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/umtxvar.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. A mutex synchronizes access to
230 * most fields. Some fields are loaded or modified without the mutex.
231 *
232 * Locking protocols:
233 * (c) constant after initialization
234 * (f) flag, set with the tdq lock held, cleared on local CPU
235 * (l) all accesses are CPU-local
236 * (ls) stores are performed by the local CPU, loads may be lockless
237 * (t) all accesses are protected by the tdq mutex
238 * (ts) stores are serialized by the tdq mutex, loads may be lockless
239 */
240 struct tdq {
241 /*
242 * Ordered to improve efficiency of cpu_search() and switch().
243 * tdq_lock is padded to avoid false sharing with tdq_load and
244 * tdq_cpu_idle.
245 */
246 struct mtx_padalign tdq_lock; /* run queue lock. */
247 struct cpu_group *tdq_cg; /* (c) Pointer to cpu topology. */
248 struct thread *tdq_curthread; /* (t) Current executing thread. */
249 int tdq_load; /* (ts) Aggregate load. */
250 int tdq_sysload; /* (ts) For loadavg, !ITHD load. */
251 int tdq_cpu_idle; /* (ls) cpu_idle() is active. */
252 int tdq_transferable; /* (ts) Transferable thread count. */
253 short tdq_switchcnt; /* (l) Switches this tick. */
254 short tdq_oldswitchcnt; /* (l) Switches last tick. */
255 u_char tdq_lowpri; /* (ts) Lowest priority thread. */
256 u_char tdq_owepreempt; /* (f) Remote preemption pending. */
257 u_char tdq_idx; /* (t) Current insert index. */
258 u_char tdq_ridx; /* (t) Current removal index. */
259 int tdq_id; /* (c) cpuid. */
260 struct runq tdq_realtime; /* (t) real-time run queue. */
261 struct runq tdq_timeshare; /* (t) timeshare run queue. */
262 struct runq tdq_idle; /* (t) Queue of IDLE threads. */
263 char tdq_name[TDQ_NAME_LEN];
264 #ifdef KTR
265 char tdq_loadname[TDQ_LOADNAME_LEN];
266 #endif
267 };
268
269 /* Idle thread states and config. */
270 #define TDQ_RUNNING 1
271 #define TDQ_IDLE 2
272
273 /* Lockless accessors. */
274 #define TDQ_LOAD(tdq) atomic_load_int(&(tdq)->tdq_load)
275 #define TDQ_TRANSFERABLE(tdq) atomic_load_int(&(tdq)->tdq_transferable)
276 #define TDQ_SWITCHCNT(tdq) (atomic_load_short(&(tdq)->tdq_switchcnt) + \
277 atomic_load_short(&(tdq)->tdq_oldswitchcnt))
278 #define TDQ_SWITCHCNT_INC(tdq) (atomic_store_short(&(tdq)->tdq_switchcnt, \
279 atomic_load_short(&(tdq)->tdq_switchcnt) + 1))
280
281 #ifdef SMP
282 struct cpu_group __read_mostly *cpu_top; /* CPU topology */
283
284 #define SCHED_AFFINITY_DEFAULT (max(1, hz / 1000))
285 #define SCHED_AFFINITY(ts, t) ((ts)->ts_rltick > ticks - ((t) * affinity))
286
287 /*
288 * Run-time tunables.
289 */
290 static int rebalance = 1;
291 static int balance_interval = 128; /* Default set in sched_initticks(). */
292 static int __read_mostly affinity;
293 static int __read_mostly steal_idle = 1;
294 static int __read_mostly steal_thresh = 2;
295 static int __read_mostly always_steal = 0;
296 static int __read_mostly trysteal_limit = 2;
297
298 /*
299 * One thread queue per processor.
300 */
301 static struct tdq __read_mostly *balance_tdq;
302 static int balance_ticks;
303 DPCPU_DEFINE_STATIC(struct tdq, tdq);
304 DPCPU_DEFINE_STATIC(uint32_t, randomval);
305
306 #define TDQ_SELF() ((struct tdq *)PCPU_GET(sched))
307 #define TDQ_CPU(x) (DPCPU_ID_PTR((x), tdq))
308 #define TDQ_ID(x) ((x)->tdq_id)
309 #else /* !SMP */
310 static struct tdq tdq_cpu;
311
312 #define TDQ_ID(x) (0)
313 #define TDQ_SELF() (&tdq_cpu)
314 #define TDQ_CPU(x) (&tdq_cpu)
315 #endif
316
317 #define TDQ_LOCK_ASSERT(t, type) mtx_assert(TDQ_LOCKPTR((t)), (type))
318 #define TDQ_LOCK(t) mtx_lock_spin(TDQ_LOCKPTR((t)))
319 #define TDQ_LOCK_FLAGS(t, f) mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f))
320 #define TDQ_TRYLOCK(t) mtx_trylock_spin(TDQ_LOCKPTR((t)))
321 #define TDQ_TRYLOCK_FLAGS(t, f) mtx_trylock_spin_flags(TDQ_LOCKPTR((t)), (f))
322 #define TDQ_UNLOCK(t) mtx_unlock_spin(TDQ_LOCKPTR((t)))
323 #define TDQ_LOCKPTR(t) ((struct mtx *)(&(t)->tdq_lock))
324
325 static void sched_setpreempt(int);
326 static void sched_priority(struct thread *);
327 static void sched_thread_priority(struct thread *, u_char);
328 static int sched_interact_score(struct thread *);
329 static void sched_interact_update(struct thread *);
330 static void sched_interact_fork(struct thread *);
331 static void sched_pctcpu_update(struct td_sched *, int);
332
333 /* Operations on per processor queues */
334 static struct thread *tdq_choose(struct tdq *);
335 static void tdq_setup(struct tdq *, int i);
336 static void tdq_load_add(struct tdq *, struct thread *);
337 static void tdq_load_rem(struct tdq *, struct thread *);
338 static __inline void tdq_runq_add(struct tdq *, struct thread *, int);
339 static __inline void tdq_runq_rem(struct tdq *, struct thread *);
340 static inline int sched_shouldpreempt(int, int, int);
341 static void tdq_print(int cpu);
342 static void runq_print(struct runq *rq);
343 static int tdq_add(struct tdq *, struct thread *, int);
344 #ifdef SMP
345 static int tdq_move(struct tdq *, struct tdq *);
346 static int tdq_idled(struct tdq *);
347 static void tdq_notify(struct tdq *, int lowpri);
348 static struct thread *tdq_steal(struct tdq *, int);
349 static struct thread *runq_steal(struct runq *, int);
350 static int sched_pickcpu(struct thread *, int);
351 static void sched_balance(void);
352 static bool sched_balance_pair(struct tdq *, struct tdq *);
353 static inline struct tdq *sched_setcpu(struct thread *, int, int);
354 static inline void thread_unblock_switch(struct thread *, struct mtx *);
355 static int sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS);
356 static int sysctl_kern_sched_topology_spec_internal(struct sbuf *sb,
357 struct cpu_group *cg, int indent);
358 #endif
359
360 static void sched_setup(void *dummy);
361 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
362
363 static void sched_initticks(void *dummy);
364 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
365 NULL);
366
367 SDT_PROVIDER_DEFINE(sched);
368
369 SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *",
370 "struct proc *", "uint8_t");
371 SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *",
372 "struct proc *", "void *");
373 SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *",
374 "struct proc *", "void *", "int");
375 SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *",
376 "struct proc *", "uint8_t", "struct thread *");
377 SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int");
378 SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *",
379 "struct proc *");
380 SDT_PROBE_DEFINE(sched, , , on__cpu);
381 SDT_PROBE_DEFINE(sched, , , remain__cpu);
382 SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *",
383 "struct proc *");
384
385 /*
386 * Print the threads waiting on a run-queue.
387 */
388 static void
389 runq_print(struct runq *rq)
390 {
391 struct rqhead *rqh;
392 struct thread *td;
393 int pri;
394 int j;
395 int i;
396
397 for (i = 0; i < RQB_LEN; i++) {
398 printf("\t\trunq bits %d 0x%zx\n",
399 i, rq->rq_status.rqb_bits[i]);
400 for (j = 0; j < RQB_BPW; j++)
401 if (rq->rq_status.rqb_bits[i] & (1ul << j)) {
402 pri = j + (i << RQB_L2BPW);
403 rqh = &rq->rq_queues[pri];
404 TAILQ_FOREACH(td, rqh, td_runq) {
405 printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
406 td, td->td_name, td->td_priority,
407 td->td_rqindex, pri);
408 }
409 }
410 }
411 }
412
413 /*
414 * Print the status of a per-cpu thread queue. Should be a ddb show cmd.
415 */
416 static void __unused
417 tdq_print(int cpu)
418 {
419 struct tdq *tdq;
420
421 tdq = TDQ_CPU(cpu);
422
423 printf("tdq %d:\n", TDQ_ID(tdq));
424 printf("\tlock %p\n", TDQ_LOCKPTR(tdq));
425 printf("\tLock name: %s\n", tdq->tdq_name);
426 printf("\tload: %d\n", tdq->tdq_load);
427 printf("\tswitch cnt: %d\n", tdq->tdq_switchcnt);
428 printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt);
429 printf("\ttimeshare idx: %d\n", tdq->tdq_idx);
430 printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
431 printf("\tload transferable: %d\n", tdq->tdq_transferable);
432 printf("\tlowest priority: %d\n", tdq->tdq_lowpri);
433 printf("\trealtime runq:\n");
434 runq_print(&tdq->tdq_realtime);
435 printf("\ttimeshare runq:\n");
436 runq_print(&tdq->tdq_timeshare);
437 printf("\tidle runq:\n");
438 runq_print(&tdq->tdq_idle);
439 }
440
441 static inline int
442 sched_shouldpreempt(int pri, int cpri, int remote)
443 {
444 /*
445 * If the new priority is not better than the current priority there is
446 * nothing to do.
447 */
448 if (pri >= cpri)
449 return (0);
450 /*
451 * Always preempt idle.
452 */
453 if (cpri >= PRI_MIN_IDLE)
454 return (1);
455 /*
456 * If preemption is disabled don't preempt others.
457 */
458 if (preempt_thresh == 0)
459 return (0);
460 /*
461 * Preempt if we exceed the threshold.
462 */
463 if (pri <= preempt_thresh)
464 return (1);
465 /*
466 * If we're interactive or better and there is non-interactive
467 * or worse running preempt only remote processors.
468 */
469 if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT)
470 return (1);
471 return (0);
472 }
473
474 /*
475 * Add a thread to the actual run-queue. Keeps transferable counts up to
476 * date with what is actually on the run-queue. Selects the correct
477 * queue position for timeshare threads.
478 */
479 static __inline void
480 tdq_runq_add(struct tdq *tdq, struct thread *td, int flags)
481 {
482 struct td_sched *ts;
483 u_char pri;
484
485 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
486 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
487
488 pri = td->td_priority;
489 ts = td_get_sched(td);
490 TD_SET_RUNQ(td);
491 if (THREAD_CAN_MIGRATE(td)) {
492 tdq->tdq_transferable++;
493 ts->ts_flags |= TSF_XFERABLE;
494 }
495 if (pri < PRI_MIN_BATCH) {
496 ts->ts_runq = &tdq->tdq_realtime;
497 } else if (pri <= PRI_MAX_BATCH) {
498 ts->ts_runq = &tdq->tdq_timeshare;
499 KASSERT(pri <= PRI_MAX_BATCH && pri >= PRI_MIN_BATCH,
500 ("Invalid priority %d on timeshare runq", pri));
501 /*
502 * This queue contains only priorities between MIN and MAX
503 * batch. Use the whole queue to represent these values.
504 */
505 if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) {
506 pri = RQ_NQS * (pri - PRI_MIN_BATCH) / PRI_BATCH_RANGE;
507 pri = (pri + tdq->tdq_idx) % RQ_NQS;
508 /*
509 * This effectively shortens the queue by one so we
510 * can have a one slot difference between idx and
511 * ridx while we wait for threads to drain.
512 */
513 if (tdq->tdq_ridx != tdq->tdq_idx &&
514 pri == tdq->tdq_ridx)
515 pri = (unsigned char)(pri - 1) % RQ_NQS;
516 } else
517 pri = tdq->tdq_ridx;
518 runq_add_pri(ts->ts_runq, td, pri, flags);
519 return;
520 } else
521 ts->ts_runq = &tdq->tdq_idle;
522 runq_add(ts->ts_runq, td, flags);
523 }
524
525 /*
526 * Remove a thread from a run-queue. This typically happens when a thread
527 * is selected to run. Running threads are not on the queue and the
528 * transferable count does not reflect them.
529 */
530 static __inline void
531 tdq_runq_rem(struct tdq *tdq, struct thread *td)
532 {
533 struct td_sched *ts;
534
535 ts = td_get_sched(td);
536 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
537 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
538 KASSERT(ts->ts_runq != NULL,
539 ("tdq_runq_remove: thread %p null ts_runq", td));
540 if (ts->ts_flags & TSF_XFERABLE) {
541 tdq->tdq_transferable--;
542 ts->ts_flags &= ~TSF_XFERABLE;
543 }
544 if (ts->ts_runq == &tdq->tdq_timeshare) {
545 if (tdq->tdq_idx != tdq->tdq_ridx)
546 runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx);
547 else
548 runq_remove_idx(ts->ts_runq, td, NULL);
549 } else
550 runq_remove(ts->ts_runq, td);
551 }
552
553 /*
554 * Load is maintained for all threads RUNNING and ON_RUNQ. Add the load
555 * for this thread to the referenced thread queue.
556 */
557 static void
558 tdq_load_add(struct tdq *tdq, struct thread *td)
559 {
560
561 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
562 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
563
564 tdq->tdq_load++;
565 if ((td->td_flags & TDF_NOLOAD) == 0)
566 tdq->tdq_sysload++;
567 KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
568 SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
569 }
570
571 /*
572 * Remove the load from a thread that is transitioning to a sleep state or
573 * exiting.
574 */
575 static void
576 tdq_load_rem(struct tdq *tdq, struct thread *td)
577 {
578
579 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
580 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
581 KASSERT(tdq->tdq_load != 0,
582 ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
583
584 tdq->tdq_load--;
585 if ((td->td_flags & TDF_NOLOAD) == 0)
586 tdq->tdq_sysload--;
587 KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
588 SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
589 }
590
591 /*
592 * Bound timeshare latency by decreasing slice size as load increases. We
593 * consider the maximum latency as the sum of the threads waiting to run
594 * aside from curthread and target no more than sched_slice latency but
595 * no less than sched_slice_min runtime.
596 */
597 static inline int
598 tdq_slice(struct tdq *tdq)
599 {
600 int load;
601
602 /*
603 * It is safe to use sys_load here because this is called from
604 * contexts where timeshare threads are running and so there
605 * cannot be higher priority load in the system.
606 */
607 load = tdq->tdq_sysload - 1;
608 if (load >= SCHED_SLICE_MIN_DIVISOR)
609 return (sched_slice_min);
610 if (load <= 1)
611 return (sched_slice);
612 return (sched_slice / load);
613 }
614
615 /*
616 * Set lowpri to its exact value by searching the run-queue and
617 * evaluating curthread. curthread may be passed as an optimization.
618 */
619 static void
620 tdq_setlowpri(struct tdq *tdq, struct thread *ctd)
621 {
622 struct thread *td;
623
624 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
625 if (ctd == NULL)
626 ctd = tdq->tdq_curthread;
627 td = tdq_choose(tdq);
628 if (td == NULL || td->td_priority > ctd->td_priority)
629 tdq->tdq_lowpri = ctd->td_priority;
630 else
631 tdq->tdq_lowpri = td->td_priority;
632 }
633
634 #ifdef SMP
635 /*
636 * We need some randomness. Implement a classic Linear Congruential
637 * Generator X_{n+1}=(aX_n+c) mod m. These values are optimized for
638 * m = 2^32, a = 69069 and c = 5. We only return the upper 16 bits
639 * of the random state (in the low bits of our answer) to keep
640 * the maximum randomness.
641 */
642 static uint32_t
643 sched_random(void)
644 {
645 uint32_t *rndptr;
646
647 rndptr = DPCPU_PTR(randomval);
648 *rndptr = *rndptr * 69069 + 5;
649
650 return (*rndptr >> 16);
651 }
652
653 struct cpu_search {
654 cpuset_t *cs_mask; /* The mask of allowed CPUs to choose from. */
655 int cs_prefer; /* Prefer this CPU and groups including it. */
656 int cs_running; /* The thread is now running at cs_prefer. */
657 int cs_pri; /* Min priority for low. */
658 int cs_load; /* Max load for low, min load for high. */
659 int cs_trans; /* Min transferable load for high. */
660 };
661
662 struct cpu_search_res {
663 int csr_cpu; /* The best CPU found. */
664 int csr_load; /* The load of cs_cpu. */
665 };
666
667 /*
668 * Search the tree of cpu_groups for the lowest or highest loaded CPU.
669 * These routines actually compare the load on all paths through the tree
670 * and find the least loaded cpu on the least loaded path, which may differ
671 * from the least loaded cpu in the system. This balances work among caches
672 * and buses.
673 */
674 static int
675 cpu_search_lowest(const struct cpu_group *cg, const struct cpu_search *s,
676 struct cpu_search_res *r)
677 {
678 struct cpu_search_res lr;
679 struct tdq *tdq;
680 int c, bload, l, load, p, total;
681
682 total = 0;
683 bload = INT_MAX;
684 r->csr_cpu = -1;
685
686 /* Loop through children CPU groups if there are any. */
687 if (cg->cg_children > 0) {
688 for (c = cg->cg_children - 1; c >= 0; c--) {
689 load = cpu_search_lowest(&cg->cg_child[c], s, &lr);
690 total += load;
691
692 /*
693 * When balancing do not prefer SMT groups with load >1.
694 * It allows round-robin between SMT groups with equal
695 * load within parent group for more fair scheduling.
696 */
697 if (__predict_false(s->cs_running) &&
698 (cg->cg_child[c].cg_flags & CG_FLAG_THREAD) &&
699 load >= 128 && (load & 128) != 0)
700 load += 128;
701
702 if (lr.csr_cpu >= 0 && (load < bload ||
703 (load == bload && lr.csr_load < r->csr_load))) {
704 bload = load;
705 r->csr_cpu = lr.csr_cpu;
706 r->csr_load = lr.csr_load;
707 }
708 }
709 return (total);
710 }
711
712 /* Loop through children CPUs otherwise. */
713 for (c = cg->cg_last; c >= cg->cg_first; c--) {
714 if (!CPU_ISSET(c, &cg->cg_mask))
715 continue;
716 tdq = TDQ_CPU(c);
717 l = TDQ_LOAD(tdq);
718 if (c == s->cs_prefer) {
719 if (__predict_false(s->cs_running))
720 l--;
721 p = 128;
722 } else
723 p = 0;
724 load = l * 256;
725 total += load - p;
726
727 /*
728 * Check this CPU is acceptable.
729 * If the threads is already on the CPU, don't look on the TDQ
730 * priority, since it can be the priority of the thread itself.
731 */
732 if (l > s->cs_load ||
733 (atomic_load_char(&tdq->tdq_lowpri) <= s->cs_pri &&
734 (!s->cs_running || c != s->cs_prefer)) ||
735 !CPU_ISSET(c, s->cs_mask))
736 continue;
737
738 /*
739 * When balancing do not prefer CPUs with load > 1.
740 * It allows round-robin between CPUs with equal load
741 * within the CPU group for more fair scheduling.
742 */
743 if (__predict_false(s->cs_running) && l > 0)
744 p = 0;
745
746 load -= sched_random() % 128;
747 if (bload > load - p) {
748 bload = load - p;
749 r->csr_cpu = c;
750 r->csr_load = load;
751 }
752 }
753 return (total);
754 }
755
756 static int
757 cpu_search_highest(const struct cpu_group *cg, const struct cpu_search *s,
758 struct cpu_search_res *r)
759 {
760 struct cpu_search_res lr;
761 struct tdq *tdq;
762 int c, bload, l, load, total;
763
764 total = 0;
765 bload = INT_MIN;
766 r->csr_cpu = -1;
767
768 /* Loop through children CPU groups if there are any. */
769 if (cg->cg_children > 0) {
770 for (c = cg->cg_children - 1; c >= 0; c--) {
771 load = cpu_search_highest(&cg->cg_child[c], s, &lr);
772 total += load;
773 if (lr.csr_cpu >= 0 && (load > bload ||
774 (load == bload && lr.csr_load > r->csr_load))) {
775 bload = load;
776 r->csr_cpu = lr.csr_cpu;
777 r->csr_load = lr.csr_load;
778 }
779 }
780 return (total);
781 }
782
783 /* Loop through children CPUs otherwise. */
784 for (c = cg->cg_last; c >= cg->cg_first; c--) {
785 if (!CPU_ISSET(c, &cg->cg_mask))
786 continue;
787 tdq = TDQ_CPU(c);
788 l = TDQ_LOAD(tdq);
789 load = l * 256;
790 total += load;
791
792 /*
793 * Check this CPU is acceptable.
794 */
795 if (l < s->cs_load || TDQ_TRANSFERABLE(tdq) < s->cs_trans ||
796 !CPU_ISSET(c, s->cs_mask))
797 continue;
798
799 load -= sched_random() % 256;
800 if (load > bload) {
801 bload = load;
802 r->csr_cpu = c;
803 }
804 }
805 r->csr_load = bload;
806 return (total);
807 }
808
809 /*
810 * Find the cpu with the least load via the least loaded path that has a
811 * lowpri greater than pri pri. A pri of -1 indicates any priority is
812 * acceptable.
813 */
814 static inline int
815 sched_lowest(const struct cpu_group *cg, cpuset_t *mask, int pri, int maxload,
816 int prefer, int running)
817 {
818 struct cpu_search s;
819 struct cpu_search_res r;
820
821 s.cs_prefer = prefer;
822 s.cs_running = running;
823 s.cs_mask = mask;
824 s.cs_pri = pri;
825 s.cs_load = maxload;
826 cpu_search_lowest(cg, &s, &r);
827 return (r.csr_cpu);
828 }
829
830 /*
831 * Find the cpu with the highest load via the highest loaded path.
832 */
833 static inline int
834 sched_highest(const struct cpu_group *cg, cpuset_t *mask, int minload,
835 int mintrans)
836 {
837 struct cpu_search s;
838 struct cpu_search_res r;
839
840 s.cs_mask = mask;
841 s.cs_load = minload;
842 s.cs_trans = mintrans;
843 cpu_search_highest(cg, &s, &r);
844 return (r.csr_cpu);
845 }
846
847 static void
848 sched_balance_group(struct cpu_group *cg)
849 {
850 struct tdq *tdq;
851 struct thread *td;
852 cpuset_t hmask, lmask;
853 int high, low, anylow;
854
855 CPU_FILL(&hmask);
856 for (;;) {
857 high = sched_highest(cg, &hmask, 1, 0);
858 /* Stop if there is no more CPU with transferrable threads. */
859 if (high == -1)
860 break;
861 CPU_CLR(high, &hmask);
862 CPU_COPY(&hmask, &lmask);
863 /* Stop if there is no more CPU left for low. */
864 if (CPU_EMPTY(&lmask))
865 break;
866 tdq = TDQ_CPU(high);
867 if (TDQ_LOAD(tdq) == 1) {
868 /*
869 * There is only one running thread. We can't move
870 * it from here, so tell it to pick new CPU by itself.
871 */
872 TDQ_LOCK(tdq);
873 td = tdq->tdq_curthread;
874 if (td->td_lock == TDQ_LOCKPTR(tdq) &&
875 (td->td_flags & TDF_IDLETD) == 0 &&
876 THREAD_CAN_MIGRATE(td)) {
877 td->td_flags |= TDF_PICKCPU;
878 ast_sched_locked(td, TDA_SCHED);
879 if (high != curcpu)
880 ipi_cpu(high, IPI_AST);
881 }
882 TDQ_UNLOCK(tdq);
883 break;
884 }
885 anylow = 1;
886 nextlow:
887 if (TDQ_TRANSFERABLE(tdq) == 0)
888 continue;
889 low = sched_lowest(cg, &lmask, -1, TDQ_LOAD(tdq) - 1, high, 1);
890 /* Stop if we looked well and found no less loaded CPU. */
891 if (anylow && low == -1)
892 break;
893 /* Go to next high if we found no less loaded CPU. */
894 if (low == -1)
895 continue;
896 /* Transfer thread from high to low. */
897 if (sched_balance_pair(tdq, TDQ_CPU(low))) {
898 /* CPU that got thread can no longer be a donor. */
899 CPU_CLR(low, &hmask);
900 } else {
901 /*
902 * If failed, then there is no threads on high
903 * that can run on this low. Drop low from low
904 * mask and look for different one.
905 */
906 CPU_CLR(low, &lmask);
907 anylow = 0;
908 goto nextlow;
909 }
910 }
911 }
912
913 static void
914 sched_balance(void)
915 {
916 struct tdq *tdq;
917
918 balance_ticks = max(balance_interval / 2, 1) +
919 (sched_random() % balance_interval);
920 tdq = TDQ_SELF();
921 TDQ_UNLOCK(tdq);
922 sched_balance_group(cpu_top);
923 TDQ_LOCK(tdq);
924 }
925
926 /*
927 * Lock two thread queues using their address to maintain lock order.
928 */
929 static void
930 tdq_lock_pair(struct tdq *one, struct tdq *two)
931 {
932 if (one < two) {
933 TDQ_LOCK(one);
934 TDQ_LOCK_FLAGS(two, MTX_DUPOK);
935 } else {
936 TDQ_LOCK(two);
937 TDQ_LOCK_FLAGS(one, MTX_DUPOK);
938 }
939 }
940
941 /*
942 * Unlock two thread queues. Order is not important here.
943 */
944 static void
945 tdq_unlock_pair(struct tdq *one, struct tdq *two)
946 {
947 TDQ_UNLOCK(one);
948 TDQ_UNLOCK(two);
949 }
950
951 /*
952 * Transfer load between two imbalanced thread queues. Returns true if a thread
953 * was moved between the queues, and false otherwise.
954 */
955 static bool
956 sched_balance_pair(struct tdq *high, struct tdq *low)
957 {
958 int cpu, lowpri;
959 bool ret;
960
961 ret = false;
962 tdq_lock_pair(high, low);
963
964 /*
965 * Transfer a thread from high to low.
966 */
967 if (high->tdq_transferable != 0 && high->tdq_load > low->tdq_load) {
968 lowpri = tdq_move(high, low);
969 if (lowpri != -1) {
970 /*
971 * In case the target isn't the current CPU notify it of
972 * the new load, possibly sending an IPI to force it to
973 * reschedule. Otherwise maybe schedule a preemption.
974 */
975 cpu = TDQ_ID(low);
976 if (cpu != PCPU_GET(cpuid))
977 tdq_notify(low, lowpri);
978 else
979 sched_setpreempt(low->tdq_lowpri);
980 ret = true;
981 }
982 }
983 tdq_unlock_pair(high, low);
984 return (ret);
985 }
986
987 /*
988 * Move a thread from one thread queue to another. Returns -1 if the source
989 * queue was empty, else returns the maximum priority of all threads in
990 * the destination queue prior to the addition of the new thread. In the latter
991 * case, this priority can be used to determine whether an IPI needs to be
992 * delivered.
993 */
994 static int
995 tdq_move(struct tdq *from, struct tdq *to)
996 {
997 struct thread *td;
998 int cpu;
999
1000 TDQ_LOCK_ASSERT(from, MA_OWNED);
1001 TDQ_LOCK_ASSERT(to, MA_OWNED);
1002
1003 cpu = TDQ_ID(to);
1004 td = tdq_steal(from, cpu);
1005 if (td == NULL)
1006 return (-1);
1007
1008 /*
1009 * Although the run queue is locked the thread may be
1010 * blocked. We can not set the lock until it is unblocked.
1011 */
1012 thread_lock_block_wait(td);
1013 sched_rem(td);
1014 THREAD_LOCKPTR_ASSERT(td, TDQ_LOCKPTR(from));
1015 td->td_lock = TDQ_LOCKPTR(to);
1016 td_get_sched(td)->ts_cpu = cpu;
1017 return (tdq_add(to, td, SRQ_YIELDING));
1018 }
1019
1020 /*
1021 * This tdq has idled. Try to steal a thread from another cpu and switch
1022 * to it.
1023 */
1024 static int
1025 tdq_idled(struct tdq *tdq)
1026 {
1027 struct cpu_group *cg, *parent;
1028 struct tdq *steal;
1029 cpuset_t mask;
1030 int cpu, switchcnt, goup;
1031
1032 if (smp_started == 0 || steal_idle == 0 || tdq->tdq_cg == NULL)
1033 return (1);
1034 CPU_FILL(&mask);
1035 CPU_CLR(PCPU_GET(cpuid), &mask);
1036 restart:
1037 switchcnt = TDQ_SWITCHCNT(tdq);
1038 for (cg = tdq->tdq_cg, goup = 0; ; ) {
1039 cpu = sched_highest(cg, &mask, steal_thresh, 1);
1040 /*
1041 * We were assigned a thread but not preempted. Returning
1042 * 0 here will cause our caller to switch to it.
1043 */
1044 if (TDQ_LOAD(tdq))
1045 return (0);
1046
1047 /*
1048 * We found no CPU to steal from in this group. Escalate to
1049 * the parent and repeat. But if parent has only two children
1050 * groups we can avoid searching this group again by searching
1051 * the other one specifically and then escalating two levels.
1052 */
1053 if (cpu == -1) {
1054 if (goup) {
1055 cg = cg->cg_parent;
1056 goup = 0;
1057 }
1058 parent = cg->cg_parent;
1059 if (parent == NULL)
1060 return (1);
1061 if (parent->cg_children == 2) {
1062 if (cg == &parent->cg_child[0])
1063 cg = &parent->cg_child[1];
1064 else
1065 cg = &parent->cg_child[0];
1066 goup = 1;
1067 } else
1068 cg = parent;
1069 continue;
1070 }
1071 steal = TDQ_CPU(cpu);
1072 /*
1073 * The data returned by sched_highest() is stale and
1074 * the chosen CPU no longer has an eligible thread.
1075 *
1076 * Testing this ahead of tdq_lock_pair() only catches
1077 * this situation about 20% of the time on an 8 core
1078 * 16 thread Ryzen 7, but it still helps performance.
1079 */
1080 if (TDQ_LOAD(steal) < steal_thresh ||
1081 TDQ_TRANSFERABLE(steal) == 0)
1082 goto restart;
1083 /*
1084 * Try to lock both queues. If we are assigned a thread while
1085 * waited for the lock, switch to it now instead of stealing.
1086 * If we can't get the lock, then somebody likely got there
1087 * first so continue searching.
1088 */
1089 TDQ_LOCK(tdq);
1090 if (tdq->tdq_load > 0) {
1091 mi_switch(SW_VOL | SWT_IDLE);
1092 return (0);
1093 }
1094 if (TDQ_TRYLOCK_FLAGS(steal, MTX_DUPOK) == 0) {
1095 TDQ_UNLOCK(tdq);
1096 CPU_CLR(cpu, &mask);
1097 continue;
1098 }
1099 /*
1100 * The data returned by sched_highest() is stale and
1101 * the chosen CPU no longer has an eligible thread, or
1102 * we were preempted and the CPU loading info may be out
1103 * of date. The latter is rare. In either case restart
1104 * the search.
1105 */
1106 if (TDQ_LOAD(steal) < steal_thresh ||
1107 TDQ_TRANSFERABLE(steal) == 0 ||
1108 switchcnt != TDQ_SWITCHCNT(tdq)) {
1109 tdq_unlock_pair(tdq, steal);
1110 goto restart;
1111 }
1112 /*
1113 * Steal the thread and switch to it.
1114 */
1115 if (tdq_move(steal, tdq) != -1)
1116 break;
1117 /*
1118 * We failed to acquire a thread even though it looked
1119 * like one was available. This could be due to affinity
1120 * restrictions or for other reasons. Loop again after
1121 * removing this CPU from the set. The restart logic
1122 * above does not restore this CPU to the set due to the
1123 * likelyhood of failing here again.
1124 */
1125 CPU_CLR(cpu, &mask);
1126 tdq_unlock_pair(tdq, steal);
1127 }
1128 TDQ_UNLOCK(steal);
1129 mi_switch(SW_VOL | SWT_IDLE);
1130 return (0);
1131 }
1132
1133 /*
1134 * Notify a remote cpu of new work. Sends an IPI if criteria are met.
1135 *
1136 * "lowpri" is the minimum scheduling priority among all threads on
1137 * the queue prior to the addition of the new thread.
1138 */
1139 static void
1140 tdq_notify(struct tdq *tdq, int lowpri)
1141 {
1142 int cpu;
1143
1144 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
1145 KASSERT(tdq->tdq_lowpri <= lowpri,
1146 ("tdq_notify: lowpri %d > tdq_lowpri %d", lowpri, tdq->tdq_lowpri));
1147
1148 if (tdq->tdq_owepreempt)
1149 return;
1150
1151 /*
1152 * Check to see if the newly added thread should preempt the one
1153 * currently running.
1154 */
1155 if (!sched_shouldpreempt(tdq->tdq_lowpri, lowpri, 1))
1156 return;
1157
1158 /*
1159 * Make sure that our caller's earlier update to tdq_load is
1160 * globally visible before we read tdq_cpu_idle. Idle thread
1161 * accesses both of them without locks, and the order is important.
1162 */
1163 atomic_thread_fence_seq_cst();
1164
1165 /*
1166 * Try to figure out if we can signal the idle thread instead of sending
1167 * an IPI. This check is racy; at worst, we will deliever an IPI
1168 * unnecessarily.
1169 */
1170 cpu = TDQ_ID(tdq);
1171 if (TD_IS_IDLETHREAD(tdq->tdq_curthread) &&
1172 (atomic_load_int(&tdq->tdq_cpu_idle) == 0 || cpu_idle_wakeup(cpu)))
1173 return;
1174
1175 /*
1176 * The run queues have been updated, so any switch on the remote CPU
1177 * will satisfy the preemption request.
1178 */
1179 tdq->tdq_owepreempt = 1;
1180 ipi_cpu(cpu, IPI_PREEMPT);
1181 }
1182
1183 /*
1184 * Steals load from a timeshare queue. Honors the rotating queue head
1185 * index.
1186 */
1187 static struct thread *
1188 runq_steal_from(struct runq *rq, int cpu, u_char start)
1189 {
1190 struct rqbits *rqb;
1191 struct rqhead *rqh;
1192 struct thread *td, *first;
1193 int bit;
1194 int i;
1195
1196 rqb = &rq->rq_status;
1197 bit = start & (RQB_BPW -1);
1198 first = NULL;
1199 again:
1200 for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
1201 if (rqb->rqb_bits[i] == 0)
1202 continue;
1203 if (bit == 0)
1204 bit = RQB_FFS(rqb->rqb_bits[i]);
1205 for (; bit < RQB_BPW; bit++) {
1206 if ((rqb->rqb_bits[i] & (1ul << bit)) == 0)
1207 continue;
1208 rqh = &rq->rq_queues[bit + (i << RQB_L2BPW)];
1209 TAILQ_FOREACH(td, rqh, td_runq) {
1210 if (first) {
1211 if (THREAD_CAN_MIGRATE(td) &&
1212 THREAD_CAN_SCHED(td, cpu))
1213 return (td);
1214 } else
1215 first = td;
1216 }
1217 }
1218 }
1219 if (start != 0) {
1220 start = 0;
1221 goto again;
1222 }
1223
1224 if (first && THREAD_CAN_MIGRATE(first) &&
1225 THREAD_CAN_SCHED(first, cpu))
1226 return (first);
1227 return (NULL);
1228 }
1229
1230 /*
1231 * Steals load from a standard linear queue.
1232 */
1233 static struct thread *
1234 runq_steal(struct runq *rq, int cpu)
1235 {
1236 struct rqhead *rqh;
1237 struct rqbits *rqb;
1238 struct thread *td;
1239 int word;
1240 int bit;
1241
1242 rqb = &rq->rq_status;
1243 for (word = 0; word < RQB_LEN; word++) {
1244 if (rqb->rqb_bits[word] == 0)
1245 continue;
1246 for (bit = 0; bit < RQB_BPW; bit++) {
1247 if ((rqb->rqb_bits[word] & (1ul << bit)) == 0)
1248 continue;
1249 rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)];
1250 TAILQ_FOREACH(td, rqh, td_runq)
1251 if (THREAD_CAN_MIGRATE(td) &&
1252 THREAD_CAN_SCHED(td, cpu))
1253 return (td);
1254 }
1255 }
1256 return (NULL);
1257 }
1258
1259 /*
1260 * Attempt to steal a thread in priority order from a thread queue.
1261 */
1262 static struct thread *
1263 tdq_steal(struct tdq *tdq, int cpu)
1264 {
1265 struct thread *td;
1266
1267 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
1268 if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL)
1269 return (td);
1270 if ((td = runq_steal_from(&tdq->tdq_timeshare,
1271 cpu, tdq->tdq_ridx)) != NULL)
1272 return (td);
1273 return (runq_steal(&tdq->tdq_idle, cpu));
1274 }
1275
1276 /*
1277 * Sets the thread lock and ts_cpu to match the requested cpu. Unlocks the
1278 * current lock and returns with the assigned queue locked.
1279 */
1280 static inline struct tdq *
1281 sched_setcpu(struct thread *td, int cpu, int flags)
1282 {
1283
1284 struct tdq *tdq;
1285 struct mtx *mtx;
1286
1287 THREAD_LOCK_ASSERT(td, MA_OWNED);
1288 tdq = TDQ_CPU(cpu);
1289 td_get_sched(td)->ts_cpu = cpu;
1290 /*
1291 * If the lock matches just return the queue.
1292 */
1293 if (td->td_lock == TDQ_LOCKPTR(tdq)) {
1294 KASSERT((flags & SRQ_HOLD) == 0,
1295 ("sched_setcpu: Invalid lock for SRQ_HOLD"));
1296 return (tdq);
1297 }
1298
1299 /*
1300 * The hard case, migration, we need to block the thread first to
1301 * prevent order reversals with other cpus locks.
1302 */
1303 spinlock_enter();
1304 mtx = thread_lock_block(td);
1305 if ((flags & SRQ_HOLD) == 0)
1306 mtx_unlock_spin(mtx);
1307 TDQ_LOCK(tdq);
1308 thread_lock_unblock(td, TDQ_LOCKPTR(tdq));
1309 spinlock_exit();
1310 return (tdq);
1311 }
1312
1313 SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding");
1314 SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity");
1315 SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity");
1316 SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load");
1317 SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu");
1318 SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration");
1319
1320 static int
1321 sched_pickcpu(struct thread *td, int flags)
1322 {
1323 struct cpu_group *cg, *ccg;
1324 struct td_sched *ts;
1325 struct tdq *tdq;
1326 cpuset_t *mask;
1327 int cpu, pri, r, self, intr;
1328
1329 self = PCPU_GET(cpuid);
1330 ts = td_get_sched(td);
1331 KASSERT(!CPU_ABSENT(ts->ts_cpu), ("sched_pickcpu: Start scheduler on "
1332 "absent CPU %d for thread %s.", ts->ts_cpu, td->td_name));
1333 if (smp_started == 0)
1334 return (self);
1335 /*
1336 * Don't migrate a running thread from sched_switch().
1337 */
1338 if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td))
1339 return (ts->ts_cpu);
1340 /*
1341 * Prefer to run interrupt threads on the processors that generate
1342 * the interrupt.
1343 */
1344 if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) &&
1345 curthread->td_intr_nesting_level) {
1346 tdq = TDQ_SELF();
1347 if (tdq->tdq_lowpri >= PRI_MIN_IDLE) {
1348 SCHED_STAT_INC(pickcpu_idle_affinity);
1349 return (self);
1350 }
1351 ts->ts_cpu = self;
1352 intr = 1;
1353 cg = tdq->tdq_cg;
1354 goto llc;
1355 } else {
1356 intr = 0;
1357 tdq = TDQ_CPU(ts->ts_cpu);
1358 cg = tdq->tdq_cg;
1359 }
1360 /*
1361 * If the thread can run on the last cpu and the affinity has not
1362 * expired and it is idle, run it there.
1363 */
1364 if (THREAD_CAN_SCHED(td, ts->ts_cpu) &&
1365 atomic_load_char(&tdq->tdq_lowpri) >= PRI_MIN_IDLE &&
1366 SCHED_AFFINITY(ts, CG_SHARE_L2)) {
1367 if (cg->cg_flags & CG_FLAG_THREAD) {
1368 /* Check all SMT threads for being idle. */
1369 for (cpu = cg->cg_first; cpu <= cg->cg_last; cpu++) {
1370 pri =
1371 atomic_load_char(&TDQ_CPU(cpu)->tdq_lowpri);
1372 if (CPU_ISSET(cpu, &cg->cg_mask) &&
1373 pri < PRI_MIN_IDLE)
1374 break;
1375 }
1376 if (cpu > cg->cg_last) {
1377 SCHED_STAT_INC(pickcpu_idle_affinity);
1378 return (ts->ts_cpu);
1379 }
1380 } else {
1381 SCHED_STAT_INC(pickcpu_idle_affinity);
1382 return (ts->ts_cpu);
1383 }
1384 }
1385 llc:
1386 /*
1387 * Search for the last level cache CPU group in the tree.
1388 * Skip SMT, identical groups and caches with expired affinity.
1389 * Interrupt threads affinity is explicit and never expires.
1390 */
1391 for (ccg = NULL; cg != NULL; cg = cg->cg_parent) {
1392 if (cg->cg_flags & CG_FLAG_THREAD)
1393 continue;
1394 if (cg->cg_children == 1 || cg->cg_count == 1)
1395 continue;
1396 if (cg->cg_level == CG_SHARE_NONE ||
1397 (!intr && !SCHED_AFFINITY(ts, cg->cg_level)))
1398 continue;
1399 ccg = cg;
1400 }
1401 /* Found LLC shared by all CPUs, so do a global search. */
1402 if (ccg == cpu_top)
1403 ccg = NULL;
1404 cpu = -1;
1405 mask = &td->td_cpuset->cs_mask;
1406 pri = td->td_priority;
1407 r = TD_IS_RUNNING(td);
1408 /*
1409 * Try hard to keep interrupts within found LLC. Search the LLC for
1410 * the least loaded CPU we can run now. For NUMA systems it should
1411 * be within target domain, and it also reduces scheduling overhead.
1412 */
1413 if (ccg != NULL && intr) {
1414 cpu = sched_lowest(ccg, mask, pri, INT_MAX, ts->ts_cpu, r);
1415 if (cpu >= 0)
1416 SCHED_STAT_INC(pickcpu_intrbind);
1417 } else
1418 /* Search the LLC for the least loaded idle CPU we can run now. */
1419 if (ccg != NULL) {
1420 cpu = sched_lowest(ccg, mask, max(pri, PRI_MAX_TIMESHARE),
1421 INT_MAX, ts->ts_cpu, r);
1422 if (cpu >= 0)
1423 SCHED_STAT_INC(pickcpu_affinity);
1424 }
1425 /* Search globally for the least loaded CPU we can run now. */
1426 if (cpu < 0) {
1427 cpu = sched_lowest(cpu_top, mask, pri, INT_MAX, ts->ts_cpu, r);
1428 if (cpu >= 0)
1429 SCHED_STAT_INC(pickcpu_lowest);
1430 }
1431 /* Search globally for the least loaded CPU. */
1432 if (cpu < 0) {
1433 cpu = sched_lowest(cpu_top, mask, -1, INT_MAX, ts->ts_cpu, r);
1434 if (cpu >= 0)
1435 SCHED_STAT_INC(pickcpu_lowest);
1436 }
1437 KASSERT(cpu >= 0, ("sched_pickcpu: Failed to find a cpu."));
1438 KASSERT(!CPU_ABSENT(cpu), ("sched_pickcpu: Picked absent CPU %d.", cpu));
1439 /*
1440 * Compare the lowest loaded cpu to current cpu.
1441 */
1442 tdq = TDQ_CPU(cpu);
1443 if (THREAD_CAN_SCHED(td, self) && TDQ_SELF()->tdq_lowpri > pri &&
1444 atomic_load_char(&tdq->tdq_lowpri) < PRI_MIN_IDLE &&
1445 TDQ_LOAD(TDQ_SELF()) <= TDQ_LOAD(tdq) + 1) {
1446 SCHED_STAT_INC(pickcpu_local);
1447 cpu = self;
1448 }
1449 if (cpu != ts->ts_cpu)
1450 SCHED_STAT_INC(pickcpu_migration);
1451 return (cpu);
1452 }
1453 #endif
1454
1455 /*
1456 * Pick the highest priority task we have and return it.
1457 */
1458 static struct thread *
1459 tdq_choose(struct tdq *tdq)
1460 {
1461 struct thread *td;
1462
1463 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
1464 td = runq_choose(&tdq->tdq_realtime);
1465 if (td != NULL)
1466 return (td);
1467 td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
1468 if (td != NULL) {
1469 KASSERT(td->td_priority >= PRI_MIN_BATCH,
1470 ("tdq_choose: Invalid priority on timeshare queue %d",
1471 td->td_priority));
1472 return (td);
1473 }
1474 td = runq_choose(&tdq->tdq_idle);
1475 if (td != NULL) {
1476 KASSERT(td->td_priority >= PRI_MIN_IDLE,
1477 ("tdq_choose: Invalid priority on idle queue %d",
1478 td->td_priority));
1479 return (td);
1480 }
1481
1482 return (NULL);
1483 }
1484
1485 /*
1486 * Initialize a thread queue.
1487 */
1488 static void
1489 tdq_setup(struct tdq *tdq, int id)
1490 {
1491
1492 if (bootverbose)
1493 printf("ULE: setup cpu %d\n", id);
1494 runq_init(&tdq->tdq_realtime);
1495 runq_init(&tdq->tdq_timeshare);
1496 runq_init(&tdq->tdq_idle);
1497 tdq->tdq_id = id;
1498 snprintf(tdq->tdq_name, sizeof(tdq->tdq_name),
1499 "sched lock %d", (int)TDQ_ID(tdq));
1500 mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock", MTX_SPIN);
1501 #ifdef KTR
1502 snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname),
1503 "CPU %d load", (int)TDQ_ID(tdq));
1504 #endif
1505 }
1506
1507 #ifdef SMP
1508 static void
1509 sched_setup_smp(void)
1510 {
1511 struct tdq *tdq;
1512 int i;
1513
1514 cpu_top = smp_topo();
1515 CPU_FOREACH(i) {
1516 tdq = DPCPU_ID_PTR(i, tdq);
1517 tdq_setup(tdq, i);
1518 tdq->tdq_cg = smp_topo_find(cpu_top, i);
1519 if (tdq->tdq_cg == NULL)
1520 panic("Can't find cpu group for %d\n", i);
1521 DPCPU_ID_SET(i, randomval, i * 69069 + 5);
1522 }
1523 PCPU_SET(sched, DPCPU_PTR(tdq));
1524 balance_tdq = TDQ_SELF();
1525 }
1526 #endif
1527
1528 /*
1529 * Setup the thread queues and initialize the topology based on MD
1530 * information.
1531 */
1532 static void
1533 sched_setup(void *dummy)
1534 {
1535 struct tdq *tdq;
1536
1537 #ifdef SMP
1538 sched_setup_smp();
1539 #else
1540 tdq_setup(TDQ_SELF(), 0);
1541 #endif
1542 tdq = TDQ_SELF();
1543
1544 /* Add thread0's load since it's running. */
1545 TDQ_LOCK(tdq);
1546 thread0.td_lock = TDQ_LOCKPTR(tdq);
1547 tdq_load_add(tdq, &thread0);
1548 tdq->tdq_curthread = &thread0;
1549 tdq->tdq_lowpri = thread0.td_priority;
1550 TDQ_UNLOCK(tdq);
1551 }
1552
1553 /*
1554 * This routine determines time constants after stathz and hz are setup.
1555 */
1556 /* ARGSUSED */
1557 static void
1558 sched_initticks(void *dummy)
1559 {
1560 int incr;
1561
1562 realstathz = stathz ? stathz : hz;
1563 sched_slice = realstathz / SCHED_SLICE_DEFAULT_DIVISOR;
1564 sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
1565 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
1566 realstathz);
1567
1568 /*
1569 * tickincr is shifted out by 10 to avoid rounding errors due to
1570 * hz not being evenly divisible by stathz on all platforms.
1571 */
1572 incr = (hz << SCHED_TICK_SHIFT) / realstathz;
1573 /*
1574 * This does not work for values of stathz that are more than
1575 * 1 << SCHED_TICK_SHIFT * hz. In practice this does not happen.
1576 */
1577 if (incr == 0)
1578 incr = 1;
1579 tickincr = incr;
1580 #ifdef SMP
1581 /*
1582 * Set the default balance interval now that we know
1583 * what realstathz is.
1584 */
1585 balance_interval = realstathz;
1586 balance_ticks = balance_interval;
1587 affinity = SCHED_AFFINITY_DEFAULT;
1588 #endif
1589 if (sched_idlespinthresh < 0)
1590 sched_idlespinthresh = 2 * max(10000, 6 * hz) / realstathz;
1591 }
1592
1593 /*
1594 * This is the core of the interactivity algorithm. Determines a score based
1595 * on past behavior. It is the ratio of sleep time to run time scaled to
1596 * a [0, 100] integer. This is the voluntary sleep time of a process, which
1597 * differs from the cpu usage because it does not account for time spent
1598 * waiting on a run-queue. Would be prettier if we had floating point.
1599 *
1600 * When a thread's sleep time is greater than its run time the
1601 * calculation is:
1602 *
1603 * scaling factor
1604 * interactivity score = ---------------------
1605 * sleep time / run time
1606 *
1607 *
1608 * When a thread's run time is greater than its sleep time the
1609 * calculation is:
1610 *
1611 * scaling factor
1612 * interactivity score = 2 * scaling factor - ---------------------
1613 * run time / sleep time
1614 */
1615 static int
1616 sched_interact_score(struct thread *td)
1617 {
1618 struct td_sched *ts;
1619 int div;
1620
1621 ts = td_get_sched(td);
1622 /*
1623 * The score is only needed if this is likely to be an interactive
1624 * task. Don't go through the expense of computing it if there's
1625 * no chance.
1626 */
1627 if (sched_interact <= SCHED_INTERACT_HALF &&
1628 ts->ts_runtime >= ts->ts_slptime)
1629 return (SCHED_INTERACT_HALF);
1630
1631 if (ts->ts_runtime > ts->ts_slptime) {
1632 div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF);
1633 return (SCHED_INTERACT_HALF +
1634 (SCHED_INTERACT_HALF - (ts->ts_slptime / div)));
1635 }
1636 if (ts->ts_slptime > ts->ts_runtime) {
1637 div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF);
1638 return (ts->ts_runtime / div);
1639 }
1640 /* runtime == slptime */
1641 if (ts->ts_runtime)
1642 return (SCHED_INTERACT_HALF);
1643
1644 /*
1645 * This can happen if slptime and runtime are 0.
1646 */
1647 return (0);
1648
1649 }
1650
1651 /*
1652 * Scale the scheduling priority according to the "interactivity" of this
1653 * process.
1654 */
1655 static void
1656 sched_priority(struct thread *td)
1657 {
1658 u_int pri, score;
1659
1660 if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
1661 return;
1662 /*
1663 * If the score is interactive we place the thread in the realtime
1664 * queue with a priority that is less than kernel and interrupt
1665 * priorities. These threads are not subject to nice restrictions.
1666 *
1667 * Scores greater than this are placed on the normal timeshare queue
1668 * where the priority is partially decided by the most recent cpu
1669 * utilization and the rest is decided by nice value.
1670 *
1671 * The nice value of the process has a linear effect on the calculated
1672 * score. Negative nice values make it easier for a thread to be
1673 * considered interactive.
1674 */
1675 score = imax(0, sched_interact_score(td) + td->td_proc->p_nice);
1676 if (score < sched_interact) {
1677 pri = PRI_MIN_INTERACT;
1678 pri += (PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) * score /
1679 sched_interact;
1680 KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT,
1681 ("sched_priority: invalid interactive priority %u score %u",
1682 pri, score));
1683 } else {
1684 pri = SCHED_PRI_MIN;
1685 if (td_get_sched(td)->ts_ticks)
1686 pri += min(SCHED_PRI_TICKS(td_get_sched(td)),
1687 SCHED_PRI_RANGE - 1);
1688 pri += SCHED_PRI_NICE(td->td_proc->p_nice);
1689 KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH,
1690 ("sched_priority: invalid priority %u: nice %d, "
1691 "ticks %d ftick %d ltick %d tick pri %d",
1692 pri, td->td_proc->p_nice, td_get_sched(td)->ts_ticks,
1693 td_get_sched(td)->ts_ftick, td_get_sched(td)->ts_ltick,
1694 SCHED_PRI_TICKS(td_get_sched(td))));
1695 }
1696 sched_user_prio(td, pri);
1697
1698 return;
1699 }
1700
1701 /*
1702 * This routine enforces a maximum limit on the amount of scheduling history
1703 * kept. It is called after either the slptime or runtime is adjusted. This
1704 * function is ugly due to integer math.
1705 */
1706 static void
1707 sched_interact_update(struct thread *td)
1708 {
1709 struct td_sched *ts;
1710 u_int sum;
1711
1712 ts = td_get_sched(td);
1713 sum = ts->ts_runtime + ts->ts_slptime;
1714 if (sum < SCHED_SLP_RUN_MAX)
1715 return;
1716 /*
1717 * This only happens from two places:
1718 * 1) We have added an unusual amount of run time from fork_exit.
1719 * 2) We have added an unusual amount of sleep time from sched_sleep().
1720 */
1721 if (sum > SCHED_SLP_RUN_MAX * 2) {
1722 if (ts->ts_runtime > ts->ts_slptime) {
1723 ts->ts_runtime = SCHED_SLP_RUN_MAX;
1724 ts->ts_slptime = 1;
1725 } else {
1726 ts->ts_slptime = SCHED_SLP_RUN_MAX;
1727 ts->ts_runtime = 1;
1728 }
1729 return;
1730 }
1731 /*
1732 * If we have exceeded by more than 1/5th then the algorithm below
1733 * will not bring us back into range. Dividing by two here forces
1734 * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX]
1735 */
1736 if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) {
1737 ts->ts_runtime /= 2;
1738 ts->ts_slptime /= 2;
1739 return;
1740 }
1741 ts->ts_runtime = (ts->ts_runtime / 5) * 4;
1742 ts->ts_slptime = (ts->ts_slptime / 5) * 4;
1743 }
1744
1745 /*
1746 * Scale back the interactivity history when a child thread is created. The
1747 * history is inherited from the parent but the thread may behave totally
1748 * differently. For example, a shell spawning a compiler process. We want
1749 * to learn that the compiler is behaving badly very quickly.
1750 */
1751 static void
1752 sched_interact_fork(struct thread *td)
1753 {
1754 struct td_sched *ts;
1755 int ratio;
1756 int sum;
1757
1758 ts = td_get_sched(td);
1759 sum = ts->ts_runtime + ts->ts_slptime;
1760 if (sum > SCHED_SLP_RUN_FORK) {
1761 ratio = sum / SCHED_SLP_RUN_FORK;
1762 ts->ts_runtime /= ratio;
1763 ts->ts_slptime /= ratio;
1764 }
1765 }
1766
1767 /*
1768 * Called from proc0_init() to setup the scheduler fields.
1769 */
1770 void
1771 schedinit(void)
1772 {
1773 struct td_sched *ts0;
1774
1775 /*
1776 * Set up the scheduler specific parts of thread0.
1777 */
1778 ts0 = td_get_sched(&thread0);
1779 ts0->ts_ltick = ticks;
1780 ts0->ts_ftick = ticks;
1781 ts0->ts_slice = 0;
1782 ts0->ts_cpu = curcpu; /* set valid CPU number */
1783 }
1784
1785 /*
1786 * schedinit_ap() is needed prior to calling sched_throw(NULL) to ensure that
1787 * the pcpu requirements are met for any calls in the period between curthread
1788 * initialization and sched_throw(). One can safely add threads to the queue
1789 * before sched_throw(), for instance, as long as the thread lock is setup
1790 * correctly.
1791 *
1792 * TDQ_SELF() relies on the below sched pcpu setting; it may be used only
1793 * after schedinit_ap().
1794 */
1795 void
1796 schedinit_ap(void)
1797 {
1798
1799 #ifdef SMP
1800 PCPU_SET(sched, DPCPU_PTR(tdq));
1801 #endif
1802 PCPU_GET(idlethread)->td_lock = TDQ_LOCKPTR(TDQ_SELF());
1803 }
1804
1805 /*
1806 * This is only somewhat accurate since given many processes of the same
1807 * priority they will switch when their slices run out, which will be
1808 * at most sched_slice stathz ticks.
1809 */
1810 int
1811 sched_rr_interval(void)
1812 {
1813
1814 /* Convert sched_slice from stathz to hz. */
1815 return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz));
1816 }
1817
1818 /*
1819 * Update the percent cpu tracking information when it is requested or
1820 * the total history exceeds the maximum. We keep a sliding history of
1821 * tick counts that slowly decays. This is less precise than the 4BSD
1822 * mechanism since it happens with less regular and frequent events.
1823 */
1824 static void
1825 sched_pctcpu_update(struct td_sched *ts, int run)
1826 {
1827 int t = ticks;
1828
1829 /*
1830 * The signed difference may be negative if the thread hasn't run for
1831 * over half of the ticks rollover period.
1832 */
1833 if ((u_int)(t - ts->ts_ltick) >= SCHED_TICK_TARG) {
1834 ts->ts_ticks = 0;
1835 ts->ts_ftick = t - SCHED_TICK_TARG;
1836 } else if (t - ts->ts_ftick >= SCHED_TICK_MAX) {
1837 ts->ts_ticks = (ts->ts_ticks / (ts->ts_ltick - ts->ts_ftick)) *
1838 (ts->ts_ltick - (t - SCHED_TICK_TARG));
1839 ts->ts_ftick = t - SCHED_TICK_TARG;
1840 }
1841 if (run)
1842 ts->ts_ticks += (t - ts->ts_ltick) << SCHED_TICK_SHIFT;
1843 ts->ts_ltick = t;
1844 }
1845
1846 /*
1847 * Adjust the priority of a thread. Move it to the appropriate run-queue
1848 * if necessary. This is the back-end for several priority related
1849 * functions.
1850 */
1851 static void
1852 sched_thread_priority(struct thread *td, u_char prio)
1853 {
1854 struct tdq *tdq;
1855 int oldpri;
1856
1857 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio",
1858 "prio:%d", td->td_priority, "new prio:%d", prio,
1859 KTR_ATTR_LINKED, sched_tdname(curthread));
1860 SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio);
1861 if (td != curthread && prio < td->td_priority) {
1862 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
1863 "lend prio", "prio:%d", td->td_priority, "new prio:%d",
1864 prio, KTR_ATTR_LINKED, sched_tdname(td));
1865 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio,
1866 curthread);
1867 }
1868 THREAD_LOCK_ASSERT(td, MA_OWNED);
1869 if (td->td_priority == prio)
1870 return;
1871 /*
1872 * If the priority has been elevated due to priority
1873 * propagation, we may have to move ourselves to a new
1874 * queue. This could be optimized to not re-add in some
1875 * cases.
1876 */
1877 if (TD_ON_RUNQ(td) && prio < td->td_priority) {
1878 sched_rem(td);
1879 td->td_priority = prio;
1880 sched_add(td, SRQ_BORROWING | SRQ_HOLDTD);
1881 return;
1882 }
1883 /*
1884 * If the thread is currently running we may have to adjust the lowpri
1885 * information so other cpus are aware of our current priority.
1886 */
1887 if (TD_IS_RUNNING(td)) {
1888 tdq = TDQ_CPU(td_get_sched(td)->ts_cpu);
1889 oldpri = td->td_priority;
1890 td->td_priority = prio;
1891 if (prio < tdq->tdq_lowpri)
1892 tdq->tdq_lowpri = prio;
1893 else if (tdq->tdq_lowpri == oldpri)
1894 tdq_setlowpri(tdq, td);
1895 return;
1896 }
1897 td->td_priority = prio;
1898 }
1899
1900 /*
1901 * Update a thread's priority when it is lent another thread's
1902 * priority.
1903 */
1904 void
1905 sched_lend_prio(struct thread *td, u_char prio)
1906 {
1907
1908 td->td_flags |= TDF_BORROWING;
1909 sched_thread_priority(td, prio);
1910 }
1911
1912 /*
1913 * Restore a thread's priority when priority propagation is
1914 * over. The prio argument is the minimum priority the thread
1915 * needs to have to satisfy other possible priority lending
1916 * requests. If the thread's regular priority is less
1917 * important than prio, the thread will keep a priority boost
1918 * of prio.
1919 */
1920 void
1921 sched_unlend_prio(struct thread *td, u_char prio)
1922 {
1923 u_char base_pri;
1924
1925 if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
1926 td->td_base_pri <= PRI_MAX_TIMESHARE)
1927 base_pri = td->td_user_pri;
1928 else
1929 base_pri = td->td_base_pri;
1930 if (prio >= base_pri) {
1931 td->td_flags &= ~TDF_BORROWING;
1932 sched_thread_priority(td, base_pri);
1933 } else
1934 sched_lend_prio(td, prio);
1935 }
1936
1937 /*
1938 * Standard entry for setting the priority to an absolute value.
1939 */
1940 void
1941 sched_prio(struct thread *td, u_char prio)
1942 {
1943 u_char oldprio;
1944
1945 /* First, update the base priority. */
1946 td->td_base_pri = prio;
1947
1948 /*
1949 * If the thread is borrowing another thread's priority, don't
1950 * ever lower the priority.
1951 */
1952 if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
1953 return;
1954
1955 /* Change the real priority. */
1956 oldprio = td->td_priority;
1957 sched_thread_priority(td, prio);
1958
1959 /*
1960 * If the thread is on a turnstile, then let the turnstile update
1961 * its state.
1962 */
1963 if (TD_ON_LOCK(td) && oldprio != prio)
1964 turnstile_adjust(td, oldprio);
1965 }
1966
1967 /*
1968 * Set the base interrupt thread priority.
1969 */
1970 void
1971 sched_ithread_prio(struct thread *td, u_char prio)
1972 {
1973 THREAD_LOCK_ASSERT(td, MA_OWNED);
1974 MPASS(td->td_pri_class == PRI_ITHD);
1975 td->td_base_ithread_pri = prio;
1976 sched_prio(td, prio);
1977 }
1978
1979 /*
1980 * Set the base user priority, does not effect current running priority.
1981 */
1982 void
1983 sched_user_prio(struct thread *td, u_char prio)
1984 {
1985
1986 td->td_base_user_pri = prio;
1987 if (td->td_lend_user_pri <= prio)
1988 return;
1989 td->td_user_pri = prio;
1990 }
1991
1992 void
1993 sched_lend_user_prio(struct thread *td, u_char prio)
1994 {
1995
1996 THREAD_LOCK_ASSERT(td, MA_OWNED);
1997 td->td_lend_user_pri = prio;
1998 td->td_user_pri = min(prio, td->td_base_user_pri);
1999 if (td->td_priority > td->td_user_pri)
2000 sched_prio(td, td->td_user_pri);
2001 else if (td->td_priority != td->td_user_pri)
2002 ast_sched_locked(td, TDA_SCHED);
2003 }
2004
2005 /*
2006 * Like the above but first check if there is anything to do.
2007 */
2008 void
2009 sched_lend_user_prio_cond(struct thread *td, u_char prio)
2010 {
2011
2012 if (td->td_lend_user_pri != prio)
2013 goto lend;
2014 if (td->td_user_pri != min(prio, td->td_base_user_pri))
2015 goto lend;
2016 if (td->td_priority != td->td_user_pri)
2017 goto lend;
2018 return;
2019
2020 lend:
2021 thread_lock(td);
2022 sched_lend_user_prio(td, prio);
2023 thread_unlock(td);
2024 }
2025
2026 #ifdef SMP
2027 /*
2028 * This tdq is about to idle. Try to steal a thread from another CPU before
2029 * choosing the idle thread.
2030 */
2031 static void
2032 tdq_trysteal(struct tdq *tdq)
2033 {
2034 struct cpu_group *cg, *parent;
2035 struct tdq *steal;
2036 cpuset_t mask;
2037 int cpu, i, goup;
2038
2039 if (smp_started == 0 || steal_idle == 0 || trysteal_limit == 0 ||
2040 tdq->tdq_cg == NULL)
2041 return;
2042 CPU_FILL(&mask);
2043 CPU_CLR(PCPU_GET(cpuid), &mask);
2044 /* We don't want to be preempted while we're iterating. */
2045 spinlock_enter();
2046 TDQ_UNLOCK(tdq);
2047 for (i = 1, cg = tdq->tdq_cg, goup = 0; ; ) {
2048 cpu = sched_highest(cg, &mask, steal_thresh, 1);
2049 /*
2050 * If a thread was added while interrupts were disabled don't
2051 * steal one here.
2052 */
2053 if (TDQ_LOAD(tdq) > 0) {
2054 TDQ_LOCK(tdq);
2055 break;
2056 }
2057
2058 /*
2059 * We found no CPU to steal from in this group. Escalate to
2060 * the parent and repeat. But if parent has only two children
2061 * groups we can avoid searching this group again by searching
2062 * the other one specifically and then escalating two levels.
2063 */
2064 if (cpu == -1) {
2065 if (goup) {
2066 cg = cg->cg_parent;
2067 goup = 0;
2068 }
2069 if (++i > trysteal_limit) {
2070 TDQ_LOCK(tdq);
2071 break;
2072 }
2073 parent = cg->cg_parent;
2074 if (parent == NULL) {
2075 TDQ_LOCK(tdq);
2076 break;
2077 }
2078 if (parent->cg_children == 2) {
2079 if (cg == &parent->cg_child[0])
2080 cg = &parent->cg_child[1];
2081 else
2082 cg = &parent->cg_child[0];
2083 goup = 1;
2084 } else
2085 cg = parent;
2086 continue;
2087 }
2088 steal = TDQ_CPU(cpu);
2089 /*
2090 * The data returned by sched_highest() is stale and
2091 * the chosen CPU no longer has an eligible thread.
2092 * At this point unconditionally exit the loop to bound
2093 * the time spent in the critcal section.
2094 */
2095 if (TDQ_LOAD(steal) < steal_thresh ||
2096 TDQ_TRANSFERABLE(steal) == 0)
2097 continue;
2098 /*
2099 * Try to lock both queues. If we are assigned a thread while
2100 * waited for the lock, switch to it now instead of stealing.
2101 * If we can't get the lock, then somebody likely got there
2102 * first.
2103 */
2104 TDQ_LOCK(tdq);
2105 if (tdq->tdq_load > 0)
2106 break;
2107 if (TDQ_TRYLOCK_FLAGS(steal, MTX_DUPOK) == 0)
2108 break;
2109 /*
2110 * The data returned by sched_highest() is stale and
2111 * the chosen CPU no longer has an eligible thread.
2112 */
2113 if (TDQ_LOAD(steal) < steal_thresh ||
2114 TDQ_TRANSFERABLE(steal) == 0) {
2115 TDQ_UNLOCK(steal);
2116 break;
2117 }
2118 /*
2119 * If we fail to acquire one due to affinity restrictions,
2120 * bail out and let the idle thread to a more complete search
2121 * outside of a critical section.
2122 */
2123 if (tdq_move(steal, tdq) == -1) {
2124 TDQ_UNLOCK(steal);
2125 break;
2126 }
2127 TDQ_UNLOCK(steal);
2128 break;
2129 }
2130 spinlock_exit();
2131 }
2132 #endif
2133
2134 /*
2135 * Handle migration from sched_switch(). This happens only for
2136 * cpu binding.
2137 */
2138 static struct mtx *
2139 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags)
2140 {
2141 struct tdq *tdn;
2142 #ifdef SMP
2143 int lowpri;
2144 #endif
2145
2146 KASSERT(THREAD_CAN_MIGRATE(td) ||
2147 (td_get_sched(td)->ts_flags & TSF_BOUND) != 0,
2148 ("Thread %p shouldn't migrate", td));
2149 KASSERT(!CPU_ABSENT(td_get_sched(td)->ts_cpu), ("sched_switch_migrate: "
2150 "thread %s queued on absent CPU %d.", td->td_name,
2151 td_get_sched(td)->ts_cpu));
2152 tdn = TDQ_CPU(td_get_sched(td)->ts_cpu);
2153 #ifdef SMP
2154 tdq_load_rem(tdq, td);
2155 /*
2156 * Do the lock dance required to avoid LOR. We have an
2157 * extra spinlock nesting from sched_switch() which will
2158 * prevent preemption while we're holding neither run-queue lock.
2159 */
2160 TDQ_UNLOCK(tdq);
2161 TDQ_LOCK(tdn);
2162 lowpri = tdq_add(tdn, td, flags);
2163 tdq_notify(tdn, lowpri);
2164 TDQ_UNLOCK(tdn);
2165 TDQ_LOCK(tdq);
2166 #endif
2167 return (TDQ_LOCKPTR(tdn));
2168 }
2169
2170 /*
2171 * thread_lock_unblock() that does not assume td_lock is blocked.
2172 */
2173 static inline void
2174 thread_unblock_switch(struct thread *td, struct mtx *mtx)
2175 {
2176 atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock,
2177 (uintptr_t)mtx);
2178 }
2179
2180 /*
2181 * Switch threads. This function has to handle threads coming in while
2182 * blocked for some reason, running, or idle. It also must deal with
2183 * migrating a thread from one queue to another as running threads may
2184 * be assigned elsewhere via binding.
2185 */
2186 void
2187 sched_switch(struct thread *td, int flags)
2188 {
2189 struct thread *newtd;
2190 struct tdq *tdq;
2191 struct td_sched *ts;
2192 struct mtx *mtx;
2193 int srqflag;
2194 int cpuid, preempted;
2195 #ifdef SMP
2196 int pickcpu;
2197 #endif
2198
2199 THREAD_LOCK_ASSERT(td, MA_OWNED);
2200
2201 cpuid = PCPU_GET(cpuid);
2202 tdq = TDQ_SELF();
2203 ts = td_get_sched(td);
2204 sched_pctcpu_update(ts, 1);
2205 #ifdef SMP
2206 pickcpu = (td->td_flags & TDF_PICKCPU) != 0;
2207 if (pickcpu)
2208 ts->ts_rltick = ticks - affinity * MAX_CACHE_LEVELS;
2209 else
2210 ts->ts_rltick = ticks;
2211 #endif
2212 td->td_lastcpu = td->td_oncpu;
2213 preempted = (td->td_flags & TDF_SLICEEND) == 0 &&
2214 (flags & SW_PREEMPT) != 0;
2215 td->td_flags &= ~(TDF_PICKCPU | TDF_SLICEEND);
2216 ast_unsched_locked(td, TDA_SCHED);
2217 td->td_owepreempt = 0;
2218 atomic_store_char(&tdq->tdq_owepreempt, 0);
2219 if (!TD_IS_IDLETHREAD(td))
2220 TDQ_SWITCHCNT_INC(tdq);
2221
2222 /*
2223 * Always block the thread lock so we can drop the tdq lock early.
2224 */
2225 mtx = thread_lock_block(td);
2226 spinlock_enter();
2227 if (TD_IS_IDLETHREAD(td)) {
2228 MPASS(mtx == TDQ_LOCKPTR(tdq));
2229 TD_SET_CAN_RUN(td);
2230 } else if (TD_IS_RUNNING(td)) {
2231 MPASS(mtx == TDQ_LOCKPTR(tdq));
2232 srqflag = preempted ?
2233 SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
2234 SRQ_OURSELF|SRQ_YIELDING;
2235 #ifdef SMP
2236 if (THREAD_CAN_MIGRATE(td) && (!THREAD_CAN_SCHED(td, ts->ts_cpu)
2237 || pickcpu))
2238 ts->ts_cpu = sched_pickcpu(td, 0);
2239 #endif
2240 if (ts->ts_cpu == cpuid)
2241 tdq_runq_add(tdq, td, srqflag);
2242 else
2243 mtx = sched_switch_migrate(tdq, td, srqflag);
2244 } else {
2245 /* This thread must be going to sleep. */
2246 if (mtx != TDQ_LOCKPTR(tdq)) {
2247 mtx_unlock_spin(mtx);
2248 TDQ_LOCK(tdq);
2249 }
2250 tdq_load_rem(tdq, td);
2251 #ifdef SMP
2252 if (tdq->tdq_load == 0)
2253 tdq_trysteal(tdq);
2254 #endif
2255 }
2256
2257 #if (KTR_COMPILE & KTR_SCHED) != 0
2258 if (TD_IS_IDLETHREAD(td))
2259 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle",
2260 "prio:%d", td->td_priority);
2261 else
2262 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td),
2263 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg,
2264 "lockname:\"%s\"", td->td_lockname);
2265 #endif
2266
2267 /*
2268 * We enter here with the thread blocked and assigned to the
2269 * appropriate cpu run-queue or sleep-queue and with the current
2270 * thread-queue locked.
2271 */
2272 TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
2273 MPASS(td == tdq->tdq_curthread);
2274 newtd = choosethread();
2275 sched_pctcpu_update(td_get_sched(newtd), 0);
2276 TDQ_UNLOCK(tdq);
2277
2278 /*
2279 * Call the MD code to switch contexts if necessary.
2280 */
2281 if (td != newtd) {
2282 #ifdef HWPMC_HOOKS
2283 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
2284 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
2285 #endif
2286 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc);
2287
2288 #ifdef KDTRACE_HOOKS
2289 /*
2290 * If DTrace has set the active vtime enum to anything
2291 * other than INACTIVE (0), then it should have set the
2292 * function to call.
2293 */
2294 if (dtrace_vtime_active)
2295 (*dtrace_vtime_switch_func)(newtd);
2296 #endif
2297 td->td_oncpu = NOCPU;
2298 cpu_switch(td, newtd, mtx);
2299 cpuid = td->td_oncpu = PCPU_GET(cpuid);
2300
2301 SDT_PROBE0(sched, , , on__cpu);
2302 #ifdef HWPMC_HOOKS
2303 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
2304 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
2305 #endif
2306 } else {
2307 thread_unblock_switch(td, mtx);
2308 SDT_PROBE0(sched, , , remain__cpu);
2309 }
2310 KASSERT(curthread->td_md.md_spinlock_count == 1,
2311 ("invalid count %d", curthread->td_md.md_spinlock_count));
2312
2313 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
2314 "prio:%d", td->td_priority);
2315 }
2316
2317 /*
2318 * Adjust thread priorities as a result of a nice request.
2319 */
2320 void
2321 sched_nice(struct proc *p, int nice)
2322 {
2323 struct thread *td;
2324
2325 PROC_LOCK_ASSERT(p, MA_OWNED);
2326
2327 p->p_nice = nice;
2328 FOREACH_THREAD_IN_PROC(p, td) {
2329 thread_lock(td);
2330 sched_priority(td);
2331 sched_prio(td, td->td_base_user_pri);
2332 thread_unlock(td);
2333 }
2334 }
2335
2336 /*
2337 * Record the sleep time for the interactivity scorer.
2338 */
2339 void
2340 sched_sleep(struct thread *td, int prio)
2341 {
2342
2343 THREAD_LOCK_ASSERT(td, MA_OWNED);
2344
2345 td->td_slptick = ticks;
2346 if (TD_IS_SUSPENDED(td) || prio >= PSOCK)
2347 td->td_flags |= TDF_CANSWAP;
2348 if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
2349 return;
2350 if (static_boost == 1 && prio)
2351 sched_prio(td, prio);
2352 else if (static_boost && td->td_priority > static_boost)
2353 sched_prio(td, static_boost);
2354 }
2355
2356 /*
2357 * Schedule a thread to resume execution and record how long it voluntarily
2358 * slept. We also update the pctcpu, interactivity, and priority.
2359 *
2360 * Requires the thread lock on entry, drops on exit.
2361 */
2362 void
2363 sched_wakeup(struct thread *td, int srqflags)
2364 {
2365 struct td_sched *ts;
2366 int slptick;
2367
2368 THREAD_LOCK_ASSERT(td, MA_OWNED);
2369 ts = td_get_sched(td);
2370 td->td_flags &= ~TDF_CANSWAP;
2371
2372 /*
2373 * If we slept for more than a tick update our interactivity and
2374 * priority.
2375 */
2376 slptick = td->td_slptick;
2377 td->td_slptick = 0;
2378 if (slptick && slptick != ticks) {
2379 ts->ts_slptime += (ticks - slptick) << SCHED_TICK_SHIFT;
2380 sched_interact_update(td);
2381 sched_pctcpu_update(ts, 0);
2382 }
2383
2384 /*
2385 * When resuming an idle ithread, restore its base ithread
2386 * priority.
2387 */
2388 if (PRI_BASE(td->td_pri_class) == PRI_ITHD &&
2389 td->td_priority != td->td_base_ithread_pri)
2390 sched_prio(td, td->td_base_ithread_pri);
2391
2392 /*
2393 * Reset the slice value since we slept and advanced the round-robin.
2394 */
2395 ts->ts_slice = 0;
2396 sched_add(td, SRQ_BORING | srqflags);
2397 }
2398
2399 /*
2400 * Penalize the parent for creating a new child and initialize the child's
2401 * priority.
2402 */
2403 void
2404 sched_fork(struct thread *td, struct thread *child)
2405 {
2406 THREAD_LOCK_ASSERT(td, MA_OWNED);
2407 sched_pctcpu_update(td_get_sched(td), 1);
2408 sched_fork_thread(td, child);
2409 /*
2410 * Penalize the parent and child for forking.
2411 */
2412 sched_interact_fork(child);
2413 sched_priority(child);
2414 td_get_sched(td)->ts_runtime += tickincr;
2415 sched_interact_update(td);
2416 sched_priority(td);
2417 }
2418
2419 /*
2420 * Fork a new thread, may be within the same process.
2421 */
2422 void
2423 sched_fork_thread(struct thread *td, struct thread *child)
2424 {
2425 struct td_sched *ts;
2426 struct td_sched *ts2;
2427 struct tdq *tdq;
2428
2429 tdq = TDQ_SELF();
2430 THREAD_LOCK_ASSERT(td, MA_OWNED);
2431 /*
2432 * Initialize child.
2433 */
2434 ts = td_get_sched(td);
2435 ts2 = td_get_sched(child);
2436 child->td_oncpu = NOCPU;
2437 child->td_lastcpu = NOCPU;
2438 child->td_lock = TDQ_LOCKPTR(tdq);
2439 child->td_cpuset = cpuset_ref(td->td_cpuset);
2440 child->td_domain.dr_policy = td->td_cpuset->cs_domain;
2441 ts2->ts_cpu = ts->ts_cpu;
2442 ts2->ts_flags = 0;
2443 /*
2444 * Grab our parents cpu estimation information.
2445 */
2446 ts2->ts_ticks = ts->ts_ticks;
2447 ts2->ts_ltick = ts->ts_ltick;
2448 ts2->ts_ftick = ts->ts_ftick;
2449 /*
2450 * Do not inherit any borrowed priority from the parent.
2451 */
2452 child->td_priority = child->td_base_pri;
2453 /*
2454 * And update interactivity score.
2455 */
2456 ts2->ts_slptime = ts->ts_slptime;
2457 ts2->ts_runtime = ts->ts_runtime;
2458 /* Attempt to quickly learn interactivity. */
2459 ts2->ts_slice = tdq_slice(tdq) - sched_slice_min;
2460 #ifdef KTR
2461 bzero(ts2->ts_name, sizeof(ts2->ts_name));
2462 #endif
2463 }
2464
2465 /*
2466 * Adjust the priority class of a thread.
2467 */
2468 void
2469 sched_class(struct thread *td, int class)
2470 {
2471
2472 THREAD_LOCK_ASSERT(td, MA_OWNED);
2473 if (td->td_pri_class == class)
2474 return;
2475 td->td_pri_class = class;
2476 }
2477
2478 /*
2479 * Return some of the child's priority and interactivity to the parent.
2480 */
2481 void
2482 sched_exit(struct proc *p, struct thread *child)
2483 {
2484 struct thread *td;
2485
2486 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit",
2487 "prio:%d", child->td_priority);
2488 PROC_LOCK_ASSERT(p, MA_OWNED);
2489 td = FIRST_THREAD_IN_PROC(p);
2490 sched_exit_thread(td, child);
2491 }
2492
2493 /*
2494 * Penalize another thread for the time spent on this one. This helps to
2495 * worsen the priority and interactivity of processes which schedule batch
2496 * jobs such as make. This has little effect on the make process itself but
2497 * causes new processes spawned by it to receive worse scores immediately.
2498 */
2499 void
2500 sched_exit_thread(struct thread *td, struct thread *child)
2501 {
2502
2503 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit",
2504 "prio:%d", child->td_priority);
2505 /*
2506 * Give the child's runtime to the parent without returning the
2507 * sleep time as a penalty to the parent. This causes shells that
2508 * launch expensive things to mark their children as expensive.
2509 */
2510 thread_lock(td);
2511 td_get_sched(td)->ts_runtime += td_get_sched(child)->ts_runtime;
2512 sched_interact_update(td);
2513 sched_priority(td);
2514 thread_unlock(td);
2515 }
2516
2517 void
2518 sched_preempt(struct thread *td)
2519 {
2520 struct tdq *tdq;
2521 int flags;
2522
2523 SDT_PROBE2(sched, , , surrender, td, td->td_proc);
2524
2525 thread_lock(td);
2526 tdq = TDQ_SELF();
2527 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2528 if (td->td_priority > tdq->tdq_lowpri) {
2529 if (td->td_critnest == 1) {
2530 flags = SW_INVOL | SW_PREEMPT;
2531 flags |= TD_IS_IDLETHREAD(td) ? SWT_REMOTEWAKEIDLE :
2532 SWT_REMOTEPREEMPT;
2533 mi_switch(flags);
2534 /* Switch dropped thread lock. */
2535 return;
2536 }
2537 td->td_owepreempt = 1;
2538 } else {
2539 tdq->tdq_owepreempt = 0;
2540 }
2541 thread_unlock(td);
2542 }
2543
2544 /*
2545 * Fix priorities on return to user-space. Priorities may be elevated due
2546 * to static priorities in msleep() or similar.
2547 */
2548 void
2549 sched_userret_slowpath(struct thread *td)
2550 {
2551
2552 thread_lock(td);
2553 td->td_priority = td->td_user_pri;
2554 td->td_base_pri = td->td_user_pri;
2555 tdq_setlowpri(TDQ_SELF(), td);
2556 thread_unlock(td);
2557 }
2558
2559 SCHED_STAT_DEFINE(ithread_demotions, "Interrupt thread priority demotions");
2560 SCHED_STAT_DEFINE(ithread_preemptions,
2561 "Interrupt thread preemptions due to time-sharing");
2562
2563 /*
2564 * Return time slice for a given thread. For ithreads this is
2565 * sched_slice. For other threads it is tdq_slice(tdq).
2566 */
2567 static inline int
2568 td_slice(struct thread *td, struct tdq *tdq)
2569 {
2570 if (PRI_BASE(td->td_pri_class) == PRI_ITHD)
2571 return (sched_slice);
2572 return (tdq_slice(tdq));
2573 }
2574
2575 /*
2576 * Handle a stathz tick. This is really only relevant for timeshare
2577 * and interrupt threads.
2578 */
2579 void
2580 sched_clock(struct thread *td, int cnt)
2581 {
2582 struct tdq *tdq;
2583 struct td_sched *ts;
2584
2585 THREAD_LOCK_ASSERT(td, MA_OWNED);
2586 tdq = TDQ_SELF();
2587 #ifdef SMP
2588 /*
2589 * We run the long term load balancer infrequently on the first cpu.
2590 */
2591 if (balance_tdq == tdq && smp_started != 0 && rebalance != 0 &&
2592 balance_ticks != 0) {
2593 balance_ticks -= cnt;
2594 if (balance_ticks <= 0)
2595 sched_balance();
2596 }
2597 #endif
2598 /*
2599 * Save the old switch count so we have a record of the last ticks
2600 * activity. Initialize the new switch count based on our load.
2601 * If there is some activity seed it to reflect that.
2602 */
2603 tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt;
2604 tdq->tdq_switchcnt = tdq->tdq_load;
2605
2606 /*
2607 * Advance the insert index once for each tick to ensure that all
2608 * threads get a chance to run.
2609 */
2610 if (tdq->tdq_idx == tdq->tdq_ridx) {
2611 tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS;
2612 if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx]))
2613 tdq->tdq_ridx = tdq->tdq_idx;
2614 }
2615 ts = td_get_sched(td);
2616 sched_pctcpu_update(ts, 1);
2617 if ((td->td_pri_class & PRI_FIFO_BIT) || TD_IS_IDLETHREAD(td))
2618 return;
2619
2620 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) {
2621 /*
2622 * We used a tick; charge it to the thread so
2623 * that we can compute our interactivity.
2624 */
2625 td_get_sched(td)->ts_runtime += tickincr * cnt;
2626 sched_interact_update(td);
2627 sched_priority(td);
2628 }
2629
2630 /*
2631 * Force a context switch if the current thread has used up a full
2632 * time slice (default is 100ms).
2633 */
2634 ts->ts_slice += cnt;
2635 if (ts->ts_slice >= td_slice(td, tdq)) {
2636 ts->ts_slice = 0;
2637
2638 /*
2639 * If an ithread uses a full quantum, demote its
2640 * priority and preempt it.
2641 */
2642 if (PRI_BASE(td->td_pri_class) == PRI_ITHD) {
2643 SCHED_STAT_INC(ithread_preemptions);
2644 td->td_owepreempt = 1;
2645 if (td->td_base_pri + RQ_PPQ < PRI_MAX_ITHD) {
2646 SCHED_STAT_INC(ithread_demotions);
2647 sched_prio(td, td->td_base_pri + RQ_PPQ);
2648 }
2649 } else {
2650 ast_sched_locked(td, TDA_SCHED);
2651 td->td_flags |= TDF_SLICEEND;
2652 }
2653 }
2654 }
2655
2656 u_int
2657 sched_estcpu(struct thread *td __unused)
2658 {
2659
2660 return (0);
2661 }
2662
2663 /*
2664 * Return whether the current CPU has runnable tasks. Used for in-kernel
2665 * cooperative idle threads.
2666 */
2667 int
2668 sched_runnable(void)
2669 {
2670 struct tdq *tdq;
2671 int load;
2672
2673 load = 1;
2674
2675 tdq = TDQ_SELF();
2676 if ((curthread->td_flags & TDF_IDLETD) != 0) {
2677 if (TDQ_LOAD(tdq) > 0)
2678 goto out;
2679 } else
2680 if (TDQ_LOAD(tdq) - 1 > 0)
2681 goto out;
2682 load = 0;
2683 out:
2684 return (load);
2685 }
2686
2687 /*
2688 * Choose the highest priority thread to run. The thread is removed from
2689 * the run-queue while running however the load remains.
2690 */
2691 struct thread *
2692 sched_choose(void)
2693 {
2694 struct thread *td;
2695 struct tdq *tdq;
2696
2697 tdq = TDQ_SELF();
2698 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2699 td = tdq_choose(tdq);
2700 if (td != NULL) {
2701 tdq_runq_rem(tdq, td);
2702 tdq->tdq_lowpri = td->td_priority;
2703 } else {
2704 tdq->tdq_lowpri = PRI_MAX_IDLE;
2705 td = PCPU_GET(idlethread);
2706 }
2707 tdq->tdq_curthread = td;
2708 return (td);
2709 }
2710
2711 /*
2712 * Set owepreempt if the currently running thread has lower priority than "pri".
2713 * Preemption never happens directly in ULE, we always request it once we exit a
2714 * critical section.
2715 */
2716 static void
2717 sched_setpreempt(int pri)
2718 {
2719 struct thread *ctd;
2720 int cpri;
2721
2722 ctd = curthread;
2723 THREAD_LOCK_ASSERT(ctd, MA_OWNED);
2724
2725 cpri = ctd->td_priority;
2726 if (pri < cpri)
2727 ast_sched_locked(ctd, TDA_SCHED);
2728 if (KERNEL_PANICKED() || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
2729 return;
2730 if (!sched_shouldpreempt(pri, cpri, 0))
2731 return;
2732 ctd->td_owepreempt = 1;
2733 }
2734
2735 /*
2736 * Add a thread to a thread queue. Select the appropriate runq and add the
2737 * thread to it. This is the internal function called when the tdq is
2738 * predetermined.
2739 */
2740 static int
2741 tdq_add(struct tdq *tdq, struct thread *td, int flags)
2742 {
2743 int lowpri;
2744
2745 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2746 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
2747 KASSERT((td->td_inhibitors == 0),
2748 ("sched_add: trying to run inhibited thread"));
2749 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
2750 ("sched_add: bad thread state"));
2751 KASSERT(td->td_flags & TDF_INMEM,
2752 ("sched_add: thread swapped out"));
2753
2754 lowpri = tdq->tdq_lowpri;
2755 if (td->td_priority < lowpri)
2756 tdq->tdq_lowpri = td->td_priority;
2757 tdq_runq_add(tdq, td, flags);
2758 tdq_load_add(tdq, td);
2759 return (lowpri);
2760 }
2761
2762 /*
2763 * Select the target thread queue and add a thread to it. Request
2764 * preemption or IPI a remote processor if required.
2765 *
2766 * Requires the thread lock on entry, drops on exit.
2767 */
2768 void
2769 sched_add(struct thread *td, int flags)
2770 {
2771 struct tdq *tdq;
2772 #ifdef SMP
2773 int cpu, lowpri;
2774 #endif
2775
2776 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
2777 "prio:%d", td->td_priority, KTR_ATTR_LINKED,
2778 sched_tdname(curthread));
2779 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
2780 KTR_ATTR_LINKED, sched_tdname(td));
2781 SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL,
2782 flags & SRQ_PREEMPTED);
2783 THREAD_LOCK_ASSERT(td, MA_OWNED);
2784 /*
2785 * Recalculate the priority before we select the target cpu or
2786 * run-queue.
2787 */
2788 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
2789 sched_priority(td);
2790 #ifdef SMP
2791 /*
2792 * Pick the destination cpu and if it isn't ours transfer to the
2793 * target cpu.
2794 */
2795 cpu = sched_pickcpu(td, flags);
2796 tdq = sched_setcpu(td, cpu, flags);
2797 lowpri = tdq_add(tdq, td, flags);
2798 if (cpu != PCPU_GET(cpuid))
2799 tdq_notify(tdq, lowpri);
2800 else if (!(flags & SRQ_YIELDING))
2801 sched_setpreempt(td->td_priority);
2802 #else
2803 tdq = TDQ_SELF();
2804 /*
2805 * Now that the thread is moving to the run-queue, set the lock
2806 * to the scheduler's lock.
2807 */
2808 if (td->td_lock != TDQ_LOCKPTR(tdq)) {
2809 TDQ_LOCK(tdq);
2810 if ((flags & SRQ_HOLD) != 0)
2811 td->td_lock = TDQ_LOCKPTR(tdq);
2812 else
2813 thread_lock_set(td, TDQ_LOCKPTR(tdq));
2814 }
2815 (void)tdq_add(tdq, td, flags);
2816 if (!(flags & SRQ_YIELDING))
2817 sched_setpreempt(td->td_priority);
2818 #endif
2819 if (!(flags & SRQ_HOLDTD))
2820 thread_unlock(td);
2821 }
2822
2823 /*
2824 * Remove a thread from a run-queue without running it. This is used
2825 * when we're stealing a thread from a remote queue. Otherwise all threads
2826 * exit by calling sched_exit_thread() and sched_throw() themselves.
2827 */
2828 void
2829 sched_rem(struct thread *td)
2830 {
2831 struct tdq *tdq;
2832
2833 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
2834 "prio:%d", td->td_priority);
2835 SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL);
2836 tdq = TDQ_CPU(td_get_sched(td)->ts_cpu);
2837 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2838 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
2839 KASSERT(TD_ON_RUNQ(td),
2840 ("sched_rem: thread not on run queue"));
2841 tdq_runq_rem(tdq, td);
2842 tdq_load_rem(tdq, td);
2843 TD_SET_CAN_RUN(td);
2844 if (td->td_priority == tdq->tdq_lowpri)
2845 tdq_setlowpri(tdq, NULL);
2846 }
2847
2848 /*
2849 * Fetch cpu utilization information. Updates on demand.
2850 */
2851 fixpt_t
2852 sched_pctcpu(struct thread *td)
2853 {
2854 fixpt_t pctcpu;
2855 struct td_sched *ts;
2856
2857 pctcpu = 0;
2858 ts = td_get_sched(td);
2859
2860 THREAD_LOCK_ASSERT(td, MA_OWNED);
2861 sched_pctcpu_update(ts, TD_IS_RUNNING(td));
2862 if (ts->ts_ticks) {
2863 int rtick;
2864
2865 /* How many rtick per second ? */
2866 rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
2867 pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
2868 }
2869
2870 return (pctcpu);
2871 }
2872
2873 /*
2874 * Enforce affinity settings for a thread. Called after adjustments to
2875 * cpumask.
2876 */
2877 void
2878 sched_affinity(struct thread *td)
2879 {
2880 #ifdef SMP
2881 struct td_sched *ts;
2882
2883 THREAD_LOCK_ASSERT(td, MA_OWNED);
2884 ts = td_get_sched(td);
2885 if (THREAD_CAN_SCHED(td, ts->ts_cpu))
2886 return;
2887 if (TD_ON_RUNQ(td)) {
2888 sched_rem(td);
2889 sched_add(td, SRQ_BORING | SRQ_HOLDTD);
2890 return;
2891 }
2892 if (!TD_IS_RUNNING(td))
2893 return;
2894 /*
2895 * Force a switch before returning to userspace. If the
2896 * target thread is not running locally send an ipi to force
2897 * the issue.
2898 */
2899 ast_sched_locked(td, TDA_SCHED);
2900 if (td != curthread)
2901 ipi_cpu(ts->ts_cpu, IPI_PREEMPT);
2902 #endif
2903 }
2904
2905 /*
2906 * Bind a thread to a target cpu.
2907 */
2908 void
2909 sched_bind(struct thread *td, int cpu)
2910 {
2911 struct td_sched *ts;
2912
2913 THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
2914 KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
2915 ts = td_get_sched(td);
2916 if (ts->ts_flags & TSF_BOUND)
2917 sched_unbind(td);
2918 KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td));
2919 ts->ts_flags |= TSF_BOUND;
2920 sched_pin();
2921 if (PCPU_GET(cpuid) == cpu)
2922 return;
2923 ts->ts_cpu = cpu;
2924 /* When we return from mi_switch we'll be on the correct cpu. */
2925 mi_switch(SW_VOL);
2926 thread_lock(td);
2927 }
2928
2929 /*
2930 * Release a bound thread.
2931 */
2932 void
2933 sched_unbind(struct thread *td)
2934 {
2935 struct td_sched *ts;
2936
2937 THREAD_LOCK_ASSERT(td, MA_OWNED);
2938 KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
2939 ts = td_get_sched(td);
2940 if ((ts->ts_flags & TSF_BOUND) == 0)
2941 return;
2942 ts->ts_flags &= ~TSF_BOUND;
2943 sched_unpin();
2944 }
2945
2946 int
2947 sched_is_bound(struct thread *td)
2948 {
2949 THREAD_LOCK_ASSERT(td, MA_OWNED);
2950 return (td_get_sched(td)->ts_flags & TSF_BOUND);
2951 }
2952
2953 /*
2954 * Basic yield call.
2955 */
2956 void
2957 sched_relinquish(struct thread *td)
2958 {
2959 thread_lock(td);
2960 mi_switch(SW_VOL | SWT_RELINQUISH);
2961 }
2962
2963 /*
2964 * Return the total system load.
2965 */
2966 int
2967 sched_load(void)
2968 {
2969 #ifdef SMP
2970 int total;
2971 int i;
2972
2973 total = 0;
2974 CPU_FOREACH(i)
2975 total += atomic_load_int(&TDQ_CPU(i)->tdq_sysload);
2976 return (total);
2977 #else
2978 return (atomic_load_int(&TDQ_SELF()->tdq_sysload));
2979 #endif
2980 }
2981
2982 int
2983 sched_sizeof_proc(void)
2984 {
2985 return (sizeof(struct proc));
2986 }
2987
2988 int
2989 sched_sizeof_thread(void)
2990 {
2991 return (sizeof(struct thread) + sizeof(struct td_sched));
2992 }
2993
2994 #ifdef SMP
2995 #define TDQ_IDLESPIN(tdq) \
2996 ((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0)
2997 #else
2998 #define TDQ_IDLESPIN(tdq) 1
2999 #endif
3000
3001 /*
3002 * The actual idle process.
3003 */
3004 void
3005 sched_idletd(void *dummy)
3006 {
3007 struct thread *td;
3008 struct tdq *tdq;
3009 int oldswitchcnt, switchcnt;
3010 int i;
3011
3012 mtx_assert(&Giant, MA_NOTOWNED);
3013 td = curthread;
3014 tdq = TDQ_SELF();
3015 THREAD_NO_SLEEPING();
3016 oldswitchcnt = -1;
3017 for (;;) {
3018 if (TDQ_LOAD(tdq)) {
3019 thread_lock(td);
3020 mi_switch(SW_VOL | SWT_IDLE);
3021 }
3022 switchcnt = TDQ_SWITCHCNT(tdq);
3023 #ifdef SMP
3024 if (always_steal || switchcnt != oldswitchcnt) {
3025 oldswitchcnt = switchcnt;
3026 if (tdq_idled(tdq) == 0)
3027 continue;
3028 }
3029 switchcnt = TDQ_SWITCHCNT(tdq);
3030 #else
3031 oldswitchcnt = switchcnt;
3032 #endif
3033 /*
3034 * If we're switching very frequently, spin while checking
3035 * for load rather than entering a low power state that
3036 * may require an IPI. However, don't do any busy
3037 * loops while on SMT machines as this simply steals
3038 * cycles from cores doing useful work.
3039 */
3040 if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) {
3041 for (i = 0; i < sched_idlespins; i++) {
3042 if (TDQ_LOAD(tdq))
3043 break;
3044 cpu_spinwait();
3045 }
3046 }
3047
3048 /* If there was context switch during spin, restart it. */
3049 switchcnt = TDQ_SWITCHCNT(tdq);
3050 if (TDQ_LOAD(tdq) != 0 || switchcnt != oldswitchcnt)
3051 continue;
3052
3053 /* Run main MD idle handler. */
3054 atomic_store_int(&tdq->tdq_cpu_idle, 1);
3055 /*
3056 * Make sure that the tdq_cpu_idle update is globally visible
3057 * before cpu_idle() reads tdq_load. The order is important
3058 * to avoid races with tdq_notify().
3059 */
3060 atomic_thread_fence_seq_cst();
3061 /*
3062 * Checking for again after the fence picks up assigned
3063 * threads often enough to make it worthwhile to do so in
3064 * order to avoid calling cpu_idle().
3065 */
3066 if (TDQ_LOAD(tdq) != 0) {
3067 atomic_store_int(&tdq->tdq_cpu_idle, 0);
3068 continue;
3069 }
3070 cpu_idle(switchcnt * 4 > sched_idlespinthresh);
3071 atomic_store_int(&tdq->tdq_cpu_idle, 0);
3072
3073 /*
3074 * Account thread-less hardware interrupts and
3075 * other wakeup reasons equal to context switches.
3076 */
3077 switchcnt = TDQ_SWITCHCNT(tdq);
3078 if (switchcnt != oldswitchcnt)
3079 continue;
3080 TDQ_SWITCHCNT_INC(tdq);
3081 oldswitchcnt++;
3082 }
3083 }
3084
3085 /*
3086 * sched_throw_grab() chooses a thread from the queue to switch to
3087 * next. It returns with the tdq lock dropped in a spinlock section to
3088 * keep interrupts disabled until the CPU is running in a proper threaded
3089 * context.
3090 */
3091 static struct thread *
3092 sched_throw_grab(struct tdq *tdq)
3093 {
3094 struct thread *newtd;
3095
3096 newtd = choosethread();
3097 spinlock_enter();
3098 TDQ_UNLOCK(tdq);
3099 KASSERT(curthread->td_md.md_spinlock_count == 1,
3100 ("invalid count %d", curthread->td_md.md_spinlock_count));
3101 return (newtd);
3102 }
3103
3104 /*
3105 * A CPU is entering for the first time.
3106 */
3107 void
3108 sched_ap_entry(void)
3109 {
3110 struct thread *newtd;
3111 struct tdq *tdq;
3112
3113 tdq = TDQ_SELF();
3114
3115 /* This should have been setup in schedinit_ap(). */
3116 THREAD_LOCKPTR_ASSERT(curthread, TDQ_LOCKPTR(tdq));
3117
3118 TDQ_LOCK(tdq);
3119 /* Correct spinlock nesting. */
3120 spinlock_exit();
3121 PCPU_SET(switchtime, cpu_ticks());
3122 PCPU_SET(switchticks, ticks);
3123
3124 newtd = sched_throw_grab(tdq);
3125
3126 /* doesn't return */
3127 cpu_throw(NULL, newtd);
3128 }
3129
3130 /*
3131 * A thread is exiting.
3132 */
3133 void
3134 sched_throw(struct thread *td)
3135 {
3136 struct thread *newtd;
3137 struct tdq *tdq;
3138
3139 tdq = TDQ_SELF();
3140
3141 MPASS(td != NULL);
3142 THREAD_LOCK_ASSERT(td, MA_OWNED);
3143 THREAD_LOCKPTR_ASSERT(td, TDQ_LOCKPTR(tdq));
3144
3145 tdq_load_rem(tdq, td);
3146 td->td_lastcpu = td->td_oncpu;
3147 td->td_oncpu = NOCPU;
3148 thread_lock_block(td);
3149
3150 newtd = sched_throw_grab(tdq);
3151
3152 /* doesn't return */
3153 cpu_switch(td, newtd, TDQ_LOCKPTR(tdq));
3154 }
3155
3156 /*
3157 * This is called from fork_exit(). Just acquire the correct locks and
3158 * let fork do the rest of the work.
3159 */
3160 void
3161 sched_fork_exit(struct thread *td)
3162 {
3163 struct tdq *tdq;
3164 int cpuid;
3165
3166 /*
3167 * Finish setting up thread glue so that it begins execution in a
3168 * non-nested critical section with the scheduler lock held.
3169 */
3170 KASSERT(curthread->td_md.md_spinlock_count == 1,
3171 ("invalid count %d", curthread->td_md.md_spinlock_count));
3172 cpuid = PCPU_GET(cpuid);
3173 tdq = TDQ_SELF();
3174 TDQ_LOCK(tdq);
3175 spinlock_exit();
3176 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
3177 td->td_oncpu = cpuid;
3178 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
3179 "prio:%d", td->td_priority);
3180 SDT_PROBE0(sched, , , on__cpu);
3181 }
3182
3183 /*
3184 * Create on first use to catch odd startup conditions.
3185 */
3186 char *
3187 sched_tdname(struct thread *td)
3188 {
3189 #ifdef KTR
3190 struct td_sched *ts;
3191
3192 ts = td_get_sched(td);
3193 if (ts->ts_name[0] == '\0')
3194 snprintf(ts->ts_name, sizeof(ts->ts_name),
3195 "%s tid %d", td->td_name, td->td_tid);
3196 return (ts->ts_name);
3197 #else
3198 return (td->td_name);
3199 #endif
3200 }
3201
3202 #ifdef KTR
3203 void
3204 sched_clear_tdname(struct thread *td)
3205 {
3206 struct td_sched *ts;
3207
3208 ts = td_get_sched(td);
3209 ts->ts_name[0] = '\0';
3210 }
3211 #endif
3212
3213 #ifdef SMP
3214
3215 /*
3216 * Build the CPU topology dump string. Is recursively called to collect
3217 * the topology tree.
3218 */
3219 static int
3220 sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg,
3221 int indent)
3222 {
3223 char cpusetbuf[CPUSETBUFSIZ];
3224 int i, first;
3225
3226 sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent,
3227 "", 1 + indent / 2, cg->cg_level);
3228 sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"%s\">", indent, "",
3229 cg->cg_count, cpusetobj_strprint(cpusetbuf, &cg->cg_mask));
3230 first = TRUE;
3231 for (i = cg->cg_first; i <= cg->cg_last; i++) {
3232 if (CPU_ISSET(i, &cg->cg_mask)) {
3233 if (!first)
3234 sbuf_printf(sb, ", ");
3235 else
3236 first = FALSE;
3237 sbuf_printf(sb, "%d", i);
3238 }
3239 }
3240 sbuf_printf(sb, "</cpu>\n");
3241
3242 if (cg->cg_flags != 0) {
3243 sbuf_printf(sb, "%*s <flags>", indent, "");
3244 if ((cg->cg_flags & CG_FLAG_HTT) != 0)
3245 sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>");
3246 if ((cg->cg_flags & CG_FLAG_THREAD) != 0)
3247 sbuf_printf(sb, "<flag name=\"THREAD\">THREAD group</flag>");
3248 if ((cg->cg_flags & CG_FLAG_SMT) != 0)
3249 sbuf_printf(sb, "<flag name=\"SMT\">SMT group</flag>");
3250 if ((cg->cg_flags & CG_FLAG_NODE) != 0)
3251 sbuf_printf(sb, "<flag name=\"NODE\">NUMA node</flag>");
3252 sbuf_printf(sb, "</flags>\n");
3253 }
3254
3255 if (cg->cg_children > 0) {
3256 sbuf_printf(sb, "%*s <children>\n", indent, "");
3257 for (i = 0; i < cg->cg_children; i++)
3258 sysctl_kern_sched_topology_spec_internal(sb,
3259 &cg->cg_child[i], indent+2);
3260 sbuf_printf(sb, "%*s </children>\n", indent, "");
3261 }
3262 sbuf_printf(sb, "%*s</group>\n", indent, "");
3263 return (0);
3264 }
3265
3266 /*
3267 * Sysctl handler for retrieving topology dump. It's a wrapper for
3268 * the recursive sysctl_kern_smp_topology_spec_internal().
3269 */
3270 static int
3271 sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS)
3272 {
3273 struct sbuf *topo;
3274 int err;
3275
3276 KASSERT(cpu_top != NULL, ("cpu_top isn't initialized"));
3277
3278 topo = sbuf_new_for_sysctl(NULL, NULL, 512, req);
3279 if (topo == NULL)
3280 return (ENOMEM);
3281
3282 sbuf_printf(topo, "<groups>\n");
3283 err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1);
3284 sbuf_printf(topo, "</groups>\n");
3285
3286 if (err == 0) {
3287 err = sbuf_finish(topo);
3288 }
3289 sbuf_delete(topo);
3290 return (err);
3291 }
3292
3293 #endif
3294
3295 static int
3296 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
3297 {
3298 int error, new_val, period;
3299
3300 period = 1000000 / realstathz;
3301 new_val = period * sched_slice;
3302 error = sysctl_handle_int(oidp, &new_val, 0, req);
3303 if (error != 0 || req->newptr == NULL)
3304 return (error);
3305 if (new_val <= 0)
3306 return (EINVAL);
3307 sched_slice = imax(1, (new_val + period / 2) / period);
3308 sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
3309 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
3310 realstathz);
3311 return (0);
3312 }
3313
3314 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
3315 "Scheduler");
3316 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0,
3317 "Scheduler name");
3318 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum,
3319 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
3320 sysctl_kern_quantum, "I",
3321 "Quantum for timeshare threads in microseconds");
3322 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
3323 "Quantum for timeshare threads in stathz ticks");
3324 SYSCTL_UINT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0,
3325 "Interactivity score threshold");
3326 SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW,
3327 &preempt_thresh, 0,
3328 "Maximal (lowest) priority for preemption");
3329 SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost, 0,
3330 "Assign static kernel priorities to sleeping threads");
3331 SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins, 0,
3332 "Number of times idle thread will spin waiting for new work");
3333 SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW,
3334 &sched_idlespinthresh, 0,
3335 "Threshold before we will permit idle thread spinning");
3336 #ifdef SMP
3337 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0,
3338 "Number of hz ticks to keep thread affinity for");
3339 SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0,
3340 "Enables the long-term load balancer");
3341 SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW,
3342 &balance_interval, 0,
3343 "Average period in stathz ticks to run the long-term balancer");
3344 SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0,
3345 "Attempts to steal work from other cores before idling");
3346 SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0,
3347 "Minimum load on remote CPU before we'll steal");
3348 SYSCTL_INT(_kern_sched, OID_AUTO, trysteal_limit, CTLFLAG_RW, &trysteal_limit,
3349 0, "Topological distance limit for stealing threads in sched_switch()");
3350 SYSCTL_INT(_kern_sched, OID_AUTO, always_steal, CTLFLAG_RW, &always_steal, 0,
3351 "Always run the stealer from the idle thread");
3352 SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING |
3353 CTLFLAG_MPSAFE | CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A",
3354 "XML dump of detected CPU topology");
3355 #endif
3356
3357 /* ps compat. All cpu percentages from ULE are weighted. */
3358 static int ccpu = 0;
3359 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0,
3360 "Decay factor used for updating %CPU in 4BSD scheduler");
Cache object: 233dfe1e5ecd2290de58821446d37fff
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