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;
122 typedef struct usched_dfly_pcpu *dfly_pcpu_t;
124 static void dfly_acquire_curproc(struct lwp *lp);
125 static void dfly_release_curproc(struct lwp *lp);
126 static void dfly_select_curproc(globaldata_t gd);
127 static void dfly_setrunqueue(struct lwp *lp);
128 static void dfly_setrunqueue_dd(dfly_pcpu_t rdd, struct lwp *lp);
129 static void dfly_schedulerclock(struct lwp *lp, sysclock_t period,
131 static void dfly_recalculate_estcpu(struct lwp *lp);
132 static void dfly_resetpriority(struct lwp *lp);
133 static void dfly_forking(struct lwp *plp, struct lwp *lp);
134 static void dfly_exiting(struct lwp *lp, struct proc *);
135 static void dfly_uload_update(struct lwp *lp);
136 static void dfly_yield(struct lwp *lp);
137 static void dfly_changeqcpu_locked(struct lwp *lp,
138 dfly_pcpu_t dd, dfly_pcpu_t rdd);
139 static dfly_pcpu_t dfly_choose_best_queue(struct lwp *lp);
140 static dfly_pcpu_t dfly_choose_worst_queue(dfly_pcpu_t dd);
141 static dfly_pcpu_t dfly_choose_queue_simple(dfly_pcpu_t dd, struct lwp *lp);
142 static void dfly_need_user_resched_remote(void *dummy);
143 static struct lwp *dfly_chooseproc_locked(dfly_pcpu_t rdd, dfly_pcpu_t dd,
144 struct lwp *chklp, int worst);
145 static void dfly_remrunqueue_locked(dfly_pcpu_t dd, struct lwp *lp);
146 static void dfly_setrunqueue_locked(dfly_pcpu_t dd, struct lwp *lp);
147 static void dfly_changedcpu(struct lwp *lp);
149 struct usched usched_dfly = {
151 "dfly", "Original DragonFly Scheduler",
152 NULL, /* default registration */
153 NULL, /* default deregistration */
154 dfly_acquire_curproc,
155 dfly_release_curproc,
158 dfly_recalculate_estcpu,
163 NULL, /* setcpumask not supported */
169 * We have NQS (32) run queues per scheduling class. For the normal
170 * class, there are 128 priorities scaled onto these 32 queues. New
171 * processes are added to the last entry in each queue, and processes
172 * are selected for running by taking them from the head and maintaining
173 * a simple FIFO arrangement. Realtime and Idle priority processes have
174 * and explicit 0-31 priority which maps directly onto their class queue
175 * index. When a queue has something in it, the corresponding bit is
176 * set in the queuebits variable, allowing a single read to determine
177 * the state of all 32 queues and then a ffs() to find the first busy
180 static cpumask_t dfly_curprocmask = -1; /* currently running a user process */
181 static cpumask_t dfly_rdyprocmask; /* ready to accept a user process */
182 static volatile int dfly_scancpu;
183 static volatile int dfly_ucount; /* total running on whole system */
184 static struct usched_dfly_pcpu dfly_pcpu[MAXCPU];
185 static struct sysctl_ctx_list usched_dfly_sysctl_ctx;
186 static struct sysctl_oid *usched_dfly_sysctl_tree;
188 /* Debug info exposed through debug.* sysctl */
190 static int usched_dfly_debug = -1;
191 SYSCTL_INT(_debug, OID_AUTO, dfly_scdebug, CTLFLAG_RW,
192 &usched_dfly_debug, 0,
193 "Print debug information for this pid");
195 static int usched_dfly_pid_debug = -1;
196 SYSCTL_INT(_debug, OID_AUTO, dfly_pid_debug, CTLFLAG_RW,
197 &usched_dfly_pid_debug, 0,
198 "Print KTR debug information for this pid");
200 static int usched_dfly_chooser = 0;
201 SYSCTL_INT(_debug, OID_AUTO, dfly_chooser, CTLFLAG_RW,
202 &usched_dfly_chooser, 0,
203 "Print KTR debug information for this pid");
206 * Tunning usched_dfly - configurable through kern.usched_dfly.
208 * weight1 - Tries to keep threads on their current cpu. If you
209 * make this value too large the scheduler will not be
210 * able to load-balance large loads.
212 * weight2 - If non-zero, detects thread pairs undergoing synchronous
213 * communications and tries to move them closer together.
214 * Behavior is adjusted by bit 4 of features (0x10).
216 * WARNING! Weight2 is a ridiculously sensitive parameter,
217 * a small value is recommended.
219 * weight3 - Weighting based on the number of recently runnable threads
220 * on the userland scheduling queue (ignoring their loads).
221 * A nominal value here prevents high-priority (low-load)
222 * threads from accumulating on one cpu core when other
223 * cores are available.
225 * This value should be left fairly small relative to weight1
228 * weight4 - Weighting based on other cpu queues being available
229 * or running processes with higher lwp_priority's.
231 * This allows a thread to migrate to another nearby cpu if it
232 * is unable to run on the current cpu based on the other cpu
233 * being idle or running a lower priority (higher lwp_priority)
234 * thread. This value should be large enough to override weight1
236 * features - These flags can be set or cleared to enable or disable various
239 * 0x01 Enable idle-cpu pulling (default)
240 * 0x02 Enable proactive pushing (default)
241 * 0x04 Enable rebalancing rover (default)
242 * 0x08 Enable more proactive pushing (default)
243 * 0x10 (flip weight2 limit on same cpu) (default)
244 * 0x20 choose best cpu for forked process
245 * 0x40 choose current cpu for forked process
246 * 0x80 choose random cpu for forked process (default)
248 static int usched_dfly_smt = 0;
249 static int usched_dfly_cache_coherent = 0;
250 static int usched_dfly_weight1 = 200; /* keep thread on current cpu */
251 static int usched_dfly_weight2 = 180; /* synchronous peer's current cpu */
252 static int usched_dfly_weight3 = 40; /* number of threads on queue */
253 static int usched_dfly_weight4 = 160; /* availability of idle cores */
254 static int usched_dfly_features = 0x8F; /* allow pulls */
255 static int usched_dfly_fast_resched = 0;/* delta priority / resched */
256 static int usched_dfly_swmask = ~PPQMASK; /* allow pulls */
257 static int usched_dfly_rrinterval = (ESTCPUFREQ + 9) / 10;
258 static int usched_dfly_decay = 8;
260 /* KTR debug printings */
262 KTR_INFO_MASTER(usched);
264 #if !defined(KTR_USCHED_DFLY)
265 #define KTR_USCHED_DFLY KTR_ALL
268 KTR_INFO(KTR_USCHED_DFLY, usched, chooseproc, 0,
269 "USCHED_DFLY(chooseproc: pid %d, old_cpuid %d, curr_cpuid %d)",
270 pid_t pid, int old_cpuid, int curr);
273 * This function is called when the kernel intends to return to userland.
274 * It is responsible for making the thread the current designated userland
275 * thread for this cpu, blocking if necessary.
277 * The kernel will not depress our LWKT priority until after we return,
278 * in case we have to shove over to another cpu.
280 * We must determine our thread's disposition before we switch away. This
281 * is very sensitive code.
283 * WARNING! THIS FUNCTION IS ALLOWED TO CAUSE THE CURRENT THREAD TO MIGRATE
284 * TO ANOTHER CPU! Because most of the kernel assumes that no migration will
285 * occur, this function is called only under very controlled circumstances.
288 dfly_acquire_curproc(struct lwp *lp)
297 * Make sure we aren't sitting on a tsleep queue.
300 crit_enter_quick(td);
301 if (td->td_flags & TDF_TSLEEPQ)
303 dfly_recalculate_estcpu(lp);
306 dd = &dfly_pcpu[gd->gd_cpuid];
309 * Process any pending interrupts/ipi's, then handle reschedule
310 * requests. dfly_release_curproc() will try to assign a new
311 * uschedcp that isn't us and otherwise NULL it out.
314 if ((td->td_mpflags & TDF_MP_BATCH_DEMARC) &&
315 lp->lwp_rrcount >= usched_dfly_rrinterval / 2) {
319 if (user_resched_wanted()) {
320 if (dd->uschedcp == lp)
322 clear_user_resched();
323 dfly_release_curproc(lp);
327 * Loop until we are the current user thread.
329 * NOTE: dd spinlock not held at top of loop.
331 if (dd->uschedcp == lp)
334 while (dd->uschedcp != lp) {
337 spin_lock(&dd->spin);
340 * We are not or are no longer the current lwp and a forced
341 * reschedule was requested. Figure out the best cpu to
342 * run on (our current cpu will be given significant weight).
344 * (if a reschedule was not requested we want to move this
345 * step after the uschedcp tests).
348 (usched_dfly_features & 0x08) &&
349 (rdd = dfly_choose_best_queue(lp)) != dd) {
350 dfly_changeqcpu_locked(lp, dd, rdd);
351 spin_unlock(&dd->spin);
352 lwkt_deschedule(lp->lwp_thread);
353 dfly_setrunqueue_dd(rdd, lp);
356 dd = &dfly_pcpu[gd->gd_cpuid];
361 * Either no reschedule was requested or the best queue was
362 * dd, and no current process has been selected. We can
363 * trivially become the current lwp on the current cpu.
365 if (dd->uschedcp == NULL) {
366 atomic_set_cpumask(&dfly_curprocmask, gd->gd_cpumask);
368 dd->upri = lp->lwp_priority;
369 KKASSERT(lp->lwp_qcpu == dd->cpuid);
370 spin_unlock(&dd->spin);
375 * Can we steal the current designated user thread?
377 * If we do the other thread will stall when it tries to
378 * return to userland, possibly rescheduling elsewhere.
380 * It is important to do a masked test to avoid the edge
381 * case where two near-equal-priority threads are constantly
382 * interrupting each other.
384 * In the exact match case another thread has already gained
385 * uschedcp and lowered its priority, if we steal it the
386 * other thread will stay stuck on the LWKT runq and not
387 * push to another cpu. So don't steal on equal-priority even
388 * though it might appear to be more beneficial due to not
389 * having to switch back to the other thread's context.
391 * usched_dfly_fast_resched requires that two threads be
392 * significantly far apart in priority in order to interrupt.
394 * If better but not sufficiently far apart, the current
395 * uschedcp will be interrupted at the next scheduler clock.
398 (dd->upri & ~PPQMASK) >
399 (lp->lwp_priority & ~PPQMASK) + usched_dfly_fast_resched) {
401 dd->upri = lp->lwp_priority;
402 KKASSERT(lp->lwp_qcpu == dd->cpuid);
403 spin_unlock(&dd->spin);
407 * We are not the current lwp, figure out the best cpu
408 * to run on (our current cpu will be given significant
409 * weight). Loop on cpu change.
411 if ((usched_dfly_features & 0x02) &&
412 force_resched == 0 &&
413 (rdd = dfly_choose_best_queue(lp)) != dd) {
414 dfly_changeqcpu_locked(lp, dd, rdd);
415 spin_unlock(&dd->spin);
416 lwkt_deschedule(lp->lwp_thread);
417 dfly_setrunqueue_dd(rdd, lp);
420 dd = &dfly_pcpu[gd->gd_cpuid];
425 * We cannot become the current lwp, place the lp on the
426 * run-queue of this or another cpu and deschedule ourselves.
428 * When we are reactivated we will have another chance.
430 * Reload after a switch or setrunqueue/switch possibly
431 * moved us to another cpu.
433 spin_unlock(&dd->spin);
434 lwkt_deschedule(lp->lwp_thread);
435 dfly_setrunqueue_dd(dd, lp);
438 dd = &dfly_pcpu[gd->gd_cpuid];
442 * Make sure upri is synchronized, then yield to LWKT threads as
443 * needed before returning. This could result in another reschedule.
448 KKASSERT((lp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
452 * DFLY_RELEASE_CURPROC
454 * This routine detaches the current thread from the userland scheduler,
455 * usually because the thread needs to run or block in the kernel (at
456 * kernel priority) for a while.
458 * This routine is also responsible for selecting a new thread to
459 * make the current thread.
461 * NOTE: This implementation differs from the dummy example in that
462 * dfly_select_curproc() is able to select the current process, whereas
463 * dummy_select_curproc() is not able to select the current process.
464 * This means we have to NULL out uschedcp.
466 * Additionally, note that we may already be on a run queue if releasing
467 * via the lwkt_switch() in dfly_setrunqueue().
470 dfly_release_curproc(struct lwp *lp)
472 globaldata_t gd = mycpu;
473 dfly_pcpu_t dd = &dfly_pcpu[gd->gd_cpuid];
476 * Make sure td_wakefromcpu is defaulted. This will be overwritten
479 if (dd->uschedcp == lp) {
480 KKASSERT((lp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
481 spin_lock(&dd->spin);
482 if (dd->uschedcp == lp) {
483 dd->uschedcp = NULL; /* don't let lp be selected */
484 dd->upri = PRIBASE_NULL;
485 atomic_clear_cpumask(&dfly_curprocmask, gd->gd_cpumask);
486 spin_unlock(&dd->spin);
487 dfly_select_curproc(gd);
489 spin_unlock(&dd->spin);
495 * DFLY_SELECT_CURPROC
497 * Select a new current process for this cpu and clear any pending user
498 * reschedule request. The cpu currently has no current process.
500 * This routine is also responsible for equal-priority round-robining,
501 * typically triggered from dfly_schedulerclock(). In our dummy example
502 * all the 'user' threads are LWKT scheduled all at once and we just
503 * call lwkt_switch().
505 * The calling process is not on the queue and cannot be selected.
509 dfly_select_curproc(globaldata_t gd)
511 dfly_pcpu_t dd = &dfly_pcpu[gd->gd_cpuid];
513 int cpuid = gd->gd_cpuid;
517 spin_lock(&dd->spin);
518 nlp = dfly_chooseproc_locked(dd, dd, dd->uschedcp, 0);
521 atomic_set_cpumask(&dfly_curprocmask, CPUMASK(cpuid));
522 dd->upri = nlp->lwp_priority;
525 dd->rrcount = 0; /* reset round robin */
527 spin_unlock(&dd->spin);
528 lwkt_acquire(nlp->lwp_thread);
529 lwkt_schedule(nlp->lwp_thread);
531 spin_unlock(&dd->spin);
537 * Place the specified lwp on the user scheduler's run queue. This routine
538 * must be called with the thread descheduled. The lwp must be runnable.
539 * It must not be possible for anyone else to explicitly schedule this thread.
541 * The thread may be the current thread as a special case.
544 dfly_setrunqueue(struct lwp *lp)
550 * First validate the process LWKT state.
552 KASSERT(lp->lwp_stat == LSRUN, ("setrunqueue: lwp not LSRUN"));
553 KASSERT((lp->lwp_mpflags & LWP_MP_ONRUNQ) == 0,
554 ("lwp %d/%d already on runq! flag %08x/%08x", lp->lwp_proc->p_pid,
555 lp->lwp_tid, lp->lwp_proc->p_flags, lp->lwp_flags));
556 KKASSERT((lp->lwp_thread->td_flags & TDF_RUNQ) == 0);
559 * NOTE: dd/rdd do not necessarily represent the current cpu.
560 * Instead they may represent the cpu the thread was last
561 * scheduled on or inherited by its parent.
563 dd = &dfly_pcpu[lp->lwp_qcpu];
567 * This process is not supposed to be scheduled anywhere or assigned
568 * as the current process anywhere. Assert the condition.
570 KKASSERT(rdd->uschedcp != lp);
573 * Ok, we have to setrunqueue some target cpu and request a reschedule
576 * We have to choose the best target cpu. It might not be the current
577 * target even if the current cpu has no running user thread (for
578 * example, because the current cpu might be a hyperthread and its
579 * sibling has a thread assigned).
581 * If we just forked it is most optimal to run the child on the same
582 * cpu just in case the parent decides to wait for it (thus getting
583 * off that cpu). As long as there is nothing else runnable on the
584 * cpu, that is. If we did this unconditionally a parent forking
585 * multiple children before waiting (e.g. make -j N) leaves other
586 * cpus idle that could be working.
588 if (lp->lwp_forked) {
590 if (usched_dfly_features & 0x20)
591 rdd = dfly_choose_best_queue(lp);
592 else if (usched_dfly_features & 0x40)
593 rdd = &dfly_pcpu[lp->lwp_qcpu];
594 else if (usched_dfly_features & 0x80)
595 rdd = dfly_choose_queue_simple(rdd, lp);
596 else if (dfly_pcpu[lp->lwp_qcpu].runqcount)
597 rdd = dfly_choose_best_queue(lp);
599 rdd = &dfly_pcpu[lp->lwp_qcpu];
601 rdd = dfly_choose_best_queue(lp);
602 /* rdd = &dfly_pcpu[lp->lwp_qcpu]; */
604 if (lp->lwp_qcpu != rdd->cpuid) {
605 spin_lock(&dd->spin);
606 dfly_changeqcpu_locked(lp, dd, rdd);
607 spin_unlock(&dd->spin);
609 dfly_setrunqueue_dd(rdd, lp);
613 * Change qcpu to rdd->cpuid. The dd the lp is CURRENTLY on must be
614 * spin-locked on-call. rdd does not have to be.
617 dfly_changeqcpu_locked(struct lwp *lp, dfly_pcpu_t dd, dfly_pcpu_t rdd)
619 if (lp->lwp_qcpu != rdd->cpuid) {
620 if (lp->lwp_mpflags & LWP_MP_ULOAD) {
621 atomic_clear_int(&lp->lwp_mpflags, LWP_MP_ULOAD);
622 atomic_add_int(&dd->uload, -lp->lwp_uload);
623 atomic_add_int(&dd->ucount, -1);
624 atomic_add_int(&dfly_ucount, -1);
626 lp->lwp_qcpu = rdd->cpuid;
631 * Place lp on rdd's runqueue. Nothing is locked on call. This function
632 * also performs all necessary ancillary notification actions.
635 dfly_setrunqueue_dd(dfly_pcpu_t rdd, struct lwp *lp)
640 * We might be moving the lp to another cpu's run queue, and once
641 * on the runqueue (even if it is our cpu's), another cpu can rip
644 * TDF_MIGRATING might already be set if this is part of a
645 * remrunqueue+setrunqueue sequence.
647 if ((lp->lwp_thread->td_flags & TDF_MIGRATING) == 0)
648 lwkt_giveaway(lp->lwp_thread);
650 rgd = globaldata_find(rdd->cpuid);
653 * We lose control of the lp the moment we release the spinlock
654 * after having placed it on the queue. i.e. another cpu could pick
655 * it up, or it could exit, or its priority could be further
656 * adjusted, or something like that.
658 * WARNING! rdd can point to a foreign cpu!
660 spin_lock(&rdd->spin);
661 dfly_setrunqueue_locked(rdd, lp);
664 * Potentially interrupt the currently-running thread
666 if ((rdd->upri & ~PPQMASK) <= (lp->lwp_priority & ~PPQMASK)) {
668 * Currently running thread is better or same, do not
671 spin_unlock(&rdd->spin);
672 } else if ((rdd->upri & ~PPQMASK) <= (lp->lwp_priority & ~PPQMASK) +
673 usched_dfly_fast_resched) {
675 * Currently running thread is not better, but not so bad
676 * that we need to interrupt it. Let it run for one more
680 rdd->uschedcp->lwp_rrcount < usched_dfly_rrinterval) {
681 rdd->uschedcp->lwp_rrcount = usched_dfly_rrinterval - 1;
683 spin_unlock(&rdd->spin);
684 } else if (rgd == mycpu) {
686 * We should interrupt the currently running thread, which
687 * is on the current cpu.
689 spin_unlock(&rdd->spin);
690 if (rdd->uschedcp == NULL) {
691 wakeup_mycpu(&rdd->helper_thread); /* XXX */
698 * We should interrupt the currently running thread, which
699 * is on a different cpu.
701 spin_unlock(&rdd->spin);
702 lwkt_send_ipiq(rgd, dfly_need_user_resched_remote, NULL);
707 * This routine is called from a systimer IPI. It MUST be MP-safe and
708 * the BGL IS NOT HELD ON ENTRY. This routine is called at ESTCPUFREQ on
713 dfly_schedulerclock(struct lwp *lp, sysclock_t period, sysclock_t cpstamp)
715 globaldata_t gd = mycpu;
716 dfly_pcpu_t dd = &dfly_pcpu[gd->gd_cpuid];
719 * Spinlocks also hold a critical section so there should not be
722 KKASSERT(gd->gd_spinlocks == 0);
728 * Do we need to round-robin? We round-robin 10 times a second.
729 * This should only occur for cpu-bound batch processes.
731 if (++lp->lwp_rrcount >= usched_dfly_rrinterval) {
732 lp->lwp_thread->td_wakefromcpu = -1;
737 * Adjust estcpu upward using a real time equivalent calculation,
738 * and recalculate lp's priority.
740 lp->lwp_estcpu = ESTCPULIM(lp->lwp_estcpu + ESTCPUMAX / ESTCPUFREQ + 1);
741 dfly_resetpriority(lp);
744 * Rebalance two cpus every 8 ticks, pulling the worst thread
745 * from the worst cpu's queue into a rotating cpu number.
747 * This mechanic is needed because the push algorithms can
748 * steady-state in an non-optimal configuration. We need to mix it
749 * up a little, even if it means breaking up a paired thread, so
750 * the push algorithms can rebalance the degenerate conditions.
751 * This portion of the algorithm exists to ensure stability at the
752 * selected weightings.
754 * Because we might be breaking up optimal conditions we do not want
755 * to execute this too quickly, hence we only rebalance approximately
756 * ~7-8 times per second. The push's, on the otherhand, are capable
757 * moving threads to other cpus at a much higher rate.
759 * We choose the most heavily loaded thread from the worst queue
760 * in order to ensure that multiple heavy-weight threads on the same
761 * queue get broken up, and also because these threads are the most
762 * likely to be able to remain in place. Hopefully then any pairings,
763 * if applicable, migrate to where these threads are.
765 if ((usched_dfly_features & 0x04) &&
766 ((u_int)sched_ticks & 7) == 0 &&
767 (u_int)sched_ticks / 8 % ncpus == gd->gd_cpuid) {
774 rdd = dfly_choose_worst_queue(dd);
776 spin_lock(&dd->spin);
777 if (spin_trylock(&rdd->spin)) {
778 nlp = dfly_chooseproc_locked(rdd, dd, NULL, 1);
779 spin_unlock(&rdd->spin);
781 spin_unlock(&dd->spin);
783 spin_unlock(&dd->spin);
789 /* dd->spin held if nlp != NULL */
792 * Either schedule it or add it to our queue.
795 (nlp->lwp_priority & ~PPQMASK) < (dd->upri & ~PPQMASK)) {
796 atomic_set_cpumask(&dfly_curprocmask, dd->cpumask);
797 dd->upri = nlp->lwp_priority;
800 dd->rrcount = 0; /* reset round robin */
802 spin_unlock(&dd->spin);
803 lwkt_acquire(nlp->lwp_thread);
804 lwkt_schedule(nlp->lwp_thread);
806 dfly_setrunqueue_locked(dd, nlp);
807 spin_unlock(&dd->spin);
813 * Called from acquire and from kern_synch's one-second timer (one of the
814 * callout helper threads) with a critical section held.
816 * Adjust p_estcpu based on our single-cpu load, p_nice, and compensate for
817 * overall system load.
819 * Note that no recalculation occurs for a process which sleeps and wakes
820 * up in the same tick. That is, a system doing thousands of context
821 * switches per second will still only do serious estcpu calculations
822 * ESTCPUFREQ times per second.
826 dfly_recalculate_estcpu(struct lwp *lp)
828 globaldata_t gd = mycpu;
836 * We have to subtract periodic to get the last schedclock
837 * timeout time, otherwise we would get the upcoming timeout.
838 * Keep in mind that a process can migrate between cpus and
839 * while the scheduler clock should be very close, boundary
840 * conditions could lead to a small negative delta.
842 cpbase = gd->gd_schedclock.time - gd->gd_schedclock.periodic;
844 if (lp->lwp_slptime > 1) {
846 * Too much time has passed, do a coarse correction.
848 lp->lwp_estcpu = lp->lwp_estcpu >> 1;
849 dfly_resetpriority(lp);
850 lp->lwp_cpbase = cpbase;
853 } else if (lp->lwp_cpbase != cpbase) {
855 * Adjust estcpu if we are in a different tick. Don't waste
856 * time if we are in the same tick.
858 * First calculate the number of ticks in the measurement
859 * interval. The ttlticks calculation can wind up 0 due to
860 * a bug in the handling of lwp_slptime (as yet not found),
861 * so make sure we do not get a divide by 0 panic.
863 ttlticks = (cpbase - lp->lwp_cpbase) /
864 gd->gd_schedclock.periodic;
865 if ((ssysclock_t)ttlticks < 0) {
867 lp->lwp_cpbase = cpbase;
871 updatepcpu(lp, lp->lwp_cpticks, ttlticks);
874 * Calculate the percentage of one cpu being used then
875 * compensate for any system load in excess of ncpus.
877 * For example, if we have 8 cores and 16 running cpu-bound
878 * processes then all things being equal each process will
879 * get 50% of one cpu. We need to pump this value back
880 * up to 100% so the estcpu calculation properly adjusts
881 * the process's dynamic priority.
883 * estcpu is scaled by ESTCPUMAX, pctcpu is scaled by FSCALE.
885 estcpu = (lp->lwp_pctcpu * ESTCPUMAX) >> FSHIFT;
886 ucount = dfly_ucount;
887 if (ucount > ncpus) {
888 estcpu += estcpu * (ucount - ncpus) / ncpus;
891 if (usched_dfly_debug == lp->lwp_proc->p_pid) {
892 kprintf("pid %d lwp %p estcpu %3d %3d cp %d/%d",
893 lp->lwp_proc->p_pid, lp,
894 estcpu, lp->lwp_estcpu,
895 lp->lwp_cpticks, ttlticks);
899 * Adjust lp->lwp_esetcpu. The decay factor determines how
900 * quickly lwp_estcpu collapses to its realtime calculation.
901 * A slower collapse gives us a more accurate number over
902 * the long term but can create problems with bursty threads
903 * or threads which become cpu hogs.
905 * To solve this problem, newly started lwps and lwps which
906 * are restarting after having been asleep for a while are
907 * given a much, much faster decay in order to quickly
908 * detect whether they become cpu-bound.
910 * NOTE: p_nice is accounted for in dfly_resetpriority(),
911 * and not here, but we must still ensure that a
912 * cpu-bound nice -20 process does not completely
913 * override a cpu-bound nice +20 process.
915 * NOTE: We must use ESTCPULIM() here to deal with any
918 decay_factor = usched_dfly_decay;
919 if (decay_factor < 1)
921 if (decay_factor > 1024)
924 if (lp->lwp_estfast < usched_dfly_decay) {
926 lp->lwp_estcpu = ESTCPULIM(
927 (lp->lwp_estcpu * lp->lwp_estfast + estcpu) /
928 (lp->lwp_estfast + 1));
930 lp->lwp_estcpu = ESTCPULIM(
931 (lp->lwp_estcpu * decay_factor + estcpu) /
935 if (usched_dfly_debug == lp->lwp_proc->p_pid)
936 kprintf(" finalestcpu %d\n", lp->lwp_estcpu);
937 dfly_resetpriority(lp);
938 lp->lwp_cpbase += ttlticks * gd->gd_schedclock.periodic;
944 * Compute the priority of a process when running in user mode.
945 * Arrange to reschedule if the resulting priority is better
946 * than that of the current process.
948 * This routine may be called with any process.
950 * This routine is called by fork1() for initial setup with the process
951 * of the run queue, and also may be called normally with the process on or
955 dfly_resetpriority(struct lwp *lp)
968 * Lock the scheduler (lp) belongs to. This can be on a different
969 * cpu. Handle races. This loop breaks out with the appropriate
975 rdd = &dfly_pcpu[rcpu];
976 spin_lock(&rdd->spin);
977 if (rcpu == lp->lwp_qcpu)
979 spin_unlock(&rdd->spin);
983 * Calculate the new priority and queue type
985 newrqtype = lp->lwp_rtprio.type;
988 case RTP_PRIO_REALTIME:
990 newpriority = PRIBASE_REALTIME +
991 (lp->lwp_rtprio.prio & PRIMASK);
993 case RTP_PRIO_NORMAL:
997 estcpu = lp->lwp_estcpu;
1000 * p_nice piece Adds (0-40) * 2 0-80
1001 * estcpu Adds 16384 * 4 / 512 0-128
1003 newpriority = (lp->lwp_proc->p_nice - PRIO_MIN) * PPQ / NICEPPQ;
1004 newpriority += estcpu * PPQ / ESTCPUPPQ;
1005 newpriority = newpriority * MAXPRI / (PRIO_RANGE * PPQ /
1006 NICEPPQ + ESTCPUMAX * PPQ / ESTCPUPPQ);
1007 newpriority = PRIBASE_NORMAL + (newpriority & PRIMASK);
1010 newpriority = PRIBASE_IDLE + (lp->lwp_rtprio.prio & PRIMASK);
1012 case RTP_PRIO_THREAD:
1013 newpriority = PRIBASE_THREAD + (lp->lwp_rtprio.prio & PRIMASK);
1016 panic("Bad RTP_PRIO %d", newrqtype);
1021 * The LWKT scheduler doesn't dive usched structures, give it a hint
1022 * on the relative priority of user threads running in the kernel.
1023 * The LWKT scheduler will always ensure that a user thread running
1024 * in the kernel will get cpu some time, regardless of its upri,
1025 * but can decide not to instantly switch from one kernel or user
1026 * mode user thread to a kernel-mode user thread when it has a less
1027 * desireable user priority.
1029 * td_upri has normal sense (higher values are more desireable), so
1032 lp->lwp_thread->td_upri = -(newpriority & usched_dfly_swmask);
1035 * The newpriority incorporates the queue type so do a simple masked
1036 * check to determine if the process has moved to another queue. If
1037 * it has, and it is currently on a run queue, then move it.
1039 * Since uload is ~PPQMASK masked, no modifications are necessary if
1040 * we end up in the same run queue.
1042 if ((lp->lwp_priority ^ newpriority) & ~PPQMASK) {
1043 if (lp->lwp_mpflags & LWP_MP_ONRUNQ) {
1044 dfly_remrunqueue_locked(rdd, lp);
1045 lp->lwp_priority = newpriority;
1046 lp->lwp_rqtype = newrqtype;
1047 lp->lwp_rqindex = (newpriority & PRIMASK) / PPQ;
1048 dfly_setrunqueue_locked(rdd, lp);
1051 lp->lwp_priority = newpriority;
1052 lp->lwp_rqtype = newrqtype;
1053 lp->lwp_rqindex = (newpriority & PRIMASK) / PPQ;
1058 * In the same PPQ, uload cannot change.
1060 lp->lwp_priority = newpriority;
1066 * Adjust effective load.
1068 * Calculate load then scale up or down geometrically based on p_nice.
1069 * Processes niced up (positive) are less important, and processes
1070 * niced downard (negative) are more important. The higher the uload,
1071 * the more important the thread.
1073 /* 0-511, 0-100% cpu */
1074 delta_uload = lp->lwp_estcpu / NQS;
1075 delta_uload -= delta_uload * lp->lwp_proc->p_nice / (PRIO_MAX + 1);
1078 delta_uload -= lp->lwp_uload;
1079 lp->lwp_uload += delta_uload;
1080 if (lp->lwp_mpflags & LWP_MP_ULOAD)
1081 atomic_add_int(&dfly_pcpu[lp->lwp_qcpu].uload, delta_uload);
1084 * Determine if we need to reschedule the target cpu. This only
1085 * occurs if the LWP is already on a scheduler queue, which means
1086 * that idle cpu notification has already occured. At most we
1087 * need only issue a need_user_resched() on the appropriate cpu.
1089 * The LWP may be owned by a CPU different from the current one,
1090 * in which case dd->uschedcp may be modified without an MP lock
1091 * or a spinlock held. The worst that happens is that the code
1092 * below causes a spurious need_user_resched() on the target CPU
1093 * and dd->pri to be wrong for a short period of time, both of
1094 * which are harmless.
1096 * If checkpri is 0 we are adjusting the priority of the current
1097 * process, possibly higher (less desireable), so ignore the upri
1098 * check which will fail in that case.
1101 if ((dfly_rdyprocmask & CPUMASK(rcpu)) &&
1103 (rdd->upri & ~PRIMASK) >
1104 (lp->lwp_priority & ~PRIMASK))) {
1105 if (rcpu == mycpu->gd_cpuid) {
1106 spin_unlock(&rdd->spin);
1107 need_user_resched();
1109 spin_unlock(&rdd->spin);
1110 lwkt_send_ipiq(globaldata_find(rcpu),
1111 dfly_need_user_resched_remote,
1115 spin_unlock(&rdd->spin);
1118 spin_unlock(&rdd->spin);
1125 dfly_yield(struct lwp *lp)
1128 /* FUTURE (or something similar) */
1129 switch(lp->lwp_rqtype) {
1130 case RTP_PRIO_NORMAL:
1131 lp->lwp_estcpu = ESTCPULIM(lp->lwp_estcpu + ESTCPUINCR);
1137 need_user_resched();
1141 * Thread was forcefully migrated to another cpu. Normally forced migrations
1142 * are used for iterations and the kernel returns to the original cpu before
1143 * returning and this is not needed. However, if the kernel migrates a
1144 * thread to another cpu and wants to leave it there, it has to call this
1147 * Note that the lwkt_migratecpu() function also released the thread, so
1148 * we don't have to worry about that.
1152 dfly_changedcpu(struct lwp *lp)
1154 dfly_pcpu_t dd = &dfly_pcpu[lp->lwp_qcpu];
1155 dfly_pcpu_t rdd = &dfly_pcpu[mycpu->gd_cpuid];
1158 spin_lock(&dd->spin);
1159 dfly_changeqcpu_locked(lp, dd, rdd);
1160 spin_unlock(&dd->spin);
1165 * Called from fork1() when a new child process is being created.
1167 * Give the child process an initial estcpu that is more batch then
1168 * its parent and dock the parent for the fork (but do not
1169 * reschedule the parent).
1173 * XXX lwp should be "spawning" instead of "forking"
1176 dfly_forking(struct lwp *plp, struct lwp *lp)
1179 * Put the child 4 queue slots (out of 32) higher than the parent
1180 * (less desireable than the parent).
1182 lp->lwp_estcpu = ESTCPULIM(plp->lwp_estcpu + ESTCPUPPQ * 4);
1184 lp->lwp_estfast = 0;
1187 * Dock the parent a cost for the fork, protecting us from fork
1188 * bombs. If the parent is forking quickly make the child more
1191 plp->lwp_estcpu = ESTCPULIM(plp->lwp_estcpu + ESTCPUPPQ / 16);
1195 * Called when a lwp is being removed from this scheduler, typically
1196 * during lwp_exit(). We have to clean out any ULOAD accounting before
1197 * we can let the lp go. The dd->spin lock is not needed for uload
1200 * Scheduler dequeueing has already occurred, no further action in that
1204 dfly_exiting(struct lwp *lp, struct proc *child_proc)
1206 dfly_pcpu_t dd = &dfly_pcpu[lp->lwp_qcpu];
1208 if (lp->lwp_mpflags & LWP_MP_ULOAD) {
1209 atomic_clear_int(&lp->lwp_mpflags, LWP_MP_ULOAD);
1210 atomic_add_int(&dd->uload, -lp->lwp_uload);
1211 atomic_add_int(&dd->ucount, -1);
1212 atomic_add_int(&dfly_ucount, -1);
1217 * This function cannot block in any way, but spinlocks are ok.
1219 * Update the uload based on the state of the thread (whether it is going
1220 * to sleep or running again). The uload is meant to be a longer-term
1221 * load and not an instantanious load.
1224 dfly_uload_update(struct lwp *lp)
1226 dfly_pcpu_t dd = &dfly_pcpu[lp->lwp_qcpu];
1228 if (lp->lwp_thread->td_flags & TDF_RUNQ) {
1229 if ((lp->lwp_mpflags & LWP_MP_ULOAD) == 0) {
1230 spin_lock(&dd->spin);
1231 if ((lp->lwp_mpflags & LWP_MP_ULOAD) == 0) {
1232 atomic_set_int(&lp->lwp_mpflags,
1234 atomic_add_int(&dd->uload, lp->lwp_uload);
1235 atomic_add_int(&dd->ucount, 1);
1236 atomic_add_int(&dfly_ucount, 1);
1238 spin_unlock(&dd->spin);
1240 } else if (lp->lwp_slptime > 0) {
1241 if (lp->lwp_mpflags & LWP_MP_ULOAD) {
1242 spin_lock(&dd->spin);
1243 if (lp->lwp_mpflags & LWP_MP_ULOAD) {
1244 atomic_clear_int(&lp->lwp_mpflags,
1246 atomic_add_int(&dd->uload, -lp->lwp_uload);
1247 atomic_add_int(&dd->ucount, -1);
1248 atomic_add_int(&dfly_ucount, -1);
1250 spin_unlock(&dd->spin);
1256 * chooseproc() is called when a cpu needs a user process to LWKT schedule,
1257 * it selects a user process and returns it. If chklp is non-NULL and chklp
1258 * has a better or equal priority then the process that would otherwise be
1259 * chosen, NULL is returned.
1261 * Until we fix the RUNQ code the chklp test has to be strict or we may
1262 * bounce between processes trying to acquire the current process designation.
1264 * Must be called with rdd->spin locked. The spinlock is left intact through
1265 * the entire routine. dd->spin does not have to be locked.
1267 * If worst is non-zero this function finds the worst thread instead of the
1268 * best thread (used by the schedulerclock-based rover).
1272 dfly_chooseproc_locked(dfly_pcpu_t rdd, dfly_pcpu_t dd,
1273 struct lwp *chklp, int worst)
1283 rtqbits = rdd->rtqueuebits;
1284 tsqbits = rdd->queuebits;
1285 idqbits = rdd->idqueuebits;
1289 pri = bsrl(idqbits);
1290 q = &rdd->idqueues[pri];
1291 which = &rdd->idqueuebits;
1292 } else if (tsqbits) {
1293 pri = bsrl(tsqbits);
1294 q = &rdd->queues[pri];
1295 which = &rdd->queuebits;
1296 } else if (rtqbits) {
1297 pri = bsrl(rtqbits);
1298 q = &rdd->rtqueues[pri];
1299 which = &rdd->rtqueuebits;
1303 lp = TAILQ_LAST(q, rq);
1306 pri = bsfl(rtqbits);
1307 q = &rdd->rtqueues[pri];
1308 which = &rdd->rtqueuebits;
1309 } else if (tsqbits) {
1310 pri = bsfl(tsqbits);
1311 q = &rdd->queues[pri];
1312 which = &rdd->queuebits;
1313 } else if (idqbits) {
1314 pri = bsfl(idqbits);
1315 q = &rdd->idqueues[pri];
1316 which = &rdd->idqueuebits;
1320 lp = TAILQ_FIRST(q);
1322 KASSERT(lp, ("chooseproc: no lwp on busy queue"));
1325 * If the passed lwp <chklp> is reasonably close to the selected
1326 * lwp <lp>, return NULL (indicating that <chklp> should be kept).
1328 * Note that we must error on the side of <chklp> to avoid bouncing
1329 * between threads in the acquire code.
1332 if (chklp->lwp_priority < lp->lwp_priority + PPQ)
1336 KTR_COND_LOG(usched_chooseproc,
1337 lp->lwp_proc->p_pid == usched_dfly_pid_debug,
1338 lp->lwp_proc->p_pid,
1339 lp->lwp_thread->td_gd->gd_cpuid,
1342 KASSERT((lp->lwp_mpflags & LWP_MP_ONRUNQ) != 0, ("not on runq6!"));
1343 atomic_clear_int(&lp->lwp_mpflags, LWP_MP_ONRUNQ);
1344 TAILQ_REMOVE(q, lp, lwp_procq);
1347 *which &= ~(1 << pri);
1350 * If we are choosing a process from rdd with the intent to
1351 * move it to dd, lwp_qcpu must be adjusted while rdd's spinlock
1355 if (lp->lwp_mpflags & LWP_MP_ULOAD) {
1356 atomic_add_int(&rdd->uload, -lp->lwp_uload);
1357 atomic_add_int(&rdd->ucount, -1);
1358 atomic_add_int(&dfly_ucount, -1);
1360 lp->lwp_qcpu = dd->cpuid;
1361 atomic_add_int(&dd->uload, lp->lwp_uload);
1362 atomic_add_int(&dd->ucount, 1);
1363 atomic_add_int(&dfly_ucount, 1);
1364 atomic_set_int(&lp->lwp_mpflags, LWP_MP_ULOAD);
1370 * USED TO PUSH RUNNABLE LWPS TO THE LEAST LOADED CPU.
1372 * Choose a cpu node to schedule lp on, hopefully nearby its current
1375 * We give the current node a modest advantage for obvious reasons.
1377 * We also give the node the thread was woken up FROM a slight advantage
1378 * in order to try to schedule paired threads which synchronize/block waiting
1379 * for each other fairly close to each other. Similarly in a network setting
1380 * this feature will also attempt to place a user process near the kernel
1381 * protocol thread that is feeding it data. THIS IS A CRITICAL PART of the
1382 * algorithm as it heuristically groups synchronizing processes for locality
1383 * of reference in multi-socket systems.
1385 * We check against running processes and give a big advantage if there
1388 * The caller will normally dfly_setrunqueue() lp on the returned queue.
1390 * When the topology is known choose a cpu whos group has, in aggregate,
1391 * has the lowest weighted load.
1395 dfly_choose_best_queue(struct lwp *lp)
1402 dfly_pcpu_t dd = &dfly_pcpu[lp->lwp_qcpu];
1412 * When the topology is unknown choose a random cpu that is hopefully
1415 if (dd->cpunode == NULL)
1416 return (dfly_choose_queue_simple(dd, lp));
1421 if ((wakecpu = lp->lwp_thread->td_wakefromcpu) >= 0)
1422 wakemask = dfly_pcpu[wakecpu].cpumask;
1427 * When the topology is known choose a cpu whos group has, in
1428 * aggregate, has the lowest weighted load.
1430 cpup = root_cpu_node;
1435 * Degenerate case super-root
1437 if (cpup->child_node && cpup->child_no == 1) {
1438 cpup = cpup->child_node;
1445 if (cpup->child_node == NULL) {
1446 rdd = &dfly_pcpu[BSFCPUMASK(cpup->members)];
1451 lowest_load = 0x7FFFFFFF;
1453 for (n = 0; n < cpup->child_no; ++n) {
1455 * Accumulate load information for all cpus
1456 * which are members of this node.
1458 cpun = &cpup->child_node[n];
1459 mask = cpun->members & usched_global_cpumask &
1460 smp_active_mask & lp->lwp_cpumask;
1468 cpuid = BSFCPUMASK(mask);
1469 rdd = &dfly_pcpu[cpuid];
1471 load += rdd->ucount * usched_dfly_weight3;
1473 if (rdd->uschedcp == NULL &&
1474 rdd->runqcount == 0 &&
1475 globaldata_find(cpuid)->gd_tdrunqcount == 0
1477 load -= usched_dfly_weight4;
1480 else if (rdd->upri > lp->lwp_priority + PPQ) {
1481 load -= usched_dfly_weight4 / 2;
1484 mask &= ~CPUMASK(cpuid);
1489 * Compensate if the lp is already accounted for in
1490 * the aggregate uload for this mask set. We want
1491 * to calculate the loads as if lp were not present,
1492 * otherwise the calculation is bogus.
1494 if ((lp->lwp_mpflags & LWP_MP_ULOAD) &&
1495 (dd->cpumask & cpun->members)) {
1496 load -= lp->lwp_uload;
1497 load -= usched_dfly_weight3;
1503 * Advantage the cpu group (lp) is already on.
1505 if (cpun->members & dd->cpumask)
1506 load -= usched_dfly_weight1;
1509 * Advantage the cpu group we want to pair (lp) to,
1510 * but don't let it go to the exact same cpu as
1511 * the wakecpu target.
1513 * We do this by checking whether cpun is a
1514 * terminal node or not. All cpun's at the same
1515 * level will either all be terminal or all not
1518 * If it is and we match we disadvantage the load.
1519 * If it is and we don't match we advantage the load.
1521 * Also note that we are effectively disadvantaging
1522 * all-but-one by the same amount, so it won't effect
1523 * the weight1 factor for the all-but-one nodes.
1525 if (cpun->members & wakemask) {
1526 if (cpun->child_node != NULL) {
1528 load -= usched_dfly_weight2;
1530 if (usched_dfly_features & 0x10)
1531 load += usched_dfly_weight2;
1533 load -= usched_dfly_weight2;
1538 * Calculate the best load
1540 if (cpub == NULL || lowest_load > load ||
1541 (lowest_load == load &&
1542 (cpun->members & dd->cpumask))
1550 if (usched_dfly_chooser)
1551 kprintf("lp %02d->%02d %s\n",
1552 lp->lwp_qcpu, rdd->cpuid, lp->lwp_proc->p_comm);
1557 * USED TO PULL RUNNABLE LWPS FROM THE MOST LOADED CPU.
1559 * Choose the worst queue close to dd's cpu node with a non-empty runq
1560 * that is NOT dd. Also require that the moving of the highest-load thread
1561 * from rdd to dd does not cause the uload's to cross each other.
1563 * This is used by the thread chooser when the current cpu's queues are
1564 * empty to steal a thread from another cpu's queue. We want to offload
1565 * the most heavily-loaded queue.
1569 dfly_choose_worst_queue(dfly_pcpu_t dd)
1587 * When the topology is unknown choose a random cpu that is hopefully
1590 if (dd->cpunode == NULL) {
1595 * When the topology is known choose a cpu whos group has, in
1596 * aggregate, has the lowest weighted load.
1598 cpup = root_cpu_node;
1602 * Degenerate case super-root
1604 if (cpup->child_node && cpup->child_no == 1) {
1605 cpup = cpup->child_node;
1612 if (cpup->child_node == NULL) {
1613 rdd = &dfly_pcpu[BSFCPUMASK(cpup->members)];
1620 for (n = 0; n < cpup->child_no; ++n) {
1622 * Accumulate load information for all cpus
1623 * which are members of this node.
1625 cpun = &cpup->child_node[n];
1626 mask = cpun->members & usched_global_cpumask &
1634 cpuid = BSFCPUMASK(mask);
1635 rdd = &dfly_pcpu[cpuid];
1637 load += rdd->ucount * usched_dfly_weight3;
1638 if (rdd->uschedcp == NULL &&
1639 rdd->runqcount == 0 &&
1640 globaldata_find(cpuid)->gd_tdrunqcount == 0
1642 load -= usched_dfly_weight4;
1645 else if (rdd->upri > dd->upri + PPQ) {
1646 load -= usched_dfly_weight4 / 2;
1649 mask &= ~CPUMASK(cpuid);
1655 * Prefer candidates which are somewhat closer to
1658 if (dd->cpumask & cpun->members)
1659 load += usched_dfly_weight1;
1662 * The best candidate is the one with the worst
1665 if (cpub == NULL || highest_load < load) {
1666 highest_load = load;
1674 * We never return our own node (dd), and only return a remote
1675 * node if it's load is significantly worse than ours (i.e. where
1676 * stealing a thread would be considered reasonable).
1678 * This also helps us avoid breaking paired threads apart which
1679 * can have disastrous effects on performance.
1686 if (rdd->rtqueuebits && hpri < (pri = bsrl(rdd->rtqueuebits)))
1688 if (rdd->queuebits && hpri < (pri = bsrl(rdd->queuebits)))
1690 if (rdd->idqueuebits && hpri < (pri = bsrl(rdd->idqueuebits)))
1693 if (rdd->uload - hpri < dd->uload + hpri)
1701 dfly_choose_queue_simple(dfly_pcpu_t dd, struct lwp *lp)
1709 * Fallback to the original heuristic, select random cpu,
1710 * first checking cpus not currently running a user thread.
1713 cpuid = (dfly_scancpu & 0xFFFF) % ncpus;
1714 mask = ~dfly_curprocmask & dfly_rdyprocmask & lp->lwp_cpumask &
1715 smp_active_mask & usched_global_cpumask;
1718 tmpmask = ~(CPUMASK(cpuid) - 1);
1720 cpuid = BSFCPUMASK(mask & tmpmask);
1722 cpuid = BSFCPUMASK(mask);
1723 rdd = &dfly_pcpu[cpuid];
1725 if ((rdd->upri & ~PPQMASK) >= (lp->lwp_priority & ~PPQMASK))
1727 mask &= ~CPUMASK(cpuid);
1731 * Then cpus which might have a currently running lp
1733 cpuid = (dfly_scancpu & 0xFFFF) % ncpus;
1734 mask = dfly_curprocmask & dfly_rdyprocmask &
1735 lp->lwp_cpumask & smp_active_mask & usched_global_cpumask;
1738 tmpmask = ~(CPUMASK(cpuid) - 1);
1740 cpuid = BSFCPUMASK(mask & tmpmask);
1742 cpuid = BSFCPUMASK(mask);
1743 rdd = &dfly_pcpu[cpuid];
1745 if ((rdd->upri & ~PPQMASK) > (lp->lwp_priority & ~PPQMASK))
1747 mask &= ~CPUMASK(cpuid);
1751 * If we cannot find a suitable cpu we reload from dfly_scancpu
1752 * and round-robin. Other cpus will pickup as they release their
1753 * current lwps or become ready.
1755 * Avoid a degenerate system lockup case if usched_global_cpumask
1756 * is set to 0 or otherwise does not cover lwp_cpumask.
1758 * We only kick the target helper thread in this case, we do not
1759 * set the user resched flag because
1761 cpuid = (dfly_scancpu & 0xFFFF) % ncpus;
1762 if ((CPUMASK(cpuid) & usched_global_cpumask) == 0)
1764 rdd = &dfly_pcpu[cpuid];
1771 dfly_need_user_resched_remote(void *dummy)
1773 globaldata_t gd = mycpu;
1774 dfly_pcpu_t dd = &dfly_pcpu[gd->gd_cpuid];
1777 * Flag reschedule needed
1779 need_user_resched();
1782 * If no user thread is currently running we need to kick the helper
1783 * on our cpu to recover. Otherwise the cpu will never schedule
1786 * We cannot schedule the process ourselves because this is an
1787 * IPI callback and we cannot acquire spinlocks in an IPI callback.
1789 * Call wakeup_mycpu to avoid sending IPIs to other CPUs
1791 if (dd->uschedcp == NULL && (dfly_rdyprocmask & gd->gd_cpumask)) {
1792 atomic_clear_cpumask(&dfly_rdyprocmask, gd->gd_cpumask);
1793 wakeup_mycpu(&dd->helper_thread);
1798 * dfly_remrunqueue_locked() removes a given process from the run queue
1799 * that it is on, clearing the queue busy bit if it becomes empty.
1801 * Note that user process scheduler is different from the LWKT schedule.
1802 * The user process scheduler only manages user processes but it uses LWKT
1803 * underneath, and a user process operating in the kernel will often be
1804 * 'released' from our management.
1806 * uload is NOT adjusted here. It is only adjusted if the lwkt_thread goes
1807 * to sleep or the lwp is moved to a different runq.
1810 dfly_remrunqueue_locked(dfly_pcpu_t rdd, struct lwp *lp)
1816 KKASSERT(rdd->runqcount >= 0);
1818 pri = lp->lwp_rqindex;
1820 switch(lp->lwp_rqtype) {
1821 case RTP_PRIO_NORMAL:
1822 q = &rdd->queues[pri];
1823 which = &rdd->queuebits;
1825 case RTP_PRIO_REALTIME:
1827 q = &rdd->rtqueues[pri];
1828 which = &rdd->rtqueuebits;
1831 q = &rdd->idqueues[pri];
1832 which = &rdd->idqueuebits;
1835 panic("remrunqueue: invalid rtprio type");
1838 KKASSERT(lp->lwp_mpflags & LWP_MP_ONRUNQ);
1839 atomic_clear_int(&lp->lwp_mpflags, LWP_MP_ONRUNQ);
1840 TAILQ_REMOVE(q, lp, lwp_procq);
1842 if (TAILQ_EMPTY(q)) {
1843 KASSERT((*which & (1 << pri)) != 0,
1844 ("remrunqueue: remove from empty queue"));
1845 *which &= ~(1 << pri);
1850 * dfly_setrunqueue_locked()
1852 * Add a process whos rqtype and rqindex had previously been calculated
1853 * onto the appropriate run queue. Determine if the addition requires
1854 * a reschedule on a cpu and return the cpuid or -1.
1856 * NOTE: Lower priorities are better priorities.
1858 * NOTE ON ULOAD: This variable specifies the aggregate load on a cpu, the
1859 * sum of the rough lwp_priority for all running and runnable
1860 * processes. Lower priority processes (higher lwp_priority
1861 * values) actually DO count as more load, not less, because
1862 * these are the programs which require the most care with
1863 * regards to cpu selection.
1866 dfly_setrunqueue_locked(dfly_pcpu_t rdd, struct lwp *lp)
1872 KKASSERT(lp->lwp_qcpu == rdd->cpuid);
1874 if ((lp->lwp_mpflags & LWP_MP_ULOAD) == 0) {
1875 atomic_set_int(&lp->lwp_mpflags, LWP_MP_ULOAD);
1876 atomic_add_int(&dfly_pcpu[lp->lwp_qcpu].uload, lp->lwp_uload);
1877 atomic_add_int(&dfly_pcpu[lp->lwp_qcpu].ucount, 1);
1878 atomic_add_int(&dfly_ucount, 1);
1881 pri = lp->lwp_rqindex;
1883 switch(lp->lwp_rqtype) {
1884 case RTP_PRIO_NORMAL:
1885 q = &rdd->queues[pri];
1886 which = &rdd->queuebits;
1888 case RTP_PRIO_REALTIME:
1890 q = &rdd->rtqueues[pri];
1891 which = &rdd->rtqueuebits;
1894 q = &rdd->idqueues[pri];
1895 which = &rdd->idqueuebits;
1898 panic("remrunqueue: invalid rtprio type");
1903 * Place us on the selected queue. Determine if we should be
1904 * placed at the head of the queue or at the end.
1906 * We are placed at the tail if our round-robin count has expired,
1907 * or is about to expire and the system thinks its a good place to
1908 * round-robin, or there is already a next thread on the queue
1909 * (it might be trying to pick up where it left off and we don't
1910 * want to interfere).
1912 KKASSERT((lp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
1913 atomic_set_int(&lp->lwp_mpflags, LWP_MP_ONRUNQ);
1916 if (lp->lwp_rrcount >= usched_dfly_rrinterval ||
1917 (lp->lwp_rrcount >= usched_dfly_rrinterval / 2 &&
1918 (lp->lwp_thread->td_mpflags & TDF_MP_BATCH_DEMARC)) ||
1921 atomic_clear_int(&lp->lwp_thread->td_mpflags,
1922 TDF_MP_BATCH_DEMARC);
1923 lp->lwp_rrcount = 0;
1924 TAILQ_INSERT_TAIL(q, lp, lwp_procq);
1927 lp->lwp_rrcount = 0;
1928 TAILQ_INSERT_HEAD(q, lp, lwp_procq);
1934 * For SMP systems a user scheduler helper thread is created for each
1935 * cpu and is used to allow one cpu to wakeup another for the purposes of
1936 * scheduling userland threads from setrunqueue().
1938 * UP systems do not need the helper since there is only one cpu.
1940 * We can't use the idle thread for this because we might block.
1941 * Additionally, doing things this way allows us to HLT idle cpus
1945 dfly_helper_thread(void *dummy)
1955 cpuid = gd->gd_cpuid; /* doesn't change */
1956 mask = gd->gd_cpumask; /* doesn't change */
1957 dd = &dfly_pcpu[cpuid];
1960 * Since we only want to be woken up only when no user processes
1961 * are scheduled on a cpu, run at an ultra low priority.
1963 lwkt_setpri_self(TDPRI_USER_SCHEDULER);
1965 tsleep(&dd->helper_thread, 0, "schslp", 0);
1969 * We use the LWKT deschedule-interlock trick to avoid racing
1970 * dfly_rdyprocmask. This means we cannot block through to the
1971 * manual lwkt_switch() call we make below.
1974 tsleep_interlock(&dd->helper_thread, 0);
1976 spin_lock(&dd->spin);
1978 atomic_set_cpumask(&dfly_rdyprocmask, mask);
1979 clear_user_resched(); /* This satisfied the reschedule request */
1981 dd->rrcount = 0; /* Reset the round-robin counter */
1984 if (dd->runqcount || dd->uschedcp != NULL) {
1986 * Threads are available. A thread may or may not be
1987 * currently scheduled. Get the best thread already queued
1990 nlp = dfly_chooseproc_locked(dd, dd, dd->uschedcp, 0);
1992 atomic_set_cpumask(&dfly_curprocmask, mask);
1993 dd->upri = nlp->lwp_priority;
1996 dd->rrcount = 0; /* reset round robin */
1998 spin_unlock(&dd->spin);
1999 lwkt_acquire(nlp->lwp_thread);
2000 lwkt_schedule(nlp->lwp_thread);
2003 * This situation should not occur because we had
2004 * at least one thread available.
2006 spin_unlock(&dd->spin);
2008 } else if (usched_dfly_features & 0x01) {
2010 * This cpu is devoid of runnable threads, steal a thread
2011 * from another cpu. Since we're stealing, might as well
2012 * load balance at the same time.
2014 * We choose the highest-loaded thread from the worst queue.
2016 * NOTE! This function only returns a non-NULL rdd when
2017 * another cpu's queue is obviously overloaded. We
2018 * do not want to perform the type of rebalancing
2019 * the schedclock does here because it would result
2020 * in insane process pulling when 'steady' state is
2021 * partially unbalanced (e.g. 6 runnables and only
2024 rdd = dfly_choose_worst_queue(dd);
2025 if (rdd && spin_trylock(&rdd->spin)) {
2026 nlp = dfly_chooseproc_locked(rdd, dd, NULL, 1);
2027 spin_unlock(&rdd->spin);
2032 atomic_set_cpumask(&dfly_curprocmask, mask);
2033 dd->upri = nlp->lwp_priority;
2036 dd->rrcount = 0; /* reset round robin */
2038 spin_unlock(&dd->spin);
2039 lwkt_acquire(nlp->lwp_thread);
2040 lwkt_schedule(nlp->lwp_thread);
2043 * Leave the thread on our run queue. Another
2044 * scheduler will try to pull it later.
2046 spin_unlock(&dd->spin);
2050 * devoid of runnable threads and not allowed to steal
2053 spin_unlock(&dd->spin);
2057 * We're descheduled unless someone scheduled us. Switch away.
2058 * Exiting the critical section will cause splz() to be called
2059 * for us if interrupts and such are pending.
2062 tsleep(&dd->helper_thread, PINTERLOCKED, "schslp", 0);
2068 sysctl_usched_dfly_stick_to_level(SYSCTL_HANDLER_ARGS)
2072 new_val = usched_dfly_stick_to_level;
2074 error = sysctl_handle_int(oidp, &new_val, 0, req);
2075 if (error != 0 || req->newptr == NULL)
2077 if (new_val > cpu_topology_levels_number - 1 || new_val < 0)
2079 usched_dfly_stick_to_level = new_val;
2085 * Setup the queues and scheduler helpers (scheduler helpers are SMP only).
2086 * Note that curprocmask bit 0 has already been cleared by rqinit() and
2087 * we should not mess with it further.
2090 usched_dfly_cpu_init(void)
2095 int smt_not_supported = 0;
2096 int cache_coherent_not_supported = 0;
2099 kprintf("Start scheduler helpers on cpus:\n");
2101 sysctl_ctx_init(&usched_dfly_sysctl_ctx);
2102 usched_dfly_sysctl_tree =
2103 SYSCTL_ADD_NODE(&usched_dfly_sysctl_ctx,
2104 SYSCTL_STATIC_CHILDREN(_kern), OID_AUTO,
2105 "usched_dfly", CTLFLAG_RD, 0, "");
2107 for (i = 0; i < ncpus; ++i) {
2108 dfly_pcpu_t dd = &dfly_pcpu[i];
2109 cpumask_t mask = CPUMASK(i);
2111 if ((mask & smp_active_mask) == 0)
2114 spin_init(&dd->spin);
2115 dd->cpunode = get_cpu_node_by_cpuid(i);
2117 dd->cpumask = CPUMASK(i);
2118 for (j = 0; j < NQS; j++) {
2119 TAILQ_INIT(&dd->queues[j]);
2120 TAILQ_INIT(&dd->rtqueues[j]);
2121 TAILQ_INIT(&dd->idqueues[j]);
2123 atomic_clear_cpumask(&dfly_curprocmask, 1);
2125 if (dd->cpunode == NULL) {
2126 smt_not_supported = 1;
2127 cache_coherent_not_supported = 1;
2129 kprintf ("\tcpu%d - WARNING: No CPU NODE "
2130 "found for cpu\n", i);
2132 switch (dd->cpunode->type) {
2135 kprintf ("\tcpu%d - HyperThreading "
2136 "available. Core siblings: ",
2140 smt_not_supported = 1;
2143 kprintf ("\tcpu%d - No HT available, "
2144 "multi-core/physical "
2145 "cpu. Physical siblings: ",
2149 smt_not_supported = 1;
2152 kprintf ("\tcpu%d - No HT available, "
2153 "single-core/physical cpu. "
2154 "Package Siblings: ",
2158 /* Let's go for safe defaults here */
2159 smt_not_supported = 1;
2160 cache_coherent_not_supported = 1;
2162 kprintf ("\tcpu%d - Unknown cpunode->"
2163 "type=%u. Siblings: ",
2165 (u_int)dd->cpunode->type);
2170 if (dd->cpunode->parent_node != NULL) {
2171 CPUSET_FOREACH(cpuid, dd->cpunode->parent_node->members)
2172 kprintf("cpu%d ", cpuid);
2175 kprintf(" no siblings\n");
2180 lwkt_create(dfly_helper_thread, NULL, NULL, &dd->helper_thread,
2181 0, i, "usched %d", i);
2184 * Allow user scheduling on the target cpu. cpu #0 has already
2185 * been enabled in rqinit().
2188 atomic_clear_cpumask(&dfly_curprocmask, mask);
2189 atomic_set_cpumask(&dfly_rdyprocmask, mask);
2190 dd->upri = PRIBASE_NULL;
2194 /* usched_dfly sysctl configurable parameters */
2196 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2197 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2198 OID_AUTO, "rrinterval", CTLFLAG_RW,
2199 &usched_dfly_rrinterval, 0, "");
2200 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2201 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2202 OID_AUTO, "decay", CTLFLAG_RW,
2203 &usched_dfly_decay, 0, "Extra decay when not running");
2205 /* Add enable/disable option for SMT scheduling if supported */
2206 if (smt_not_supported) {
2207 usched_dfly_smt = 0;
2208 SYSCTL_ADD_STRING(&usched_dfly_sysctl_ctx,
2209 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2210 OID_AUTO, "smt", CTLFLAG_RD,
2211 "NOT SUPPORTED", 0, "SMT NOT SUPPORTED");
2213 usched_dfly_smt = 1;
2214 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2215 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2216 OID_AUTO, "smt", CTLFLAG_RW,
2217 &usched_dfly_smt, 0, "Enable SMT scheduling");
2221 * Add enable/disable option for cache coherent scheduling
2224 if (cache_coherent_not_supported) {
2225 usched_dfly_cache_coherent = 0;
2226 SYSCTL_ADD_STRING(&usched_dfly_sysctl_ctx,
2227 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2228 OID_AUTO, "cache_coherent", CTLFLAG_RD,
2230 "Cache coherence NOT SUPPORTED");
2232 usched_dfly_cache_coherent = 1;
2233 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2234 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2235 OID_AUTO, "cache_coherent", CTLFLAG_RW,
2236 &usched_dfly_cache_coherent, 0,
2237 "Enable/Disable cache coherent scheduling");
2239 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2240 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2241 OID_AUTO, "weight1", CTLFLAG_RW,
2242 &usched_dfly_weight1, 200,
2243 "Weight selection for current cpu");
2245 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2246 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2247 OID_AUTO, "weight2", CTLFLAG_RW,
2248 &usched_dfly_weight2, 180,
2249 "Weight selection for wakefrom cpu");
2251 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2252 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2253 OID_AUTO, "weight3", CTLFLAG_RW,
2254 &usched_dfly_weight3, 40,
2255 "Weight selection for num threads on queue");
2257 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2258 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2259 OID_AUTO, "weight4", CTLFLAG_RW,
2260 &usched_dfly_weight4, 160,
2261 "Availability of other idle cpus");
2263 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2264 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2265 OID_AUTO, "fast_resched", CTLFLAG_RW,
2266 &usched_dfly_fast_resched, 0,
2267 "Availability of other idle cpus");
2269 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2270 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2271 OID_AUTO, "features", CTLFLAG_RW,
2272 &usched_dfly_features, 0x8F,
2273 "Allow pulls into empty queues");
2275 SYSCTL_ADD_INT(&usched_dfly_sysctl_ctx,
2276 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2277 OID_AUTO, "swmask", CTLFLAG_RW,
2278 &usched_dfly_swmask, ~PPQMASK,
2279 "Queue mask to force thread switch");
2282 SYSCTL_ADD_PROC(&usched_dfly_sysctl_ctx,
2283 SYSCTL_CHILDREN(usched_dfly_sysctl_tree),
2284 OID_AUTO, "stick_to_level",
2285 CTLTYPE_INT | CTLFLAG_RW,
2286 NULL, sizeof usched_dfly_stick_to_level,
2287 sysctl_usched_dfly_stick_to_level, "I",
2288 "Stick a process to this level. See sysctl"
2289 "paremter hw.cpu_topology.level_description");
2293 SYSINIT(uschedtd, SI_BOOT2_USCHED, SI_ORDER_SECOND,
2294 usched_dfly_cpu_init, NULL)