask; /* doesn't change */
2016 dd = &dfly_pcpu[cpuid];
2019 * Since we only want to be woken up only when no user processes
2020 * are scheduled on a cpu, run at an ultra low priority.
2022 lwkt_setpri_self(TDPRI_USER_SCHEDULER);
2024 tsleep(&dd->helper_thread, 0, "schslp", 0);
2028 * We use the LWKT deschedule-interlock trick to avoid racing
2029 * dfly_rdyprocmask. This means we cannot block through to the
2030 * manual lwkt_switch() call we make below.
2033 tsleep_interlock(&dd->helper_thread, 0);
2035 spin_lock(&dd->spin);
2037 atomic_set_cpumask(&dfly_rdyprocmask, mask);
2038 clear_user_resched(); /* This satisfied the reschedule request */
2040 dd->rrcount = 0; /* Reset the round-robin counter */
2043 if (dd->runqcount || dd->uschedcp != NULL) {
2045 * Threads are available. A thread may or may not be
2046 * currently scheduled. Get the best thread already queued
2049 nlp = dfly_chooseproc_locked(dd, dd, dd->uschedcp, 0);
2051 atomic_set_cpumask(&dfly_curprocmask, mask);
2052 dd->upri = nlp->lwp_priority;
2055 dd->rrcount = 0; /* reset round robin */
2057 spin_unlock(&dd->spin);
2058 lwkt_acquire(nlp->lwp_thread);
2059 lwkt_schedule(nlp->lwp_thread);
2062 * This situation should not occur because we had
2063 * at least one thread available.
2065 spin_unlock(&dd->spin);
2067 } else if (usched_dfly_features & 0x01) {
2069 * This cpu is devoid of runnable threads, steal a thread
2070 * from another cpu. Since we're stealing, might as well
2071 * load balance at the same time.
2073 * We choose the highest-loaded thread from the worst queue.
2075 * NOTE! This function only returns a non-NULL rdd when
2076 * another cpu's queue is obviously overloaded. We
2077 * do not want to perform the type of rebalancing
2078 * the schedclock does here because it would result
2079 * in insane process pulling when 'steady' state is
2080 * partially unbalanced (e.g. 6 runnables and only
2083 rdd = dfly_choose_worst_queue(dd);
2084 if (rdd && spin_trylock(&rdd->spin)) {
2085 nlp = dfly_chooseproc_locked(rdd, dd, NULL, 1);
2086 spin_unlock(&rdd->spin);
2091 atomic_set_cpumask(&dfly_curprocmask, mask);
2092 dd->upri = nlp->lwp_priority;
2095 dd->rrcount = 0; /* reset round robin */
2097 spin_unlock(&dd->spin);
2098 lwkt_acquire(nlp->lwp_thread);
2099 lwkt_schedule(nlp->lwp_thread);
2102 * Leave the thread on our run queue. Another
2103 * scheduler will try to pull it later.
2105 spin_unlock(&dd->spin);
2109 * devoid of runnable threads and not allowed to steal
2112 spin_unlock(&dd->spin);
2116 * We're descheduled unless someone scheduled us. Switch away.
2117 * Exiting the critical section will cause splz() to be called
2118 * for us if interrupts and such are pending.
2121 tsleep(&dd->helper_thread, PINTERLOCKED, "schslp", 0);
2127 sysctl_usched_dfly_stick_to_level(SYSCTL_HANDLER_ARGS)
2131 new_val = usched_dfly_stick_to_level;
2133 error = sysctl_handle_int(oidp, &new_val, 0, req);
2134 if (error != 0 || req->newptr == NULL)
2136 if (new_val > cpu_topology_levels_number - 1 || new_val < 0)
2138 usched_dfly_stick_to_level = new_val;
2144 * Setup our scheduler helpers. Note that curprocmask bit 0 has already
2145 * been cleared by rqinit() and we should not mess with it further.
2148 dfly_helper_thread_cpu_init(void)
2153 int smt_not_supported = 0;
2154 int cache_coherent_not_supported = 0;
2157 kprintf("Start scheduler helpers on cpus:\n");
2159 sysctl_ctx_init(&usched_dfly_sysctl_ctx);
2160 usched_dfly_sysctl_tree =
2161 SYSCTL_ADD_NODE(&usched_dfly_sysctl_ctx,
2162 SYSCTL_STATIC_CHILDREN(_kern), OID_AUTO,
2163 "usched_dfly", CTLFLAG_RD, 0, "");
2165 for (i = 0; i < ncpus; ++i) {
2166 dfly_pcpu_t dd = &dfly_pcpu[i];
2167 cpumask_t mask = CPUMASK(i);
2169 if ((mask & smp_active_mask) == 0)
2172 spin_init(&dd->spin);
2173 dd->cpunode = get_cpu_node_by_cpuid(i);
2175 dd->cpumask = CPUMASK(i);
2176 for (j = 0; j < NQS; j++) {
2177 TAILQ_INIT(&dd->queues[j]);
2178 TAILQ_INIT(&dd->rtqueues[j]);
2179 TAILQ_INIT(&dd->idqueues[j]);
2181 atomic_clear_cpumask(&dfly_curprocmask, 1);
2183 if (dd->cpunode == NULL) {
2184 smt_not_supported = 1;
2185 cache_coherent_not_supported = 1;
2187 kprintf ("\tcpu%d - WARNING: No CPU NODE "
2188 "found for cpu\n", i);
2190 switch (dd->cpunode->type) {
2193 kprintf ("\tcpu%d - HyperThreading "
2194 "available. Core siblings: ",
2198 smt_not_supported = 1;
2201 kprintf ("\tcpu%d - No HT available, "
2202 "multi-core/physical "
2203 "cpu. Physical siblings: ",
2207 smt_not_supported = 1;
2210 kprintf ("\tcpu%d - No HT available, "
2211 "single-core/physical cpu. "
2212 "Package Siblings: ",
2216 /* Let's go for safe defaults here */
2217 smt_not_supported = 1;
2218 cache_coherent_not_supported = 1;
2220 kprintf ("\tcpu%d - Unknown cpunode->"
2221 "type=%u. Siblings: ",
2223 (u_int)dd->cpunode->type);
2228 if (dd->cpunode->parent_node != NULL) {
2229 CPUSET_FOREACH(cpuid, dd->cpunode->parent_node->members)
2230 kprintf("cpu%d ", cpuid);
2233 kprintf(" no siblings\n");
2238 lwkt_create(dfly_helper_thread, NULL, NULL, &dd->helper_thread,
2239 0, i, "usched %d", i);
2242 * Allow user scheduling on the target cpu. cpu #0 has already
2243 * been enabled in rqinit().
2246 atomic_clear_cpumask(&dfly_curprocmask, mask);
2247 atomic_set_cpumask(&dfly_rdyprocmask, mask);
2248 dd->upri = PRIBASE_NULL;
2252 /* usched_dfly sysctl configurable parameters */
2254 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2255 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2256 OID_AUTO, "rrinterval", CTLFLAG_RW,
2257 &usched_dfly_rrinterval, 0, "");
2258 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2259 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2260 OID_AUTO, "decay", CTLFLAG_RW,
2261 &usched_dfly_decay, 0, "Extra decay when not running");
2263 /* Add enable/disable option for SMT scheduling if supported */
2264 if (smt_not_supported) {
2265 usched_dfly_smt = 0;
2266 SYSCTL_ADD_STRING(&usched_dfly_sysctl_ctx,
2267 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2268 OID_AUTO, "smt", CTLFLAG_RD,
2269 "NOT SUPPORTED", 0, "SMT NOT SUPPORTED");
2271 usched_dfly_smt = 1;
2272 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2273 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2274 OID_AUTO, "smt", CTLFLAG_RW,
2275 &usched_dfly_smt, 0, "Enable SMT scheduling");
2279 * Add enable/disable option for cache coherent scheduling
2282 if (cache_coherent_not_supported) {
2283 usched_dfly_cache_coherent = 0;
2284 SYSCTL_ADD_STRING(&usched_dfly_sysctl_ctx,
2285 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2286 OID_AUTO, "cache_coherent", CTLFLAG_RD,
2288 "Cache coherence NOT SUPPORTED");
2290 usched_dfly_cache_coherent = 1;
2291 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2292 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2293 OID_AUTO, "cache_coherent", CTLFLAG_RW,
2294 &usched_dfly_cache_coherent, 0,
2295 "Enable/Disable cache coherent scheduling");
2297 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2298 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2299 OID_AUTO, "weight1", CTLFLAG_RW,
2300 &usched_dfly_weight1, 200,
2301 "Weight selection for current cpu");
2303 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2304 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2305 OID_AUTO, "weight2", CTLFLAG_RW,
2306 &usched_dfly_weight2, 180,
2307 "Weight selection for wakefrom cpu");
2309 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2310 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2311 OID_AUTO, "weight3", CTLFLAG_RW,
2312 &usched_dfly_weight3, 40,
2313 "Weight selection for num threads on queue");
2315 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2316 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2317 OID_AUTO, "weight4", CTLFLAG_RW,
2318 &usched_dfly_weight4, 160,
2319 "Availability of other idle cpus");
2321 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2322 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2323 OID_AUTO, "fast_resched", CTLFLAG_RW,
2324 &usched_dfly_fast_resched, 0,
2325 "Availability of other idle cpus");
2327 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2328 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2329 OID_AUTO, "features", CTLFLAG_RW,
2330 &usched_dfly_features, 0x8F,
2331 "Allow pulls into empty queues");
2333 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2334 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2335 OID_AUTO, "swmask", CTLFLAG_RW,
2336 &usched_dfly_swmask, ~PPQMASK,
2337 "Queue mask to force thread switch");
2341 SYSCTL_ADD_PROC(&usched_dfly_sysctl_ctx,
2342 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2343 OID_AUTO, "stick_to_level",
2344 CTLTYPE_INT | CTLFLAG_RW,
2345 NULL, sizeof usched_dfly_stick_to_level,
2346 sysctl_usched_dfly_stick_to_level, "I",
2347 "Stick a process to this level. See sysctl"
2348 "paremter hw.cpu_topology.level_description");
2352 SYSINIT(uschedtd, SI_BOOT2_USCHED, SI_ORDER_SECOND,
2353 dfly_helper_thread_cpu_init, NULL)
2355 #else /* No SMP options - just add the configurable parameters to sysctl */
2358 sched_sysctl_tree_init(void)
2360 sysctl_ctx_init(&usched_dfly_sysctl_ctx);
2361 usched_dfly_sysctl_tree =
2362 SYSCTL_ADD_NODE(&usched_dfly_sysctl_ctx,
2363 SYSCTL_STATIC_CHILDREN(_kern), OID_AUTO,
2364 "usched_dfly", CTLFLAG_RD, 0, "");
2366 /* usched_dfly sysctl configurable parameters */
2367 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2368 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2369 OID_AUTO, "rrinterval", CTLFLAG_RW,
2370 &usched_dfly_rrinterval, 0, "");
2371 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2372 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2373 OID_AUTO, "decay", CTLFLAG_RW,
2374 &usched_dfly_decay, 0, "Extra decay when not running");
2376 SYSINIT(uschedtd, SI_BOOT2_USCHED, SI_ORDER_SECOND,
2377 sched_sysctl_tree_init, NULL)