2 * Copyright (c) 1999 Peter Wemm <peter@FreeBSD.org>
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * $DragonFly: src/sys/kern/usched_bsd4.c,v 1.26 2008/11/01 23:31:19 dillon Exp $
29 #include <sys/param.h>
30 #include <sys/systm.h>
31 #include <sys/kernel.h>
33 #include <sys/queue.h>
35 #include <sys/rtprio.h>
37 #include <sys/sysctl.h>
38 #include <sys/resourcevar.h>
39 #include <sys/spinlock.h>
40 #include <machine/cpu.h>
41 #include <machine/smp.h>
43 #include <sys/thread2.h>
44 #include <sys/spinlock2.h>
45 #include <sys/mplock2.h>
48 * Priorities. Note that with 32 run queues per scheduler each queue
49 * represents four priority levels.
53 #define PRIMASK (MAXPRI - 1)
54 #define PRIBASE_REALTIME 0
55 #define PRIBASE_NORMAL MAXPRI
56 #define PRIBASE_IDLE (MAXPRI * 2)
57 #define PRIBASE_THREAD (MAXPRI * 3)
58 #define PRIBASE_NULL (MAXPRI * 4)
60 #define NQS 32 /* 32 run queues. */
61 #define PPQ (MAXPRI / NQS) /* priorities per queue */
62 #define PPQMASK (PPQ - 1)
65 * NICEPPQ - number of nice units per priority queue
66 * ESTCPURAMP - number of scheduler ticks for estcpu to switch queues
68 * ESTCPUPPQ - number of estcpu units per priority queue
69 * ESTCPUMAX - number of estcpu units
70 * ESTCPUINCR - amount we have to increment p_estcpu per scheduling tick at
76 #define ESTCPUMAX (ESTCPUPPQ * NQS)
77 #define ESTCPUINCR (ESTCPUPPQ / ESTCPURAMP)
78 #define PRIO_RANGE (PRIO_MAX - PRIO_MIN + 1)
80 #define ESTCPULIM(v) min((v), ESTCPUMAX)
84 #define lwp_priority lwp_usdata.bsd4.priority
85 #define lwp_rqindex lwp_usdata.bsd4.rqindex
86 #define lwp_origcpu lwp_usdata.bsd4.origcpu
87 #define lwp_estcpu lwp_usdata.bsd4.estcpu
88 #define lwp_rqtype lwp_usdata.bsd4.rqtype
90 static void bsd4_acquire_curproc(struct lwp *lp);
91 static void bsd4_release_curproc(struct lwp *lp);
92 static void bsd4_select_curproc(globaldata_t gd);
93 static void bsd4_setrunqueue(struct lwp *lp);
94 static void bsd4_schedulerclock(struct lwp *lp, sysclock_t period,
96 static void bsd4_recalculate_estcpu(struct lwp *lp);
97 static void bsd4_resetpriority(struct lwp *lp);
98 static void bsd4_forking(struct lwp *plp, struct lwp *lp);
99 static void bsd4_exiting(struct lwp *plp, struct lwp *lp);
100 static void bsd4_yield(struct lwp *lp);
103 static void need_user_resched_remote(void *dummy);
105 static struct lwp *chooseproc_locked(struct lwp *chklp);
106 static void bsd4_remrunqueue_locked(struct lwp *lp);
107 static void bsd4_setrunqueue_locked(struct lwp *lp);
109 struct usched usched_bsd4 = {
111 "bsd4", "Original DragonFly Scheduler",
112 NULL, /* default registration */
113 NULL, /* default deregistration */
114 bsd4_acquire_curproc,
115 bsd4_release_curproc,
118 bsd4_recalculate_estcpu,
122 NULL, /* setcpumask not supported */
126 struct usched_bsd4_pcpu {
127 struct thread helper_thread;
130 struct lwp *uschedcp;
133 typedef struct usched_bsd4_pcpu *bsd4_pcpu_t;
136 * We have NQS (32) run queues per scheduling class. For the normal
137 * class, there are 128 priorities scaled onto these 32 queues. New
138 * processes are added to the last entry in each queue, and processes
139 * are selected for running by taking them from the head and maintaining
140 * a simple FIFO arrangement. Realtime and Idle priority processes have
141 * and explicit 0-31 priority which maps directly onto their class queue
142 * index. When a queue has something in it, the corresponding bit is
143 * set in the queuebits variable, allowing a single read to determine
144 * the state of all 32 queues and then a ffs() to find the first busy
147 static struct rq bsd4_queues[NQS];
148 static struct rq bsd4_rtqueues[NQS];
149 static struct rq bsd4_idqueues[NQS];
150 static u_int32_t bsd4_queuebits;
151 static u_int32_t bsd4_rtqueuebits;
152 static u_int32_t bsd4_idqueuebits;
153 static cpumask_t bsd4_curprocmask = -1; /* currently running a user process */
154 static cpumask_t bsd4_rdyprocmask; /* ready to accept a user process */
155 static int bsd4_runqcount;
157 static volatile int bsd4_scancpu;
159 static struct spinlock bsd4_spin;
160 static struct usched_bsd4_pcpu bsd4_pcpu[MAXCPU];
162 SYSCTL_INT(_debug, OID_AUTO, bsd4_runqcount, CTLFLAG_RD, &bsd4_runqcount, 0,
163 "Number of run queues");
165 static int usched_nonoptimal;
166 SYSCTL_INT(_debug, OID_AUTO, usched_nonoptimal, CTLFLAG_RW,
167 &usched_nonoptimal, 0, "acquire_curproc() was not optimal");
168 static int usched_optimal;
169 SYSCTL_INT(_debug, OID_AUTO, usched_optimal, CTLFLAG_RW,
170 &usched_optimal, 0, "acquire_curproc() was optimal");
172 static int usched_debug = -1;
173 SYSCTL_INT(_debug, OID_AUTO, scdebug, CTLFLAG_RW, &usched_debug, 0,
174 "Print debug information for this pid");
176 static int remote_resched_nonaffinity;
177 static int remote_resched_affinity;
178 static int choose_affinity;
179 SYSCTL_INT(_debug, OID_AUTO, remote_resched_nonaffinity, CTLFLAG_RD,
180 &remote_resched_nonaffinity, 0, "Number of remote rescheds");
181 SYSCTL_INT(_debug, OID_AUTO, remote_resched_affinity, CTLFLAG_RD,
182 &remote_resched_affinity, 0, "Number of remote rescheds");
183 SYSCTL_INT(_debug, OID_AUTO, choose_affinity, CTLFLAG_RD,
184 &choose_affinity, 0, "chooseproc() was smart");
187 static int usched_bsd4_rrinterval = (ESTCPUFREQ + 9) / 10;
188 SYSCTL_INT(_kern, OID_AUTO, usched_bsd4_rrinterval, CTLFLAG_RW,
189 &usched_bsd4_rrinterval, 0, "");
190 static int usched_bsd4_decay = ESTCPUINCR / 2;
191 SYSCTL_INT(_kern, OID_AUTO, usched_bsd4_decay, CTLFLAG_RW,
192 &usched_bsd4_decay, 0, "");
195 * Initialize the run queues at boot time.
202 spin_init(&bsd4_spin);
203 for (i = 0; i < NQS; i++) {
204 TAILQ_INIT(&bsd4_queues[i]);
205 TAILQ_INIT(&bsd4_rtqueues[i]);
206 TAILQ_INIT(&bsd4_idqueues[i]);
208 atomic_clear_int(&bsd4_curprocmask, 1);
210 SYSINIT(runqueue, SI_BOOT2_USCHED, SI_ORDER_FIRST, rqinit, NULL)
213 * BSD4_ACQUIRE_CURPROC
215 * This function is called when the kernel intends to return to userland.
216 * It is responsible for making the thread the current designated userland
217 * thread for this cpu, blocking if necessary.
219 * The kernel has already depressed our LWKT priority so we must not switch
220 * until we have either assigned or disposed of the thread.
222 * WARNING! THIS FUNCTION IS ALLOWED TO CAUSE THE CURRENT THREAD TO MIGRATE
223 * TO ANOTHER CPU! Because most of the kernel assumes that no migration will
224 * occur, this function is called only under very controlled circumstances.
229 bsd4_acquire_curproc(struct lwp *lp)
236 bsd4_recalculate_estcpu(lp);
239 * If a reschedule was requested give another thread the
242 if (user_resched_wanted()) {
243 clear_user_resched();
244 bsd4_release_curproc(lp);
248 * Loop until we are the current user thread
252 * Reload after a switch or setrunqueue/switch possibly
253 * moved us to another cpu.
255 clear_lwkt_resched();
257 dd = &bsd4_pcpu[gd->gd_cpuid];
260 * Become the currently scheduled user thread for this cpu
261 * if we can do so trivially.
263 * We can steal another thread's current thread designation
264 * on this cpu since if we are running that other thread
265 * must not be, so we can safely deschedule it.
267 if (dd->uschedcp == lp) {
268 dd->upri = lp->lwp_priority;
269 } else if (dd->uschedcp == NULL) {
270 atomic_set_int(&bsd4_curprocmask, gd->gd_cpumask);
272 dd->upri = lp->lwp_priority;
273 } else if (dd->upri > lp->lwp_priority) {
276 dd->upri = lp->lwp_priority;
277 lwkt_deschedule(olp->lwp_thread);
278 bsd4_setrunqueue(olp);
280 lwkt_deschedule(lp->lwp_thread);
281 bsd4_setrunqueue(lp);
286 * Other threads at our current user priority have already
287 * put in their bids, but we must run any kernel threads
288 * at higher priorities, and we could lose our bid to
289 * another thread trying to return to user mode in the
292 * If we lose our bid we will be descheduled and put on
293 * the run queue. When we are reactivated we will have
297 } while (dd->uschedcp != lp);
300 KKASSERT((lp->lwp_flag & LWP_ONRUNQ) == 0);
304 * BSD4_RELEASE_CURPROC
306 * This routine detaches the current thread from the userland scheduler,
307 * usually because the thread needs to run or block in the kernel (at
308 * kernel priority) for a while.
310 * This routine is also responsible for selecting a new thread to
311 * make the current thread.
313 * NOTE: This implementation differs from the dummy example in that
314 * bsd4_select_curproc() is able to select the current process, whereas
315 * dummy_select_curproc() is not able to select the current process.
316 * This means we have to NULL out uschedcp.
318 * Additionally, note that we may already be on a run queue if releasing
319 * via the lwkt_switch() in bsd4_setrunqueue().
321 * WARNING! The MP lock may be in an unsynchronized state due to the
322 * way get_mplock() works and the fact that this function may be called
323 * from a passive release during a lwkt_switch(). try_mplock() will deal
324 * with this for us but you should be aware that td_mpcount may not be
330 bsd4_release_curproc(struct lwp *lp)
332 globaldata_t gd = mycpu;
333 bsd4_pcpu_t dd = &bsd4_pcpu[gd->gd_cpuid];
335 if (dd->uschedcp == lp) {
337 KKASSERT((lp->lwp_flag & LWP_ONRUNQ) == 0);
338 dd->uschedcp = NULL; /* don't let lp be selected */
339 dd->upri = PRIBASE_NULL;
340 atomic_clear_int(&bsd4_curprocmask, gd->gd_cpumask);
341 bsd4_select_curproc(gd);
347 * BSD4_SELECT_CURPROC
349 * Select a new current process for this cpu and clear any pending user
350 * reschedule request. The cpu currently has no current process.
352 * This routine is also responsible for equal-priority round-robining,
353 * typically triggered from bsd4_schedulerclock(). In our dummy example
354 * all the 'user' threads are LWKT scheduled all at once and we just
355 * call lwkt_switch().
357 * The calling process is not on the queue and cannot be selected.
363 bsd4_select_curproc(globaldata_t gd)
365 bsd4_pcpu_t dd = &bsd4_pcpu[gd->gd_cpuid];
367 int cpuid = gd->gd_cpuid;
371 spin_lock(&bsd4_spin);
372 if ((nlp = chooseproc_locked(dd->uschedcp)) != NULL) {
373 atomic_set_int(&bsd4_curprocmask, 1 << cpuid);
374 dd->upri = nlp->lwp_priority;
376 spin_unlock(&bsd4_spin);
378 lwkt_acquire(nlp->lwp_thread);
380 lwkt_schedule(nlp->lwp_thread);
381 } else if (bsd4_runqcount && (bsd4_rdyprocmask & (1 << cpuid))) {
382 atomic_clear_int(&bsd4_rdyprocmask, 1 << cpuid);
383 spin_unlock(&bsd4_spin);
384 lwkt_schedule(&dd->helper_thread);
386 spin_unlock(&bsd4_spin);
394 * Place the specified lwp on the user scheduler's run queue. This routine
395 * must be called with the thread descheduled. The lwp must be runnable.
397 * The thread may be the current thread as a special case.
402 bsd4_setrunqueue(struct lwp *lp)
413 * First validate the process state relative to the current cpu.
414 * We don't need the spinlock for this, just a critical section.
415 * We are in control of the process.
418 KASSERT(lp->lwp_stat == LSRUN, ("setrunqueue: lwp not LSRUN"));
419 KASSERT((lp->lwp_flag & LWP_ONRUNQ) == 0,
420 ("lwp %d/%d already on runq! flag %08x/%08x", lp->lwp_proc->p_pid,
421 lp->lwp_tid, lp->lwp_proc->p_flag, lp->lwp_flag));
422 KKASSERT((lp->lwp_thread->td_flags & TDF_RUNQ) == 0);
425 * Note: gd and dd are relative to the target thread's last cpu,
426 * NOT our current cpu.
428 gd = lp->lwp_thread->td_gd;
429 dd = &bsd4_pcpu[gd->gd_cpuid];
432 * This process is not supposed to be scheduled anywhere or assigned
433 * as the current process anywhere. Assert the condition.
435 KKASSERT(dd->uschedcp != lp);
439 * If we are not SMP we do not have a scheduler helper to kick
440 * and must directly activate the process if none are scheduled.
442 * This is really only an issue when bootstrapping init since
443 * the caller in all other cases will be a user process, and
444 * even if released (dd->uschedcp == NULL), that process will
445 * kickstart the scheduler when it returns to user mode from
448 if (dd->uschedcp == NULL) {
449 atomic_set_int(&bsd4_curprocmask, gd->gd_cpumask);
451 dd->upri = lp->lwp_priority;
452 lwkt_schedule(lp->lwp_thread);
460 * XXX fixme. Could be part of a remrunqueue/setrunqueue
461 * operation when the priority is recalculated, so TDF_MIGRATING
462 * may already be set.
464 if ((lp->lwp_thread->td_flags & TDF_MIGRATING) == 0)
465 lwkt_giveaway(lp->lwp_thread);
469 * We lose control of lp the moment we release the spinlock after
470 * having placed lp on the queue. i.e. another cpu could pick it
471 * up and it could exit, or its priority could be further adjusted,
472 * or something like that.
474 spin_lock(&bsd4_spin);
475 bsd4_setrunqueue_locked(lp);
479 * Kick the scheduler helper on one of the other cpu's
480 * and request a reschedule if appropriate.
482 cpuid = (bsd4_scancpu & 0xFFFF) % ncpus;
484 mask = ~bsd4_curprocmask & bsd4_rdyprocmask &
485 lp->lwp_cpumask & smp_active_mask;
486 spin_unlock(&bsd4_spin);
489 tmpmask = ~((1 << cpuid) - 1);
491 cpuid = bsfl(mask & tmpmask);
494 gd = globaldata_find(cpuid);
495 dd = &bsd4_pcpu[cpuid];
497 if ((dd->upri & ~PPQMASK) > (lp->lwp_priority & ~PPQMASK)) {
499 need_user_resched_remote(NULL);
501 lwkt_send_ipiq(gd, need_user_resched_remote, NULL);
504 mask &= ~(1 << cpuid);
508 * Request a reschedule if appropriate.
510 spin_unlock(&bsd4_spin);
511 if ((dd->upri & ~PPQMASK) > (lp->lwp_priority & ~PPQMASK)) {
519 * This routine is called from a systimer IPI. It MUST be MP-safe and
520 * the BGL IS NOT HELD ON ENTRY. This routine is called at ESTCPUFREQ on
527 bsd4_schedulerclock(struct lwp *lp, sysclock_t period, sysclock_t cpstamp)
529 globaldata_t gd = mycpu;
530 bsd4_pcpu_t dd = &bsd4_pcpu[gd->gd_cpuid];
533 * Do we need to round-robin? We round-robin 10 times a second.
534 * This should only occur for cpu-bound batch processes.
536 if (++dd->rrcount >= usched_bsd4_rrinterval) {
542 * As the process accumulates cpu time p_estcpu is bumped and may
543 * push the process into another scheduling queue. It typically
544 * takes 4 ticks to bump the queue.
546 lp->lwp_estcpu = ESTCPULIM(lp->lwp_estcpu + ESTCPUINCR);
549 * Reducing p_origcpu over time causes more of our estcpu to be
550 * returned to the parent when we exit. This is a small tweak
551 * for the batch detection heuristic.
557 * Spinlocks also hold a critical section so there should not be
560 KKASSERT(gd->gd_spinlocks_wr == 0);
562 bsd4_resetpriority(lp);
565 * if we can't call bsd4_resetpriority for some reason we must call
566 * need user_resched().
573 * Called from acquire and from kern_synch's one-second timer (one of the
574 * callout helper threads) with a critical section held.
576 * Decay p_estcpu based on the number of ticks we haven't been running
577 * and our p_nice. As the load increases each process observes a larger
578 * number of idle ticks (because other processes are running in them).
579 * This observation leads to a larger correction which tends to make the
580 * system more 'batchy'.
582 * Note that no recalculation occurs for a process which sleeps and wakes
583 * up in the same tick. That is, a system doing thousands of context
584 * switches per second will still only do serious estcpu calculations
585 * ESTCPUFREQ times per second.
591 bsd4_recalculate_estcpu(struct lwp *lp)
593 globaldata_t gd = mycpu;
601 * We have to subtract periodic to get the last schedclock
602 * timeout time, otherwise we would get the upcoming timeout.
603 * Keep in mind that a process can migrate between cpus and
604 * while the scheduler clock should be very close, boundary
605 * conditions could lead to a small negative delta.
607 cpbase = gd->gd_schedclock.time - gd->gd_schedclock.periodic;
609 if (lp->lwp_slptime > 1) {
611 * Too much time has passed, do a coarse correction.
613 lp->lwp_estcpu = lp->lwp_estcpu >> 1;
614 bsd4_resetpriority(lp);
615 lp->lwp_cpbase = cpbase;
617 } else if (lp->lwp_cpbase != cpbase) {
619 * Adjust estcpu if we are in a different tick. Don't waste
620 * time if we are in the same tick.
622 * First calculate the number of ticks in the measurement
623 * interval. The nticks calculation can wind up 0 due to
624 * a bug in the handling of lwp_slptime (as yet not found),
625 * so make sure we do not get a divide by 0 panic.
627 nticks = (cpbase - lp->lwp_cpbase) / gd->gd_schedclock.periodic;
630 updatepcpu(lp, lp->lwp_cpticks, nticks);
632 if ((nleft = nticks - lp->lwp_cpticks) < 0)
634 if (usched_debug == lp->lwp_proc->p_pid) {
635 kprintf("pid %d tid %d estcpu %d cpticks %d nticks %d nleft %d",
636 lp->lwp_proc->p_pid, lp->lwp_tid, lp->lwp_estcpu,
637 lp->lwp_cpticks, nticks, nleft);
641 * Calculate a decay value based on ticks remaining scaled
642 * down by the instantanious load and p_nice.
644 if ((loadfac = bsd4_runqcount) < 2)
646 ndecay = nleft * usched_bsd4_decay * 2 *
647 (PRIO_MAX * 2 - lp->lwp_proc->p_nice) / (loadfac * PRIO_MAX * 2);
650 * Adjust p_estcpu. Handle a border case where batch jobs
651 * can get stalled long enough to decay to zero when they
654 if (lp->lwp_estcpu > ndecay * 2)
655 lp->lwp_estcpu -= ndecay;
657 lp->lwp_estcpu >>= 1;
659 if (usched_debug == lp->lwp_proc->p_pid)
660 kprintf(" ndecay %d estcpu %d\n", ndecay, lp->lwp_estcpu);
661 bsd4_resetpriority(lp);
662 lp->lwp_cpbase = cpbase;
668 * Compute the priority of a process when running in user mode.
669 * Arrange to reschedule if the resulting priority is better
670 * than that of the current process.
672 * This routine may be called with any process.
674 * This routine is called by fork1() for initial setup with the process
675 * of the run queue, and also may be called normally with the process on or
681 bsd4_resetpriority(struct lwp *lp)
689 * Calculate the new priority and queue type
692 spin_lock(&bsd4_spin);
694 newrqtype = lp->lwp_rtprio.type;
697 case RTP_PRIO_REALTIME:
699 newpriority = PRIBASE_REALTIME +
700 (lp->lwp_rtprio.prio & PRIMASK);
702 case RTP_PRIO_NORMAL:
703 newpriority = (lp->lwp_proc->p_nice - PRIO_MIN) * PPQ / NICEPPQ;
704 newpriority += lp->lwp_estcpu * PPQ / ESTCPUPPQ;
705 newpriority = newpriority * MAXPRI / (PRIO_RANGE * PPQ /
706 NICEPPQ + ESTCPUMAX * PPQ / ESTCPUPPQ);
707 newpriority = PRIBASE_NORMAL + (newpriority & PRIMASK);
710 newpriority = PRIBASE_IDLE + (lp->lwp_rtprio.prio & PRIMASK);
712 case RTP_PRIO_THREAD:
713 newpriority = PRIBASE_THREAD + (lp->lwp_rtprio.prio & PRIMASK);
716 panic("Bad RTP_PRIO %d", newrqtype);
721 * The newpriority incorporates the queue type so do a simple masked
722 * check to determine if the process has moved to another queue. If
723 * it has, and it is currently on a run queue, then move it.
725 if ((lp->lwp_priority ^ newpriority) & ~PPQMASK) {
726 lp->lwp_priority = newpriority;
727 if (lp->lwp_flag & LWP_ONRUNQ) {
728 bsd4_remrunqueue_locked(lp);
729 lp->lwp_rqtype = newrqtype;
730 lp->lwp_rqindex = (newpriority & PRIMASK) / PPQ;
731 bsd4_setrunqueue_locked(lp);
732 reschedcpu = lp->lwp_thread->td_gd->gd_cpuid;
734 lp->lwp_rqtype = newrqtype;
735 lp->lwp_rqindex = (newpriority & PRIMASK) / PPQ;
739 lp->lwp_priority = newpriority;
742 spin_unlock(&bsd4_spin);
745 * Determine if we need to reschedule the target cpu. This only
746 * occurs if the LWP is already on a scheduler queue, which means
747 * that idle cpu notification has already occured. At most we
748 * need only issue a need_user_resched() on the appropriate cpu.
750 * The LWP may be owned by a CPU different from the current one,
751 * in which case dd->uschedcp may be modified without an MP lock
752 * or a spinlock held. The worst that happens is that the code
753 * below causes a spurious need_user_resched() on the target CPU
754 * and dd->pri to be wrong for a short period of time, both of
755 * which are harmless.
757 if (reschedcpu >= 0) {
758 dd = &bsd4_pcpu[reschedcpu];
759 if ((dd->upri & ~PRIMASK) > (lp->lwp_priority & ~PRIMASK)) {
760 dd->upri = lp->lwp_priority;
762 if (reschedcpu == mycpu->gd_cpuid) {
765 lwkt_send_ipiq(lp->lwp_thread->td_gd,
766 need_user_resched_remote, NULL);
781 bsd4_yield(struct lwp *lp)
784 /* FUTURE (or something similar) */
785 switch(lp->lwp_rqtype) {
786 case RTP_PRIO_NORMAL:
787 lp->lwp_estcpu = ESTCPULIM(lp->lwp_estcpu + ESTCPUINCR);
797 * Called from fork1() when a new child process is being created.
799 * Give the child process an initial estcpu that is more batch then
800 * its parent and dock the parent for the fork (but do not
801 * reschedule the parent). This comprises the main part of our batch
802 * detection heuristic for both parallel forking and sequential execs.
804 * Interactive processes will decay the boosted estcpu quickly while batch
805 * processes will tend to compound it.
806 * XXX lwp should be "spawning" instead of "forking"
811 bsd4_forking(struct lwp *plp, struct lwp *lp)
813 lp->lwp_estcpu = ESTCPULIM(plp->lwp_estcpu + ESTCPUPPQ);
814 lp->lwp_origcpu = lp->lwp_estcpu;
815 plp->lwp_estcpu = ESTCPULIM(plp->lwp_estcpu + ESTCPUPPQ);
819 * Called when the parent reaps a child. Propogate cpu use by the child
820 * back to the parent.
825 bsd4_exiting(struct lwp *plp, struct lwp *lp)
829 if (plp->lwp_proc->p_pid != 1) {
830 delta = lp->lwp_estcpu - lp->lwp_origcpu;
832 plp->lwp_estcpu = ESTCPULIM(plp->lwp_estcpu + delta);
838 * chooseproc() is called when a cpu needs a user process to LWKT schedule,
839 * it selects a user process and returns it. If chklp is non-NULL and chklp
840 * has a better or equal priority then the process that would otherwise be
841 * chosen, NULL is returned.
843 * Until we fix the RUNQ code the chklp test has to be strict or we may
844 * bounce between processes trying to acquire the current process designation.
846 * MPSAFE - must be called with bsd4_spin exclusive held. The spinlock is
847 * left intact through the entire routine.
851 chooseproc_locked(struct lwp *chklp)
855 u_int32_t *which, *which2;
862 rtqbits = bsd4_rtqueuebits;
863 tsqbits = bsd4_queuebits;
864 idqbits = bsd4_idqueuebits;
865 cpumask = mycpu->gd_cpumask;
872 q = &bsd4_rtqueues[pri];
873 which = &bsd4_rtqueuebits;
875 } else if (tsqbits) {
877 q = &bsd4_queues[pri];
878 which = &bsd4_queuebits;
880 } else if (idqbits) {
882 q = &bsd4_idqueues[pri];
883 which = &bsd4_idqueuebits;
889 KASSERT(lp, ("chooseproc: no lwp on busy queue"));
892 while ((lp->lwp_cpumask & cpumask) == 0) {
893 lp = TAILQ_NEXT(lp, lwp_procq);
895 *which2 &= ~(1 << pri);
902 * If the passed lwp <chklp> is reasonably close to the selected
903 * lwp <lp>, return NULL (indicating that <chklp> should be kept).
905 * Note that we must error on the side of <chklp> to avoid bouncing
906 * between threads in the acquire code.
909 if (chklp->lwp_priority < lp->lwp_priority + PPQ)
915 * If the chosen lwp does not reside on this cpu spend a few
916 * cycles looking for a better candidate at the same priority level.
917 * This is a fallback check, setrunqueue() tries to wakeup the
918 * correct cpu and is our front-line affinity.
920 if (lp->lwp_thread->td_gd != mycpu &&
921 (chklp = TAILQ_NEXT(lp, lwp_procq)) != NULL
923 if (chklp->lwp_thread->td_gd == mycpu) {
930 TAILQ_REMOVE(q, lp, lwp_procq);
933 *which &= ~(1 << pri);
934 KASSERT((lp->lwp_flag & LWP_ONRUNQ) != 0, ("not on runq6!"));
935 lp->lwp_flag &= ~LWP_ONRUNQ;
942 * Called via an ipi message to reschedule on another cpu. If no
943 * user thread is active on the target cpu we wake the scheduler
944 * helper thread up to help schedule one.
950 need_user_resched_remote(void *dummy)
952 globaldata_t gd = mycpu;
953 bsd4_pcpu_t dd = &bsd4_pcpu[gd->gd_cpuid];
955 if (dd->uschedcp == NULL && (bsd4_rdyprocmask & gd->gd_cpumask)) {
956 atomic_clear_int(&bsd4_rdyprocmask, gd->gd_cpumask);
957 lwkt_schedule(&dd->helper_thread);
966 * bsd4_remrunqueue_locked() removes a given process from the run queue
967 * that it is on, clearing the queue busy bit if it becomes empty.
969 * Note that user process scheduler is different from the LWKT schedule.
970 * The user process scheduler only manages user processes but it uses LWKT
971 * underneath, and a user process operating in the kernel will often be
972 * 'released' from our management.
974 * MPSAFE - bsd4_spin must be held exclusively on call
977 bsd4_remrunqueue_locked(struct lwp *lp)
983 KKASSERT(lp->lwp_flag & LWP_ONRUNQ);
984 lp->lwp_flag &= ~LWP_ONRUNQ;
986 KKASSERT(bsd4_runqcount >= 0);
988 pri = lp->lwp_rqindex;
989 switch(lp->lwp_rqtype) {
990 case RTP_PRIO_NORMAL:
991 q = &bsd4_queues[pri];
992 which = &bsd4_queuebits;
994 case RTP_PRIO_REALTIME:
996 q = &bsd4_rtqueues[pri];
997 which = &bsd4_rtqueuebits;
1000 q = &bsd4_idqueues[pri];
1001 which = &bsd4_idqueuebits;
1004 panic("remrunqueue: invalid rtprio type");
1007 TAILQ_REMOVE(q, lp, lwp_procq);
1008 if (TAILQ_EMPTY(q)) {
1009 KASSERT((*which & (1 << pri)) != 0,
1010 ("remrunqueue: remove from empty queue"));
1011 *which &= ~(1 << pri);
1016 * bsd4_setrunqueue_locked()
1018 * Add a process whos rqtype and rqindex had previously been calculated
1019 * onto the appropriate run queue. Determine if the addition requires
1020 * a reschedule on a cpu and return the cpuid or -1.
1022 * NOTE: Lower priorities are better priorities.
1024 * MPSAFE - bsd4_spin must be held exclusively on call
1027 bsd4_setrunqueue_locked(struct lwp *lp)
1033 KKASSERT((lp->lwp_flag & LWP_ONRUNQ) == 0);
1034 lp->lwp_flag |= LWP_ONRUNQ;
1037 pri = lp->lwp_rqindex;
1039 switch(lp->lwp_rqtype) {
1040 case RTP_PRIO_NORMAL:
1041 q = &bsd4_queues[pri];
1042 which = &bsd4_queuebits;
1044 case RTP_PRIO_REALTIME:
1046 q = &bsd4_rtqueues[pri];
1047 which = &bsd4_rtqueuebits;
1050 q = &bsd4_idqueues[pri];
1051 which = &bsd4_idqueuebits;
1054 panic("remrunqueue: invalid rtprio type");
1059 * Add to the correct queue and set the appropriate bit. If no
1060 * lower priority (i.e. better) processes are in the queue then
1061 * we want a reschedule, calculate the best cpu for the job.
1063 * Always run reschedules on the LWPs original cpu.
1065 TAILQ_INSERT_TAIL(q, lp, lwp_procq);
1072 * For SMP systems a user scheduler helper thread is created for each
1073 * cpu and is used to allow one cpu to wakeup another for the purposes of
1074 * scheduling userland threads from setrunqueue().
1076 * UP systems do not need the helper since there is only one cpu.
1078 * We can't use the idle thread for this because we might block.
1079 * Additionally, doing things this way allows us to HLT idle cpus
1085 sched_thread(void *dummy)
1098 cpuid = gd->gd_cpuid; /* doesn't change */
1099 cpumask = gd->gd_cpumask; /* doesn't change */
1100 dd = &bsd4_pcpu[cpuid];
1103 * Since we are woken up only when no user processes are scheduled
1104 * on a cpu, we can run at an ultra low priority.
1106 lwkt_setpri_self(TDPRI_USER_SCHEDULER);
1110 * We use the LWKT deschedule-interlock trick to avoid racing
1111 * bsd4_rdyprocmask. This means we cannot block through to the
1112 * manual lwkt_switch() call we make below.
1115 lwkt_deschedule_self(gd->gd_curthread);
1116 spin_lock(&bsd4_spin);
1117 atomic_set_int(&bsd4_rdyprocmask, cpumask);
1119 clear_user_resched(); /* This satisfied the reschedule request */
1120 dd->rrcount = 0; /* Reset the round-robin counter */
1122 if ((bsd4_curprocmask & cpumask) == 0) {
1124 * No thread is currently scheduled.
1126 KKASSERT(dd->uschedcp == NULL);
1127 if ((nlp = chooseproc_locked(NULL)) != NULL) {
1128 atomic_set_int(&bsd4_curprocmask, cpumask);
1129 dd->upri = nlp->lwp_priority;
1131 spin_unlock(&bsd4_spin);
1132 lwkt_acquire(nlp->lwp_thread);
1133 lwkt_schedule(nlp->lwp_thread);
1135 spin_unlock(&bsd4_spin);
1139 * Disabled for now, this can create an infinite loop.
1141 } else if (bsd4_runqcount) {
1143 * Someone scheduled us but raced. In order to not lose
1144 * track of the fact that there may be a LWP ready to go,
1145 * forward the request to another cpu if available.
1147 * Rotate through cpus starting with cpuid + 1. Since cpuid
1148 * is already masked out by gd_other_cpus, just use ~cpumask.
1150 tmpmask = bsd4_rdyprocmask & mycpu->gd_other_cpus &
1153 if (tmpmask & ~(cpumask - 1))
1154 tmpid = bsfl(tmpmask & ~(cpumask - 1));
1156 tmpid = bsfl(tmpmask);
1157 bsd4_scancpu = tmpid;
1158 atomic_clear_int(&bsd4_rdyprocmask, 1 << tmpid);
1159 spin_unlock_wr(&bsd4_spin);
1160 lwkt_schedule(&bsd4_pcpu[tmpid].helper_thread);
1162 spin_unlock_wr(&bsd4_spin);
1167 * The runq is empty.
1169 spin_unlock(&bsd4_spin);
1177 * Setup our scheduler helpers. Note that curprocmask bit 0 has already
1178 * been cleared by rqinit() and we should not mess with it further.
1181 sched_thread_cpu_init(void)
1186 kprintf("start scheduler helpers on cpus:");
1188 for (i = 0; i < ncpus; ++i) {
1189 bsd4_pcpu_t dd = &bsd4_pcpu[i];
1190 cpumask_t mask = 1 << i;
1192 if ((mask & smp_active_mask) == 0)
1198 lwkt_create(sched_thread, NULL, NULL, &dd->helper_thread,
1199 TDF_STOPREQ, i, "usched %d", i);
1202 * Allow user scheduling on the target cpu. cpu #0 has already
1203 * been enabled in rqinit().
1206 atomic_clear_int(&bsd4_curprocmask, mask);
1207 atomic_set_int(&bsd4_rdyprocmask, mask);
1208 dd->upri = PRIBASE_NULL;
1213 SYSINIT(uschedtd, SI_BOOT2_USCHED, SI_ORDER_SECOND,
1214 sched_thread_cpu_init, NULL)