FreeBSD/Linux Kernel Cross Reference
sys/kern/sched_ule.c
1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2002-2007, Jeffrey Roberson <jeff@freebsd.org>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice unmodified, this list of conditions, and the following
12 * disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 /*
30 * This file implements the ULE scheduler. ULE supports independent CPU
31 * run queues and fine grain locking. It has superior interactive
32 * performance under load even on uni-processor systems.
33 *
34 * etymology:
35 * ULE is the last three letters in schedule. It owes its name to a
36 * generic user created for a scheduling system by Paul Mikesell at
37 * Isilon Systems and a general lack of creativity on the part of the author.
38 */
39
40 #include <sys/cdefs.h>
41 __FBSDID("$FreeBSD$");
42
43 #include "opt_hwpmc_hooks.h"
44 #include "opt_sched.h"
45
46 #include <sys/param.h>
47 #include <sys/systm.h>
48 #include <sys/kdb.h>
49 #include <sys/kernel.h>
50 #include <sys/ktr.h>
51 #include <sys/limits.h>
52 #include <sys/lock.h>
53 #include <sys/mutex.h>
54 #include <sys/proc.h>
55 #include <sys/resource.h>
56 #include <sys/resourcevar.h>
57 #include <sys/sched.h>
58 #include <sys/sdt.h>
59 #include <sys/smp.h>
60 #include <sys/sx.h>
61 #include <sys/sysctl.h>
62 #include <sys/sysproto.h>
63 #include <sys/turnstile.h>
64 #include <sys/umtx.h>
65 #include <sys/vmmeter.h>
66 #include <sys/cpuset.h>
67 #include <sys/sbuf.h>
68
69 #ifdef HWPMC_HOOKS
70 #include <sys/pmckern.h>
71 #endif
72
73 #ifdef KDTRACE_HOOKS
74 #include <sys/dtrace_bsd.h>
75 int __read_mostly dtrace_vtime_active;
76 dtrace_vtime_switch_func_t dtrace_vtime_switch_func;
77 #endif
78
79 #include <machine/cpu.h>
80 #include <machine/smp.h>
81
82 #define KTR_ULE 0
83
84 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
85 #define TDQ_NAME_LEN (sizeof("sched lock ") + sizeof(__XSTRING(MAXCPU)))
86 #define TDQ_LOADNAME_LEN (sizeof("CPU ") + sizeof(__XSTRING(MAXCPU)) - 1 + sizeof(" load"))
87
88 /*
89 * Thread scheduler specific section. All fields are protected
90 * by the thread lock.
91 */
92 struct td_sched {
93 struct runq *ts_runq; /* Run-queue we're queued on. */
94 short ts_flags; /* TSF_* flags. */
95 int ts_cpu; /* CPU that we have affinity for. */
96 int ts_rltick; /* Real last tick, for affinity. */
97 int ts_slice; /* Ticks of slice remaining. */
98 u_int ts_slptime; /* Number of ticks we vol. slept */
99 u_int ts_runtime; /* Number of ticks we were running */
100 int ts_ltick; /* Last tick that we were running on */
101 int ts_ftick; /* First tick that we were running on */
102 int ts_ticks; /* Tick count */
103 #ifdef KTR
104 char ts_name[TS_NAME_LEN];
105 #endif
106 };
107 /* flags kept in ts_flags */
108 #define TSF_BOUND 0x0001 /* Thread can not migrate. */
109 #define TSF_XFERABLE 0x0002 /* Thread was added as transferable. */
110
111 #define THREAD_CAN_MIGRATE(td) ((td)->td_pinned == 0)
112 #define THREAD_CAN_SCHED(td, cpu) \
113 CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
114
115 _Static_assert(sizeof(struct thread) + sizeof(struct td_sched) <=
116 sizeof(struct thread0_storage),
117 "increase struct thread0_storage.t0st_sched size");
118
119 /*
120 * Priority ranges used for interactive and non-interactive timeshare
121 * threads. The timeshare priorities are split up into four ranges.
122 * The first range handles interactive threads. The last three ranges
123 * (NHALF, x, and NHALF) handle non-interactive threads with the outer
124 * ranges supporting nice values.
125 */
126 #define PRI_TIMESHARE_RANGE (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE + 1)
127 #define PRI_INTERACT_RANGE ((PRI_TIMESHARE_RANGE - SCHED_PRI_NRESV) / 2)
128 #define PRI_BATCH_RANGE (PRI_TIMESHARE_RANGE - PRI_INTERACT_RANGE)
129
130 #define PRI_MIN_INTERACT PRI_MIN_TIMESHARE
131 #define PRI_MAX_INTERACT (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE - 1)
132 #define PRI_MIN_BATCH (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE)
133 #define PRI_MAX_BATCH PRI_MAX_TIMESHARE
134
135 /*
136 * Cpu percentage computation macros and defines.
137 *
138 * SCHED_TICK_SECS: Number of seconds to average the cpu usage across.
139 * SCHED_TICK_TARG: Number of hz ticks to average the cpu usage across.
140 * SCHED_TICK_MAX: Maximum number of ticks before scaling back.
141 * SCHED_TICK_SHIFT: Shift factor to avoid rounding away results.
142 * SCHED_TICK_HZ: Compute the number of hz ticks for a given ticks count.
143 * SCHED_TICK_TOTAL: Gives the amount of time we've been recording ticks.
144 */
145 #define SCHED_TICK_SECS 10
146 #define SCHED_TICK_TARG (hz * SCHED_TICK_SECS)
147 #define SCHED_TICK_MAX (SCHED_TICK_TARG + hz)
148 #define SCHED_TICK_SHIFT 10
149 #define SCHED_TICK_HZ(ts) ((ts)->ts_ticks >> SCHED_TICK_SHIFT)
150 #define SCHED_TICK_TOTAL(ts) (max((ts)->ts_ltick - (ts)->ts_ftick, hz))
151
152 /*
153 * These macros determine priorities for non-interactive threads. They are
154 * assigned a priority based on their recent cpu utilization as expressed
155 * by the ratio of ticks to the tick total. NHALF priorities at the start
156 * and end of the MIN to MAX timeshare range are only reachable with negative
157 * or positive nice respectively.
158 *
159 * PRI_RANGE: Priority range for utilization dependent priorities.
160 * PRI_NRESV: Number of nice values.
161 * PRI_TICKS: Compute a priority in PRI_RANGE from the ticks count and total.
162 * PRI_NICE: Determines the part of the priority inherited from nice.
163 */
164 #define SCHED_PRI_NRESV (PRIO_MAX - PRIO_MIN)
165 #define SCHED_PRI_NHALF (SCHED_PRI_NRESV / 2)
166 #define SCHED_PRI_MIN (PRI_MIN_BATCH + SCHED_PRI_NHALF)
167 #define SCHED_PRI_MAX (PRI_MAX_BATCH - SCHED_PRI_NHALF)
168 #define SCHED_PRI_RANGE (SCHED_PRI_MAX - SCHED_PRI_MIN + 1)
169 #define SCHED_PRI_TICKS(ts) \
170 (SCHED_TICK_HZ((ts)) / \
171 (roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE))
172 #define SCHED_PRI_NICE(nice) (nice)
173
174 /*
175 * These determine the interactivity of a process. Interactivity differs from
176 * cpu utilization in that it expresses the voluntary time slept vs time ran
177 * while cpu utilization includes all time not running. This more accurately
178 * models the intent of the thread.
179 *
180 * SLP_RUN_MAX: Maximum amount of sleep time + run time we'll accumulate
181 * before throttling back.
182 * SLP_RUN_FORK: Maximum slp+run time to inherit at fork time.
183 * INTERACT_MAX: Maximum interactivity value. Smaller is better.
184 * INTERACT_THRESH: Threshold for placement on the current runq.
185 */
186 #define SCHED_SLP_RUN_MAX ((hz * 5) << SCHED_TICK_SHIFT)
187 #define SCHED_SLP_RUN_FORK ((hz / 2) << SCHED_TICK_SHIFT)
188 #define SCHED_INTERACT_MAX (100)
189 #define SCHED_INTERACT_HALF (SCHED_INTERACT_MAX / 2)
190 #define SCHED_INTERACT_THRESH (30)
191
192 /*
193 * These parameters determine the slice behavior for batch work.
194 */
195 #define SCHED_SLICE_DEFAULT_DIVISOR 10 /* ~94 ms, 12 stathz ticks. */
196 #define SCHED_SLICE_MIN_DIVISOR 6 /* DEFAULT/MIN = ~16 ms. */
197
198 /* Flags kept in td_flags. */
199 #define TDF_PICKCPU TDF_SCHED0 /* Thread should pick new CPU. */
200 #define TDF_SLICEEND TDF_SCHED2 /* Thread time slice is over. */
201
202 /*
203 * tickincr: Converts a stathz tick into a hz domain scaled by
204 * the shift factor. Without the shift the error rate
205 * due to rounding would be unacceptably high.
206 * realstathz: stathz is sometimes 0 and run off of hz.
207 * sched_slice: Runtime of each thread before rescheduling.
208 * preempt_thresh: Priority threshold for preemption and remote IPIs.
209 */
210 static u_int __read_mostly sched_interact = SCHED_INTERACT_THRESH;
211 static int __read_mostly tickincr = 8 << SCHED_TICK_SHIFT;
212 static int __read_mostly realstathz = 127; /* reset during boot. */
213 static int __read_mostly sched_slice = 10; /* reset during boot. */
214 static int __read_mostly sched_slice_min = 1; /* reset during boot. */
215 #ifdef PREEMPTION
216 #ifdef FULL_PREEMPTION
217 static int __read_mostly preempt_thresh = PRI_MAX_IDLE;
218 #else
219 static int __read_mostly preempt_thresh = PRI_MIN_KERN;
220 #endif
221 #else
222 static int __read_mostly preempt_thresh = 0;
223 #endif
224 static int __read_mostly static_boost = PRI_MIN_BATCH;
225 static int __read_mostly sched_idlespins = 10000;
226 static int __read_mostly sched_idlespinthresh = -1;
227
228 /*
229 * tdq - per processor runqs and statistics. All fields are protected by the
230 * tdq_lock. The load and lowpri may be accessed without to avoid excess
231 * locking in sched_pickcpu();
232 */
233 struct tdq {
234 /*
235 * Ordered to improve efficiency of cpu_search() and switch().
236 * tdq_lock is padded to avoid false sharing with tdq_load and
237 * tdq_cpu_idle.
238 */
239 struct mtx_padalign tdq_lock; /* run queue lock. */
240 struct cpu_group *tdq_cg; /* Pointer to cpu topology. */
241 volatile int tdq_load; /* Aggregate load. */
242 volatile int tdq_cpu_idle; /* cpu_idle() is active. */
243 int tdq_sysload; /* For loadavg, !ITHD load. */
244 volatile int tdq_transferable; /* Transferable thread count. */
245 volatile short tdq_switchcnt; /* Switches this tick. */
246 volatile short tdq_oldswitchcnt; /* Switches last tick. */
247 u_char tdq_lowpri; /* Lowest priority thread. */
248 u_char tdq_owepreempt; /* Remote preemption pending. */
249 u_char tdq_idx; /* Current insert index. */
250 u_char tdq_ridx; /* Current removal index. */
251 int tdq_id; /* cpuid. */
252 struct runq tdq_realtime; /* real-time run queue. */
253 struct runq tdq_timeshare; /* timeshare run queue. */
254 struct runq tdq_idle; /* Queue of IDLE threads. */
255 char tdq_name[TDQ_NAME_LEN];
256 #ifdef KTR
257 char tdq_loadname[TDQ_LOADNAME_LEN];
258 #endif
259 } __aligned(64);
260
261 /* Idle thread states and config. */
262 #define TDQ_RUNNING 1
263 #define TDQ_IDLE 2
264
265 #ifdef SMP
266 struct cpu_group __read_mostly *cpu_top; /* CPU topology */
267
268 #define SCHED_AFFINITY_DEFAULT (max(1, hz / 1000))
269 #define SCHED_AFFINITY(ts, t) ((ts)->ts_rltick > ticks - ((t) * affinity))
270
271 /*
272 * Run-time tunables.
273 */
274 static int rebalance = 1;
275 static int balance_interval = 128; /* Default set in sched_initticks(). */
276 static int __read_mostly affinity;
277 static int __read_mostly steal_idle = 1;
278 static int __read_mostly steal_thresh = 2;
279 static int __read_mostly always_steal = 0;
280 static int __read_mostly trysteal_limit = 2;
281
282 /*
283 * One thread queue per processor.
284 */
285 static struct tdq __read_mostly *balance_tdq;
286 static int balance_ticks;
287 DPCPU_DEFINE_STATIC(struct tdq, tdq);
288 DPCPU_DEFINE_STATIC(uint32_t, randomval);
289
290 #define TDQ_SELF() ((struct tdq *)PCPU_GET(sched))
291 #define TDQ_CPU(x) (DPCPU_ID_PTR((x), tdq))
292 #define TDQ_ID(x) ((x)->tdq_id)
293 #else /* !SMP */
294 static struct tdq tdq_cpu;
295
296 #define TDQ_ID(x) (0)
297 #define TDQ_SELF() (&tdq_cpu)
298 #define TDQ_CPU(x) (&tdq_cpu)
299 #endif
300
301 #define TDQ_LOCK_ASSERT(t, type) mtx_assert(TDQ_LOCKPTR((t)), (type))
302 #define TDQ_LOCK(t) mtx_lock_spin(TDQ_LOCKPTR((t)))
303 #define TDQ_LOCK_FLAGS(t, f) mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f))
304 #define TDQ_TRYLOCK(t) mtx_trylock_spin(TDQ_LOCKPTR((t)))
305 #define TDQ_TRYLOCK_FLAGS(t, f) mtx_trylock_spin_flags(TDQ_LOCKPTR((t)), (f))
306 #define TDQ_UNLOCK(t) mtx_unlock_spin(TDQ_LOCKPTR((t)))
307 #define TDQ_LOCKPTR(t) ((struct mtx *)(&(t)->tdq_lock))
308
309 static void sched_priority(struct thread *);
310 static void sched_thread_priority(struct thread *, u_char);
311 static int sched_interact_score(struct thread *);
312 static void sched_interact_update(struct thread *);
313 static void sched_interact_fork(struct thread *);
314 static void sched_pctcpu_update(struct td_sched *, int);
315
316 /* Operations on per processor queues */
317 static struct thread *tdq_choose(struct tdq *);
318 static void tdq_setup(struct tdq *, int i);
319 static void tdq_load_add(struct tdq *, struct thread *);
320 static void tdq_load_rem(struct tdq *, struct thread *);
321 static __inline void tdq_runq_add(struct tdq *, struct thread *, int);
322 static __inline void tdq_runq_rem(struct tdq *, struct thread *);
323 static inline int sched_shouldpreempt(int, int, int);
324 void tdq_print(int cpu);
325 static void runq_print(struct runq *rq);
326 static void tdq_add(struct tdq *, struct thread *, int);
327 #ifdef SMP
328 static struct thread *tdq_move(struct tdq *, struct tdq *);
329 static int tdq_idled(struct tdq *);
330 static void tdq_notify(struct tdq *, struct thread *);
331 static struct thread *tdq_steal(struct tdq *, int);
332 static struct thread *runq_steal(struct runq *, int);
333 static int sched_pickcpu(struct thread *, int);
334 static void sched_balance(void);
335 static int sched_balance_pair(struct tdq *, struct tdq *);
336 static inline struct tdq *sched_setcpu(struct thread *, int, int);
337 static inline void thread_unblock_switch(struct thread *, struct mtx *);
338 static int sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS);
339 static int sysctl_kern_sched_topology_spec_internal(struct sbuf *sb,
340 struct cpu_group *cg, int indent);
341 #endif
342
343 static void sched_setup(void *dummy);
344 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
345
346 static void sched_initticks(void *dummy);
347 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
348 NULL);
349
350 SDT_PROVIDER_DEFINE(sched);
351
352 SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *",
353 "struct proc *", "uint8_t");
354 SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *",
355 "struct proc *", "void *");
356 SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *",
357 "struct proc *", "void *", "int");
358 SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *",
359 "struct proc *", "uint8_t", "struct thread *");
360 SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int");
361 SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *",
362 "struct proc *");
363 SDT_PROBE_DEFINE(sched, , , on__cpu);
364 SDT_PROBE_DEFINE(sched, , , remain__cpu);
365 SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *",
366 "struct proc *");
367
368 /*
369 * Print the threads waiting on a run-queue.
370 */
371 static void
372 runq_print(struct runq *rq)
373 {
374 struct rqhead *rqh;
375 struct thread *td;
376 int pri;
377 int j;
378 int i;
379
380 for (i = 0; i < RQB_LEN; i++) {
381 printf("\t\trunq bits %d 0x%zx\n",
382 i, rq->rq_status.rqb_bits[i]);
383 for (j = 0; j < RQB_BPW; j++)
384 if (rq->rq_status.rqb_bits[i] & (1ul << j)) {
385 pri = j + (i << RQB_L2BPW);
386 rqh = &rq->rq_queues[pri];
387 TAILQ_FOREACH(td, rqh, td_runq) {
388 printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
389 td, td->td_name, td->td_priority,
390 td->td_rqindex, pri);
391 }
392 }
393 }
394 }
395
396 /*
397 * Print the status of a per-cpu thread queue. Should be a ddb show cmd.
398 */
399 void
400 tdq_print(int cpu)
401 {
402 struct tdq *tdq;
403
404 tdq = TDQ_CPU(cpu);
405
406 printf("tdq %d:\n", TDQ_ID(tdq));
407 printf("\tlock %p\n", TDQ_LOCKPTR(tdq));
408 printf("\tLock name: %s\n", tdq->tdq_name);
409 printf("\tload: %d\n", tdq->tdq_load);
410 printf("\tswitch cnt: %d\n", tdq->tdq_switchcnt);
411 printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt);
412 printf("\ttimeshare idx: %d\n", tdq->tdq_idx);
413 printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
414 printf("\tload transferable: %d\n", tdq->tdq_transferable);
415 printf("\tlowest priority: %d\n", tdq->tdq_lowpri);
416 printf("\trealtime runq:\n");
417 runq_print(&tdq->tdq_realtime);
418 printf("\ttimeshare runq:\n");
419 runq_print(&tdq->tdq_timeshare);
420 printf("\tidle runq:\n");
421 runq_print(&tdq->tdq_idle);
422 }
423
424 static inline int
425 sched_shouldpreempt(int pri, int cpri, int remote)
426 {
427 /*
428 * If the new priority is not better than the current priority there is
429 * nothing to do.
430 */
431 if (pri >= cpri)
432 return (0);
433 /*
434 * Always preempt idle.
435 */
436 if (cpri >= PRI_MIN_IDLE)
437 return (1);
438 /*
439 * If preemption is disabled don't preempt others.
440 */
441 if (preempt_thresh == 0)
442 return (0);
443 /*
444 * Preempt if we exceed the threshold.
445 */
446 if (pri <= preempt_thresh)
447 return (1);
448 /*
449 * If we're interactive or better and there is non-interactive
450 * or worse running preempt only remote processors.
451 */
452 if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT)
453 return (1);
454 return (0);
455 }
456
457 /*
458 * Add a thread to the actual run-queue. Keeps transferable counts up to
459 * date with what is actually on the run-queue. Selects the correct
460 * queue position for timeshare threads.
461 */
462 static __inline void
463 tdq_runq_add(struct tdq *tdq, struct thread *td, int flags)
464 {
465 struct td_sched *ts;
466 u_char pri;
467
468 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
469 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
470
471 pri = td->td_priority;
472 ts = td_get_sched(td);
473 TD_SET_RUNQ(td);
474 if (THREAD_CAN_MIGRATE(td)) {
475 tdq->tdq_transferable++;
476 ts->ts_flags |= TSF_XFERABLE;
477 }
478 if (pri < PRI_MIN_BATCH) {
479 ts->ts_runq = &tdq->tdq_realtime;
480 } else if (pri <= PRI_MAX_BATCH) {
481 ts->ts_runq = &tdq->tdq_timeshare;
482 KASSERT(pri <= PRI_MAX_BATCH && pri >= PRI_MIN_BATCH,
483 ("Invalid priority %d on timeshare runq", pri));
484 /*
485 * This queue contains only priorities between MIN and MAX
486 * realtime. Use the whole queue to represent these values.
487 */
488 if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) {
489 pri = RQ_NQS * (pri - PRI_MIN_BATCH) / PRI_BATCH_RANGE;
490 pri = (pri + tdq->tdq_idx) % RQ_NQS;
491 /*
492 * This effectively shortens the queue by one so we
493 * can have a one slot difference between idx and
494 * ridx while we wait for threads to drain.
495 */
496 if (tdq->tdq_ridx != tdq->tdq_idx &&
497 pri == tdq->tdq_ridx)
498 pri = (unsigned char)(pri - 1) % RQ_NQS;
499 } else
500 pri = tdq->tdq_ridx;
501 runq_add_pri(ts->ts_runq, td, pri, flags);
502 return;
503 } else
504 ts->ts_runq = &tdq->tdq_idle;
505 runq_add(ts->ts_runq, td, flags);
506 }
507
508 /*
509 * Remove a thread from a run-queue. This typically happens when a thread
510 * is selected to run. Running threads are not on the queue and the
511 * transferable count does not reflect them.
512 */
513 static __inline void
514 tdq_runq_rem(struct tdq *tdq, struct thread *td)
515 {
516 struct td_sched *ts;
517
518 ts = td_get_sched(td);
519 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
520 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
521 KASSERT(ts->ts_runq != NULL,
522 ("tdq_runq_remove: thread %p null ts_runq", td));
523 if (ts->ts_flags & TSF_XFERABLE) {
524 tdq->tdq_transferable--;
525 ts->ts_flags &= ~TSF_XFERABLE;
526 }
527 if (ts->ts_runq == &tdq->tdq_timeshare) {
528 if (tdq->tdq_idx != tdq->tdq_ridx)
529 runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx);
530 else
531 runq_remove_idx(ts->ts_runq, td, NULL);
532 } else
533 runq_remove(ts->ts_runq, td);
534 }
535
536 /*
537 * Load is maintained for all threads RUNNING and ON_RUNQ. Add the load
538 * for this thread to the referenced thread queue.
539 */
540 static void
541 tdq_load_add(struct tdq *tdq, struct thread *td)
542 {
543
544 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
545 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
546
547 tdq->tdq_load++;
548 if ((td->td_flags & TDF_NOLOAD) == 0)
549 tdq->tdq_sysload++;
550 KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
551 SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
552 }
553
554 /*
555 * Remove the load from a thread that is transitioning to a sleep state or
556 * exiting.
557 */
558 static void
559 tdq_load_rem(struct tdq *tdq, struct thread *td)
560 {
561
562 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
563 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
564 KASSERT(tdq->tdq_load != 0,
565 ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
566
567 tdq->tdq_load--;
568 if ((td->td_flags & TDF_NOLOAD) == 0)
569 tdq->tdq_sysload--;
570 KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
571 SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
572 }
573
574 /*
575 * Bound timeshare latency by decreasing slice size as load increases. We
576 * consider the maximum latency as the sum of the threads waiting to run
577 * aside from curthread and target no more than sched_slice latency but
578 * no less than sched_slice_min runtime.
579 */
580 static inline int
581 tdq_slice(struct tdq *tdq)
582 {
583 int load;
584
585 /*
586 * It is safe to use sys_load here because this is called from
587 * contexts where timeshare threads are running and so there
588 * cannot be higher priority load in the system.
589 */
590 load = tdq->tdq_sysload - 1;
591 if (load >= SCHED_SLICE_MIN_DIVISOR)
592 return (sched_slice_min);
593 if (load <= 1)
594 return (sched_slice);
595 return (sched_slice / load);
596 }
597
598 /*
599 * Set lowpri to its exact value by searching the run-queue and
600 * evaluating curthread. curthread may be passed as an optimization.
601 */
602 static void
603 tdq_setlowpri(struct tdq *tdq, struct thread *ctd)
604 {
605 struct thread *td;
606
607 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
608 if (ctd == NULL)
609 ctd = pcpu_find(TDQ_ID(tdq))->pc_curthread;
610 td = tdq_choose(tdq);
611 if (td == NULL || td->td_priority > ctd->td_priority)
612 tdq->tdq_lowpri = ctd->td_priority;
613 else
614 tdq->tdq_lowpri = td->td_priority;
615 }
616
617 #ifdef SMP
618 /*
619 * We need some randomness. Implement a classic Linear Congruential
620 * Generator X_{n+1}=(aX_n+c) mod m. These values are optimized for
621 * m = 2^32, a = 69069 and c = 5. We only return the upper 16 bits
622 * of the random state (in the low bits of our answer) to keep
623 * the maximum randomness.
624 */
625 static uint32_t
626 sched_random(void)
627 {
628 uint32_t *rndptr;
629
630 rndptr = DPCPU_PTR(randomval);
631 *rndptr = *rndptr * 69069 + 5;
632
633 return (*rndptr >> 16);
634 }
635
636 struct cpu_search {
637 cpuset_t *cs_mask; /* The mask of allowed CPUs to choose from. */
638 int cs_prefer; /* Prefer this CPU and groups including it. */
639 int cs_running; /* The thread is now running at cs_prefer. */
640 int cs_pri; /* Min priority for low. */
641 int cs_load; /* Max load for low, min load for high. */
642 int cs_trans; /* Min transferable load for high. */
643 };
644
645 struct cpu_search_res {
646 int csr_cpu; /* The best CPU found. */
647 int csr_load; /* The load of cs_cpu. */
648 };
649
650 /*
651 * Search the tree of cpu_groups for the lowest or highest loaded CPU.
652 * These routines actually compare the load on all paths through the tree
653 * and find the least loaded cpu on the least loaded path, which may differ
654 * from the least loaded cpu in the system. This balances work among caches
655 * and buses.
656 */
657 static int
658 cpu_search_lowest(const struct cpu_group *cg, const struct cpu_search *s,
659 struct cpu_search_res *r)
660 {
661 struct cpu_search_res lr;
662 struct tdq *tdq;
663 int c, bload, l, load, p, total;
664
665 total = 0;
666 bload = INT_MAX;
667 r->csr_cpu = -1;
668
669 /* Loop through children CPU groups if there are any. */
670 if (cg->cg_children > 0) {
671 for (c = cg->cg_children - 1; c >= 0; c--) {
672 load = cpu_search_lowest(&cg->cg_child[c], s, &lr);
673 total += load;
674
675 /*
676 * When balancing do not prefer SMT groups with load >1.
677 * It allows round-robin between SMT groups with equal
678 * load within parent group for more fair scheduling.
679 */
680 if (__predict_false(s->cs_running) &&
681 (cg->cg_child[c].cg_flags & CG_FLAG_THREAD) &&
682 load >= 128 && (load & 128) != 0)
683 load += 128;
684
685 if (lr.csr_cpu >= 0 && (load < bload ||
686 (load == bload && lr.csr_load < r->csr_load))) {
687 bload = load;
688 r->csr_cpu = lr.csr_cpu;
689 r->csr_load = lr.csr_load;
690 }
691 }
692 return (total);
693 }
694
695 /* Loop through children CPUs otherwise. */
696 for (c = cg->cg_last; c >= cg->cg_first; c--) {
697 if (!CPU_ISSET(c, &cg->cg_mask))
698 continue;
699 tdq = TDQ_CPU(c);
700 l = tdq->tdq_load;
701 if (c == s->cs_prefer) {
702 if (__predict_false(s->cs_running))
703 l--;
704 p = 128;
705 } else
706 p = 0;
707 load = l * 256;
708 total += load - p;
709
710 /*
711 * Check this CPU is acceptable.
712 * If the threads is already on the CPU, don't look on the TDQ
713 * priority, since it can be the priority of the thread itself.
714 */
715 if (l > s->cs_load || (tdq->tdq_lowpri <= s->cs_pri &&
716 (!s->cs_running || c != s->cs_prefer)) ||
717 !CPU_ISSET(c, s->cs_mask))
718 continue;
719
720 /*
721 * When balancing do not prefer CPUs with load > 1.
722 * It allows round-robin between CPUs with equal load
723 * within the CPU group for more fair scheduling.
724 */
725 if (__predict_false(s->cs_running) && l > 0)
726 p = 0;
727
728 load -= sched_random() % 128;
729 if (bload > load - p) {
730 bload = load - p;
731 r->csr_cpu = c;
732 r->csr_load = load;
733 }
734 }
735 return (total);
736 }
737
738 static int
739 cpu_search_highest(const struct cpu_group *cg, const struct cpu_search *s,
740 struct cpu_search_res *r)
741 {
742 struct cpu_search_res lr;
743 struct tdq *tdq;
744 int c, bload, l, load, total;
745
746 total = 0;
747 bload = INT_MIN;
748 r->csr_cpu = -1;
749
750 /* Loop through children CPU groups if there are any. */
751 if (cg->cg_children > 0) {
752 for (c = cg->cg_children - 1; c >= 0; c--) {
753 load = cpu_search_highest(&cg->cg_child[c], s, &lr);
754 total += load;
755 if (lr.csr_cpu >= 0 && (load > bload ||
756 (load == bload && lr.csr_load > r->csr_load))) {
757 bload = load;
758 r->csr_cpu = lr.csr_cpu;
759 r->csr_load = lr.csr_load;
760 }
761 }
762 return (total);
763 }
764
765 /* Loop through children CPUs otherwise. */
766 for (c = cg->cg_last; c >= cg->cg_first; c--) {
767 if (!CPU_ISSET(c, &cg->cg_mask))
768 continue;
769 tdq = TDQ_CPU(c);
770 l = tdq->tdq_load;
771 load = l * 256;
772 total += load;
773
774 /*
775 * Check this CPU is acceptable.
776 */
777 if (l < s->cs_load || (tdq->tdq_transferable < s->cs_trans) ||
778 !CPU_ISSET(c, s->cs_mask))
779 continue;
780
781 load -= sched_random() % 256;
782 if (load > bload) {
783 bload = load;
784 r->csr_cpu = c;
785 }
786 }
787 r->csr_load = bload;
788 return (total);
789 }
790
791 /*
792 * Find the cpu with the least load via the least loaded path that has a
793 * lowpri greater than pri pri. A pri of -1 indicates any priority is
794 * acceptable.
795 */
796 static inline int
797 sched_lowest(const struct cpu_group *cg, cpuset_t *mask, int pri, int maxload,
798 int prefer, int running)
799 {
800 struct cpu_search s;
801 struct cpu_search_res r;
802
803 s.cs_prefer = prefer;
804 s.cs_running = running;
805 s.cs_mask = mask;
806 s.cs_pri = pri;
807 s.cs_load = maxload;
808 cpu_search_lowest(cg, &s, &r);
809 return (r.csr_cpu);
810 }
811
812 /*
813 * Find the cpu with the highest load via the highest loaded path.
814 */
815 static inline int
816 sched_highest(const struct cpu_group *cg, cpuset_t *mask, int minload,
817 int mintrans)
818 {
819 struct cpu_search s;
820 struct cpu_search_res r;
821
822 s.cs_mask = mask;
823 s.cs_load = minload;
824 s.cs_trans = mintrans;
825 cpu_search_highest(cg, &s, &r);
826 return (r.csr_cpu);
827 }
828
829 static void
830 sched_balance_group(struct cpu_group *cg)
831 {
832 struct tdq *tdq;
833 struct thread *td;
834 cpuset_t hmask, lmask;
835 int high, low, anylow;
836
837 CPU_FILL(&hmask);
838 for (;;) {
839 high = sched_highest(cg, &hmask, 1, 0);
840 /* Stop if there is no more CPU with transferrable threads. */
841 if (high == -1)
842 break;
843 CPU_CLR(high, &hmask);
844 CPU_COPY(&hmask, &lmask);
845 /* Stop if there is no more CPU left for low. */
846 if (CPU_EMPTY(&lmask))
847 break;
848 tdq = TDQ_CPU(high);
849 if (tdq->tdq_load == 1) {
850 /*
851 * There is only one running thread. We can't move
852 * it from here, so tell it to pick new CPU by itself.
853 */
854 TDQ_LOCK(tdq);
855 td = pcpu_find(high)->pc_curthread;
856 if ((td->td_flags & TDF_IDLETD) == 0 &&
857 THREAD_CAN_MIGRATE(td)) {
858 td->td_flags |= TDF_NEEDRESCHED | TDF_PICKCPU;
859 if (high != curcpu)
860 ipi_cpu(high, IPI_AST);
861 }
862 TDQ_UNLOCK(tdq);
863 break;
864 }
865 anylow = 1;
866 nextlow:
867 if (tdq->tdq_transferable == 0)
868 continue;
869 low = sched_lowest(cg, &lmask, -1, tdq->tdq_load - 1, high, 1);
870 /* Stop if we looked well and found no less loaded CPU. */
871 if (anylow && low == -1)
872 break;
873 /* Go to next high if we found no less loaded CPU. */
874 if (low == -1)
875 continue;
876 /* Transfer thread from high to low. */
877 if (sched_balance_pair(tdq, TDQ_CPU(low))) {
878 /* CPU that got thread can no longer be a donor. */
879 CPU_CLR(low, &hmask);
880 } else {
881 /*
882 * If failed, then there is no threads on high
883 * that can run on this low. Drop low from low
884 * mask and look for different one.
885 */
886 CPU_CLR(low, &lmask);
887 anylow = 0;
888 goto nextlow;
889 }
890 }
891 }
892
893 static void
894 sched_balance(void)
895 {
896 struct tdq *tdq;
897
898 balance_ticks = max(balance_interval / 2, 1) +
899 (sched_random() % balance_interval);
900 tdq = TDQ_SELF();
901 TDQ_UNLOCK(tdq);
902 sched_balance_group(cpu_top);
903 TDQ_LOCK(tdq);
904 }
905
906 /*
907 * Lock two thread queues using their address to maintain lock order.
908 */
909 static void
910 tdq_lock_pair(struct tdq *one, struct tdq *two)
911 {
912 if (one < two) {
913 TDQ_LOCK(one);
914 TDQ_LOCK_FLAGS(two, MTX_DUPOK);
915 } else {
916 TDQ_LOCK(two);
917 TDQ_LOCK_FLAGS(one, MTX_DUPOK);
918 }
919 }
920
921 /*
922 * Unlock two thread queues. Order is not important here.
923 */
924 static void
925 tdq_unlock_pair(struct tdq *one, struct tdq *two)
926 {
927 TDQ_UNLOCK(one);
928 TDQ_UNLOCK(two);
929 }
930
931 /*
932 * Transfer load between two imbalanced thread queues.
933 */
934 static int
935 sched_balance_pair(struct tdq *high, struct tdq *low)
936 {
937 struct thread *td;
938 int cpu;
939
940 tdq_lock_pair(high, low);
941 td = NULL;
942 /*
943 * Transfer a thread from high to low.
944 */
945 if (high->tdq_transferable != 0 && high->tdq_load > low->tdq_load &&
946 (td = tdq_move(high, low)) != NULL) {
947 /*
948 * In case the target isn't the current cpu notify it of the
949 * new load, possibly sending an IPI to force it to reschedule.
950 */
951 cpu = TDQ_ID(low);
952 if (cpu != PCPU_GET(cpuid))
953 tdq_notify(low, td);
954 }
955 tdq_unlock_pair(high, low);
956 return (td != NULL);
957 }
958
959 /*
960 * Move a thread from one thread queue to another.
961 */
962 static struct thread *
963 tdq_move(struct tdq *from, struct tdq *to)
964 {
965 struct thread *td;
966 struct tdq *tdq;
967 int cpu;
968
969 TDQ_LOCK_ASSERT(from, MA_OWNED);
970 TDQ_LOCK_ASSERT(to, MA_OWNED);
971
972 tdq = from;
973 cpu = TDQ_ID(to);
974 td = tdq_steal(tdq, cpu);
975 if (td == NULL)
976 return (NULL);
977
978 /*
979 * Although the run queue is locked the thread may be
980 * blocked. We can not set the lock until it is unblocked.
981 */
982 thread_lock_block_wait(td);
983 sched_rem(td);
984 THREAD_LOCKPTR_ASSERT(td, TDQ_LOCKPTR(from));
985 td->td_lock = TDQ_LOCKPTR(to);
986 td_get_sched(td)->ts_cpu = cpu;
987 tdq_add(to, td, SRQ_YIELDING);
988
989 return (td);
990 }
991
992 /*
993 * This tdq has idled. Try to steal a thread from another cpu and switch
994 * to it.
995 */
996 static int
997 tdq_idled(struct tdq *tdq)
998 {
999 struct cpu_group *cg, *parent;
1000 struct tdq *steal;
1001 cpuset_t mask;
1002 int cpu, switchcnt, goup;
1003
1004 if (smp_started == 0 || steal_idle == 0 || tdq->tdq_cg == NULL)
1005 return (1);
1006 CPU_FILL(&mask);
1007 CPU_CLR(PCPU_GET(cpuid), &mask);
1008 restart:
1009 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
1010 for (cg = tdq->tdq_cg, goup = 0; ; ) {
1011 cpu = sched_highest(cg, &mask, steal_thresh, 1);
1012 /*
1013 * We were assigned a thread but not preempted. Returning
1014 * 0 here will cause our caller to switch to it.
1015 */
1016 if (tdq->tdq_load)
1017 return (0);
1018
1019 /*
1020 * We found no CPU to steal from in this group. Escalate to
1021 * the parent and repeat. But if parent has only two children
1022 * groups we can avoid searching this group again by searching
1023 * the other one specifically and then escalating two levels.
1024 */
1025 if (cpu == -1) {
1026 if (goup) {
1027 cg = cg->cg_parent;
1028 goup = 0;
1029 }
1030 parent = cg->cg_parent;
1031 if (parent == NULL)
1032 return (1);
1033 if (parent->cg_children == 2) {
1034 if (cg == &parent->cg_child[0])
1035 cg = &parent->cg_child[1];
1036 else
1037 cg = &parent->cg_child[0];
1038 goup = 1;
1039 } else
1040 cg = parent;
1041 continue;
1042 }
1043 steal = TDQ_CPU(cpu);
1044 /*
1045 * The data returned by sched_highest() is stale and
1046 * the chosen CPU no longer has an eligible thread.
1047 *
1048 * Testing this ahead of tdq_lock_pair() only catches
1049 * this situation about 20% of the time on an 8 core
1050 * 16 thread Ryzen 7, but it still helps performance.
1051 */
1052 if (steal->tdq_load < steal_thresh ||
1053 steal->tdq_transferable == 0)
1054 goto restart;
1055 /*
1056 * Try to lock both queues. If we are assigned a thread while
1057 * waited for the lock, switch to it now instead of stealing.
1058 * If we can't get the lock, then somebody likely got there
1059 * first so continue searching.
1060 */
1061 TDQ_LOCK(tdq);
1062 if (tdq->tdq_load > 0) {
1063 mi_switch(SW_VOL | SWT_IDLE);
1064 return (0);
1065 }
1066 if (TDQ_TRYLOCK_FLAGS(steal, MTX_DUPOK) == 0) {
1067 TDQ_UNLOCK(tdq);
1068 CPU_CLR(cpu, &mask);
1069 continue;
1070 }
1071 /*
1072 * The data returned by sched_highest() is stale and
1073 * the chosen CPU no longer has an eligible thread, or
1074 * we were preempted and the CPU loading info may be out
1075 * of date. The latter is rare. In either case restart
1076 * the search.
1077 */
1078 if (steal->tdq_load < steal_thresh ||
1079 steal->tdq_transferable == 0 ||
1080 switchcnt != tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt) {
1081 tdq_unlock_pair(tdq, steal);
1082 goto restart;
1083 }
1084 /*
1085 * Steal the thread and switch to it.
1086 */
1087 if (tdq_move(steal, tdq) != NULL)
1088 break;
1089 /*
1090 * We failed to acquire a thread even though it looked
1091 * like one was available. This could be due to affinity
1092 * restrictions or for other reasons. Loop again after
1093 * removing this CPU from the set. The restart logic
1094 * above does not restore this CPU to the set due to the
1095 * likelyhood of failing here again.
1096 */
1097 CPU_CLR(cpu, &mask);
1098 tdq_unlock_pair(tdq, steal);
1099 }
1100 TDQ_UNLOCK(steal);
1101 mi_switch(SW_VOL | SWT_IDLE);
1102 return (0);
1103 }
1104
1105 /*
1106 * Notify a remote cpu of new work. Sends an IPI if criteria are met.
1107 */
1108 static void
1109 tdq_notify(struct tdq *tdq, struct thread *td)
1110 {
1111 struct thread *ctd;
1112 int pri;
1113 int cpu;
1114
1115 if (tdq->tdq_owepreempt)
1116 return;
1117 cpu = td_get_sched(td)->ts_cpu;
1118 pri = td->td_priority;
1119 ctd = pcpu_find(cpu)->pc_curthread;
1120 if (!sched_shouldpreempt(pri, ctd->td_priority, 1))
1121 return;
1122
1123 /*
1124 * Make sure that our caller's earlier update to tdq_load is
1125 * globally visible before we read tdq_cpu_idle. Idle thread
1126 * accesses both of them without locks, and the order is important.
1127 */
1128 atomic_thread_fence_seq_cst();
1129
1130 if (TD_IS_IDLETHREAD(ctd)) {
1131 /*
1132 * If the MD code has an idle wakeup routine try that before
1133 * falling back to IPI.
1134 */
1135 if (!tdq->tdq_cpu_idle || cpu_idle_wakeup(cpu))
1136 return;
1137 }
1138
1139 /*
1140 * The run queues have been updated, so any switch on the remote CPU
1141 * will satisfy the preemption request.
1142 */
1143 tdq->tdq_owepreempt = 1;
1144 ipi_cpu(cpu, IPI_PREEMPT);
1145 }
1146
1147 /*
1148 * Steals load from a timeshare queue. Honors the rotating queue head
1149 * index.
1150 */
1151 static struct thread *
1152 runq_steal_from(struct runq *rq, int cpu, u_char start)
1153 {
1154 struct rqbits *rqb;
1155 struct rqhead *rqh;
1156 struct thread *td, *first;
1157 int bit;
1158 int i;
1159
1160 rqb = &rq->rq_status;
1161 bit = start & (RQB_BPW -1);
1162 first = NULL;
1163 again:
1164 for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
1165 if (rqb->rqb_bits[i] == 0)
1166 continue;
1167 if (bit == 0)
1168 bit = RQB_FFS(rqb->rqb_bits[i]);
1169 for (; bit < RQB_BPW; bit++) {
1170 if ((rqb->rqb_bits[i] & (1ul << bit)) == 0)
1171 continue;
1172 rqh = &rq->rq_queues[bit + (i << RQB_L2BPW)];
1173 TAILQ_FOREACH(td, rqh, td_runq) {
1174 if (first) {
1175 if (THREAD_CAN_MIGRATE(td) &&
1176 THREAD_CAN_SCHED(td, cpu))
1177 return (td);
1178 } else
1179 first = td;
1180 }
1181 }
1182 }
1183 if (start != 0) {
1184 start = 0;
1185 goto again;
1186 }
1187
1188 if (first && THREAD_CAN_MIGRATE(first) &&
1189 THREAD_CAN_SCHED(first, cpu))
1190 return (first);
1191 return (NULL);
1192 }
1193
1194 /*
1195 * Steals load from a standard linear queue.
1196 */
1197 static struct thread *
1198 runq_steal(struct runq *rq, int cpu)
1199 {
1200 struct rqhead *rqh;
1201 struct rqbits *rqb;
1202 struct thread *td;
1203 int word;
1204 int bit;
1205
1206 rqb = &rq->rq_status;
1207 for (word = 0; word < RQB_LEN; word++) {
1208 if (rqb->rqb_bits[word] == 0)
1209 continue;
1210 for (bit = 0; bit < RQB_BPW; bit++) {
1211 if ((rqb->rqb_bits[word] & (1ul << bit)) == 0)
1212 continue;
1213 rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)];
1214 TAILQ_FOREACH(td, rqh, td_runq)
1215 if (THREAD_CAN_MIGRATE(td) &&
1216 THREAD_CAN_SCHED(td, cpu))
1217 return (td);
1218 }
1219 }
1220 return (NULL);
1221 }
1222
1223 /*
1224 * Attempt to steal a thread in priority order from a thread queue.
1225 */
1226 static struct thread *
1227 tdq_steal(struct tdq *tdq, int cpu)
1228 {
1229 struct thread *td;
1230
1231 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
1232 if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL)
1233 return (td);
1234 if ((td = runq_steal_from(&tdq->tdq_timeshare,
1235 cpu, tdq->tdq_ridx)) != NULL)
1236 return (td);
1237 return (runq_steal(&tdq->tdq_idle, cpu));
1238 }
1239
1240 /*
1241 * Sets the thread lock and ts_cpu to match the requested cpu. Unlocks the
1242 * current lock and returns with the assigned queue locked.
1243 */
1244 static inline struct tdq *
1245 sched_setcpu(struct thread *td, int cpu, int flags)
1246 {
1247
1248 struct tdq *tdq;
1249 struct mtx *mtx;
1250
1251 THREAD_LOCK_ASSERT(td, MA_OWNED);
1252 tdq = TDQ_CPU(cpu);
1253 td_get_sched(td)->ts_cpu = cpu;
1254 /*
1255 * If the lock matches just return the queue.
1256 */
1257 if (td->td_lock == TDQ_LOCKPTR(tdq)) {
1258 KASSERT((flags & SRQ_HOLD) == 0,
1259 ("sched_setcpu: Invalid lock for SRQ_HOLD"));
1260 return (tdq);
1261 }
1262
1263 /*
1264 * The hard case, migration, we need to block the thread first to
1265 * prevent order reversals with other cpus locks.
1266 */
1267 spinlock_enter();
1268 mtx = thread_lock_block(td);
1269 if ((flags & SRQ_HOLD) == 0)
1270 mtx_unlock_spin(mtx);
1271 TDQ_LOCK(tdq);
1272 thread_lock_unblock(td, TDQ_LOCKPTR(tdq));
1273 spinlock_exit();
1274 return (tdq);
1275 }
1276
1277 SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding");
1278 SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity");
1279 SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity");
1280 SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load");
1281 SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu");
1282 SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration");
1283
1284 static int
1285 sched_pickcpu(struct thread *td, int flags)
1286 {
1287 struct cpu_group *cg, *ccg;
1288 struct td_sched *ts;
1289 struct tdq *tdq;
1290 cpuset_t *mask;
1291 int cpu, pri, r, self, intr;
1292
1293 self = PCPU_GET(cpuid);
1294 ts = td_get_sched(td);
1295 KASSERT(!CPU_ABSENT(ts->ts_cpu), ("sched_pickcpu: Start scheduler on "
1296 "absent CPU %d for thread %s.", ts->ts_cpu, td->td_name));
1297 if (smp_started == 0)
1298 return (self);
1299 /*
1300 * Don't migrate a running thread from sched_switch().
1301 */
1302 if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td))
1303 return (ts->ts_cpu);
1304 /*
1305 * Prefer to run interrupt threads on the processors that generate
1306 * the interrupt.
1307 */
1308 if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) &&
1309 curthread->td_intr_nesting_level) {
1310 tdq = TDQ_SELF();
1311 if (tdq->tdq_lowpri >= PRI_MIN_IDLE) {
1312 SCHED_STAT_INC(pickcpu_idle_affinity);
1313 return (self);
1314 }
1315 ts->ts_cpu = self;
1316 intr = 1;
1317 cg = tdq->tdq_cg;
1318 goto llc;
1319 } else {
1320 intr = 0;
1321 tdq = TDQ_CPU(ts->ts_cpu);
1322 cg = tdq->tdq_cg;
1323 }
1324 /*
1325 * If the thread can run on the last cpu and the affinity has not
1326 * expired and it is idle, run it there.
1327 */
1328 if (THREAD_CAN_SCHED(td, ts->ts_cpu) &&
1329 tdq->tdq_lowpri >= PRI_MIN_IDLE &&
1330 SCHED_AFFINITY(ts, CG_SHARE_L2)) {
1331 if (cg->cg_flags & CG_FLAG_THREAD) {
1332 /* Check all SMT threads for being idle. */
1333 for (cpu = cg->cg_first; cpu <= cg->cg_last; cpu++) {
1334 if (CPU_ISSET(cpu, &cg->cg_mask) &&
1335 TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE)
1336 break;
1337 }
1338 if (cpu > cg->cg_last) {
1339 SCHED_STAT_INC(pickcpu_idle_affinity);
1340 return (ts->ts_cpu);
1341 }
1342 } else {
1343 SCHED_STAT_INC(pickcpu_idle_affinity);
1344 return (ts->ts_cpu);
1345 }
1346 }
1347 llc:
1348 /*
1349 * Search for the last level cache CPU group in the tree.
1350 * Skip SMT, identical groups and caches with expired affinity.
1351 * Interrupt threads affinity is explicit and never expires.
1352 */
1353 for (ccg = NULL; cg != NULL; cg = cg->cg_parent) {
1354 if (cg->cg_flags & CG_FLAG_THREAD)
1355 continue;
1356 if (cg->cg_children == 1 || cg->cg_count == 1)
1357 continue;
1358 if (cg->cg_level == CG_SHARE_NONE ||
1359 (!intr && !SCHED_AFFINITY(ts, cg->cg_level)))
1360 continue;
1361 ccg = cg;
1362 }
1363 /* Found LLC shared by all CPUs, so do a global search. */
1364 if (ccg == cpu_top)
1365 ccg = NULL;
1366 cpu = -1;
1367 mask = &td->td_cpuset->cs_mask;
1368 pri = td->td_priority;
1369 r = TD_IS_RUNNING(td);
1370 /*
1371 * Try hard to keep interrupts within found LLC. Search the LLC for
1372 * the least loaded CPU we can run now. For NUMA systems it should
1373 * be within target domain, and it also reduces scheduling overhead.
1374 */
1375 if (ccg != NULL && intr) {
1376 cpu = sched_lowest(ccg, mask, pri, INT_MAX, ts->ts_cpu, r);
1377 if (cpu >= 0)
1378 SCHED_STAT_INC(pickcpu_intrbind);
1379 } else
1380 /* Search the LLC for the least loaded idle CPU we can run now. */
1381 if (ccg != NULL) {
1382 cpu = sched_lowest(ccg, mask, max(pri, PRI_MAX_TIMESHARE),
1383 INT_MAX, ts->ts_cpu, r);
1384 if (cpu >= 0)
1385 SCHED_STAT_INC(pickcpu_affinity);
1386 }
1387 /* Search globally for the least loaded CPU we can run now. */
1388 if (cpu < 0) {
1389 cpu = sched_lowest(cpu_top, mask, pri, INT_MAX, ts->ts_cpu, r);
1390 if (cpu >= 0)
1391 SCHED_STAT_INC(pickcpu_lowest);
1392 }
1393 /* Search globally for the least loaded CPU. */
1394 if (cpu < 0) {
1395 cpu = sched_lowest(cpu_top, mask, -1, INT_MAX, ts->ts_cpu, r);
1396 if (cpu >= 0)
1397 SCHED_STAT_INC(pickcpu_lowest);
1398 }
1399 KASSERT(cpu >= 0, ("sched_pickcpu: Failed to find a cpu."));
1400 KASSERT(!CPU_ABSENT(cpu), ("sched_pickcpu: Picked absent CPU %d.", cpu));
1401 /*
1402 * Compare the lowest loaded cpu to current cpu.
1403 */
1404 tdq = TDQ_CPU(cpu);
1405 if (THREAD_CAN_SCHED(td, self) && TDQ_SELF()->tdq_lowpri > pri &&
1406 tdq->tdq_lowpri < PRI_MIN_IDLE &&
1407 TDQ_SELF()->tdq_load <= tdq->tdq_load + 1) {
1408 SCHED_STAT_INC(pickcpu_local);
1409 cpu = self;
1410 }
1411 if (cpu != ts->ts_cpu)
1412 SCHED_STAT_INC(pickcpu_migration);
1413 return (cpu);
1414 }
1415 #endif
1416
1417 /*
1418 * Pick the highest priority task we have and return it.
1419 */
1420 static struct thread *
1421 tdq_choose(struct tdq *tdq)
1422 {
1423 struct thread *td;
1424
1425 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
1426 td = runq_choose(&tdq->tdq_realtime);
1427 if (td != NULL)
1428 return (td);
1429 td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
1430 if (td != NULL) {
1431 KASSERT(td->td_priority >= PRI_MIN_BATCH,
1432 ("tdq_choose: Invalid priority on timeshare queue %d",
1433 td->td_priority));
1434 return (td);
1435 }
1436 td = runq_choose(&tdq->tdq_idle);
1437 if (td != NULL) {
1438 KASSERT(td->td_priority >= PRI_MIN_IDLE,
1439 ("tdq_choose: Invalid priority on idle queue %d",
1440 td->td_priority));
1441 return (td);
1442 }
1443
1444 return (NULL);
1445 }
1446
1447 /*
1448 * Initialize a thread queue.
1449 */
1450 static void
1451 tdq_setup(struct tdq *tdq, int id)
1452 {
1453
1454 if (bootverbose)
1455 printf("ULE: setup cpu %d\n", id);
1456 runq_init(&tdq->tdq_realtime);
1457 runq_init(&tdq->tdq_timeshare);
1458 runq_init(&tdq->tdq_idle);
1459 tdq->tdq_id = id;
1460 snprintf(tdq->tdq_name, sizeof(tdq->tdq_name),
1461 "sched lock %d", (int)TDQ_ID(tdq));
1462 mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock", MTX_SPIN);
1463 #ifdef KTR
1464 snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname),
1465 "CPU %d load", (int)TDQ_ID(tdq));
1466 #endif
1467 }
1468
1469 #ifdef SMP
1470 static void
1471 sched_setup_smp(void)
1472 {
1473 struct tdq *tdq;
1474 int i;
1475
1476 cpu_top = smp_topo();
1477 CPU_FOREACH(i) {
1478 tdq = DPCPU_ID_PTR(i, tdq);
1479 tdq_setup(tdq, i);
1480 tdq->tdq_cg = smp_topo_find(cpu_top, i);
1481 if (tdq->tdq_cg == NULL)
1482 panic("Can't find cpu group for %d\n", i);
1483 DPCPU_ID_SET(i, randomval, i * 69069 + 5);
1484 }
1485 PCPU_SET(sched, DPCPU_PTR(tdq));
1486 balance_tdq = TDQ_SELF();
1487 }
1488 #endif
1489
1490 /*
1491 * Setup the thread queues and initialize the topology based on MD
1492 * information.
1493 */
1494 static void
1495 sched_setup(void *dummy)
1496 {
1497 struct tdq *tdq;
1498
1499 #ifdef SMP
1500 sched_setup_smp();
1501 #else
1502 tdq_setup(TDQ_SELF(), 0);
1503 #endif
1504 tdq = TDQ_SELF();
1505
1506 /* Add thread0's load since it's running. */
1507 TDQ_LOCK(tdq);
1508 thread0.td_lock = TDQ_LOCKPTR(tdq);
1509 tdq_load_add(tdq, &thread0);
1510 tdq->tdq_lowpri = thread0.td_priority;
1511 TDQ_UNLOCK(tdq);
1512 }
1513
1514 /*
1515 * This routine determines time constants after stathz and hz are setup.
1516 */
1517 /* ARGSUSED */
1518 static void
1519 sched_initticks(void *dummy)
1520 {
1521 int incr;
1522
1523 realstathz = stathz ? stathz : hz;
1524 sched_slice = realstathz / SCHED_SLICE_DEFAULT_DIVISOR;
1525 sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
1526 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
1527 realstathz);
1528
1529 /*
1530 * tickincr is shifted out by 10 to avoid rounding errors due to
1531 * hz not being evenly divisible by stathz on all platforms.
1532 */
1533 incr = (hz << SCHED_TICK_SHIFT) / realstathz;
1534 /*
1535 * This does not work for values of stathz that are more than
1536 * 1 << SCHED_TICK_SHIFT * hz. In practice this does not happen.
1537 */
1538 if (incr == 0)
1539 incr = 1;
1540 tickincr = incr;
1541 #ifdef SMP
1542 /*
1543 * Set the default balance interval now that we know
1544 * what realstathz is.
1545 */
1546 balance_interval = realstathz;
1547 balance_ticks = balance_interval;
1548 affinity = SCHED_AFFINITY_DEFAULT;
1549 #endif
1550 if (sched_idlespinthresh < 0)
1551 sched_idlespinthresh = 2 * max(10000, 6 * hz) / realstathz;
1552 }
1553
1554 /*
1555 * This is the core of the interactivity algorithm. Determines a score based
1556 * on past behavior. It is the ratio of sleep time to run time scaled to
1557 * a [0, 100] integer. This is the voluntary sleep time of a process, which
1558 * differs from the cpu usage because it does not account for time spent
1559 * waiting on a run-queue. Would be prettier if we had floating point.
1560 *
1561 * When a thread's sleep time is greater than its run time the
1562 * calculation is:
1563 *
1564 * scaling factor
1565 * interactivity score = ---------------------
1566 * sleep time / run time
1567 *
1568 *
1569 * When a thread's run time is greater than its sleep time the
1570 * calculation is:
1571 *
1572 * scaling factor
1573 * interactivity score = --------------------- + scaling factor
1574 * run time / sleep time
1575 */
1576 static int
1577 sched_interact_score(struct thread *td)
1578 {
1579 struct td_sched *ts;
1580 int div;
1581
1582 ts = td_get_sched(td);
1583 /*
1584 * The score is only needed if this is likely to be an interactive
1585 * task. Don't go through the expense of computing it if there's
1586 * no chance.
1587 */
1588 if (sched_interact <= SCHED_INTERACT_HALF &&
1589 ts->ts_runtime >= ts->ts_slptime)
1590 return (SCHED_INTERACT_HALF);
1591
1592 if (ts->ts_runtime > ts->ts_slptime) {
1593 div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF);
1594 return (SCHED_INTERACT_HALF +
1595 (SCHED_INTERACT_HALF - (ts->ts_slptime / div)));
1596 }
1597 if (ts->ts_slptime > ts->ts_runtime) {
1598 div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF);
1599 return (ts->ts_runtime / div);
1600 }
1601 /* runtime == slptime */
1602 if (ts->ts_runtime)
1603 return (SCHED_INTERACT_HALF);
1604
1605 /*
1606 * This can happen if slptime and runtime are 0.
1607 */
1608 return (0);
1609
1610 }
1611
1612 /*
1613 * Scale the scheduling priority according to the "interactivity" of this
1614 * process.
1615 */
1616 static void
1617 sched_priority(struct thread *td)
1618 {
1619 u_int pri, score;
1620
1621 if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
1622 return;
1623 /*
1624 * If the score is interactive we place the thread in the realtime
1625 * queue with a priority that is less than kernel and interrupt
1626 * priorities. These threads are not subject to nice restrictions.
1627 *
1628 * Scores greater than this are placed on the normal timeshare queue
1629 * where the priority is partially decided by the most recent cpu
1630 * utilization and the rest is decided by nice value.
1631 *
1632 * The nice value of the process has a linear effect on the calculated
1633 * score. Negative nice values make it easier for a thread to be
1634 * considered interactive.
1635 */
1636 score = imax(0, sched_interact_score(td) + td->td_proc->p_nice);
1637 if (score < sched_interact) {
1638 pri = PRI_MIN_INTERACT;
1639 pri += (PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) * score /
1640 sched_interact;
1641 KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT,
1642 ("sched_priority: invalid interactive priority %u score %u",
1643 pri, score));
1644 } else {
1645 pri = SCHED_PRI_MIN;
1646 if (td_get_sched(td)->ts_ticks)
1647 pri += min(SCHED_PRI_TICKS(td_get_sched(td)),
1648 SCHED_PRI_RANGE - 1);
1649 pri += SCHED_PRI_NICE(td->td_proc->p_nice);
1650 KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH,
1651 ("sched_priority: invalid priority %u: nice %d, "
1652 "ticks %d ftick %d ltick %d tick pri %d",
1653 pri, td->td_proc->p_nice, td_get_sched(td)->ts_ticks,
1654 td_get_sched(td)->ts_ftick, td_get_sched(td)->ts_ltick,
1655 SCHED_PRI_TICKS(td_get_sched(td))));
1656 }
1657 sched_user_prio(td, pri);
1658
1659 return;
1660 }
1661
1662 /*
1663 * This routine enforces a maximum limit on the amount of scheduling history
1664 * kept. It is called after either the slptime or runtime is adjusted. This
1665 * function is ugly due to integer math.
1666 */
1667 static void
1668 sched_interact_update(struct thread *td)
1669 {
1670 struct td_sched *ts;
1671 u_int sum;
1672
1673 ts = td_get_sched(td);
1674 sum = ts->ts_runtime + ts->ts_slptime;
1675 if (sum < SCHED_SLP_RUN_MAX)
1676 return;
1677 /*
1678 * This only happens from two places:
1679 * 1) We have added an unusual amount of run time from fork_exit.
1680 * 2) We have added an unusual amount of sleep time from sched_sleep().
1681 */
1682 if (sum > SCHED_SLP_RUN_MAX * 2) {
1683 if (ts->ts_runtime > ts->ts_slptime) {
1684 ts->ts_runtime = SCHED_SLP_RUN_MAX;
1685 ts->ts_slptime = 1;
1686 } else {
1687 ts->ts_slptime = SCHED_SLP_RUN_MAX;
1688 ts->ts_runtime = 1;
1689 }
1690 return;
1691 }
1692 /*
1693 * If we have exceeded by more than 1/5th then the algorithm below
1694 * will not bring us back into range. Dividing by two here forces
1695 * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX]
1696 */
1697 if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) {
1698 ts->ts_runtime /= 2;
1699 ts->ts_slptime /= 2;
1700 return;
1701 }
1702 ts->ts_runtime = (ts->ts_runtime / 5) * 4;
1703 ts->ts_slptime = (ts->ts_slptime / 5) * 4;
1704 }
1705
1706 /*
1707 * Scale back the interactivity history when a child thread is created. The
1708 * history is inherited from the parent but the thread may behave totally
1709 * differently. For example, a shell spawning a compiler process. We want
1710 * to learn that the compiler is behaving badly very quickly.
1711 */
1712 static void
1713 sched_interact_fork(struct thread *td)
1714 {
1715 struct td_sched *ts;
1716 int ratio;
1717 int sum;
1718
1719 ts = td_get_sched(td);
1720 sum = ts->ts_runtime + ts->ts_slptime;
1721 if (sum > SCHED_SLP_RUN_FORK) {
1722 ratio = sum / SCHED_SLP_RUN_FORK;
1723 ts->ts_runtime /= ratio;
1724 ts->ts_slptime /= ratio;
1725 }
1726 }
1727
1728 /*
1729 * Called from proc0_init() to setup the scheduler fields.
1730 */
1731 void
1732 schedinit(void)
1733 {
1734 struct td_sched *ts0;
1735
1736 /*
1737 * Set up the scheduler specific parts of thread0.
1738 */
1739 ts0 = td_get_sched(&thread0);
1740 ts0->ts_ltick = ticks;
1741 ts0->ts_ftick = ticks;
1742 ts0->ts_slice = 0;
1743 ts0->ts_cpu = curcpu; /* set valid CPU number */
1744 }
1745
1746 /*
1747 * This is only somewhat accurate since given many processes of the same
1748 * priority they will switch when their slices run out, which will be
1749 * at most sched_slice stathz ticks.
1750 */
1751 int
1752 sched_rr_interval(void)
1753 {
1754
1755 /* Convert sched_slice from stathz to hz. */
1756 return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz));
1757 }
1758
1759 /*
1760 * Update the percent cpu tracking information when it is requested or
1761 * the total history exceeds the maximum. We keep a sliding history of
1762 * tick counts that slowly decays. This is less precise than the 4BSD
1763 * mechanism since it happens with less regular and frequent events.
1764 */
1765 static void
1766 sched_pctcpu_update(struct td_sched *ts, int run)
1767 {
1768 int t = ticks;
1769
1770 /*
1771 * The signed difference may be negative if the thread hasn't run for
1772 * over half of the ticks rollover period.
1773 */
1774 if ((u_int)(t - ts->ts_ltick) >= SCHED_TICK_TARG) {
1775 ts->ts_ticks = 0;
1776 ts->ts_ftick = t - SCHED_TICK_TARG;
1777 } else if (t - ts->ts_ftick >= SCHED_TICK_MAX) {
1778 ts->ts_ticks = (ts->ts_ticks / (ts->ts_ltick - ts->ts_ftick)) *
1779 (ts->ts_ltick - (t - SCHED_TICK_TARG));
1780 ts->ts_ftick = t - SCHED_TICK_TARG;
1781 }
1782 if (run)
1783 ts->ts_ticks += (t - ts->ts_ltick) << SCHED_TICK_SHIFT;
1784 ts->ts_ltick = t;
1785 }
1786
1787 /*
1788 * Adjust the priority of a thread. Move it to the appropriate run-queue
1789 * if necessary. This is the back-end for several priority related
1790 * functions.
1791 */
1792 static void
1793 sched_thread_priority(struct thread *td, u_char prio)
1794 {
1795 struct td_sched *ts;
1796 struct tdq *tdq;
1797 int oldpri;
1798
1799 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio",
1800 "prio:%d", td->td_priority, "new prio:%d", prio,
1801 KTR_ATTR_LINKED, sched_tdname(curthread));
1802 SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio);
1803 if (td != curthread && prio < td->td_priority) {
1804 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
1805 "lend prio", "prio:%d", td->td_priority, "new prio:%d",
1806 prio, KTR_ATTR_LINKED, sched_tdname(td));
1807 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio,
1808 curthread);
1809 }
1810 ts = td_get_sched(td);
1811 THREAD_LOCK_ASSERT(td, MA_OWNED);
1812 if (td->td_priority == prio)
1813 return;
1814 /*
1815 * If the priority has been elevated due to priority
1816 * propagation, we may have to move ourselves to a new
1817 * queue. This could be optimized to not re-add in some
1818 * cases.
1819 */
1820 if (TD_ON_RUNQ(td) && prio < td->td_priority) {
1821 sched_rem(td);
1822 td->td_priority = prio;
1823 sched_add(td, SRQ_BORROWING | SRQ_HOLDTD);
1824 return;
1825 }
1826 /*
1827 * If the thread is currently running we may have to adjust the lowpri
1828 * information so other cpus are aware of our current priority.
1829 */
1830 if (TD_IS_RUNNING(td)) {
1831 tdq = TDQ_CPU(ts->ts_cpu);
1832 oldpri = td->td_priority;
1833 td->td_priority = prio;
1834 if (prio < tdq->tdq_lowpri)
1835 tdq->tdq_lowpri = prio;
1836 else if (tdq->tdq_lowpri == oldpri)
1837 tdq_setlowpri(tdq, td);
1838 return;
1839 }
1840 td->td_priority = prio;
1841 }
1842
1843 /*
1844 * Update a thread's priority when it is lent another thread's
1845 * priority.
1846 */
1847 void
1848 sched_lend_prio(struct thread *td, u_char prio)
1849 {
1850
1851 td->td_flags |= TDF_BORROWING;
1852 sched_thread_priority(td, prio);
1853 }
1854
1855 /*
1856 * Restore a thread's priority when priority propagation is
1857 * over. The prio argument is the minimum priority the thread
1858 * needs to have to satisfy other possible priority lending
1859 * requests. If the thread's regular priority is less
1860 * important than prio, the thread will keep a priority boost
1861 * of prio.
1862 */
1863 void
1864 sched_unlend_prio(struct thread *td, u_char prio)
1865 {
1866 u_char base_pri;
1867
1868 if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
1869 td->td_base_pri <= PRI_MAX_TIMESHARE)
1870 base_pri = td->td_user_pri;
1871 else
1872 base_pri = td->td_base_pri;
1873 if (prio >= base_pri) {
1874 td->td_flags &= ~TDF_BORROWING;
1875 sched_thread_priority(td, base_pri);
1876 } else
1877 sched_lend_prio(td, prio);
1878 }
1879
1880 /*
1881 * Standard entry for setting the priority to an absolute value.
1882 */
1883 void
1884 sched_prio(struct thread *td, u_char prio)
1885 {
1886 u_char oldprio;
1887
1888 /* First, update the base priority. */
1889 td->td_base_pri = prio;
1890
1891 /*
1892 * If the thread is borrowing another thread's priority, don't
1893 * ever lower the priority.
1894 */
1895 if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
1896 return;
1897
1898 /* Change the real priority. */
1899 oldprio = td->td_priority;
1900 sched_thread_priority(td, prio);
1901
1902 /*
1903 * If the thread is on a turnstile, then let the turnstile update
1904 * its state.
1905 */
1906 if (TD_ON_LOCK(td) && oldprio != prio)
1907 turnstile_adjust(td, oldprio);
1908 }
1909
1910 /*
1911 * Set the base user priority, does not effect current running priority.
1912 */
1913 void
1914 sched_user_prio(struct thread *td, u_char prio)
1915 {
1916
1917 td->td_base_user_pri = prio;
1918 if (td->td_lend_user_pri <= prio)
1919 return;
1920 td->td_user_pri = prio;
1921 }
1922
1923 void
1924 sched_lend_user_prio(struct thread *td, u_char prio)
1925 {
1926
1927 THREAD_LOCK_ASSERT(td, MA_OWNED);
1928 td->td_lend_user_pri = prio;
1929 td->td_user_pri = min(prio, td->td_base_user_pri);
1930 if (td->td_priority > td->td_user_pri)
1931 sched_prio(td, td->td_user_pri);
1932 else if (td->td_priority != td->td_user_pri)
1933 td->td_flags |= TDF_NEEDRESCHED;
1934 }
1935
1936 /*
1937 * Like the above but first check if there is anything to do.
1938 */
1939 void
1940 sched_lend_user_prio_cond(struct thread *td, u_char prio)
1941 {
1942
1943 if (td->td_lend_user_pri != prio)
1944 goto lend;
1945 if (td->td_user_pri != min(prio, td->td_base_user_pri))
1946 goto lend;
1947 if (td->td_priority != td->td_user_pri)
1948 goto lend;
1949 return;
1950
1951 lend:
1952 thread_lock(td);
1953 sched_lend_user_prio(td, prio);
1954 thread_unlock(td);
1955 }
1956
1957 #ifdef SMP
1958 /*
1959 * This tdq is about to idle. Try to steal a thread from another CPU before
1960 * choosing the idle thread.
1961 */
1962 static void
1963 tdq_trysteal(struct tdq *tdq)
1964 {
1965 struct cpu_group *cg, *parent;
1966 struct tdq *steal;
1967 cpuset_t mask;
1968 int cpu, i, goup;
1969
1970 if (smp_started == 0 || steal_idle == 0 || trysteal_limit == 0 ||
1971 tdq->tdq_cg == NULL)
1972 return;
1973 CPU_FILL(&mask);
1974 CPU_CLR(PCPU_GET(cpuid), &mask);
1975 /* We don't want to be preempted while we're iterating. */
1976 spinlock_enter();
1977 TDQ_UNLOCK(tdq);
1978 for (i = 1, cg = tdq->tdq_cg, goup = 0; ; ) {
1979 cpu = sched_highest(cg, &mask, steal_thresh, 1);
1980 /*
1981 * If a thread was added while interrupts were disabled don't
1982 * steal one here.
1983 */
1984 if (tdq->tdq_load > 0) {
1985 TDQ_LOCK(tdq);
1986 break;
1987 }
1988
1989 /*
1990 * We found no CPU to steal from in this group. Escalate to
1991 * the parent and repeat. But if parent has only two children
1992 * groups we can avoid searching this group again by searching
1993 * the other one specifically and then escalating two levels.
1994 */
1995 if (cpu == -1) {
1996 if (goup) {
1997 cg = cg->cg_parent;
1998 goup = 0;
1999 }
2000 if (++i > trysteal_limit) {
2001 TDQ_LOCK(tdq);
2002 break;
2003 }
2004 parent = cg->cg_parent;
2005 if (parent == NULL) {
2006 TDQ_LOCK(tdq);
2007 break;
2008 }
2009 if (parent->cg_children == 2) {
2010 if (cg == &parent->cg_child[0])
2011 cg = &parent->cg_child[1];
2012 else
2013 cg = &parent->cg_child[0];
2014 goup = 1;
2015 } else
2016 cg = parent;
2017 continue;
2018 }
2019 steal = TDQ_CPU(cpu);
2020 /*
2021 * The data returned by sched_highest() is stale and
2022 * the chosen CPU no longer has an eligible thread.
2023 * At this point unconditionally exit the loop to bound
2024 * the time spent in the critcal section.
2025 */
2026 if (steal->tdq_load < steal_thresh ||
2027 steal->tdq_transferable == 0)
2028 continue;
2029 /*
2030 * Try to lock both queues. If we are assigned a thread while
2031 * waited for the lock, switch to it now instead of stealing.
2032 * If we can't get the lock, then somebody likely got there
2033 * first.
2034 */
2035 TDQ_LOCK(tdq);
2036 if (tdq->tdq_load > 0)
2037 break;
2038 if (TDQ_TRYLOCK_FLAGS(steal, MTX_DUPOK) == 0)
2039 break;
2040 /*
2041 * The data returned by sched_highest() is stale and
2042 * the chosen CPU no longer has an eligible thread.
2043 */
2044 if (steal->tdq_load < steal_thresh ||
2045 steal->tdq_transferable == 0) {
2046 TDQ_UNLOCK(steal);
2047 break;
2048 }
2049 /*
2050 * If we fail to acquire one due to affinity restrictions,
2051 * bail out and let the idle thread to a more complete search
2052 * outside of a critical section.
2053 */
2054 if (tdq_move(steal, tdq) == NULL) {
2055 TDQ_UNLOCK(steal);
2056 break;
2057 }
2058 TDQ_UNLOCK(steal);
2059 break;
2060 }
2061 spinlock_exit();
2062 }
2063 #endif
2064
2065 /*
2066 * Handle migration from sched_switch(). This happens only for
2067 * cpu binding.
2068 */
2069 static struct mtx *
2070 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags)
2071 {
2072 struct tdq *tdn;
2073
2074 KASSERT(THREAD_CAN_MIGRATE(td) ||
2075 (td_get_sched(td)->ts_flags & TSF_BOUND) != 0,
2076 ("Thread %p shouldn't migrate", td));
2077 KASSERT(!CPU_ABSENT(td_get_sched(td)->ts_cpu), ("sched_switch_migrate: "
2078 "thread %s queued on absent CPU %d.", td->td_name,
2079 td_get_sched(td)->ts_cpu));
2080 tdn = TDQ_CPU(td_get_sched(td)->ts_cpu);
2081 #ifdef SMP
2082 tdq_load_rem(tdq, td);
2083 /*
2084 * Do the lock dance required to avoid LOR. We have an
2085 * extra spinlock nesting from sched_switch() which will
2086 * prevent preemption while we're holding neither run-queue lock.
2087 */
2088 TDQ_UNLOCK(tdq);
2089 TDQ_LOCK(tdn);
2090 tdq_add(tdn, td, flags);
2091 tdq_notify(tdn, td);
2092 TDQ_UNLOCK(tdn);
2093 TDQ_LOCK(tdq);
2094 #endif
2095 return (TDQ_LOCKPTR(tdn));
2096 }
2097
2098 /*
2099 * thread_lock_unblock() that does not assume td_lock is blocked.
2100 */
2101 static inline void
2102 thread_unblock_switch(struct thread *td, struct mtx *mtx)
2103 {
2104 atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock,
2105 (uintptr_t)mtx);
2106 }
2107
2108 /*
2109 * Switch threads. This function has to handle threads coming in while
2110 * blocked for some reason, running, or idle. It also must deal with
2111 * migrating a thread from one queue to another as running threads may
2112 * be assigned elsewhere via binding.
2113 */
2114 void
2115 sched_switch(struct thread *td, int flags)
2116 {
2117 struct thread *newtd;
2118 struct tdq *tdq;
2119 struct td_sched *ts;
2120 struct mtx *mtx;
2121 int srqflag;
2122 int cpuid, preempted;
2123 #ifdef SMP
2124 int pickcpu;
2125 #endif
2126
2127 THREAD_LOCK_ASSERT(td, MA_OWNED);
2128
2129 cpuid = PCPU_GET(cpuid);
2130 tdq = TDQ_SELF();
2131 ts = td_get_sched(td);
2132 sched_pctcpu_update(ts, 1);
2133 #ifdef SMP
2134 pickcpu = (td->td_flags & TDF_PICKCPU) != 0;
2135 if (pickcpu)
2136 ts->ts_rltick = ticks - affinity * MAX_CACHE_LEVELS;
2137 else
2138 ts->ts_rltick = ticks;
2139 #endif
2140 td->td_lastcpu = td->td_oncpu;
2141 preempted = (td->td_flags & TDF_SLICEEND) == 0 &&
2142 (flags & SW_PREEMPT) != 0;
2143 td->td_flags &= ~(TDF_NEEDRESCHED | TDF_PICKCPU | TDF_SLICEEND);
2144 td->td_owepreempt = 0;
2145 tdq->tdq_owepreempt = 0;
2146 if (!TD_IS_IDLETHREAD(td))
2147 tdq->tdq_switchcnt++;
2148
2149 /*
2150 * Always block the thread lock so we can drop the tdq lock early.
2151 */
2152 mtx = thread_lock_block(td);
2153 spinlock_enter();
2154 if (TD_IS_IDLETHREAD(td)) {
2155 MPASS(mtx == TDQ_LOCKPTR(tdq));
2156 TD_SET_CAN_RUN(td);
2157 } else if (TD_IS_RUNNING(td)) {
2158 MPASS(mtx == TDQ_LOCKPTR(tdq));
2159 srqflag = preempted ?
2160 SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
2161 SRQ_OURSELF|SRQ_YIELDING;
2162 #ifdef SMP
2163 if (THREAD_CAN_MIGRATE(td) && (!THREAD_CAN_SCHED(td, ts->ts_cpu)
2164 || pickcpu))
2165 ts->ts_cpu = sched_pickcpu(td, 0);
2166 #endif
2167 if (ts->ts_cpu == cpuid)
2168 tdq_runq_add(tdq, td, srqflag);
2169 else
2170 mtx = sched_switch_migrate(tdq, td, srqflag);
2171 } else {
2172 /* This thread must be going to sleep. */
2173 if (mtx != TDQ_LOCKPTR(tdq)) {
2174 mtx_unlock_spin(mtx);
2175 TDQ_LOCK(tdq);
2176 }
2177 tdq_load_rem(tdq, td);
2178 #ifdef SMP
2179 if (tdq->tdq_load == 0)
2180 tdq_trysteal(tdq);
2181 #endif
2182 }
2183
2184 #if (KTR_COMPILE & KTR_SCHED) != 0
2185 if (TD_IS_IDLETHREAD(td))
2186 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle",
2187 "prio:%d", td->td_priority);
2188 else
2189 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td),
2190 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg,
2191 "lockname:\"%s\"", td->td_lockname);
2192 #endif
2193
2194 /*
2195 * We enter here with the thread blocked and assigned to the
2196 * appropriate cpu run-queue or sleep-queue and with the current
2197 * thread-queue locked.
2198 */
2199 TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
2200 newtd = choosethread();
2201 sched_pctcpu_update(td_get_sched(newtd), 0);
2202 TDQ_UNLOCK(tdq);
2203
2204 /*
2205 * Call the MD code to switch contexts if necessary.
2206 */
2207 if (td != newtd) {
2208 #ifdef HWPMC_HOOKS
2209 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
2210 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
2211 #endif
2212 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc);
2213
2214 #ifdef KDTRACE_HOOKS
2215 /*
2216 * If DTrace has set the active vtime enum to anything
2217 * other than INACTIVE (0), then it should have set the
2218 * function to call.
2219 */
2220 if (dtrace_vtime_active)
2221 (*dtrace_vtime_switch_func)(newtd);
2222 #endif
2223 td->td_oncpu = NOCPU;
2224 cpu_switch(td, newtd, mtx);
2225 cpuid = td->td_oncpu = PCPU_GET(cpuid);
2226
2227 SDT_PROBE0(sched, , , on__cpu);
2228 #ifdef HWPMC_HOOKS
2229 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
2230 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
2231 #endif
2232 } else {
2233 thread_unblock_switch(td, mtx);
2234 SDT_PROBE0(sched, , , remain__cpu);
2235 }
2236 KASSERT(curthread->td_md.md_spinlock_count == 1,
2237 ("invalid count %d", curthread->td_md.md_spinlock_count));
2238
2239 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
2240 "prio:%d", td->td_priority);
2241 }
2242
2243 /*
2244 * Adjust thread priorities as a result of a nice request.
2245 */
2246 void
2247 sched_nice(struct proc *p, int nice)
2248 {
2249 struct thread *td;
2250
2251 PROC_LOCK_ASSERT(p, MA_OWNED);
2252
2253 p->p_nice = nice;
2254 FOREACH_THREAD_IN_PROC(p, td) {
2255 thread_lock(td);
2256 sched_priority(td);
2257 sched_prio(td, td->td_base_user_pri);
2258 thread_unlock(td);
2259 }
2260 }
2261
2262 /*
2263 * Record the sleep time for the interactivity scorer.
2264 */
2265 void
2266 sched_sleep(struct thread *td, int prio)
2267 {
2268
2269 THREAD_LOCK_ASSERT(td, MA_OWNED);
2270
2271 td->td_slptick = ticks;
2272 if (TD_IS_SUSPENDED(td) || prio >= PSOCK)
2273 td->td_flags |= TDF_CANSWAP;
2274 if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
2275 return;
2276 if (static_boost == 1 && prio)
2277 sched_prio(td, prio);
2278 else if (static_boost && td->td_priority > static_boost)
2279 sched_prio(td, static_boost);
2280 }
2281
2282 /*
2283 * Schedule a thread to resume execution and record how long it voluntarily
2284 * slept. We also update the pctcpu, interactivity, and priority.
2285 *
2286 * Requires the thread lock on entry, drops on exit.
2287 */
2288 void
2289 sched_wakeup(struct thread *td, int srqflags)
2290 {
2291 struct td_sched *ts;
2292 int slptick;
2293
2294 THREAD_LOCK_ASSERT(td, MA_OWNED);
2295 ts = td_get_sched(td);
2296 td->td_flags &= ~TDF_CANSWAP;
2297
2298 /*
2299 * If we slept for more than a tick update our interactivity and
2300 * priority.
2301 */
2302 slptick = td->td_slptick;
2303 td->td_slptick = 0;
2304 if (slptick && slptick != ticks) {
2305 ts->ts_slptime += (ticks - slptick) << SCHED_TICK_SHIFT;
2306 sched_interact_update(td);
2307 sched_pctcpu_update(ts, 0);
2308 }
2309 /*
2310 * Reset the slice value since we slept and advanced the round-robin.
2311 */
2312 ts->ts_slice = 0;
2313 sched_add(td, SRQ_BORING | srqflags);
2314 }
2315
2316 /*
2317 * Penalize the parent for creating a new child and initialize the child's
2318 * priority.
2319 */
2320 void
2321 sched_fork(struct thread *td, struct thread *child)
2322 {
2323 THREAD_LOCK_ASSERT(td, MA_OWNED);
2324 sched_pctcpu_update(td_get_sched(td), 1);
2325 sched_fork_thread(td, child);
2326 /*
2327 * Penalize the parent and child for forking.
2328 */
2329 sched_interact_fork(child);
2330 sched_priority(child);
2331 td_get_sched(td)->ts_runtime += tickincr;
2332 sched_interact_update(td);
2333 sched_priority(td);
2334 }
2335
2336 /*
2337 * Fork a new thread, may be within the same process.
2338 */
2339 void
2340 sched_fork_thread(struct thread *td, struct thread *child)
2341 {
2342 struct td_sched *ts;
2343 struct td_sched *ts2;
2344 struct tdq *tdq;
2345
2346 tdq = TDQ_SELF();
2347 THREAD_LOCK_ASSERT(td, MA_OWNED);
2348 /*
2349 * Initialize child.
2350 */
2351 ts = td_get_sched(td);
2352 ts2 = td_get_sched(child);
2353 child->td_oncpu = NOCPU;
2354 child->td_lastcpu = NOCPU;
2355 child->td_lock = TDQ_LOCKPTR(tdq);
2356 child->td_cpuset = cpuset_ref(td->td_cpuset);
2357 child->td_domain.dr_policy = td->td_cpuset->cs_domain;
2358 ts2->ts_cpu = ts->ts_cpu;
2359 ts2->ts_flags = 0;
2360 /*
2361 * Grab our parents cpu estimation information.
2362 */
2363 ts2->ts_ticks = ts->ts_ticks;
2364 ts2->ts_ltick = ts->ts_ltick;
2365 ts2->ts_ftick = ts->ts_ftick;
2366 /*
2367 * Do not inherit any borrowed priority from the parent.
2368 */
2369 child->td_priority = child->td_base_pri;
2370 /*
2371 * And update interactivity score.
2372 */
2373 ts2->ts_slptime = ts->ts_slptime;
2374 ts2->ts_runtime = ts->ts_runtime;
2375 /* Attempt to quickly learn interactivity. */
2376 ts2->ts_slice = tdq_slice(tdq) - sched_slice_min;
2377 #ifdef KTR
2378 bzero(ts2->ts_name, sizeof(ts2->ts_name));
2379 #endif
2380 }
2381
2382 /*
2383 * Adjust the priority class of a thread.
2384 */
2385 void
2386 sched_class(struct thread *td, int class)
2387 {
2388
2389 THREAD_LOCK_ASSERT(td, MA_OWNED);
2390 if (td->td_pri_class == class)
2391 return;
2392 td->td_pri_class = class;
2393 }
2394
2395 /*
2396 * Return some of the child's priority and interactivity to the parent.
2397 */
2398 void
2399 sched_exit(struct proc *p, struct thread *child)
2400 {
2401 struct thread *td;
2402
2403 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit",
2404 "prio:%d", child->td_priority);
2405 PROC_LOCK_ASSERT(p, MA_OWNED);
2406 td = FIRST_THREAD_IN_PROC(p);
2407 sched_exit_thread(td, child);
2408 }
2409
2410 /*
2411 * Penalize another thread for the time spent on this one. This helps to
2412 * worsen the priority and interactivity of processes which schedule batch
2413 * jobs such as make. This has little effect on the make process itself but
2414 * causes new processes spawned by it to receive worse scores immediately.
2415 */
2416 void
2417 sched_exit_thread(struct thread *td, struct thread *child)
2418 {
2419
2420 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit",
2421 "prio:%d", child->td_priority);
2422 /*
2423 * Give the child's runtime to the parent without returning the
2424 * sleep time as a penalty to the parent. This causes shells that
2425 * launch expensive things to mark their children as expensive.
2426 */
2427 thread_lock(td);
2428 td_get_sched(td)->ts_runtime += td_get_sched(child)->ts_runtime;
2429 sched_interact_update(td);
2430 sched_priority(td);
2431 thread_unlock(td);
2432 }
2433
2434 void
2435 sched_preempt(struct thread *td)
2436 {
2437 struct tdq *tdq;
2438 int flags;
2439
2440 SDT_PROBE2(sched, , , surrender, td, td->td_proc);
2441
2442 thread_lock(td);
2443 tdq = TDQ_SELF();
2444 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2445 if (td->td_priority > tdq->tdq_lowpri) {
2446 if (td->td_critnest == 1) {
2447 flags = SW_INVOL | SW_PREEMPT;
2448 flags |= TD_IS_IDLETHREAD(td) ? SWT_REMOTEWAKEIDLE :
2449 SWT_REMOTEPREEMPT;
2450 mi_switch(flags);
2451 /* Switch dropped thread lock. */
2452 return;
2453 }
2454 td->td_owepreempt = 1;
2455 } else {
2456 tdq->tdq_owepreempt = 0;
2457 }
2458 thread_unlock(td);
2459 }
2460
2461 /*
2462 * Fix priorities on return to user-space. Priorities may be elevated due
2463 * to static priorities in msleep() or similar.
2464 */
2465 void
2466 sched_userret_slowpath(struct thread *td)
2467 {
2468
2469 thread_lock(td);
2470 td->td_priority = td->td_user_pri;
2471 td->td_base_pri = td->td_user_pri;
2472 tdq_setlowpri(TDQ_SELF(), td);
2473 thread_unlock(td);
2474 }
2475
2476 /*
2477 * Handle a stathz tick. This is really only relevant for timeshare
2478 * threads.
2479 */
2480 void
2481 sched_clock(struct thread *td, int cnt)
2482 {
2483 struct tdq *tdq;
2484 struct td_sched *ts;
2485
2486 THREAD_LOCK_ASSERT(td, MA_OWNED);
2487 tdq = TDQ_SELF();
2488 #ifdef SMP
2489 /*
2490 * We run the long term load balancer infrequently on the first cpu.
2491 */
2492 if (balance_tdq == tdq && smp_started != 0 && rebalance != 0 &&
2493 balance_ticks != 0) {
2494 balance_ticks -= cnt;
2495 if (balance_ticks <= 0)
2496 sched_balance();
2497 }
2498 #endif
2499 /*
2500 * Save the old switch count so we have a record of the last ticks
2501 * activity. Initialize the new switch count based on our load.
2502 * If there is some activity seed it to reflect that.
2503 */
2504 tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt;
2505 tdq->tdq_switchcnt = tdq->tdq_load;
2506 /*
2507 * Advance the insert index once for each tick to ensure that all
2508 * threads get a chance to run.
2509 */
2510 if (tdq->tdq_idx == tdq->tdq_ridx) {
2511 tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS;
2512 if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx]))
2513 tdq->tdq_ridx = tdq->tdq_idx;
2514 }
2515 ts = td_get_sched(td);
2516 sched_pctcpu_update(ts, 1);
2517 if ((td->td_pri_class & PRI_FIFO_BIT) || TD_IS_IDLETHREAD(td))
2518 return;
2519
2520 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) {
2521 /*
2522 * We used a tick; charge it to the thread so
2523 * that we can compute our interactivity.
2524 */
2525 td_get_sched(td)->ts_runtime += tickincr * cnt;
2526 sched_interact_update(td);
2527 sched_priority(td);
2528 }
2529
2530 /*
2531 * Force a context switch if the current thread has used up a full
2532 * time slice (default is 100ms).
2533 */
2534 ts->ts_slice += cnt;
2535 if (ts->ts_slice >= tdq_slice(tdq)) {
2536 ts->ts_slice = 0;
2537 td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND;
2538 }
2539 }
2540
2541 u_int
2542 sched_estcpu(struct thread *td __unused)
2543 {
2544
2545 return (0);
2546 }
2547
2548 /*
2549 * Return whether the current CPU has runnable tasks. Used for in-kernel
2550 * cooperative idle threads.
2551 */
2552 int
2553 sched_runnable(void)
2554 {
2555 struct tdq *tdq;
2556 int load;
2557
2558 load = 1;
2559
2560 tdq = TDQ_SELF();
2561 if ((curthread->td_flags & TDF_IDLETD) != 0) {
2562 if (tdq->tdq_load > 0)
2563 goto out;
2564 } else
2565 if (tdq->tdq_load - 1 > 0)
2566 goto out;
2567 load = 0;
2568 out:
2569 return (load);
2570 }
2571
2572 /*
2573 * Choose the highest priority thread to run. The thread is removed from
2574 * the run-queue while running however the load remains. For SMP we set
2575 * the tdq in the global idle bitmask if it idles here.
2576 */
2577 struct thread *
2578 sched_choose(void)
2579 {
2580 struct thread *td;
2581 struct tdq *tdq;
2582
2583 tdq = TDQ_SELF();
2584 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2585 td = tdq_choose(tdq);
2586 if (td) {
2587 tdq_runq_rem(tdq, td);
2588 tdq->tdq_lowpri = td->td_priority;
2589 return (td);
2590 }
2591 tdq->tdq_lowpri = PRI_MAX_IDLE;
2592 return (PCPU_GET(idlethread));
2593 }
2594
2595 /*
2596 * Set owepreempt if necessary. Preemption never happens directly in ULE,
2597 * we always request it once we exit a critical section.
2598 */
2599 static inline void
2600 sched_setpreempt(struct thread *td)
2601 {
2602 struct thread *ctd;
2603 int cpri;
2604 int pri;
2605
2606 THREAD_LOCK_ASSERT(curthread, MA_OWNED);
2607
2608 ctd = curthread;
2609 pri = td->td_priority;
2610 cpri = ctd->td_priority;
2611 if (pri < cpri)
2612 ctd->td_flags |= TDF_NEEDRESCHED;
2613 if (KERNEL_PANICKED() || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
2614 return;
2615 if (!sched_shouldpreempt(pri, cpri, 0))
2616 return;
2617 ctd->td_owepreempt = 1;
2618 }
2619
2620 /*
2621 * Add a thread to a thread queue. Select the appropriate runq and add the
2622 * thread to it. This is the internal function called when the tdq is
2623 * predetermined.
2624 */
2625 void
2626 tdq_add(struct tdq *tdq, struct thread *td, int flags)
2627 {
2628
2629 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2630 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
2631 KASSERT((td->td_inhibitors == 0),
2632 ("sched_add: trying to run inhibited thread"));
2633 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
2634 ("sched_add: bad thread state"));
2635 KASSERT(td->td_flags & TDF_INMEM,
2636 ("sched_add: thread swapped out"));
2637
2638 if (td->td_priority < tdq->tdq_lowpri)
2639 tdq->tdq_lowpri = td->td_priority;
2640 tdq_runq_add(tdq, td, flags);
2641 tdq_load_add(tdq, td);
2642 }
2643
2644 /*
2645 * Select the target thread queue and add a thread to it. Request
2646 * preemption or IPI a remote processor if required.
2647 *
2648 * Requires the thread lock on entry, drops on exit.
2649 */
2650 void
2651 sched_add(struct thread *td, int flags)
2652 {
2653 struct tdq *tdq;
2654 #ifdef SMP
2655 int cpu;
2656 #endif
2657
2658 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
2659 "prio:%d", td->td_priority, KTR_ATTR_LINKED,
2660 sched_tdname(curthread));
2661 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
2662 KTR_ATTR_LINKED, sched_tdname(td));
2663 SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL,
2664 flags & SRQ_PREEMPTED);
2665 THREAD_LOCK_ASSERT(td, MA_OWNED);
2666 /*
2667 * Recalculate the priority before we select the target cpu or
2668 * run-queue.
2669 */
2670 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
2671 sched_priority(td);
2672 #ifdef SMP
2673 /*
2674 * Pick the destination cpu and if it isn't ours transfer to the
2675 * target cpu.
2676 */
2677 cpu = sched_pickcpu(td, flags);
2678 tdq = sched_setcpu(td, cpu, flags);
2679 tdq_add(tdq, td, flags);
2680 if (cpu != PCPU_GET(cpuid))
2681 tdq_notify(tdq, td);
2682 else if (!(flags & SRQ_YIELDING))
2683 sched_setpreempt(td);
2684 #else
2685 tdq = TDQ_SELF();
2686 /*
2687 * Now that the thread is moving to the run-queue, set the lock
2688 * to the scheduler's lock.
2689 */
2690 if (td->td_lock != TDQ_LOCKPTR(tdq)) {
2691 TDQ_LOCK(tdq);
2692 if ((flags & SRQ_HOLD) != 0)
2693 td->td_lock = TDQ_LOCKPTR(tdq);
2694 else
2695 thread_lock_set(td, TDQ_LOCKPTR(tdq));
2696 }
2697 tdq_add(tdq, td, flags);
2698 if (!(flags & SRQ_YIELDING))
2699 sched_setpreempt(td);
2700 #endif
2701 if (!(flags & SRQ_HOLDTD))
2702 thread_unlock(td);
2703 }
2704
2705 /*
2706 * Remove a thread from a run-queue without running it. This is used
2707 * when we're stealing a thread from a remote queue. Otherwise all threads
2708 * exit by calling sched_exit_thread() and sched_throw() themselves.
2709 */
2710 void
2711 sched_rem(struct thread *td)
2712 {
2713 struct tdq *tdq;
2714
2715 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
2716 "prio:%d", td->td_priority);
2717 SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL);
2718 tdq = TDQ_CPU(td_get_sched(td)->ts_cpu);
2719 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2720 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
2721 KASSERT(TD_ON_RUNQ(td),
2722 ("sched_rem: thread not on run queue"));
2723 tdq_runq_rem(tdq, td);
2724 tdq_load_rem(tdq, td);
2725 TD_SET_CAN_RUN(td);
2726 if (td->td_priority == tdq->tdq_lowpri)
2727 tdq_setlowpri(tdq, NULL);
2728 }
2729
2730 /*
2731 * Fetch cpu utilization information. Updates on demand.
2732 */
2733 fixpt_t
2734 sched_pctcpu(struct thread *td)
2735 {
2736 fixpt_t pctcpu;
2737 struct td_sched *ts;
2738
2739 pctcpu = 0;
2740 ts = td_get_sched(td);
2741
2742 THREAD_LOCK_ASSERT(td, MA_OWNED);
2743 sched_pctcpu_update(ts, TD_IS_RUNNING(td));
2744 if (ts->ts_ticks) {
2745 int rtick;
2746
2747 /* How many rtick per second ? */
2748 rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
2749 pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
2750 }
2751
2752 return (pctcpu);
2753 }
2754
2755 /*
2756 * Enforce affinity settings for a thread. Called after adjustments to
2757 * cpumask.
2758 */
2759 void
2760 sched_affinity(struct thread *td)
2761 {
2762 #ifdef SMP
2763 struct td_sched *ts;
2764
2765 THREAD_LOCK_ASSERT(td, MA_OWNED);
2766 ts = td_get_sched(td);
2767 if (THREAD_CAN_SCHED(td, ts->ts_cpu))
2768 return;
2769 if (TD_ON_RUNQ(td)) {
2770 sched_rem(td);
2771 sched_add(td, SRQ_BORING | SRQ_HOLDTD);
2772 return;
2773 }
2774 if (!TD_IS_RUNNING(td))
2775 return;
2776 /*
2777 * Force a switch before returning to userspace. If the
2778 * target thread is not running locally send an ipi to force
2779 * the issue.
2780 */
2781 td->td_flags |= TDF_NEEDRESCHED;
2782 if (td != curthread)
2783 ipi_cpu(ts->ts_cpu, IPI_PREEMPT);
2784 #endif
2785 }
2786
2787 /*
2788 * Bind a thread to a target cpu.
2789 */
2790 void
2791 sched_bind(struct thread *td, int cpu)
2792 {
2793 struct td_sched *ts;
2794
2795 THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
2796 KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
2797 ts = td_get_sched(td);
2798 if (ts->ts_flags & TSF_BOUND)
2799 sched_unbind(td);
2800 KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td));
2801 ts->ts_flags |= TSF_BOUND;
2802 sched_pin();
2803 if (PCPU_GET(cpuid) == cpu)
2804 return;
2805 ts->ts_cpu = cpu;
2806 /* When we return from mi_switch we'll be on the correct cpu. */
2807 mi_switch(SW_VOL);
2808 thread_lock(td);
2809 }
2810
2811 /*
2812 * Release a bound thread.
2813 */
2814 void
2815 sched_unbind(struct thread *td)
2816 {
2817 struct td_sched *ts;
2818
2819 THREAD_LOCK_ASSERT(td, MA_OWNED);
2820 KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
2821 ts = td_get_sched(td);
2822 if ((ts->ts_flags & TSF_BOUND) == 0)
2823 return;
2824 ts->ts_flags &= ~TSF_BOUND;
2825 sched_unpin();
2826 }
2827
2828 int
2829 sched_is_bound(struct thread *td)
2830 {
2831 THREAD_LOCK_ASSERT(td, MA_OWNED);
2832 return (td_get_sched(td)->ts_flags & TSF_BOUND);
2833 }
2834
2835 /*
2836 * Basic yield call.
2837 */
2838 void
2839 sched_relinquish(struct thread *td)
2840 {
2841 thread_lock(td);
2842 mi_switch(SW_VOL | SWT_RELINQUISH);
2843 }
2844
2845 /*
2846 * Return the total system load.
2847 */
2848 int
2849 sched_load(void)
2850 {
2851 #ifdef SMP
2852 int total;
2853 int i;
2854
2855 total = 0;
2856 CPU_FOREACH(i)
2857 total += TDQ_CPU(i)->tdq_sysload;
2858 return (total);
2859 #else
2860 return (TDQ_SELF()->tdq_sysload);
2861 #endif
2862 }
2863
2864 int
2865 sched_sizeof_proc(void)
2866 {
2867 return (sizeof(struct proc));
2868 }
2869
2870 int
2871 sched_sizeof_thread(void)
2872 {
2873 return (sizeof(struct thread) + sizeof(struct td_sched));
2874 }
2875
2876 #ifdef SMP
2877 #define TDQ_IDLESPIN(tdq) \
2878 ((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0)
2879 #else
2880 #define TDQ_IDLESPIN(tdq) 1
2881 #endif
2882
2883 /*
2884 * The actual idle process.
2885 */
2886 void
2887 sched_idletd(void *dummy)
2888 {
2889 struct thread *td;
2890 struct tdq *tdq;
2891 int oldswitchcnt, switchcnt;
2892 int i;
2893
2894 mtx_assert(&Giant, MA_NOTOWNED);
2895 td = curthread;
2896 tdq = TDQ_SELF();
2897 THREAD_NO_SLEEPING();
2898 oldswitchcnt = -1;
2899 for (;;) {
2900 if (tdq->tdq_load) {
2901 thread_lock(td);
2902 mi_switch(SW_VOL | SWT_IDLE);
2903 }
2904 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
2905 #ifdef SMP
2906 if (always_steal || switchcnt != oldswitchcnt) {
2907 oldswitchcnt = switchcnt;
2908 if (tdq_idled(tdq) == 0)
2909 continue;
2910 }
2911 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
2912 #else
2913 oldswitchcnt = switchcnt;
2914 #endif
2915 /*
2916 * If we're switching very frequently, spin while checking
2917 * for load rather than entering a low power state that
2918 * may require an IPI. However, don't do any busy
2919 * loops while on SMT machines as this simply steals
2920 * cycles from cores doing useful work.
2921 */
2922 if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) {
2923 for (i = 0; i < sched_idlespins; i++) {
2924 if (tdq->tdq_load)
2925 break;
2926 cpu_spinwait();
2927 }
2928 }
2929
2930 /* If there was context switch during spin, restart it. */
2931 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
2932 if (tdq->tdq_load != 0 || switchcnt != oldswitchcnt)
2933 continue;
2934
2935 /* Run main MD idle handler. */
2936 tdq->tdq_cpu_idle = 1;
2937 /*
2938 * Make sure that tdq_cpu_idle update is globally visible
2939 * before cpu_idle() read tdq_load. The order is important
2940 * to avoid race with tdq_notify.
2941 */
2942 atomic_thread_fence_seq_cst();
2943 /*
2944 * Checking for again after the fence picks up assigned
2945 * threads often enough to make it worthwhile to do so in
2946 * order to avoid calling cpu_idle().
2947 */
2948 if (tdq->tdq_load != 0) {
2949 tdq->tdq_cpu_idle = 0;
2950 continue;
2951 }
2952 cpu_idle(switchcnt * 4 > sched_idlespinthresh);
2953 tdq->tdq_cpu_idle = 0;
2954
2955 /*
2956 * Account thread-less hardware interrupts and
2957 * other wakeup reasons equal to context switches.
2958 */
2959 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
2960 if (switchcnt != oldswitchcnt)
2961 continue;
2962 tdq->tdq_switchcnt++;
2963 oldswitchcnt++;
2964 }
2965 }
2966
2967 /*
2968 * A CPU is entering for the first time or a thread is exiting.
2969 */
2970 void
2971 sched_throw(struct thread *td)
2972 {
2973 struct thread *newtd;
2974 struct tdq *tdq;
2975
2976 if (__predict_false(td == NULL)) {
2977 #ifdef SMP
2978 PCPU_SET(sched, DPCPU_PTR(tdq));
2979 #endif
2980 /* Correct spinlock nesting and acquire the correct lock. */
2981 tdq = TDQ_SELF();
2982 TDQ_LOCK(tdq);
2983 spinlock_exit();
2984 PCPU_SET(switchtime, cpu_ticks());
2985 PCPU_SET(switchticks, ticks);
2986 PCPU_GET(idlethread)->td_lock = TDQ_LOCKPTR(tdq);
2987 } else {
2988 tdq = TDQ_SELF();
2989 THREAD_LOCK_ASSERT(td, MA_OWNED);
2990 THREAD_LOCKPTR_ASSERT(td, TDQ_LOCKPTR(tdq));
2991 tdq_load_rem(tdq, td);
2992 td->td_lastcpu = td->td_oncpu;
2993 td->td_oncpu = NOCPU;
2994 thread_lock_block(td);
2995 }
2996 newtd = choosethread();
2997 spinlock_enter();
2998 TDQ_UNLOCK(tdq);
2999 KASSERT(curthread->td_md.md_spinlock_count == 1,
3000 ("invalid count %d", curthread->td_md.md_spinlock_count));
3001 /* doesn't return */
3002 if (__predict_false(td == NULL))
3003 cpu_throw(td, newtd); /* doesn't return */
3004 else
3005 cpu_switch(td, newtd, TDQ_LOCKPTR(tdq));
3006 }
3007
3008 /*
3009 * This is called from fork_exit(). Just acquire the correct locks and
3010 * let fork do the rest of the work.
3011 */
3012 void
3013 sched_fork_exit(struct thread *td)
3014 {
3015 struct tdq *tdq;
3016 int cpuid;
3017
3018 /*
3019 * Finish setting up thread glue so that it begins execution in a
3020 * non-nested critical section with the scheduler lock held.
3021 */
3022 KASSERT(curthread->td_md.md_spinlock_count == 1,
3023 ("invalid count %d", curthread->td_md.md_spinlock_count));
3024 cpuid = PCPU_GET(cpuid);
3025 tdq = TDQ_SELF();
3026 TDQ_LOCK(tdq);
3027 spinlock_exit();
3028 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
3029 td->td_oncpu = cpuid;
3030 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
3031 "prio:%d", td->td_priority);
3032 SDT_PROBE0(sched, , , on__cpu);
3033 }
3034
3035 /*
3036 * Create on first use to catch odd startup conditions.
3037 */
3038 char *
3039 sched_tdname(struct thread *td)
3040 {
3041 #ifdef KTR
3042 struct td_sched *ts;
3043
3044 ts = td_get_sched(td);
3045 if (ts->ts_name[0] == '\0')
3046 snprintf(ts->ts_name, sizeof(ts->ts_name),
3047 "%s tid %d", td->td_name, td->td_tid);
3048 return (ts->ts_name);
3049 #else
3050 return (td->td_name);
3051 #endif
3052 }
3053
3054 #ifdef KTR
3055 void
3056 sched_clear_tdname(struct thread *td)
3057 {
3058 struct td_sched *ts;
3059
3060 ts = td_get_sched(td);
3061 ts->ts_name[0] = '\0';
3062 }
3063 #endif
3064
3065 #ifdef SMP
3066
3067 /*
3068 * Build the CPU topology dump string. Is recursively called to collect
3069 * the topology tree.
3070 */
3071 static int
3072 sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg,
3073 int indent)
3074 {
3075 char cpusetbuf[CPUSETBUFSIZ];
3076 int i, first;
3077
3078 sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent,
3079 "", 1 + indent / 2, cg->cg_level);
3080 sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"%s\">", indent, "",
3081 cg->cg_count, cpusetobj_strprint(cpusetbuf, &cg->cg_mask));
3082 first = TRUE;
3083 for (i = cg->cg_first; i <= cg->cg_last; i++) {
3084 if (CPU_ISSET(i, &cg->cg_mask)) {
3085 if (!first)
3086 sbuf_printf(sb, ", ");
3087 else
3088 first = FALSE;
3089 sbuf_printf(sb, "%d", i);
3090 }
3091 }
3092 sbuf_printf(sb, "</cpu>\n");
3093
3094 if (cg->cg_flags != 0) {
3095 sbuf_printf(sb, "%*s <flags>", indent, "");
3096 if ((cg->cg_flags & CG_FLAG_HTT) != 0)
3097 sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>");
3098 if ((cg->cg_flags & CG_FLAG_THREAD) != 0)
3099 sbuf_printf(sb, "<flag name=\"THREAD\">THREAD group</flag>");
3100 if ((cg->cg_flags & CG_FLAG_SMT) != 0)
3101 sbuf_printf(sb, "<flag name=\"SMT\">SMT group</flag>");
3102 if ((cg->cg_flags & CG_FLAG_NODE) != 0)
3103 sbuf_printf(sb, "<flag name=\"NODE\">NUMA node</flag>");
3104 sbuf_printf(sb, "</flags>\n");
3105 }
3106
3107 if (cg->cg_children > 0) {
3108 sbuf_printf(sb, "%*s <children>\n", indent, "");
3109 for (i = 0; i < cg->cg_children; i++)
3110 sysctl_kern_sched_topology_spec_internal(sb,
3111 &cg->cg_child[i], indent+2);
3112 sbuf_printf(sb, "%*s </children>\n", indent, "");
3113 }
3114 sbuf_printf(sb, "%*s</group>\n", indent, "");
3115 return (0);
3116 }
3117
3118 /*
3119 * Sysctl handler for retrieving topology dump. It's a wrapper for
3120 * the recursive sysctl_kern_smp_topology_spec_internal().
3121 */
3122 static int
3123 sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS)
3124 {
3125 struct sbuf *topo;
3126 int err;
3127
3128 KASSERT(cpu_top != NULL, ("cpu_top isn't initialized"));
3129
3130 topo = sbuf_new_for_sysctl(NULL, NULL, 512, req);
3131 if (topo == NULL)
3132 return (ENOMEM);
3133
3134 sbuf_printf(topo, "<groups>\n");
3135 err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1);
3136 sbuf_printf(topo, "</groups>\n");
3137
3138 if (err == 0) {
3139 err = sbuf_finish(topo);
3140 }
3141 sbuf_delete(topo);
3142 return (err);
3143 }
3144
3145 #endif
3146
3147 static int
3148 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
3149 {
3150 int error, new_val, period;
3151
3152 period = 1000000 / realstathz;
3153 new_val = period * sched_slice;
3154 error = sysctl_handle_int(oidp, &new_val, 0, req);
3155 if (error != 0 || req->newptr == NULL)
3156 return (error);
3157 if (new_val <= 0)
3158 return (EINVAL);
3159 sched_slice = imax(1, (new_val + period / 2) / period);
3160 sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
3161 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
3162 realstathz);
3163 return (0);
3164 }
3165
3166 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
3167 "Scheduler");
3168 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0,
3169 "Scheduler name");
3170 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum,
3171 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
3172 sysctl_kern_quantum, "I",
3173 "Quantum for timeshare threads in microseconds");
3174 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
3175 "Quantum for timeshare threads in stathz ticks");
3176 SYSCTL_UINT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0,
3177 "Interactivity score threshold");
3178 SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW,
3179 &preempt_thresh, 0,
3180 "Maximal (lowest) priority for preemption");
3181 SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost, 0,
3182 "Assign static kernel priorities to sleeping threads");
3183 SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins, 0,
3184 "Number of times idle thread will spin waiting for new work");
3185 SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW,
3186 &sched_idlespinthresh, 0,
3187 "Threshold before we will permit idle thread spinning");
3188 #ifdef SMP
3189 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0,
3190 "Number of hz ticks to keep thread affinity for");
3191 SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0,
3192 "Enables the long-term load balancer");
3193 SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW,
3194 &balance_interval, 0,
3195 "Average period in stathz ticks to run the long-term balancer");
3196 SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0,
3197 "Attempts to steal work from other cores before idling");
3198 SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0,
3199 "Minimum load on remote CPU before we'll steal");
3200 SYSCTL_INT(_kern_sched, OID_AUTO, trysteal_limit, CTLFLAG_RW, &trysteal_limit,
3201 0, "Topological distance limit for stealing threads in sched_switch()");
3202 SYSCTL_INT(_kern_sched, OID_AUTO, always_steal, CTLFLAG_RW, &always_steal, 0,
3203 "Always run the stealer from the idle thread");
3204 SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING |
3205 CTLFLAG_MPSAFE | CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A",
3206 "XML dump of detected CPU topology");
3207 #endif
3208
3209 /* ps compat. All cpu percentages from ULE are weighted. */
3210 static int ccpu = 0;
3211 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0,
3212 "Decay factor used for updating %CPU in 4BSD scheduler");
Cache object: 8cd1a68207150bf649af8632d593f6a7
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