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--- old/usr/src/uts/common/disp/disp.c
+++ new/usr/src/uts/common/disp/disp.c
1 1 /*
2 2 * CDDL HEADER START
3 3 *
4 4 * The contents of this file are subject to the terms of the
5 5 * Common Development and Distribution License (the "License").
6 6 * You may not use this file except in compliance with the License.
7 7 *
8 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 9 * or http://www.opensolaris.org/os/licensing.
10 10 * See the License for the specific language governing permissions
11 11 * and limitations under the License.
12 12 *
13 13 * When distributing Covered Code, include this CDDL HEADER in each
14 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 15 * If applicable, add the following below this CDDL HEADER, with the
16 16 * fields enclosed by brackets "[]" replaced with your own identifying
17 17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 18 *
19 19 * CDDL HEADER END
20 20 */
21 21 /*
22 22 * Copyright 2009 Sun Microsystems, Inc. All rights reserved.
23 23 * Use is subject to license terms.
24 24 */
25 25
26 26 /* Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
27 27 /* All Rights Reserved */
28 28
29 29
30 30 #include <sys/types.h>
31 31 #include <sys/param.h>
32 32 #include <sys/sysmacros.h>
33 33 #include <sys/signal.h>
34 34 #include <sys/user.h>
35 35 #include <sys/systm.h>
36 36 #include <sys/sysinfo.h>
37 37 #include <sys/var.h>
38 38 #include <sys/errno.h>
39 39 #include <sys/cmn_err.h>
40 40 #include <sys/debug.h>
41 41 #include <sys/inline.h>
42 42 #include <sys/disp.h>
43 43 #include <sys/class.h>
44 44 #include <sys/bitmap.h>
45 45 #include <sys/kmem.h>
46 46 #include <sys/cpuvar.h>
47 47 #include <sys/vtrace.h>
48 48 #include <sys/tnf.h>
49 49 #include <sys/cpupart.h>
50 50 #include <sys/lgrp.h>
51 51 #include <sys/pg.h>
52 52 #include <sys/cmt.h>
53 53 #include <sys/bitset.h>
54 54 #include <sys/schedctl.h>
55 55 #include <sys/atomic.h>
56 56 #include <sys/dtrace.h>
57 57 #include <sys/sdt.h>
58 58 #include <sys/archsystm.h>
59 59
60 60 #include <vm/as.h>
61 61
62 62 #define BOUND_CPU 0x1
63 63 #define BOUND_PARTITION 0x2
64 64 #define BOUND_INTR 0x4
65 65
66 66 /* Dispatch queue allocation structure and functions */
67 67 struct disp_queue_info {
68 68 disp_t *dp;
69 69 dispq_t *olddispq;
70 70 dispq_t *newdispq;
71 71 ulong_t *olddqactmap;
72 72 ulong_t *newdqactmap;
73 73 int oldnglobpris;
74 74 };
75 75 static void disp_dq_alloc(struct disp_queue_info *dptr, int numpris,
76 76 disp_t *dp);
77 77 static void disp_dq_assign(struct disp_queue_info *dptr, int numpris);
78 78 static void disp_dq_free(struct disp_queue_info *dptr);
79 79
80 80 /* platform-specific routine to call when processor is idle */
81 81 static void generic_idle_cpu();
82 82 void (*idle_cpu)() = generic_idle_cpu;
83 83
84 84 /* routines invoked when a CPU enters/exits the idle loop */
85 85 static void idle_enter();
86 86 static void idle_exit();
87 87
88 88 /* platform-specific routine to call when thread is enqueued */
89 89 static void generic_enq_thread(cpu_t *, int);
90 90 void (*disp_enq_thread)(cpu_t *, int) = generic_enq_thread;
91 91
92 92 pri_t kpreemptpri; /* priority where kernel preemption applies */
93 93 pri_t upreemptpri = 0; /* priority where normal preemption applies */
94 94 pri_t intr_pri; /* interrupt thread priority base level */
95 95
96 96 #define KPQPRI -1 /* pri where cpu affinity is dropped for kpq */
97 97 pri_t kpqpri = KPQPRI; /* can be set in /etc/system */
98 98 disp_t cpu0_disp; /* boot CPU's dispatch queue */
99 99 disp_lock_t swapped_lock; /* lock swapped threads and swap queue */
100 100 int nswapped; /* total number of swapped threads */
101 101 void disp_swapped_enq(kthread_t *tp);
102 102 static void disp_swapped_setrun(kthread_t *tp);
103 103 static void cpu_resched(cpu_t *cp, pri_t tpri);
104 104
105 105 /*
106 106 * If this is set, only interrupt threads will cause kernel preemptions.
107 107 * This is done by changing the value of kpreemptpri. kpreemptpri
108 108 * will either be the max sysclass pri + 1 or the min interrupt pri.
109 109 */
110 110 int only_intr_kpreempt;
111 111
112 112 extern void set_idle_cpu(int cpun);
113 113 extern void unset_idle_cpu(int cpun);
114 114 static void setkpdq(kthread_t *tp, int borf);
115 115 #define SETKP_BACK 0
116 116 #define SETKP_FRONT 1
117 117 /*
118 118 * Parameter that determines how recently a thread must have run
119 119 * on the CPU to be considered loosely-bound to that CPU to reduce
120 120 * cold cache effects. The interval is in hertz.
121 121 */
122 122 #define RECHOOSE_INTERVAL 3
123 123 int rechoose_interval = RECHOOSE_INTERVAL;
124 124
125 125 /*
126 126 * Parameter that determines how long (in nanoseconds) a thread must
127 127 * be sitting on a run queue before it can be stolen by another CPU
128 128 * to reduce migrations. The interval is in nanoseconds.
129 129 *
130 130 * The nosteal_nsec should be set by platform code cmp_set_nosteal_interval()
131 131 * to an appropriate value. nosteal_nsec is set to NOSTEAL_UNINITIALIZED
132 132 * here indicating it is uninitiallized.
133 133 * Setting nosteal_nsec to 0 effectively disables the nosteal 'protection'.
134 134 *
135 135 */
136 136 #define NOSTEAL_UNINITIALIZED (-1)
137 137 hrtime_t nosteal_nsec = NOSTEAL_UNINITIALIZED;
138 138 extern void cmp_set_nosteal_interval(void);
139 139
140 140 id_t defaultcid; /* system "default" class; see dispadmin(1M) */
141 141
142 142 disp_lock_t transition_lock; /* lock on transitioning threads */
143 143 disp_lock_t stop_lock; /* lock on stopped threads */
144 144
145 145 static void cpu_dispqalloc(int numpris);
146 146
147 147 /*
148 148 * This gets returned by disp_getwork/disp_getbest if we couldn't steal
149 149 * a thread because it was sitting on its run queue for a very short
150 150 * period of time.
151 151 */
152 152 #define T_DONTSTEAL (kthread_t *)(-1) /* returned by disp_getwork/getbest */
153 153
154 154 static kthread_t *disp_getwork(cpu_t *to);
155 155 static kthread_t *disp_getbest(disp_t *from);
156 156 static kthread_t *disp_ratify(kthread_t *tp, disp_t *kpq);
157 157
158 158 void swtch_to(kthread_t *);
159 159
160 160 /*
161 161 * dispatcher and scheduler initialization
162 162 */
163 163
164 164 /*
165 165 * disp_setup - Common code to calculate and allocate dispatcher
166 166 * variables and structures based on the maximum priority.
167 167 */
168 168 static void
169 169 disp_setup(pri_t maxglobpri, pri_t oldnglobpris)
170 170 {
171 171 pri_t newnglobpris;
172 172
173 173 ASSERT(MUTEX_HELD(&cpu_lock));
174 174
175 175 newnglobpris = maxglobpri + 1 + LOCK_LEVEL;
176 176
177 177 if (newnglobpris > oldnglobpris) {
178 178 /*
179 179 * Allocate new kp queues for each CPU partition.
180 180 */
181 181 cpupart_kpqalloc(newnglobpris);
182 182
183 183 /*
184 184 * Allocate new dispatch queues for each CPU.
185 185 */
186 186 cpu_dispqalloc(newnglobpris);
187 187
188 188 /*
189 189 * compute new interrupt thread base priority
190 190 */
191 191 intr_pri = maxglobpri;
192 192 if (only_intr_kpreempt) {
193 193 kpreemptpri = intr_pri + 1;
194 194 if (kpqpri == KPQPRI)
195 195 kpqpri = kpreemptpri;
196 196 }
197 197 v.v_nglobpris = newnglobpris;
198 198 }
199 199 }
200 200
201 201 /*
202 202 * dispinit - Called to initialize all loaded classes and the
203 203 * dispatcher framework.
204 204 */
205 205 void
206 206 dispinit(void)
207 207 {
208 208 id_t cid;
209 209 pri_t maxglobpri;
210 210 pri_t cl_maxglobpri;
211 211
212 212 maxglobpri = -1;
213 213
214 214 /*
215 215 * Initialize transition lock, which will always be set.
216 216 */
217 217 DISP_LOCK_INIT(&transition_lock);
218 218 disp_lock_enter_high(&transition_lock);
219 219 DISP_LOCK_INIT(&stop_lock);
220 220
221 221 mutex_enter(&cpu_lock);
222 222 CPU->cpu_disp->disp_maxrunpri = -1;
223 223 CPU->cpu_disp->disp_max_unbound_pri = -1;
224 224
225 225 /*
226 226 * Initialize the default CPU partition.
227 227 */
228 228 cpupart_initialize_default();
229 229 /*
230 230 * Call the class specific initialization functions for
231 231 * all pre-installed schedulers.
232 232 *
233 233 * We pass the size of a class specific parameter
234 234 * buffer to each of the initialization functions
235 235 * to try to catch problems with backward compatibility
236 236 * of class modules.
237 237 *
238 238 * For example a new class module running on an old system
239 239 * which didn't provide sufficiently large parameter buffers
240 240 * would be bad news. Class initialization modules can check for
241 241 * this and take action if they detect a problem.
242 242 */
243 243
244 244 for (cid = 0; cid < nclass; cid++) {
245 245 sclass_t *sc;
246 246
247 247 sc = &sclass[cid];
248 248 if (SCHED_INSTALLED(sc)) {
249 249 cl_maxglobpri = sc->cl_init(cid, PC_CLPARMSZ,
250 250 &sc->cl_funcs);
251 251 if (cl_maxglobpri > maxglobpri)
252 252 maxglobpri = cl_maxglobpri;
253 253 }
254 254 }
255 255 kpreemptpri = (pri_t)v.v_maxsyspri + 1;
256 256 if (kpqpri == KPQPRI)
257 257 kpqpri = kpreemptpri;
258 258
259 259 ASSERT(maxglobpri >= 0);
260 260 disp_setup(maxglobpri, 0);
261 261
262 262 mutex_exit(&cpu_lock);
263 263
264 264 /*
265 265 * Platform specific sticky scheduler setup.
266 266 */
267 267 if (nosteal_nsec == NOSTEAL_UNINITIALIZED)
268 268 cmp_set_nosteal_interval();
269 269
270 270 /*
271 271 * Get the default class ID; this may be later modified via
272 272 * dispadmin(1M). This will load the class (normally TS) and that will
273 273 * call disp_add(), which is why we had to drop cpu_lock first.
274 274 */
275 275 if (getcid(defaultclass, &defaultcid) != 0) {
276 276 cmn_err(CE_PANIC, "Couldn't load default scheduling class '%s'",
277 277 defaultclass);
278 278 }
279 279 }
280 280
281 281 /*
282 282 * disp_add - Called with class pointer to initialize the dispatcher
283 283 * for a newly loaded class.
284 284 */
285 285 void
286 286 disp_add(sclass_t *clp)
287 287 {
288 288 pri_t maxglobpri;
289 289 pri_t cl_maxglobpri;
290 290
291 291 mutex_enter(&cpu_lock);
292 292 /*
293 293 * Initialize the scheduler class.
294 294 */
295 295 maxglobpri = (pri_t)(v.v_nglobpris - LOCK_LEVEL - 1);
296 296 cl_maxglobpri = clp->cl_init(clp - sclass, PC_CLPARMSZ, &clp->cl_funcs);
297 297 if (cl_maxglobpri > maxglobpri)
298 298 maxglobpri = cl_maxglobpri;
299 299
300 300 /*
301 301 * Save old queue information. Since we're initializing a
302 302 * new scheduling class which has just been loaded, then
303 303 * the size of the dispq may have changed. We need to handle
304 304 * that here.
305 305 */
306 306 disp_setup(maxglobpri, v.v_nglobpris);
307 307
308 308 mutex_exit(&cpu_lock);
309 309 }
310 310
311 311
312 312 /*
313 313 * For each CPU, allocate new dispatch queues
314 314 * with the stated number of priorities.
315 315 */
316 316 static void
317 317 cpu_dispqalloc(int numpris)
318 318 {
319 319 cpu_t *cpup;
320 320 struct disp_queue_info *disp_mem;
321 321 int i, num;
322 322
323 323 ASSERT(MUTEX_HELD(&cpu_lock));
324 324
325 325 disp_mem = kmem_zalloc(NCPU *
326 326 sizeof (struct disp_queue_info), KM_SLEEP);
327 327
328 328 /*
329 329 * This routine must allocate all of the memory before stopping
330 330 * the cpus because it must not sleep in kmem_alloc while the
331 331 * CPUs are stopped. Locks they hold will not be freed until they
332 332 * are restarted.
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333 333 */
334 334 i = 0;
335 335 cpup = cpu_list;
336 336 do {
337 337 disp_dq_alloc(&disp_mem[i], numpris, cpup->cpu_disp);
338 338 i++;
339 339 cpup = cpup->cpu_next;
340 340 } while (cpup != cpu_list);
341 341 num = i;
342 342
343 - pause_cpus(NULL);
343 + pause_cpus(NULL, NULL);
344 344 for (i = 0; i < num; i++)
345 345 disp_dq_assign(&disp_mem[i], numpris);
346 346 start_cpus();
347 347
348 348 /*
349 349 * I must free all of the memory after starting the cpus because
350 350 * I can not risk sleeping in kmem_free while the cpus are stopped.
351 351 */
352 352 for (i = 0; i < num; i++)
353 353 disp_dq_free(&disp_mem[i]);
354 354
355 355 kmem_free(disp_mem, NCPU * sizeof (struct disp_queue_info));
356 356 }
357 357
358 358 static void
359 359 disp_dq_alloc(struct disp_queue_info *dptr, int numpris, disp_t *dp)
360 360 {
361 361 dptr->newdispq = kmem_zalloc(numpris * sizeof (dispq_t), KM_SLEEP);
362 362 dptr->newdqactmap = kmem_zalloc(((numpris / BT_NBIPUL) + 1) *
363 363 sizeof (long), KM_SLEEP);
364 364 dptr->dp = dp;
365 365 }
366 366
367 367 static void
368 368 disp_dq_assign(struct disp_queue_info *dptr, int numpris)
369 369 {
370 370 disp_t *dp;
371 371
372 372 dp = dptr->dp;
373 373 dptr->olddispq = dp->disp_q;
374 374 dptr->olddqactmap = dp->disp_qactmap;
375 375 dptr->oldnglobpris = dp->disp_npri;
376 376
377 377 ASSERT(dptr->oldnglobpris < numpris);
378 378
379 379 if (dptr->olddispq != NULL) {
380 380 /*
381 381 * Use kcopy because bcopy is platform-specific
382 382 * and could block while we might have paused the cpus.
383 383 */
384 384 (void) kcopy(dptr->olddispq, dptr->newdispq,
385 385 dptr->oldnglobpris * sizeof (dispq_t));
386 386 (void) kcopy(dptr->olddqactmap, dptr->newdqactmap,
387 387 ((dptr->oldnglobpris / BT_NBIPUL) + 1) *
388 388 sizeof (long));
389 389 }
390 390 dp->disp_q = dptr->newdispq;
391 391 dp->disp_qactmap = dptr->newdqactmap;
392 392 dp->disp_q_limit = &dptr->newdispq[numpris];
393 393 dp->disp_npri = numpris;
394 394 }
395 395
396 396 static void
397 397 disp_dq_free(struct disp_queue_info *dptr)
398 398 {
399 399 if (dptr->olddispq != NULL)
400 400 kmem_free(dptr->olddispq,
401 401 dptr->oldnglobpris * sizeof (dispq_t));
402 402 if (dptr->olddqactmap != NULL)
403 403 kmem_free(dptr->olddqactmap,
404 404 ((dptr->oldnglobpris / BT_NBIPUL) + 1) * sizeof (long));
405 405 }
406 406
407 407 /*
408 408 * For a newly created CPU, initialize the dispatch queue.
409 409 * This is called before the CPU is known through cpu[] or on any lists.
410 410 */
411 411 void
412 412 disp_cpu_init(cpu_t *cp)
413 413 {
414 414 disp_t *dp;
415 415 dispq_t *newdispq;
416 416 ulong_t *newdqactmap;
417 417
418 418 ASSERT(MUTEX_HELD(&cpu_lock)); /* protect dispatcher queue sizes */
419 419
420 420 if (cp == cpu0_disp.disp_cpu)
421 421 dp = &cpu0_disp;
422 422 else
423 423 dp = kmem_alloc(sizeof (disp_t), KM_SLEEP);
424 424 bzero(dp, sizeof (disp_t));
425 425 cp->cpu_disp = dp;
426 426 dp->disp_cpu = cp;
427 427 dp->disp_maxrunpri = -1;
428 428 dp->disp_max_unbound_pri = -1;
429 429 DISP_LOCK_INIT(&cp->cpu_thread_lock);
430 430 /*
431 431 * Allocate memory for the dispatcher queue headers
432 432 * and the active queue bitmap.
433 433 */
434 434 newdispq = kmem_zalloc(v.v_nglobpris * sizeof (dispq_t), KM_SLEEP);
435 435 newdqactmap = kmem_zalloc(((v.v_nglobpris / BT_NBIPUL) + 1) *
436 436 sizeof (long), KM_SLEEP);
437 437 dp->disp_q = newdispq;
438 438 dp->disp_qactmap = newdqactmap;
439 439 dp->disp_q_limit = &newdispq[v.v_nglobpris];
440 440 dp->disp_npri = v.v_nglobpris;
441 441 }
442 442
443 443 void
444 444 disp_cpu_fini(cpu_t *cp)
445 445 {
446 446 ASSERT(MUTEX_HELD(&cpu_lock));
447 447
448 448 disp_kp_free(cp->cpu_disp);
449 449 if (cp->cpu_disp != &cpu0_disp)
450 450 kmem_free(cp->cpu_disp, sizeof (disp_t));
451 451 }
452 452
453 453 /*
454 454 * Allocate new, larger kpreempt dispatch queue to replace the old one.
455 455 */
456 456 void
457 457 disp_kp_alloc(disp_t *dq, pri_t npri)
458 458 {
459 459 struct disp_queue_info mem_info;
460 460
461 461 if (npri > dq->disp_npri) {
462 462 /*
463 463 * Allocate memory for the new array.
464 464 */
465 465 disp_dq_alloc(&mem_info, npri, dq);
466 466
467 467 /*
468 468 * We need to copy the old structures to the new
469 469 * and free the old.
470 470 */
471 471 disp_dq_assign(&mem_info, npri);
472 472 disp_dq_free(&mem_info);
473 473 }
474 474 }
475 475
476 476 /*
477 477 * Free dispatch queue.
478 478 * Used for the kpreempt queues for a removed CPU partition and
479 479 * for the per-CPU queues of deleted CPUs.
480 480 */
481 481 void
482 482 disp_kp_free(disp_t *dq)
483 483 {
484 484 struct disp_queue_info mem_info;
485 485
486 486 mem_info.olddispq = dq->disp_q;
487 487 mem_info.olddqactmap = dq->disp_qactmap;
488 488 mem_info.oldnglobpris = dq->disp_npri;
489 489 disp_dq_free(&mem_info);
490 490 }
491 491
492 492 /*
493 493 * End dispatcher and scheduler initialization.
494 494 */
495 495
496 496 /*
497 497 * See if there's anything to do other than remain idle.
498 498 * Return non-zero if there is.
499 499 *
500 500 * This function must be called with high spl, or with
501 501 * kernel preemption disabled to prevent the partition's
502 502 * active cpu list from changing while being traversed.
503 503 *
504 504 * This is essentially a simpler version of disp_getwork()
505 505 * to be called by CPUs preparing to "halt".
506 506 */
507 507 int
508 508 disp_anywork(void)
509 509 {
510 510 cpu_t *cp = CPU;
511 511 cpu_t *ocp;
512 512 volatile int *local_nrunnable = &cp->cpu_disp->disp_nrunnable;
513 513
514 514 if (!(cp->cpu_flags & CPU_OFFLINE)) {
515 515 if (CP_MAXRUNPRI(cp->cpu_part) >= 0)
516 516 return (1);
517 517
518 518 for (ocp = cp->cpu_next_part; ocp != cp;
519 519 ocp = ocp->cpu_next_part) {
520 520 ASSERT(CPU_ACTIVE(ocp));
521 521
522 522 /*
523 523 * Something has appeared on the local run queue.
524 524 */
525 525 if (*local_nrunnable > 0)
526 526 return (1);
527 527 /*
528 528 * If we encounter another idle CPU that will
529 529 * soon be trolling around through disp_anywork()
530 530 * terminate our walk here and let this other CPU
531 531 * patrol the next part of the list.
532 532 */
533 533 if (ocp->cpu_dispatch_pri == -1 &&
534 534 (ocp->cpu_disp_flags & CPU_DISP_HALTED) == 0)
535 535 return (0);
536 536 /*
537 537 * Work can be taken from another CPU if:
538 538 * - There is unbound work on the run queue
539 539 * - That work isn't a thread undergoing a
540 540 * - context switch on an otherwise empty queue.
541 541 * - The CPU isn't running the idle loop.
542 542 */
543 543 if (ocp->cpu_disp->disp_max_unbound_pri != -1 &&
544 544 !((ocp->cpu_disp_flags & CPU_DISP_DONTSTEAL) &&
545 545 ocp->cpu_disp->disp_nrunnable == 1) &&
546 546 ocp->cpu_dispatch_pri != -1)
547 547 return (1);
548 548 }
549 549 }
550 550 return (0);
551 551 }
552 552
553 553 /*
554 554 * Called when CPU enters the idle loop
555 555 */
556 556 static void
557 557 idle_enter()
558 558 {
559 559 cpu_t *cp = CPU;
560 560
561 561 new_cpu_mstate(CMS_IDLE, gethrtime_unscaled());
562 562 CPU_STATS_ADDQ(cp, sys, idlethread, 1);
563 563 set_idle_cpu(cp->cpu_id); /* arch-dependent hook */
564 564 }
565 565
566 566 /*
567 567 * Called when CPU exits the idle loop
568 568 */
569 569 static void
570 570 idle_exit()
571 571 {
572 572 cpu_t *cp = CPU;
573 573
574 574 new_cpu_mstate(CMS_SYSTEM, gethrtime_unscaled());
575 575 unset_idle_cpu(cp->cpu_id); /* arch-dependent hook */
576 576 }
577 577
578 578 /*
579 579 * Idle loop.
580 580 */
581 581 void
582 582 idle()
583 583 {
584 584 struct cpu *cp = CPU; /* pointer to this CPU */
585 585 kthread_t *t; /* taken thread */
586 586
587 587 idle_enter();
588 588
589 589 /*
590 590 * Uniprocessor version of idle loop.
591 591 * Do this until notified that we're on an actual multiprocessor.
592 592 */
593 593 while (ncpus == 1) {
594 594 if (cp->cpu_disp->disp_nrunnable == 0) {
595 595 (*idle_cpu)();
596 596 continue;
597 597 }
598 598 idle_exit();
599 599 swtch();
600 600
601 601 idle_enter(); /* returned from swtch */
602 602 }
603 603
604 604 /*
605 605 * Multiprocessor idle loop.
606 606 */
607 607 for (;;) {
608 608 /*
609 609 * If CPU is completely quiesced by p_online(2), just wait
610 610 * here with minimal bus traffic until put online.
611 611 */
612 612 while (cp->cpu_flags & CPU_QUIESCED)
613 613 (*idle_cpu)();
614 614
615 615 if (cp->cpu_disp->disp_nrunnable != 0) {
616 616 idle_exit();
617 617 swtch();
618 618 } else {
619 619 if (cp->cpu_flags & CPU_OFFLINE)
620 620 continue;
621 621 if ((t = disp_getwork(cp)) == NULL) {
622 622 if (cp->cpu_chosen_level != -1) {
623 623 disp_t *dp = cp->cpu_disp;
624 624 disp_t *kpq;
625 625
626 626 disp_lock_enter(&dp->disp_lock);
627 627 /*
628 628 * Set kpq under lock to prevent
629 629 * migration between partitions.
630 630 */
631 631 kpq = &cp->cpu_part->cp_kp_queue;
632 632 if (kpq->disp_maxrunpri == -1)
633 633 cp->cpu_chosen_level = -1;
634 634 disp_lock_exit(&dp->disp_lock);
635 635 }
636 636 (*idle_cpu)();
637 637 continue;
638 638 }
639 639 /*
640 640 * If there was a thread but we couldn't steal
641 641 * it, then keep trying.
642 642 */
643 643 if (t == T_DONTSTEAL)
644 644 continue;
645 645 idle_exit();
646 646 swtch_to(t);
647 647 }
648 648 idle_enter(); /* returned from swtch/swtch_to */
649 649 }
650 650 }
651 651
652 652
653 653 /*
654 654 * Preempt the currently running thread in favor of the highest
655 655 * priority thread. The class of the current thread controls
656 656 * where it goes on the dispatcher queues. If panicking, turn
657 657 * preemption off.
658 658 */
659 659 void
660 660 preempt()
661 661 {
662 662 kthread_t *t = curthread;
663 663 klwp_t *lwp = ttolwp(curthread);
664 664
665 665 if (panicstr)
666 666 return;
667 667
668 668 TRACE_0(TR_FAC_DISP, TR_PREEMPT_START, "preempt_start");
669 669
670 670 thread_lock(t);
671 671
672 672 if (t->t_state != TS_ONPROC || t->t_disp_queue != CPU->cpu_disp) {
673 673 /*
674 674 * this thread has already been chosen to be run on
675 675 * another CPU. Clear kprunrun on this CPU since we're
676 676 * already headed for swtch().
677 677 */
678 678 CPU->cpu_kprunrun = 0;
679 679 thread_unlock_nopreempt(t);
680 680 TRACE_0(TR_FAC_DISP, TR_PREEMPT_END, "preempt_end");
681 681 } else {
682 682 if (lwp != NULL)
683 683 lwp->lwp_ru.nivcsw++;
684 684 CPU_STATS_ADDQ(CPU, sys, inv_swtch, 1);
685 685 THREAD_TRANSITION(t);
686 686 CL_PREEMPT(t);
687 687 DTRACE_SCHED(preempt);
688 688 thread_unlock_nopreempt(t);
689 689
690 690 TRACE_0(TR_FAC_DISP, TR_PREEMPT_END, "preempt_end");
691 691
692 692 swtch(); /* clears CPU->cpu_runrun via disp() */
693 693 }
694 694 }
695 695
696 696 extern kthread_t *thread_unpin();
697 697
698 698 /*
699 699 * disp() - find the highest priority thread for this processor to run, and
700 700 * set it in TS_ONPROC state so that resume() can be called to run it.
701 701 */
702 702 static kthread_t *
703 703 disp()
704 704 {
705 705 cpu_t *cpup;
706 706 disp_t *dp;
707 707 kthread_t *tp;
708 708 dispq_t *dq;
709 709 int maxrunword;
710 710 pri_t pri;
711 711 disp_t *kpq;
712 712
713 713 TRACE_0(TR_FAC_DISP, TR_DISP_START, "disp_start");
714 714
715 715 cpup = CPU;
716 716 /*
717 717 * Find the highest priority loaded, runnable thread.
718 718 */
719 719 dp = cpup->cpu_disp;
720 720
721 721 reschedule:
722 722 /*
723 723 * If there is more important work on the global queue with a better
724 724 * priority than the maximum on this CPU, take it now.
725 725 */
726 726 kpq = &cpup->cpu_part->cp_kp_queue;
727 727 while ((pri = kpq->disp_maxrunpri) >= 0 &&
728 728 pri >= dp->disp_maxrunpri &&
729 729 (cpup->cpu_flags & CPU_OFFLINE) == 0 &&
730 730 (tp = disp_getbest(kpq)) != NULL) {
731 731 if (disp_ratify(tp, kpq) != NULL) {
732 732 TRACE_1(TR_FAC_DISP, TR_DISP_END,
733 733 "disp_end:tid %p", tp);
734 734 return (tp);
735 735 }
736 736 }
737 737
738 738 disp_lock_enter(&dp->disp_lock);
739 739 pri = dp->disp_maxrunpri;
740 740
741 741 /*
742 742 * If there is nothing to run, look at what's runnable on other queues.
743 743 * Choose the idle thread if the CPU is quiesced.
744 744 * Note that CPUs that have the CPU_OFFLINE flag set can still run
745 745 * interrupt threads, which will be the only threads on the CPU's own
746 746 * queue, but cannot run threads from other queues.
747 747 */
748 748 if (pri == -1) {
749 749 if (!(cpup->cpu_flags & CPU_OFFLINE)) {
750 750 disp_lock_exit(&dp->disp_lock);
751 751 if ((tp = disp_getwork(cpup)) == NULL ||
752 752 tp == T_DONTSTEAL) {
753 753 tp = cpup->cpu_idle_thread;
754 754 (void) splhigh();
755 755 THREAD_ONPROC(tp, cpup);
756 756 cpup->cpu_dispthread = tp;
757 757 cpup->cpu_dispatch_pri = -1;
758 758 cpup->cpu_runrun = cpup->cpu_kprunrun = 0;
759 759 cpup->cpu_chosen_level = -1;
760 760 }
761 761 } else {
762 762 disp_lock_exit_high(&dp->disp_lock);
763 763 tp = cpup->cpu_idle_thread;
764 764 THREAD_ONPROC(tp, cpup);
765 765 cpup->cpu_dispthread = tp;
766 766 cpup->cpu_dispatch_pri = -1;
767 767 cpup->cpu_runrun = cpup->cpu_kprunrun = 0;
768 768 cpup->cpu_chosen_level = -1;
769 769 }
770 770 TRACE_1(TR_FAC_DISP, TR_DISP_END,
771 771 "disp_end:tid %p", tp);
772 772 return (tp);
773 773 }
774 774
775 775 dq = &dp->disp_q[pri];
776 776 tp = dq->dq_first;
777 777
778 778 ASSERT(tp != NULL);
779 779 ASSERT(tp->t_schedflag & TS_LOAD); /* thread must be swapped in */
780 780
781 781 DTRACE_SCHED2(dequeue, kthread_t *, tp, disp_t *, dp);
782 782
783 783 /*
784 784 * Found it so remove it from queue.
785 785 */
786 786 dp->disp_nrunnable--;
787 787 dq->dq_sruncnt--;
788 788 if ((dq->dq_first = tp->t_link) == NULL) {
789 789 ulong_t *dqactmap = dp->disp_qactmap;
790 790
791 791 ASSERT(dq->dq_sruncnt == 0);
792 792 dq->dq_last = NULL;
793 793
794 794 /*
795 795 * The queue is empty, so the corresponding bit needs to be
796 796 * turned off in dqactmap. If nrunnable != 0 just took the
797 797 * last runnable thread off the
798 798 * highest queue, so recompute disp_maxrunpri.
799 799 */
800 800 maxrunword = pri >> BT_ULSHIFT;
801 801 dqactmap[maxrunword] &= ~BT_BIW(pri);
802 802
803 803 if (dp->disp_nrunnable == 0) {
804 804 dp->disp_max_unbound_pri = -1;
805 805 dp->disp_maxrunpri = -1;
806 806 } else {
807 807 int ipri;
808 808
809 809 ipri = bt_gethighbit(dqactmap, maxrunword);
810 810 dp->disp_maxrunpri = ipri;
811 811 if (ipri < dp->disp_max_unbound_pri)
812 812 dp->disp_max_unbound_pri = ipri;
813 813 }
814 814 } else {
815 815 tp->t_link = NULL;
816 816 }
817 817
818 818 /*
819 819 * Set TS_DONT_SWAP flag to prevent another processor from swapping
820 820 * out this thread before we have a chance to run it.
821 821 * While running, it is protected against swapping by t_lock.
822 822 */
823 823 tp->t_schedflag |= TS_DONT_SWAP;
824 824 cpup->cpu_dispthread = tp; /* protected by spl only */
825 825 cpup->cpu_dispatch_pri = pri;
826 826 ASSERT(pri == DISP_PRIO(tp));
827 827 thread_onproc(tp, cpup); /* set t_state to TS_ONPROC */
828 828 disp_lock_exit_high(&dp->disp_lock); /* drop run queue lock */
829 829
830 830 ASSERT(tp != NULL);
831 831 TRACE_1(TR_FAC_DISP, TR_DISP_END,
832 832 "disp_end:tid %p", tp);
833 833
834 834 if (disp_ratify(tp, kpq) == NULL)
835 835 goto reschedule;
836 836
837 837 return (tp);
838 838 }
839 839
840 840 /*
841 841 * swtch()
842 842 * Find best runnable thread and run it.
843 843 * Called with the current thread already switched to a new state,
844 844 * on a sleep queue, run queue, stopped, and not zombied.
845 845 * May be called at any spl level less than or equal to LOCK_LEVEL.
846 846 * Always drops spl to the base level (spl0()).
847 847 */
848 848 void
849 849 swtch()
850 850 {
851 851 kthread_t *t = curthread;
852 852 kthread_t *next;
853 853 cpu_t *cp;
854 854
855 855 TRACE_0(TR_FAC_DISP, TR_SWTCH_START, "swtch_start");
856 856
857 857 if (t->t_flag & T_INTR_THREAD)
858 858 cpu_intr_swtch_enter(t);
859 859
860 860 if (t->t_intr != NULL) {
861 861 /*
862 862 * We are an interrupt thread. Setup and return
863 863 * the interrupted thread to be resumed.
864 864 */
865 865 (void) splhigh(); /* block other scheduler action */
866 866 cp = CPU; /* now protected against migration */
867 867 ASSERT(CPU_ON_INTR(cp) == 0); /* not called with PIL > 10 */
868 868 CPU_STATS_ADDQ(cp, sys, pswitch, 1);
869 869 CPU_STATS_ADDQ(cp, sys, intrblk, 1);
870 870 next = thread_unpin();
871 871 TRACE_0(TR_FAC_DISP, TR_RESUME_START, "resume_start");
872 872 resume_from_intr(next);
873 873 } else {
874 874 #ifdef DEBUG
875 875 if (t->t_state == TS_ONPROC &&
876 876 t->t_disp_queue->disp_cpu == CPU &&
877 877 t->t_preempt == 0) {
878 878 thread_lock(t);
879 879 ASSERT(t->t_state != TS_ONPROC ||
880 880 t->t_disp_queue->disp_cpu != CPU ||
881 881 t->t_preempt != 0); /* cannot migrate */
882 882 thread_unlock_nopreempt(t);
883 883 }
884 884 #endif /* DEBUG */
885 885 cp = CPU;
886 886 next = disp(); /* returns with spl high */
887 887 ASSERT(CPU_ON_INTR(cp) == 0); /* not called with PIL > 10 */
888 888
889 889 /* OK to steal anything left on run queue */
890 890 cp->cpu_disp_flags &= ~CPU_DISP_DONTSTEAL;
891 891
892 892 if (next != t) {
893 893 hrtime_t now;
894 894
895 895 now = gethrtime_unscaled();
896 896 pg_ev_thread_swtch(cp, now, t, next);
897 897
898 898 /*
899 899 * If t was previously in the TS_ONPROC state,
900 900 * setfrontdq and setbackdq won't have set its t_waitrq.
901 901 * Since we now finally know that we're switching away
902 902 * from this thread, set its t_waitrq if it is on a run
903 903 * queue.
904 904 */
905 905 if ((t->t_state == TS_RUN) && (t->t_waitrq == 0)) {
906 906 t->t_waitrq = now;
907 907 }
908 908
909 909 /*
910 910 * restore mstate of thread that we are switching to
911 911 */
912 912 restore_mstate(next);
913 913
914 914 CPU_STATS_ADDQ(cp, sys, pswitch, 1);
915 915 cp->cpu_last_swtch = t->t_disp_time = ddi_get_lbolt();
916 916 TRACE_0(TR_FAC_DISP, TR_RESUME_START, "resume_start");
917 917
918 918 if (dtrace_vtime_active)
919 919 dtrace_vtime_switch(next);
920 920
921 921 resume(next);
922 922 /*
923 923 * The TR_RESUME_END and TR_SWTCH_END trace points
924 924 * appear at the end of resume(), because we may not
925 925 * return here
926 926 */
927 927 } else {
928 928 if (t->t_flag & T_INTR_THREAD)
929 929 cpu_intr_swtch_exit(t);
930 930 /*
931 931 * Threads that enqueue themselves on a run queue defer
932 932 * setting t_waitrq. It is then either set in swtch()
933 933 * when the CPU is actually yielded, or not at all if it
934 934 * is remaining on the CPU.
935 935 * There is however a window between where the thread
936 936 * placed itself on a run queue, and where it selects
937 937 * itself in disp(), where a third party (eg. clock()
938 938 * doing tick processing) may have re-enqueued this
939 939 * thread, setting t_waitrq in the process. We detect
940 940 * this race by noticing that despite switching to
941 941 * ourself, our t_waitrq has been set, and should be
942 942 * cleared.
943 943 */
944 944 if (t->t_waitrq != 0)
945 945 t->t_waitrq = 0;
946 946
947 947 pg_ev_thread_remain(cp, t);
948 948
949 949 DTRACE_SCHED(remain__cpu);
950 950 TRACE_0(TR_FAC_DISP, TR_SWTCH_END, "swtch_end");
951 951 (void) spl0();
952 952 }
953 953 }
954 954 }
955 955
956 956 /*
957 957 * swtch_from_zombie()
958 958 * Special case of swtch(), which allows checks for TS_ZOMB to be
959 959 * eliminated from normal resume.
960 960 * Find best runnable thread and run it.
961 961 * Called with the current thread zombied.
962 962 * Zombies cannot migrate, so CPU references are safe.
963 963 */
964 964 void
965 965 swtch_from_zombie()
966 966 {
967 967 kthread_t *next;
968 968 cpu_t *cpu = CPU;
969 969
970 970 TRACE_0(TR_FAC_DISP, TR_SWTCH_START, "swtch_start");
971 971
972 972 ASSERT(curthread->t_state == TS_ZOMB);
973 973
974 974 next = disp(); /* returns with spl high */
975 975 ASSERT(CPU_ON_INTR(CPU) == 0); /* not called with PIL > 10 */
976 976 CPU_STATS_ADDQ(CPU, sys, pswitch, 1);
977 977 ASSERT(next != curthread);
978 978 TRACE_0(TR_FAC_DISP, TR_RESUME_START, "resume_start");
979 979
980 980 pg_ev_thread_swtch(cpu, gethrtime_unscaled(), curthread, next);
981 981
982 982 restore_mstate(next);
983 983
984 984 if (dtrace_vtime_active)
985 985 dtrace_vtime_switch(next);
986 986
987 987 resume_from_zombie(next);
988 988 /*
989 989 * The TR_RESUME_END and TR_SWTCH_END trace points
990 990 * appear at the end of resume(), because we certainly will not
991 991 * return here
992 992 */
993 993 }
994 994
995 995 #if defined(DEBUG) && (defined(DISP_DEBUG) || defined(lint))
996 996
997 997 /*
998 998 * search_disp_queues()
999 999 * Search the given dispatch queues for thread tp.
1000 1000 * Return 1 if tp is found, otherwise return 0.
1001 1001 */
1002 1002 static int
1003 1003 search_disp_queues(disp_t *dp, kthread_t *tp)
1004 1004 {
1005 1005 dispq_t *dq;
1006 1006 dispq_t *eq;
1007 1007
1008 1008 disp_lock_enter_high(&dp->disp_lock);
1009 1009
1010 1010 for (dq = dp->disp_q, eq = dp->disp_q_limit; dq < eq; ++dq) {
1011 1011 kthread_t *rp;
1012 1012
1013 1013 ASSERT(dq->dq_last == NULL || dq->dq_last->t_link == NULL);
1014 1014
1015 1015 for (rp = dq->dq_first; rp; rp = rp->t_link)
1016 1016 if (tp == rp) {
1017 1017 disp_lock_exit_high(&dp->disp_lock);
1018 1018 return (1);
1019 1019 }
1020 1020 }
1021 1021 disp_lock_exit_high(&dp->disp_lock);
1022 1022
1023 1023 return (0);
1024 1024 }
1025 1025
1026 1026 /*
1027 1027 * thread_on_queue()
1028 1028 * Search all per-CPU dispatch queues and all partition-wide kpreempt
1029 1029 * queues for thread tp. Return 1 if tp is found, otherwise return 0.
1030 1030 */
1031 1031 static int
1032 1032 thread_on_queue(kthread_t *tp)
1033 1033 {
1034 1034 cpu_t *cp;
1035 1035 struct cpupart *part;
1036 1036
1037 1037 ASSERT(getpil() >= DISP_LEVEL);
1038 1038
1039 1039 /*
1040 1040 * Search the per-CPU dispatch queues for tp.
1041 1041 */
1042 1042 cp = CPU;
1043 1043 do {
1044 1044 if (search_disp_queues(cp->cpu_disp, tp))
1045 1045 return (1);
1046 1046 } while ((cp = cp->cpu_next_onln) != CPU);
1047 1047
1048 1048 /*
1049 1049 * Search the partition-wide kpreempt queues for tp.
1050 1050 */
1051 1051 part = CPU->cpu_part;
1052 1052 do {
1053 1053 if (search_disp_queues(&part->cp_kp_queue, tp))
1054 1054 return (1);
1055 1055 } while ((part = part->cp_next) != CPU->cpu_part);
1056 1056
1057 1057 return (0);
1058 1058 }
1059 1059
1060 1060 #else
1061 1061
1062 1062 #define thread_on_queue(tp) 0 /* ASSERT must be !thread_on_queue */
1063 1063
1064 1064 #endif /* DEBUG */
1065 1065
1066 1066 /*
1067 1067 * like swtch(), but switch to a specified thread taken from another CPU.
1068 1068 * called with spl high..
1069 1069 */
1070 1070 void
1071 1071 swtch_to(kthread_t *next)
1072 1072 {
1073 1073 cpu_t *cp = CPU;
1074 1074 hrtime_t now;
1075 1075
1076 1076 TRACE_0(TR_FAC_DISP, TR_SWTCH_START, "swtch_start");
1077 1077
1078 1078 /*
1079 1079 * Update context switch statistics.
1080 1080 */
1081 1081 CPU_STATS_ADDQ(cp, sys, pswitch, 1);
1082 1082
1083 1083 TRACE_0(TR_FAC_DISP, TR_RESUME_START, "resume_start");
1084 1084
1085 1085 now = gethrtime_unscaled();
1086 1086 pg_ev_thread_swtch(cp, now, curthread, next);
1087 1087
1088 1088 /* OK to steal anything left on run queue */
1089 1089 cp->cpu_disp_flags &= ~CPU_DISP_DONTSTEAL;
1090 1090
1091 1091 /* record last execution time */
1092 1092 cp->cpu_last_swtch = curthread->t_disp_time = ddi_get_lbolt();
1093 1093
1094 1094 /*
1095 1095 * If t was previously in the TS_ONPROC state, setfrontdq and setbackdq
1096 1096 * won't have set its t_waitrq. Since we now finally know that we're
1097 1097 * switching away from this thread, set its t_waitrq if it is on a run
1098 1098 * queue.
1099 1099 */
1100 1100 if ((curthread->t_state == TS_RUN) && (curthread->t_waitrq == 0)) {
1101 1101 curthread->t_waitrq = now;
1102 1102 }
1103 1103
1104 1104 /* restore next thread to previously running microstate */
1105 1105 restore_mstate(next);
1106 1106
1107 1107 if (dtrace_vtime_active)
1108 1108 dtrace_vtime_switch(next);
1109 1109
1110 1110 resume(next);
1111 1111 /*
1112 1112 * The TR_RESUME_END and TR_SWTCH_END trace points
1113 1113 * appear at the end of resume(), because we may not
1114 1114 * return here
1115 1115 */
1116 1116 }
1117 1117
1118 1118 #define CPU_IDLING(pri) ((pri) == -1)
1119 1119
1120 1120 static void
1121 1121 cpu_resched(cpu_t *cp, pri_t tpri)
1122 1122 {
1123 1123 int call_poke_cpu = 0;
1124 1124 pri_t cpupri = cp->cpu_dispatch_pri;
1125 1125
1126 1126 if (!CPU_IDLING(cpupri) && (cpupri < tpri)) {
1127 1127 TRACE_2(TR_FAC_DISP, TR_CPU_RESCHED,
1128 1128 "CPU_RESCHED:Tpri %d Cpupri %d", tpri, cpupri);
1129 1129 if (tpri >= upreemptpri && cp->cpu_runrun == 0) {
1130 1130 cp->cpu_runrun = 1;
1131 1131 aston(cp->cpu_dispthread);
1132 1132 if (tpri < kpreemptpri && cp != CPU)
1133 1133 call_poke_cpu = 1;
1134 1134 }
1135 1135 if (tpri >= kpreemptpri && cp->cpu_kprunrun == 0) {
1136 1136 cp->cpu_kprunrun = 1;
1137 1137 if (cp != CPU)
1138 1138 call_poke_cpu = 1;
1139 1139 }
1140 1140 }
1141 1141
1142 1142 /*
1143 1143 * Propagate cpu_runrun, and cpu_kprunrun to global visibility.
1144 1144 */
1145 1145 membar_enter();
1146 1146
1147 1147 if (call_poke_cpu)
1148 1148 poke_cpu(cp->cpu_id);
1149 1149 }
1150 1150
1151 1151 /*
1152 1152 * setbackdq() keeps runqs balanced such that the difference in length
1153 1153 * between the chosen runq and the next one is no more than RUNQ_MAX_DIFF.
1154 1154 * For threads with priorities below RUNQ_MATCH_PRI levels, the runq's lengths
1155 1155 * must match. When per-thread TS_RUNQMATCH flag is set, setbackdq() will
1156 1156 * try to keep runqs perfectly balanced regardless of the thread priority.
1157 1157 */
1158 1158 #define RUNQ_MATCH_PRI 16 /* pri below which queue lengths must match */
1159 1159 #define RUNQ_MAX_DIFF 2 /* maximum runq length difference */
1160 1160 #define RUNQ_LEN(cp, pri) ((cp)->cpu_disp->disp_q[pri].dq_sruncnt)
1161 1161
1162 1162 /*
1163 1163 * Macro that evaluates to true if it is likely that the thread has cache
1164 1164 * warmth. This is based on the amount of time that has elapsed since the
1165 1165 * thread last ran. If that amount of time is less than "rechoose_interval"
1166 1166 * ticks, then we decide that the thread has enough cache warmth to warrant
1167 1167 * some affinity for t->t_cpu.
1168 1168 */
1169 1169 #define THREAD_HAS_CACHE_WARMTH(thread) \
1170 1170 ((thread == curthread) || \
1171 1171 ((ddi_get_lbolt() - thread->t_disp_time) <= rechoose_interval))
1172 1172 /*
1173 1173 * Put the specified thread on the back of the dispatcher
1174 1174 * queue corresponding to its current priority.
1175 1175 *
1176 1176 * Called with the thread in transition, onproc or stopped state
1177 1177 * and locked (transition implies locked) and at high spl.
1178 1178 * Returns with the thread in TS_RUN state and still locked.
1179 1179 */
1180 1180 void
1181 1181 setbackdq(kthread_t *tp)
1182 1182 {
1183 1183 dispq_t *dq;
1184 1184 disp_t *dp;
1185 1185 cpu_t *cp;
1186 1186 pri_t tpri;
1187 1187 int bound;
1188 1188 boolean_t self;
1189 1189
1190 1190 ASSERT(THREAD_LOCK_HELD(tp));
1191 1191 ASSERT((tp->t_schedflag & TS_ALLSTART) == 0);
1192 1192 ASSERT(!thread_on_queue(tp)); /* make sure tp isn't on a runq */
1193 1193
1194 1194 /*
1195 1195 * If thread is "swapped" or on the swap queue don't
1196 1196 * queue it, but wake sched.
1197 1197 */
1198 1198 if ((tp->t_schedflag & (TS_LOAD | TS_ON_SWAPQ)) != TS_LOAD) {
1199 1199 disp_swapped_setrun(tp);
1200 1200 return;
1201 1201 }
1202 1202
1203 1203 self = (tp == curthread);
1204 1204
1205 1205 if (tp->t_bound_cpu || tp->t_weakbound_cpu)
1206 1206 bound = 1;
1207 1207 else
1208 1208 bound = 0;
1209 1209
1210 1210 tpri = DISP_PRIO(tp);
1211 1211 if (ncpus == 1)
1212 1212 cp = tp->t_cpu;
1213 1213 else if (!bound) {
1214 1214 if (tpri >= kpqpri) {
1215 1215 setkpdq(tp, SETKP_BACK);
1216 1216 return;
1217 1217 }
1218 1218
1219 1219 /*
1220 1220 * We'll generally let this thread continue to run where
1221 1221 * it last ran...but will consider migration if:
1222 1222 * - We thread probably doesn't have much cache warmth.
1223 1223 * - The CPU where it last ran is the target of an offline
1224 1224 * request.
1225 1225 * - The thread last ran outside it's home lgroup.
1226 1226 */
1227 1227 if ((!THREAD_HAS_CACHE_WARMTH(tp)) ||
1228 1228 (tp->t_cpu == cpu_inmotion)) {
1229 1229 cp = disp_lowpri_cpu(tp->t_cpu, tp->t_lpl, tpri, NULL);
1230 1230 } else if (!LGRP_CONTAINS_CPU(tp->t_lpl->lpl_lgrp, tp->t_cpu)) {
1231 1231 cp = disp_lowpri_cpu(tp->t_cpu, tp->t_lpl, tpri,
1232 1232 self ? tp->t_cpu : NULL);
1233 1233 } else {
1234 1234 cp = tp->t_cpu;
1235 1235 }
1236 1236
1237 1237 if (tp->t_cpupart == cp->cpu_part) {
1238 1238 int qlen;
1239 1239
1240 1240 /*
1241 1241 * Perform any CMT load balancing
1242 1242 */
1243 1243 cp = cmt_balance(tp, cp);
1244 1244
1245 1245 /*
1246 1246 * Balance across the run queues
1247 1247 */
1248 1248 qlen = RUNQ_LEN(cp, tpri);
1249 1249 if (tpri >= RUNQ_MATCH_PRI &&
1250 1250 !(tp->t_schedflag & TS_RUNQMATCH))
1251 1251 qlen -= RUNQ_MAX_DIFF;
1252 1252 if (qlen > 0) {
1253 1253 cpu_t *newcp;
1254 1254
1255 1255 if (tp->t_lpl->lpl_lgrpid == LGRP_ROOTID) {
1256 1256 newcp = cp->cpu_next_part;
1257 1257 } else if ((newcp = cp->cpu_next_lpl) == cp) {
1258 1258 newcp = cp->cpu_next_part;
1259 1259 }
1260 1260
1261 1261 if (RUNQ_LEN(newcp, tpri) < qlen) {
1262 1262 DTRACE_PROBE3(runq__balance,
1263 1263 kthread_t *, tp,
1264 1264 cpu_t *, cp, cpu_t *, newcp);
1265 1265 cp = newcp;
1266 1266 }
1267 1267 }
1268 1268 } else {
1269 1269 /*
1270 1270 * Migrate to a cpu in the new partition.
1271 1271 */
1272 1272 cp = disp_lowpri_cpu(tp->t_cpupart->cp_cpulist,
1273 1273 tp->t_lpl, tp->t_pri, NULL);
1274 1274 }
1275 1275 ASSERT((cp->cpu_flags & CPU_QUIESCED) == 0);
1276 1276 } else {
1277 1277 /*
1278 1278 * It is possible that t_weakbound_cpu != t_bound_cpu (for
1279 1279 * a short time until weak binding that existed when the
1280 1280 * strong binding was established has dropped) so we must
1281 1281 * favour weak binding over strong.
1282 1282 */
1283 1283 cp = tp->t_weakbound_cpu ?
1284 1284 tp->t_weakbound_cpu : tp->t_bound_cpu;
1285 1285 }
1286 1286 /*
1287 1287 * A thread that is ONPROC may be temporarily placed on the run queue
1288 1288 * but then chosen to run again by disp. If the thread we're placing on
1289 1289 * the queue is in TS_ONPROC state, don't set its t_waitrq until a
1290 1290 * replacement process is actually scheduled in swtch(). In this
1291 1291 * situation, curthread is the only thread that could be in the ONPROC
1292 1292 * state.
1293 1293 */
1294 1294 if ((!self) && (tp->t_waitrq == 0)) {
1295 1295 hrtime_t curtime;
1296 1296
1297 1297 curtime = gethrtime_unscaled();
1298 1298 (void) cpu_update_pct(tp, curtime);
1299 1299 tp->t_waitrq = curtime;
1300 1300 } else {
1301 1301 (void) cpu_update_pct(tp, gethrtime_unscaled());
1302 1302 }
1303 1303
1304 1304 dp = cp->cpu_disp;
1305 1305 disp_lock_enter_high(&dp->disp_lock);
1306 1306
1307 1307 DTRACE_SCHED3(enqueue, kthread_t *, tp, disp_t *, dp, int, 0);
1308 1308 TRACE_3(TR_FAC_DISP, TR_BACKQ, "setbackdq:pri %d cpu %p tid %p",
1309 1309 tpri, cp, tp);
1310 1310
1311 1311 #ifndef NPROBE
1312 1312 /* Kernel probe */
1313 1313 if (tnf_tracing_active)
1314 1314 tnf_thread_queue(tp, cp, tpri);
1315 1315 #endif /* NPROBE */
1316 1316
1317 1317 ASSERT(tpri >= 0 && tpri < dp->disp_npri);
1318 1318
1319 1319 THREAD_RUN(tp, &dp->disp_lock); /* set t_state to TS_RUN */
1320 1320 tp->t_disp_queue = dp;
1321 1321 tp->t_link = NULL;
1322 1322
1323 1323 dq = &dp->disp_q[tpri];
1324 1324 dp->disp_nrunnable++;
1325 1325 if (!bound)
1326 1326 dp->disp_steal = 0;
1327 1327 membar_enter();
1328 1328
1329 1329 if (dq->dq_sruncnt++ != 0) {
1330 1330 ASSERT(dq->dq_first != NULL);
1331 1331 dq->dq_last->t_link = tp;
1332 1332 dq->dq_last = tp;
1333 1333 } else {
1334 1334 ASSERT(dq->dq_first == NULL);
1335 1335 ASSERT(dq->dq_last == NULL);
1336 1336 dq->dq_first = dq->dq_last = tp;
1337 1337 BT_SET(dp->disp_qactmap, tpri);
1338 1338 if (tpri > dp->disp_maxrunpri) {
1339 1339 dp->disp_maxrunpri = tpri;
1340 1340 membar_enter();
1341 1341 cpu_resched(cp, tpri);
1342 1342 }
1343 1343 }
1344 1344
1345 1345 if (!bound && tpri > dp->disp_max_unbound_pri) {
1346 1346 if (self && dp->disp_max_unbound_pri == -1 && cp == CPU) {
1347 1347 /*
1348 1348 * If there are no other unbound threads on the
1349 1349 * run queue, don't allow other CPUs to steal
1350 1350 * this thread while we are in the middle of a
1351 1351 * context switch. We may just switch to it
1352 1352 * again right away. CPU_DISP_DONTSTEAL is cleared
1353 1353 * in swtch and swtch_to.
1354 1354 */
1355 1355 cp->cpu_disp_flags |= CPU_DISP_DONTSTEAL;
1356 1356 }
1357 1357 dp->disp_max_unbound_pri = tpri;
1358 1358 }
1359 1359 (*disp_enq_thread)(cp, bound);
1360 1360 }
1361 1361
1362 1362 /*
1363 1363 * Put the specified thread on the front of the dispatcher
1364 1364 * queue corresponding to its current priority.
1365 1365 *
1366 1366 * Called with the thread in transition, onproc or stopped state
1367 1367 * and locked (transition implies locked) and at high spl.
1368 1368 * Returns with the thread in TS_RUN state and still locked.
1369 1369 */
1370 1370 void
1371 1371 setfrontdq(kthread_t *tp)
1372 1372 {
1373 1373 disp_t *dp;
1374 1374 dispq_t *dq;
1375 1375 cpu_t *cp;
1376 1376 pri_t tpri;
1377 1377 int bound;
1378 1378
1379 1379 ASSERT(THREAD_LOCK_HELD(tp));
1380 1380 ASSERT((tp->t_schedflag & TS_ALLSTART) == 0);
1381 1381 ASSERT(!thread_on_queue(tp)); /* make sure tp isn't on a runq */
1382 1382
1383 1383 /*
1384 1384 * If thread is "swapped" or on the swap queue don't
1385 1385 * queue it, but wake sched.
1386 1386 */
1387 1387 if ((tp->t_schedflag & (TS_LOAD | TS_ON_SWAPQ)) != TS_LOAD) {
1388 1388 disp_swapped_setrun(tp);
1389 1389 return;
1390 1390 }
1391 1391
1392 1392 if (tp->t_bound_cpu || tp->t_weakbound_cpu)
1393 1393 bound = 1;
1394 1394 else
1395 1395 bound = 0;
1396 1396
1397 1397 tpri = DISP_PRIO(tp);
1398 1398 if (ncpus == 1)
1399 1399 cp = tp->t_cpu;
1400 1400 else if (!bound) {
1401 1401 if (tpri >= kpqpri) {
1402 1402 setkpdq(tp, SETKP_FRONT);
1403 1403 return;
1404 1404 }
1405 1405 cp = tp->t_cpu;
1406 1406 if (tp->t_cpupart == cp->cpu_part) {
1407 1407 /*
1408 1408 * We'll generally let this thread continue to run
1409 1409 * where it last ran, but will consider migration if:
1410 1410 * - The thread last ran outside it's home lgroup.
1411 1411 * - The CPU where it last ran is the target of an
1412 1412 * offline request (a thread_nomigrate() on the in
1413 1413 * motion CPU relies on this when forcing a preempt).
1414 1414 * - The thread isn't the highest priority thread where
1415 1415 * it last ran, and it is considered not likely to
1416 1416 * have significant cache warmth.
1417 1417 */
1418 1418 if ((!LGRP_CONTAINS_CPU(tp->t_lpl->lpl_lgrp, cp)) ||
1419 1419 (cp == cpu_inmotion)) {
1420 1420 cp = disp_lowpri_cpu(tp->t_cpu, tp->t_lpl, tpri,
1421 1421 (tp == curthread) ? cp : NULL);
1422 1422 } else if ((tpri < cp->cpu_disp->disp_maxrunpri) &&
1423 1423 (!THREAD_HAS_CACHE_WARMTH(tp))) {
1424 1424 cp = disp_lowpri_cpu(tp->t_cpu, tp->t_lpl, tpri,
1425 1425 NULL);
1426 1426 }
1427 1427 } else {
1428 1428 /*
1429 1429 * Migrate to a cpu in the new partition.
1430 1430 */
1431 1431 cp = disp_lowpri_cpu(tp->t_cpupart->cp_cpulist,
1432 1432 tp->t_lpl, tp->t_pri, NULL);
1433 1433 }
1434 1434 ASSERT((cp->cpu_flags & CPU_QUIESCED) == 0);
1435 1435 } else {
1436 1436 /*
1437 1437 * It is possible that t_weakbound_cpu != t_bound_cpu (for
1438 1438 * a short time until weak binding that existed when the
1439 1439 * strong binding was established has dropped) so we must
1440 1440 * favour weak binding over strong.
1441 1441 */
1442 1442 cp = tp->t_weakbound_cpu ?
1443 1443 tp->t_weakbound_cpu : tp->t_bound_cpu;
1444 1444 }
1445 1445
1446 1446 /*
1447 1447 * A thread that is ONPROC may be temporarily placed on the run queue
1448 1448 * but then chosen to run again by disp. If the thread we're placing on
1449 1449 * the queue is in TS_ONPROC state, don't set its t_waitrq until a
1450 1450 * replacement process is actually scheduled in swtch(). In this
1451 1451 * situation, curthread is the only thread that could be in the ONPROC
1452 1452 * state.
1453 1453 */
1454 1454 if ((tp != curthread) && (tp->t_waitrq == 0)) {
1455 1455 hrtime_t curtime;
1456 1456
1457 1457 curtime = gethrtime_unscaled();
1458 1458 (void) cpu_update_pct(tp, curtime);
1459 1459 tp->t_waitrq = curtime;
1460 1460 } else {
1461 1461 (void) cpu_update_pct(tp, gethrtime_unscaled());
1462 1462 }
1463 1463
1464 1464 dp = cp->cpu_disp;
1465 1465 disp_lock_enter_high(&dp->disp_lock);
1466 1466
1467 1467 TRACE_2(TR_FAC_DISP, TR_FRONTQ, "frontq:pri %d tid %p", tpri, tp);
1468 1468 DTRACE_SCHED3(enqueue, kthread_t *, tp, disp_t *, dp, int, 1);
1469 1469
1470 1470 #ifndef NPROBE
1471 1471 /* Kernel probe */
1472 1472 if (tnf_tracing_active)
1473 1473 tnf_thread_queue(tp, cp, tpri);
1474 1474 #endif /* NPROBE */
1475 1475
1476 1476 ASSERT(tpri >= 0 && tpri < dp->disp_npri);
1477 1477
1478 1478 THREAD_RUN(tp, &dp->disp_lock); /* set TS_RUN state and lock */
1479 1479 tp->t_disp_queue = dp;
1480 1480
1481 1481 dq = &dp->disp_q[tpri];
1482 1482 dp->disp_nrunnable++;
1483 1483 if (!bound)
1484 1484 dp->disp_steal = 0;
1485 1485 membar_enter();
1486 1486
1487 1487 if (dq->dq_sruncnt++ != 0) {
1488 1488 ASSERT(dq->dq_last != NULL);
1489 1489 tp->t_link = dq->dq_first;
1490 1490 dq->dq_first = tp;
1491 1491 } else {
1492 1492 ASSERT(dq->dq_last == NULL);
1493 1493 ASSERT(dq->dq_first == NULL);
1494 1494 tp->t_link = NULL;
1495 1495 dq->dq_first = dq->dq_last = tp;
1496 1496 BT_SET(dp->disp_qactmap, tpri);
1497 1497 if (tpri > dp->disp_maxrunpri) {
1498 1498 dp->disp_maxrunpri = tpri;
1499 1499 membar_enter();
1500 1500 cpu_resched(cp, tpri);
1501 1501 }
1502 1502 }
1503 1503
1504 1504 if (!bound && tpri > dp->disp_max_unbound_pri) {
1505 1505 if (tp == curthread && dp->disp_max_unbound_pri == -1 &&
1506 1506 cp == CPU) {
1507 1507 /*
1508 1508 * If there are no other unbound threads on the
1509 1509 * run queue, don't allow other CPUs to steal
1510 1510 * this thread while we are in the middle of a
1511 1511 * context switch. We may just switch to it
1512 1512 * again right away. CPU_DISP_DONTSTEAL is cleared
1513 1513 * in swtch and swtch_to.
1514 1514 */
1515 1515 cp->cpu_disp_flags |= CPU_DISP_DONTSTEAL;
1516 1516 }
1517 1517 dp->disp_max_unbound_pri = tpri;
1518 1518 }
1519 1519 (*disp_enq_thread)(cp, bound);
1520 1520 }
1521 1521
1522 1522 /*
1523 1523 * Put a high-priority unbound thread on the kp queue
1524 1524 */
1525 1525 static void
1526 1526 setkpdq(kthread_t *tp, int borf)
1527 1527 {
1528 1528 dispq_t *dq;
1529 1529 disp_t *dp;
1530 1530 cpu_t *cp;
1531 1531 pri_t tpri;
1532 1532
1533 1533 tpri = DISP_PRIO(tp);
1534 1534
1535 1535 dp = &tp->t_cpupart->cp_kp_queue;
1536 1536 disp_lock_enter_high(&dp->disp_lock);
1537 1537
1538 1538 TRACE_2(TR_FAC_DISP, TR_FRONTQ, "frontq:pri %d tid %p", tpri, tp);
1539 1539
1540 1540 ASSERT(tpri >= 0 && tpri < dp->disp_npri);
1541 1541 DTRACE_SCHED3(enqueue, kthread_t *, tp, disp_t *, dp, int, borf);
1542 1542 THREAD_RUN(tp, &dp->disp_lock); /* set t_state to TS_RUN */
1543 1543 tp->t_disp_queue = dp;
1544 1544 dp->disp_nrunnable++;
1545 1545 dq = &dp->disp_q[tpri];
1546 1546
1547 1547 if (dq->dq_sruncnt++ != 0) {
1548 1548 if (borf == SETKP_BACK) {
1549 1549 ASSERT(dq->dq_first != NULL);
1550 1550 tp->t_link = NULL;
1551 1551 dq->dq_last->t_link = tp;
1552 1552 dq->dq_last = tp;
1553 1553 } else {
1554 1554 ASSERT(dq->dq_last != NULL);
1555 1555 tp->t_link = dq->dq_first;
1556 1556 dq->dq_first = tp;
1557 1557 }
1558 1558 } else {
1559 1559 if (borf == SETKP_BACK) {
1560 1560 ASSERT(dq->dq_first == NULL);
1561 1561 ASSERT(dq->dq_last == NULL);
1562 1562 dq->dq_first = dq->dq_last = tp;
1563 1563 } else {
1564 1564 ASSERT(dq->dq_last == NULL);
1565 1565 ASSERT(dq->dq_first == NULL);
1566 1566 tp->t_link = NULL;
1567 1567 dq->dq_first = dq->dq_last = tp;
1568 1568 }
1569 1569 BT_SET(dp->disp_qactmap, tpri);
1570 1570 if (tpri > dp->disp_max_unbound_pri)
1571 1571 dp->disp_max_unbound_pri = tpri;
1572 1572 if (tpri > dp->disp_maxrunpri) {
1573 1573 dp->disp_maxrunpri = tpri;
1574 1574 membar_enter();
1575 1575 }
1576 1576 }
1577 1577
1578 1578 cp = tp->t_cpu;
1579 1579 if (tp->t_cpupart != cp->cpu_part) {
1580 1580 /* migrate to a cpu in the new partition */
1581 1581 cp = tp->t_cpupart->cp_cpulist;
1582 1582 }
1583 1583 cp = disp_lowpri_cpu(cp, tp->t_lpl, tp->t_pri, NULL);
1584 1584 disp_lock_enter_high(&cp->cpu_disp->disp_lock);
1585 1585 ASSERT((cp->cpu_flags & CPU_QUIESCED) == 0);
1586 1586
1587 1587 #ifndef NPROBE
1588 1588 /* Kernel probe */
1589 1589 if (tnf_tracing_active)
1590 1590 tnf_thread_queue(tp, cp, tpri);
1591 1591 #endif /* NPROBE */
1592 1592
1593 1593 if (cp->cpu_chosen_level < tpri)
1594 1594 cp->cpu_chosen_level = tpri;
1595 1595 cpu_resched(cp, tpri);
1596 1596 disp_lock_exit_high(&cp->cpu_disp->disp_lock);
1597 1597 (*disp_enq_thread)(cp, 0);
1598 1598 }
1599 1599
1600 1600 /*
1601 1601 * Remove a thread from the dispatcher queue if it is on it.
1602 1602 * It is not an error if it is not found but we return whether
1603 1603 * or not it was found in case the caller wants to check.
1604 1604 */
1605 1605 int
1606 1606 dispdeq(kthread_t *tp)
1607 1607 {
1608 1608 disp_t *dp;
1609 1609 dispq_t *dq;
1610 1610 kthread_t *rp;
1611 1611 kthread_t *trp;
1612 1612 kthread_t **ptp;
1613 1613 int tpri;
1614 1614
1615 1615 ASSERT(THREAD_LOCK_HELD(tp));
1616 1616
1617 1617 if (tp->t_state != TS_RUN)
1618 1618 return (0);
1619 1619
1620 1620 /*
1621 1621 * The thread is "swapped" or is on the swap queue and
1622 1622 * hence no longer on the run queue, so return true.
1623 1623 */
1624 1624 if ((tp->t_schedflag & (TS_LOAD | TS_ON_SWAPQ)) != TS_LOAD)
1625 1625 return (1);
1626 1626
1627 1627 tpri = DISP_PRIO(tp);
1628 1628 dp = tp->t_disp_queue;
1629 1629 ASSERT(tpri < dp->disp_npri);
1630 1630 dq = &dp->disp_q[tpri];
1631 1631 ptp = &dq->dq_first;
1632 1632 rp = *ptp;
1633 1633 trp = NULL;
1634 1634
1635 1635 ASSERT(dq->dq_last == NULL || dq->dq_last->t_link == NULL);
1636 1636
1637 1637 /*
1638 1638 * Search for thread in queue.
1639 1639 * Double links would simplify this at the expense of disp/setrun.
1640 1640 */
1641 1641 while (rp != tp && rp != NULL) {
1642 1642 trp = rp;
1643 1643 ptp = &trp->t_link;
1644 1644 rp = trp->t_link;
1645 1645 }
1646 1646
1647 1647 if (rp == NULL) {
1648 1648 panic("dispdeq: thread not on queue");
1649 1649 }
1650 1650
1651 1651 DTRACE_SCHED2(dequeue, kthread_t *, tp, disp_t *, dp);
1652 1652
1653 1653 /*
1654 1654 * Found it so remove it from queue.
1655 1655 */
1656 1656 if ((*ptp = rp->t_link) == NULL)
1657 1657 dq->dq_last = trp;
1658 1658
1659 1659 dp->disp_nrunnable--;
1660 1660 if (--dq->dq_sruncnt == 0) {
1661 1661 dp->disp_qactmap[tpri >> BT_ULSHIFT] &= ~BT_BIW(tpri);
1662 1662 if (dp->disp_nrunnable == 0) {
1663 1663 dp->disp_max_unbound_pri = -1;
1664 1664 dp->disp_maxrunpri = -1;
1665 1665 } else if (tpri == dp->disp_maxrunpri) {
1666 1666 int ipri;
1667 1667
1668 1668 ipri = bt_gethighbit(dp->disp_qactmap,
1669 1669 dp->disp_maxrunpri >> BT_ULSHIFT);
1670 1670 if (ipri < dp->disp_max_unbound_pri)
1671 1671 dp->disp_max_unbound_pri = ipri;
1672 1672 dp->disp_maxrunpri = ipri;
1673 1673 }
1674 1674 }
1675 1675 tp->t_link = NULL;
1676 1676 THREAD_TRANSITION(tp); /* put in intermediate state */
1677 1677 return (1);
1678 1678 }
1679 1679
1680 1680
1681 1681 /*
1682 1682 * dq_sruninc and dq_srundec are public functions for
1683 1683 * incrementing/decrementing the sruncnts when a thread on
1684 1684 * a dispatcher queue is made schedulable/unschedulable by
1685 1685 * resetting the TS_LOAD flag.
1686 1686 *
1687 1687 * The caller MUST have the thread lock and therefore the dispatcher
1688 1688 * queue lock so that the operation which changes
1689 1689 * the flag, the operation that checks the status of the thread to
1690 1690 * determine if it's on a disp queue AND the call to this function
1691 1691 * are one atomic operation with respect to interrupts.
1692 1692 */
1693 1693
1694 1694 /*
1695 1695 * Called by sched AFTER TS_LOAD flag is set on a swapped, runnable thread.
1696 1696 */
1697 1697 void
1698 1698 dq_sruninc(kthread_t *t)
1699 1699 {
1700 1700 ASSERT(t->t_state == TS_RUN);
1701 1701 ASSERT(t->t_schedflag & TS_LOAD);
1702 1702
1703 1703 THREAD_TRANSITION(t);
1704 1704 setfrontdq(t);
1705 1705 }
1706 1706
1707 1707 /*
1708 1708 * See comment on calling conventions above.
1709 1709 * Called by sched BEFORE TS_LOAD flag is cleared on a runnable thread.
1710 1710 */
1711 1711 void
1712 1712 dq_srundec(kthread_t *t)
1713 1713 {
1714 1714 ASSERT(t->t_schedflag & TS_LOAD);
1715 1715
1716 1716 (void) dispdeq(t);
1717 1717 disp_swapped_enq(t);
1718 1718 }
1719 1719
1720 1720 /*
1721 1721 * Change the dispatcher lock of thread to the "swapped_lock"
1722 1722 * and return with thread lock still held.
1723 1723 *
1724 1724 * Called with thread_lock held, in transition state, and at high spl.
1725 1725 */
1726 1726 void
1727 1727 disp_swapped_enq(kthread_t *tp)
1728 1728 {
1729 1729 ASSERT(THREAD_LOCK_HELD(tp));
1730 1730 ASSERT(tp->t_schedflag & TS_LOAD);
1731 1731
1732 1732 switch (tp->t_state) {
1733 1733 case TS_RUN:
1734 1734 disp_lock_enter_high(&swapped_lock);
1735 1735 THREAD_SWAP(tp, &swapped_lock); /* set TS_RUN state and lock */
1736 1736 break;
1737 1737 case TS_ONPROC:
1738 1738 disp_lock_enter_high(&swapped_lock);
1739 1739 THREAD_TRANSITION(tp);
1740 1740 wake_sched_sec = 1; /* tell clock to wake sched */
1741 1741 THREAD_SWAP(tp, &swapped_lock); /* set TS_RUN state and lock */
1742 1742 break;
1743 1743 default:
1744 1744 panic("disp_swapped: tp: %p bad t_state", (void *)tp);
1745 1745 }
1746 1746 }
1747 1747
1748 1748 /*
1749 1749 * This routine is called by setbackdq/setfrontdq if the thread is
1750 1750 * not loaded or loaded and on the swap queue.
1751 1751 *
1752 1752 * Thread state TS_SLEEP implies that a swapped thread
1753 1753 * has been woken up and needs to be swapped in by the swapper.
1754 1754 *
1755 1755 * Thread state TS_RUN, it implies that the priority of a swapped
1756 1756 * thread is being increased by scheduling class (e.g. ts_update).
1757 1757 */
1758 1758 static void
1759 1759 disp_swapped_setrun(kthread_t *tp)
1760 1760 {
1761 1761 ASSERT(THREAD_LOCK_HELD(tp));
1762 1762 ASSERT((tp->t_schedflag & (TS_LOAD | TS_ON_SWAPQ)) != TS_LOAD);
1763 1763
1764 1764 switch (tp->t_state) {
1765 1765 case TS_SLEEP:
1766 1766 disp_lock_enter_high(&swapped_lock);
1767 1767 /*
1768 1768 * Wakeup sched immediately (i.e., next tick) if the
1769 1769 * thread priority is above maxclsyspri.
1770 1770 */
1771 1771 if (DISP_PRIO(tp) > maxclsyspri)
1772 1772 wake_sched = 1;
1773 1773 else
1774 1774 wake_sched_sec = 1;
1775 1775 THREAD_RUN(tp, &swapped_lock); /* set TS_RUN state and lock */
1776 1776 break;
1777 1777 case TS_RUN: /* called from ts_update */
1778 1778 break;
1779 1779 default:
1780 1780 panic("disp_swapped_setrun: tp: %p bad t_state", (void *)tp);
1781 1781 }
1782 1782 }
1783 1783
1784 1784 /*
1785 1785 * Make a thread give up its processor. Find the processor on
1786 1786 * which this thread is executing, and have that processor
1787 1787 * preempt.
1788 1788 *
1789 1789 * We allow System Duty Cycle (SDC) threads to be preempted even if
1790 1790 * they are running at kernel priorities. To implement this, we always
1791 1791 * set cpu_kprunrun; this ensures preempt() will be called. Since SDC
1792 1792 * calls cpu_surrender() very often, we only preempt if there is anyone
1793 1793 * competing with us.
1794 1794 */
1795 1795 void
1796 1796 cpu_surrender(kthread_t *tp)
1797 1797 {
1798 1798 cpu_t *cpup;
1799 1799 int max_pri;
1800 1800 int max_run_pri;
1801 1801 klwp_t *lwp;
1802 1802
1803 1803 ASSERT(THREAD_LOCK_HELD(tp));
1804 1804
1805 1805 if (tp->t_state != TS_ONPROC)
1806 1806 return;
1807 1807 cpup = tp->t_disp_queue->disp_cpu; /* CPU thread dispatched to */
1808 1808 max_pri = cpup->cpu_disp->disp_maxrunpri; /* best pri of that CPU */
1809 1809 max_run_pri = CP_MAXRUNPRI(cpup->cpu_part);
1810 1810 if (max_pri < max_run_pri)
1811 1811 max_pri = max_run_pri;
1812 1812
1813 1813 if (tp->t_cid == sysdccid) {
1814 1814 uint_t t_pri = DISP_PRIO(tp);
1815 1815 if (t_pri > max_pri)
1816 1816 return; /* we are not competing w/ anyone */
1817 1817 cpup->cpu_runrun = cpup->cpu_kprunrun = 1;
1818 1818 } else {
1819 1819 cpup->cpu_runrun = 1;
1820 1820 if (max_pri >= kpreemptpri && cpup->cpu_kprunrun == 0) {
1821 1821 cpup->cpu_kprunrun = 1;
1822 1822 }
1823 1823 }
1824 1824
1825 1825 /*
1826 1826 * Propagate cpu_runrun, and cpu_kprunrun to global visibility.
1827 1827 */
1828 1828 membar_enter();
1829 1829
1830 1830 DTRACE_SCHED1(surrender, kthread_t *, tp);
1831 1831
1832 1832 /*
1833 1833 * Make the target thread take an excursion through trap()
1834 1834 * to do preempt() (unless we're already in trap or post_syscall,
1835 1835 * calling cpu_surrender via CL_TRAPRET).
1836 1836 */
1837 1837 if (tp != curthread || (lwp = tp->t_lwp) == NULL ||
1838 1838 lwp->lwp_state != LWP_USER) {
1839 1839 aston(tp);
1840 1840 if (cpup != CPU)
1841 1841 poke_cpu(cpup->cpu_id);
1842 1842 }
1843 1843 TRACE_2(TR_FAC_DISP, TR_CPU_SURRENDER,
1844 1844 "cpu_surrender:tid %p cpu %p", tp, cpup);
1845 1845 }
1846 1846
1847 1847 /*
1848 1848 * Commit to and ratify a scheduling decision
1849 1849 */
1850 1850 /*ARGSUSED*/
1851 1851 static kthread_t *
1852 1852 disp_ratify(kthread_t *tp, disp_t *kpq)
1853 1853 {
1854 1854 pri_t tpri, maxpri;
1855 1855 pri_t maxkpri;
1856 1856 cpu_t *cpup;
1857 1857
1858 1858 ASSERT(tp != NULL);
1859 1859 /*
1860 1860 * Commit to, then ratify scheduling decision
1861 1861 */
1862 1862 cpup = CPU;
1863 1863 if (cpup->cpu_runrun != 0)
1864 1864 cpup->cpu_runrun = 0;
1865 1865 if (cpup->cpu_kprunrun != 0)
1866 1866 cpup->cpu_kprunrun = 0;
1867 1867 if (cpup->cpu_chosen_level != -1)
1868 1868 cpup->cpu_chosen_level = -1;
1869 1869 membar_enter();
1870 1870 tpri = DISP_PRIO(tp);
1871 1871 maxpri = cpup->cpu_disp->disp_maxrunpri;
1872 1872 maxkpri = kpq->disp_maxrunpri;
1873 1873 if (maxpri < maxkpri)
1874 1874 maxpri = maxkpri;
1875 1875 if (tpri < maxpri) {
1876 1876 /*
1877 1877 * should have done better
1878 1878 * put this one back and indicate to try again
1879 1879 */
1880 1880 cpup->cpu_dispthread = curthread; /* fixup dispthread */
1881 1881 cpup->cpu_dispatch_pri = DISP_PRIO(curthread);
1882 1882 thread_lock_high(tp);
1883 1883 THREAD_TRANSITION(tp);
1884 1884 setfrontdq(tp);
1885 1885 thread_unlock_nopreempt(tp);
1886 1886
1887 1887 tp = NULL;
1888 1888 }
1889 1889 return (tp);
1890 1890 }
1891 1891
1892 1892 /*
1893 1893 * See if there is any work on the dispatcher queue for other CPUs.
1894 1894 * If there is, dequeue the best thread and return.
1895 1895 */
1896 1896 static kthread_t *
1897 1897 disp_getwork(cpu_t *cp)
1898 1898 {
1899 1899 cpu_t *ocp; /* other CPU */
1900 1900 cpu_t *ocp_start;
1901 1901 cpu_t *tcp; /* target local CPU */
1902 1902 kthread_t *tp;
1903 1903 kthread_t *retval = NULL;
1904 1904 pri_t maxpri;
1905 1905 disp_t *kpq; /* kp queue for this partition */
1906 1906 lpl_t *lpl, *lpl_leaf;
1907 1907 int leafidx, startidx;
1908 1908 hrtime_t stealtime;
1909 1909 lgrp_id_t local_id;
1910 1910
1911 1911 maxpri = -1;
1912 1912 tcp = NULL;
1913 1913
1914 1914 kpq = &cp->cpu_part->cp_kp_queue;
1915 1915 while (kpq->disp_maxrunpri >= 0) {
1916 1916 /*
1917 1917 * Try to take a thread from the kp_queue.
1918 1918 */
1919 1919 tp = (disp_getbest(kpq));
1920 1920 if (tp)
1921 1921 return (disp_ratify(tp, kpq));
1922 1922 }
1923 1923
1924 1924 kpreempt_disable(); /* protect the cpu_active list */
1925 1925
1926 1926 /*
1927 1927 * Try to find something to do on another CPU's run queue.
1928 1928 * Loop through all other CPUs looking for the one with the highest
1929 1929 * priority unbound thread.
1930 1930 *
1931 1931 * On NUMA machines, the partition's CPUs are consulted in order of
1932 1932 * distance from the current CPU. This way, the first available
1933 1933 * work found is also the closest, and will suffer the least
1934 1934 * from being migrated.
1935 1935 */
1936 1936 lpl = lpl_leaf = cp->cpu_lpl;
1937 1937 local_id = lpl_leaf->lpl_lgrpid;
1938 1938 leafidx = startidx = 0;
1939 1939
1940 1940 /*
1941 1941 * This loop traverses the lpl hierarchy. Higher level lpls represent
1942 1942 * broader levels of locality
1943 1943 */
1944 1944 do {
1945 1945 /* This loop iterates over the lpl's leaves */
1946 1946 do {
1947 1947 if (lpl_leaf != cp->cpu_lpl)
1948 1948 ocp = lpl_leaf->lpl_cpus;
1949 1949 else
1950 1950 ocp = cp->cpu_next_lpl;
1951 1951
1952 1952 /* This loop iterates over the CPUs in the leaf */
1953 1953 ocp_start = ocp;
1954 1954 do {
1955 1955 pri_t pri;
1956 1956
1957 1957 ASSERT(CPU_ACTIVE(ocp));
1958 1958
1959 1959 /*
1960 1960 * End our stroll around this lpl if:
1961 1961 *
1962 1962 * - Something became runnable on the local
1963 1963 * queue...which also ends our stroll around
1964 1964 * the partition.
1965 1965 *
1966 1966 * - We happen across another idle CPU.
1967 1967 * Since it is patrolling the next portion
1968 1968 * of the lpl's list (assuming it's not
1969 1969 * halted, or busy servicing an interrupt),
1970 1970 * move to the next higher level of locality.
1971 1971 */
1972 1972 if (cp->cpu_disp->disp_nrunnable != 0) {
1973 1973 kpreempt_enable();
1974 1974 return (NULL);
1975 1975 }
1976 1976 if (ocp->cpu_dispatch_pri == -1) {
1977 1977 if (ocp->cpu_disp_flags &
1978 1978 CPU_DISP_HALTED ||
1979 1979 ocp->cpu_intr_actv != 0)
1980 1980 continue;
1981 1981 else
1982 1982 goto next_level;
1983 1983 }
1984 1984
1985 1985 /*
1986 1986 * If there's only one thread and the CPU
1987 1987 * is in the middle of a context switch,
1988 1988 * or it's currently running the idle thread,
1989 1989 * don't steal it.
1990 1990 */
1991 1991 if ((ocp->cpu_disp_flags &
1992 1992 CPU_DISP_DONTSTEAL) &&
1993 1993 ocp->cpu_disp->disp_nrunnable == 1)
1994 1994 continue;
1995 1995
1996 1996 pri = ocp->cpu_disp->disp_max_unbound_pri;
1997 1997 if (pri > maxpri) {
1998 1998 /*
1999 1999 * Don't steal threads that we attempted
2000 2000 * to steal recently until they're ready
2001 2001 * to be stolen again.
2002 2002 */
2003 2003 stealtime = ocp->cpu_disp->disp_steal;
2004 2004 if (stealtime == 0 ||
2005 2005 stealtime - gethrtime() <= 0) {
2006 2006 maxpri = pri;
2007 2007 tcp = ocp;
2008 2008 } else {
2009 2009 /*
2010 2010 * Don't update tcp, just set
2011 2011 * the retval to T_DONTSTEAL, so
2012 2012 * that if no acceptable CPUs
2013 2013 * are found the return value
2014 2014 * will be T_DONTSTEAL rather
2015 2015 * then NULL.
2016 2016 */
2017 2017 retval = T_DONTSTEAL;
2018 2018 }
2019 2019 }
2020 2020 } while ((ocp = ocp->cpu_next_lpl) != ocp_start);
2021 2021
2022 2022 /*
2023 2023 * Iterate to the next leaf lpl in the resource set
2024 2024 * at this level of locality. If we hit the end of
2025 2025 * the set, wrap back around to the beginning.
2026 2026 *
2027 2027 * Note: This iteration is NULL terminated for a reason
2028 2028 * see lpl_topo_bootstrap() in lgrp.c for details.
2029 2029 */
2030 2030 if ((lpl_leaf = lpl->lpl_rset[++leafidx]) == NULL) {
2031 2031 leafidx = 0;
2032 2032 lpl_leaf = lpl->lpl_rset[leafidx];
2033 2033 }
2034 2034 } while (leafidx != startidx);
2035 2035
2036 2036 next_level:
2037 2037 /*
2038 2038 * Expand the search to include farther away CPUs (next
2039 2039 * locality level). The closer CPUs that have already been
2040 2040 * checked will be checked again. In doing so, idle CPUs
2041 2041 * will tend to be more aggresive about stealing from CPUs
2042 2042 * that are closer (since the closer CPUs will be considered
2043 2043 * more often).
2044 2044 * Begin at this level with the CPUs local leaf lpl.
2045 2045 */
2046 2046 if ((lpl = lpl->lpl_parent) != NULL) {
2047 2047 leafidx = startidx = lpl->lpl_id2rset[local_id];
2048 2048 lpl_leaf = lpl->lpl_rset[leafidx];
2049 2049 }
2050 2050 } while (!tcp && lpl);
2051 2051
2052 2052 kpreempt_enable();
2053 2053
2054 2054 /*
2055 2055 * If another queue looks good, and there is still nothing on
2056 2056 * the local queue, try to transfer one or more threads
2057 2057 * from it to our queue.
2058 2058 */
2059 2059 if (tcp && cp->cpu_disp->disp_nrunnable == 0) {
2060 2060 tp = disp_getbest(tcp->cpu_disp);
2061 2061 if (tp == NULL || tp == T_DONTSTEAL)
2062 2062 return (tp);
2063 2063 return (disp_ratify(tp, kpq));
2064 2064 }
2065 2065 return (retval);
2066 2066 }
2067 2067
2068 2068
2069 2069 /*
2070 2070 * disp_fix_unbound_pri()
2071 2071 * Determines the maximum priority of unbound threads on the queue.
2072 2072 * The priority is kept for the queue, but is only increased, never
2073 2073 * reduced unless some CPU is looking for something on that queue.
2074 2074 *
2075 2075 * The priority argument is the known upper limit.
2076 2076 *
2077 2077 * Perhaps this should be kept accurately, but that probably means
2078 2078 * separate bitmaps for bound and unbound threads. Since only idled
2079 2079 * CPUs will have to do this recalculation, it seems better this way.
2080 2080 */
2081 2081 static void
2082 2082 disp_fix_unbound_pri(disp_t *dp, pri_t pri)
2083 2083 {
2084 2084 kthread_t *tp;
2085 2085 dispq_t *dq;
2086 2086 ulong_t *dqactmap = dp->disp_qactmap;
2087 2087 ulong_t mapword;
2088 2088 int wx;
2089 2089
2090 2090 ASSERT(DISP_LOCK_HELD(&dp->disp_lock));
2091 2091
2092 2092 ASSERT(pri >= 0); /* checked by caller */
2093 2093
2094 2094 /*
2095 2095 * Start the search at the next lowest priority below the supplied
2096 2096 * priority. This depends on the bitmap implementation.
2097 2097 */
2098 2098 do {
2099 2099 wx = pri >> BT_ULSHIFT; /* index of word in map */
2100 2100
2101 2101 /*
2102 2102 * Form mask for all lower priorities in the word.
2103 2103 */
2104 2104 mapword = dqactmap[wx] & (BT_BIW(pri) - 1);
2105 2105
2106 2106 /*
2107 2107 * Get next lower active priority.
2108 2108 */
2109 2109 if (mapword != 0) {
2110 2110 pri = (wx << BT_ULSHIFT) + highbit(mapword) - 1;
2111 2111 } else if (wx > 0) {
2112 2112 pri = bt_gethighbit(dqactmap, wx - 1); /* sign extend */
2113 2113 if (pri < 0)
2114 2114 break;
2115 2115 } else {
2116 2116 pri = -1;
2117 2117 break;
2118 2118 }
2119 2119
2120 2120 /*
2121 2121 * Search the queue for unbound, runnable threads.
2122 2122 */
2123 2123 dq = &dp->disp_q[pri];
2124 2124 tp = dq->dq_first;
2125 2125
2126 2126 while (tp && (tp->t_bound_cpu || tp->t_weakbound_cpu)) {
2127 2127 tp = tp->t_link;
2128 2128 }
2129 2129
2130 2130 /*
2131 2131 * If a thread was found, set the priority and return.
2132 2132 */
2133 2133 } while (tp == NULL);
2134 2134
2135 2135 /*
2136 2136 * pri holds the maximum unbound thread priority or -1.
2137 2137 */
2138 2138 if (dp->disp_max_unbound_pri != pri)
2139 2139 dp->disp_max_unbound_pri = pri;
2140 2140 }
2141 2141
2142 2142 /*
2143 2143 * disp_adjust_unbound_pri() - thread is becoming unbound, so we should
2144 2144 * check if the CPU to which is was previously bound should have
2145 2145 * its disp_max_unbound_pri increased.
2146 2146 */
2147 2147 void
2148 2148 disp_adjust_unbound_pri(kthread_t *tp)
2149 2149 {
2150 2150 disp_t *dp;
2151 2151 pri_t tpri;
2152 2152
2153 2153 ASSERT(THREAD_LOCK_HELD(tp));
2154 2154
2155 2155 /*
2156 2156 * Don't do anything if the thread is not bound, or
2157 2157 * currently not runnable or swapped out.
2158 2158 */
2159 2159 if (tp->t_bound_cpu == NULL ||
2160 2160 tp->t_state != TS_RUN ||
2161 2161 tp->t_schedflag & TS_ON_SWAPQ)
2162 2162 return;
2163 2163
2164 2164 tpri = DISP_PRIO(tp);
2165 2165 dp = tp->t_bound_cpu->cpu_disp;
2166 2166 ASSERT(tpri >= 0 && tpri < dp->disp_npri);
2167 2167 if (tpri > dp->disp_max_unbound_pri)
2168 2168 dp->disp_max_unbound_pri = tpri;
2169 2169 }
2170 2170
2171 2171 /*
2172 2172 * disp_getbest()
2173 2173 * De-queue the highest priority unbound runnable thread.
2174 2174 * Returns with the thread unlocked and onproc but at splhigh (like disp()).
2175 2175 * Returns NULL if nothing found.
2176 2176 * Returns T_DONTSTEAL if the thread was not stealable.
2177 2177 * so that the caller will try again later.
2178 2178 *
2179 2179 * Passed a pointer to a dispatch queue not associated with this CPU, and
2180 2180 * its type.
2181 2181 */
2182 2182 static kthread_t *
2183 2183 disp_getbest(disp_t *dp)
2184 2184 {
2185 2185 kthread_t *tp;
2186 2186 dispq_t *dq;
2187 2187 pri_t pri;
2188 2188 cpu_t *cp, *tcp;
2189 2189 boolean_t allbound;
2190 2190
2191 2191 disp_lock_enter(&dp->disp_lock);
2192 2192
2193 2193 /*
2194 2194 * If there is nothing to run, or the CPU is in the middle of a
2195 2195 * context switch of the only thread, return NULL.
2196 2196 */
2197 2197 tcp = dp->disp_cpu;
2198 2198 cp = CPU;
2199 2199 pri = dp->disp_max_unbound_pri;
2200 2200 if (pri == -1 ||
2201 2201 (tcp != NULL && (tcp->cpu_disp_flags & CPU_DISP_DONTSTEAL) &&
2202 2202 tcp->cpu_disp->disp_nrunnable == 1)) {
2203 2203 disp_lock_exit_nopreempt(&dp->disp_lock);
2204 2204 return (NULL);
2205 2205 }
2206 2206
2207 2207 dq = &dp->disp_q[pri];
2208 2208
2209 2209
2210 2210 /*
2211 2211 * Assume that all threads are bound on this queue, and change it
2212 2212 * later when we find out that it is not the case.
2213 2213 */
2214 2214 allbound = B_TRUE;
2215 2215 for (tp = dq->dq_first; tp != NULL; tp = tp->t_link) {
2216 2216 hrtime_t now, nosteal, rqtime;
2217 2217
2218 2218 /*
2219 2219 * Skip over bound threads which could be here even
2220 2220 * though disp_max_unbound_pri indicated this level.
2221 2221 */
2222 2222 if (tp->t_bound_cpu || tp->t_weakbound_cpu)
2223 2223 continue;
2224 2224
2225 2225 /*
2226 2226 * We've got some unbound threads on this queue, so turn
2227 2227 * the allbound flag off now.
2228 2228 */
2229 2229 allbound = B_FALSE;
2230 2230
2231 2231 /*
2232 2232 * The thread is a candidate for stealing from its run queue. We
2233 2233 * don't want to steal threads that became runnable just a
2234 2234 * moment ago. This improves CPU affinity for threads that get
2235 2235 * preempted for short periods of time and go back on the run
2236 2236 * queue.
2237 2237 *
2238 2238 * We want to let it stay on its run queue if it was only placed
2239 2239 * there recently and it was running on the same CPU before that
2240 2240 * to preserve its cache investment. For the thread to remain on
2241 2241 * its run queue, ALL of the following conditions must be
2242 2242 * satisfied:
2243 2243 *
2244 2244 * - the disp queue should not be the kernel preemption queue
2245 2245 * - delayed idle stealing should not be disabled
2246 2246 * - nosteal_nsec should be non-zero
2247 2247 * - it should run with user priority
2248 2248 * - it should be on the run queue of the CPU where it was
2249 2249 * running before being placed on the run queue
2250 2250 * - it should be the only thread on the run queue (to prevent
2251 2251 * extra scheduling latency for other threads)
2252 2252 * - it should sit on the run queue for less than per-chip
2253 2253 * nosteal interval or global nosteal interval
2254 2254 * - in case of CPUs with shared cache it should sit in a run
2255 2255 * queue of a CPU from a different chip
2256 2256 *
2257 2257 * The checks are arranged so that the ones that are faster are
2258 2258 * placed earlier.
2259 2259 */
2260 2260 if (tcp == NULL ||
2261 2261 pri >= minclsyspri ||
2262 2262 tp->t_cpu != tcp)
2263 2263 break;
2264 2264
2265 2265 /*
2266 2266 * Steal immediately if, due to CMT processor architecture
2267 2267 * migraiton between cp and tcp would incur no performance
2268 2268 * penalty.
2269 2269 */
2270 2270 if (pg_cmt_can_migrate(cp, tcp))
2271 2271 break;
2272 2272
2273 2273 nosteal = nosteal_nsec;
2274 2274 if (nosteal == 0)
2275 2275 break;
2276 2276
2277 2277 /*
2278 2278 * Calculate time spent sitting on run queue
2279 2279 */
2280 2280 now = gethrtime_unscaled();
2281 2281 rqtime = now - tp->t_waitrq;
2282 2282 scalehrtime(&rqtime);
2283 2283
2284 2284 /*
2285 2285 * Steal immediately if the time spent on this run queue is more
2286 2286 * than allowed nosteal delay.
2287 2287 *
2288 2288 * Negative rqtime check is needed here to avoid infinite
2289 2289 * stealing delays caused by unlikely but not impossible
2290 2290 * drifts between CPU times on different CPUs.
2291 2291 */
2292 2292 if (rqtime > nosteal || rqtime < 0)
2293 2293 break;
2294 2294
2295 2295 DTRACE_PROBE4(nosteal, kthread_t *, tp,
2296 2296 cpu_t *, tcp, cpu_t *, cp, hrtime_t, rqtime);
2297 2297 scalehrtime(&now);
2298 2298 /*
2299 2299 * Calculate when this thread becomes stealable
2300 2300 */
2301 2301 now += (nosteal - rqtime);
2302 2302
2303 2303 /*
2304 2304 * Calculate time when some thread becomes stealable
2305 2305 */
2306 2306 if (now < dp->disp_steal)
2307 2307 dp->disp_steal = now;
2308 2308 }
2309 2309
2310 2310 /*
2311 2311 * If there were no unbound threads on this queue, find the queue
2312 2312 * where they are and then return later. The value of
2313 2313 * disp_max_unbound_pri is not always accurate because it isn't
2314 2314 * reduced until another idle CPU looks for work.
2315 2315 */
2316 2316 if (allbound)
2317 2317 disp_fix_unbound_pri(dp, pri);
2318 2318
2319 2319 /*
2320 2320 * If we reached the end of the queue and found no unbound threads
2321 2321 * then return NULL so that other CPUs will be considered. If there
2322 2322 * are unbound threads but they cannot yet be stolen, then
2323 2323 * return T_DONTSTEAL and try again later.
2324 2324 */
2325 2325 if (tp == NULL) {
2326 2326 disp_lock_exit_nopreempt(&dp->disp_lock);
2327 2327 return (allbound ? NULL : T_DONTSTEAL);
2328 2328 }
2329 2329
2330 2330 /*
2331 2331 * Found a runnable, unbound thread, so remove it from queue.
2332 2332 * dispdeq() requires that we have the thread locked, and we do,
2333 2333 * by virtue of holding the dispatch queue lock. dispdeq() will
2334 2334 * put the thread in transition state, thereby dropping the dispq
2335 2335 * lock.
2336 2336 */
2337 2337
2338 2338 #ifdef DEBUG
2339 2339 {
2340 2340 int thread_was_on_queue;
2341 2341
2342 2342 thread_was_on_queue = dispdeq(tp); /* drops disp_lock */
2343 2343 ASSERT(thread_was_on_queue);
2344 2344 }
2345 2345
2346 2346 #else /* DEBUG */
2347 2347 (void) dispdeq(tp); /* drops disp_lock */
2348 2348 #endif /* DEBUG */
2349 2349
2350 2350 /*
2351 2351 * Reset the disp_queue steal time - we do not know what is the smallest
2352 2352 * value across the queue is.
2353 2353 */
2354 2354 dp->disp_steal = 0;
2355 2355
2356 2356 tp->t_schedflag |= TS_DONT_SWAP;
2357 2357
2358 2358 /*
2359 2359 * Setup thread to run on the current CPU.
2360 2360 */
2361 2361 tp->t_disp_queue = cp->cpu_disp;
2362 2362
2363 2363 cp->cpu_dispthread = tp; /* protected by spl only */
2364 2364 cp->cpu_dispatch_pri = pri;
2365 2365
2366 2366 /*
2367 2367 * There can be a memory synchronization race between disp_getbest()
2368 2368 * and disp_ratify() vs cpu_resched() where cpu_resched() is trying
2369 2369 * to preempt the current thread to run the enqueued thread while
2370 2370 * disp_getbest() and disp_ratify() are changing the current thread
2371 2371 * to the stolen thread. This may lead to a situation where
2372 2372 * cpu_resched() tries to preempt the wrong thread and the
2373 2373 * stolen thread continues to run on the CPU which has been tagged
2374 2374 * for preemption.
2375 2375 * Later the clock thread gets enqueued but doesn't get to run on the
2376 2376 * CPU causing the system to hang.
2377 2377 *
2378 2378 * To avoid this, grabbing and dropping the disp_lock (which does
2379 2379 * a memory barrier) is needed to synchronize the execution of
2380 2380 * cpu_resched() with disp_getbest() and disp_ratify() and
2381 2381 * synchronize the memory read and written by cpu_resched(),
2382 2382 * disp_getbest(), and disp_ratify() with each other.
2383 2383 * (see CR#6482861 for more details).
2384 2384 */
2385 2385 disp_lock_enter_high(&cp->cpu_disp->disp_lock);
2386 2386 disp_lock_exit_high(&cp->cpu_disp->disp_lock);
2387 2387
2388 2388 ASSERT(pri == DISP_PRIO(tp));
2389 2389
2390 2390 DTRACE_PROBE3(steal, kthread_t *, tp, cpu_t *, tcp, cpu_t *, cp);
2391 2391
2392 2392 thread_onproc(tp, cp); /* set t_state to TS_ONPROC */
2393 2393
2394 2394 /*
2395 2395 * Return with spl high so that swtch() won't need to raise it.
2396 2396 * The disp_lock was dropped by dispdeq().
2397 2397 */
2398 2398
2399 2399 return (tp);
2400 2400 }
2401 2401
2402 2402 /*
2403 2403 * disp_bound_common() - common routine for higher level functions
2404 2404 * that check for bound threads under certain conditions.
2405 2405 * If 'threadlistsafe' is set then there is no need to acquire
2406 2406 * pidlock to stop the thread list from changing (eg, if
2407 2407 * disp_bound_* is called with cpus paused).
2408 2408 */
2409 2409 static int
2410 2410 disp_bound_common(cpu_t *cp, int threadlistsafe, int flag)
2411 2411 {
2412 2412 int found = 0;
2413 2413 kthread_t *tp;
2414 2414
2415 2415 ASSERT(flag);
2416 2416
2417 2417 if (!threadlistsafe)
2418 2418 mutex_enter(&pidlock);
2419 2419 tp = curthread; /* faster than allthreads */
2420 2420 do {
2421 2421 if (tp->t_state != TS_FREE) {
2422 2422 /*
2423 2423 * If an interrupt thread is busy, but the
2424 2424 * caller doesn't care (i.e. BOUND_INTR is off),
2425 2425 * then just ignore it and continue through.
2426 2426 */
2427 2427 if ((tp->t_flag & T_INTR_THREAD) &&
2428 2428 !(flag & BOUND_INTR))
2429 2429 continue;
2430 2430
2431 2431 /*
2432 2432 * Skip the idle thread for the CPU
2433 2433 * we're about to set offline.
2434 2434 */
2435 2435 if (tp == cp->cpu_idle_thread)
2436 2436 continue;
2437 2437
2438 2438 /*
2439 2439 * Skip the pause thread for the CPU
2440 2440 * we're about to set offline.
2441 2441 */
2442 2442 if (tp == cp->cpu_pause_thread)
2443 2443 continue;
2444 2444
2445 2445 if ((flag & BOUND_CPU) &&
2446 2446 (tp->t_bound_cpu == cp ||
2447 2447 tp->t_bind_cpu == cp->cpu_id ||
2448 2448 tp->t_weakbound_cpu == cp)) {
2449 2449 found = 1;
2450 2450 break;
2451 2451 }
2452 2452
2453 2453 if ((flag & BOUND_PARTITION) &&
2454 2454 (tp->t_cpupart == cp->cpu_part)) {
2455 2455 found = 1;
2456 2456 break;
2457 2457 }
2458 2458 }
2459 2459 } while ((tp = tp->t_next) != curthread && found == 0);
2460 2460 if (!threadlistsafe)
2461 2461 mutex_exit(&pidlock);
2462 2462 return (found);
2463 2463 }
2464 2464
2465 2465 /*
2466 2466 * disp_bound_threads - return nonzero if threads are bound to the processor.
2467 2467 * Called infrequently. Keep this simple.
2468 2468 * Includes threads that are asleep or stopped but not onproc.
2469 2469 */
2470 2470 int
2471 2471 disp_bound_threads(cpu_t *cp, int threadlistsafe)
2472 2472 {
2473 2473 return (disp_bound_common(cp, threadlistsafe, BOUND_CPU));
2474 2474 }
2475 2475
2476 2476 /*
2477 2477 * disp_bound_anythreads - return nonzero if _any_ threads are bound
2478 2478 * to the given processor, including interrupt threads.
2479 2479 */
2480 2480 int
2481 2481 disp_bound_anythreads(cpu_t *cp, int threadlistsafe)
2482 2482 {
2483 2483 return (disp_bound_common(cp, threadlistsafe, BOUND_CPU | BOUND_INTR));
2484 2484 }
2485 2485
2486 2486 /*
2487 2487 * disp_bound_partition - return nonzero if threads are bound to the same
2488 2488 * partition as the processor.
2489 2489 * Called infrequently. Keep this simple.
2490 2490 * Includes threads that are asleep or stopped but not onproc.
2491 2491 */
2492 2492 int
2493 2493 disp_bound_partition(cpu_t *cp, int threadlistsafe)
2494 2494 {
2495 2495 return (disp_bound_common(cp, threadlistsafe, BOUND_PARTITION));
2496 2496 }
2497 2497
2498 2498 /*
2499 2499 * disp_cpu_inactive - make a CPU inactive by moving all of its unbound
2500 2500 * threads to other CPUs.
2501 2501 */
2502 2502 void
2503 2503 disp_cpu_inactive(cpu_t *cp)
2504 2504 {
2505 2505 kthread_t *tp;
2506 2506 disp_t *dp = cp->cpu_disp;
2507 2507 dispq_t *dq;
2508 2508 pri_t pri;
2509 2509 int wasonq;
2510 2510
2511 2511 disp_lock_enter(&dp->disp_lock);
2512 2512 while ((pri = dp->disp_max_unbound_pri) != -1) {
2513 2513 dq = &dp->disp_q[pri];
2514 2514 tp = dq->dq_first;
2515 2515
2516 2516 /*
2517 2517 * Skip over bound threads.
2518 2518 */
2519 2519 while (tp != NULL && tp->t_bound_cpu != NULL) {
2520 2520 tp = tp->t_link;
2521 2521 }
2522 2522
2523 2523 if (tp == NULL) {
2524 2524 /* disp_max_unbound_pri must be inaccurate, so fix it */
2525 2525 disp_fix_unbound_pri(dp, pri);
2526 2526 continue;
2527 2527 }
2528 2528
2529 2529 wasonq = dispdeq(tp); /* drops disp_lock */
2530 2530 ASSERT(wasonq);
2531 2531 ASSERT(tp->t_weakbound_cpu == NULL);
2532 2532
2533 2533 setbackdq(tp);
2534 2534 /*
2535 2535 * Called from cpu_offline:
2536 2536 *
2537 2537 * cp has already been removed from the list of active cpus
2538 2538 * and tp->t_cpu has been changed so there is no risk of
2539 2539 * tp ending up back on cp.
2540 2540 *
2541 2541 * Called from cpupart_move_cpu:
2542 2542 *
2543 2543 * The cpu has moved to a new cpupart. Any threads that
2544 2544 * were on it's dispatch queues before the move remain
2545 2545 * in the old partition and can't run in the new partition.
2546 2546 */
2547 2547 ASSERT(tp->t_cpu != cp);
2548 2548 thread_unlock(tp);
2549 2549
2550 2550 disp_lock_enter(&dp->disp_lock);
2551 2551 }
2552 2552 disp_lock_exit(&dp->disp_lock);
2553 2553 }
2554 2554
2555 2555 /*
2556 2556 * disp_lowpri_cpu - find CPU running the lowest priority thread.
2557 2557 * The hint passed in is used as a starting point so we don't favor
2558 2558 * CPU 0 or any other CPU. The caller should pass in the most recently
2559 2559 * used CPU for the thread.
2560 2560 *
2561 2561 * The lgroup and priority are used to determine the best CPU to run on
2562 2562 * in a NUMA machine. The lgroup specifies which CPUs are closest while
2563 2563 * the thread priority will indicate whether the thread will actually run
2564 2564 * there. To pick the best CPU, the CPUs inside and outside of the given
2565 2565 * lgroup which are running the lowest priority threads are found. The
2566 2566 * remote CPU is chosen only if the thread will not run locally on a CPU
2567 2567 * within the lgroup, but will run on the remote CPU. If the thread
2568 2568 * cannot immediately run on any CPU, the best local CPU will be chosen.
2569 2569 *
2570 2570 * The lpl specified also identifies the cpu partition from which
2571 2571 * disp_lowpri_cpu should select a CPU.
2572 2572 *
2573 2573 * curcpu is used to indicate that disp_lowpri_cpu is being called on
2574 2574 * behalf of the current thread. (curthread is looking for a new cpu)
2575 2575 * In this case, cpu_dispatch_pri for this thread's cpu should be
2576 2576 * ignored.
2577 2577 *
2578 2578 * If a cpu is the target of an offline request then try to avoid it.
2579 2579 *
2580 2580 * This function must be called at either high SPL, or with preemption
2581 2581 * disabled, so that the "hint" CPU cannot be removed from the online
2582 2582 * CPU list while we are traversing it.
2583 2583 */
2584 2584 cpu_t *
2585 2585 disp_lowpri_cpu(cpu_t *hint, lpl_t *lpl, pri_t tpri, cpu_t *curcpu)
2586 2586 {
2587 2587 cpu_t *bestcpu;
2588 2588 cpu_t *besthomecpu;
2589 2589 cpu_t *cp, *cpstart;
2590 2590
2591 2591 pri_t bestpri;
2592 2592 pri_t cpupri;
2593 2593
2594 2594 klgrpset_t done;
2595 2595 klgrpset_t cur_set;
2596 2596
2597 2597 lpl_t *lpl_iter, *lpl_leaf;
2598 2598 int i;
2599 2599
2600 2600 /*
2601 2601 * Scan for a CPU currently running the lowest priority thread.
2602 2602 * Cannot get cpu_lock here because it is adaptive.
2603 2603 * We do not require lock on CPU list.
2604 2604 */
2605 2605 ASSERT(hint != NULL);
2606 2606 ASSERT(lpl != NULL);
2607 2607 ASSERT(lpl->lpl_ncpu > 0);
2608 2608
2609 2609 /*
2610 2610 * First examine local CPUs. Note that it's possible the hint CPU
2611 2611 * passed in in remote to the specified home lgroup. If our priority
2612 2612 * isn't sufficient enough such that we can run immediately at home,
2613 2613 * then examine CPUs remote to our home lgroup.
2614 2614 * We would like to give preference to CPUs closest to "home".
2615 2615 * If we can't find a CPU where we'll run at a given level
2616 2616 * of locality, we expand our search to include the next level.
2617 2617 */
2618 2618 bestcpu = besthomecpu = NULL;
2619 2619 klgrpset_clear(done);
2620 2620 /* start with lpl we were passed */
2621 2621
2622 2622 lpl_iter = lpl;
2623 2623
2624 2624 do {
2625 2625
2626 2626 bestpri = SHRT_MAX;
2627 2627 klgrpset_clear(cur_set);
2628 2628
2629 2629 for (i = 0; i < lpl_iter->lpl_nrset; i++) {
2630 2630 lpl_leaf = lpl_iter->lpl_rset[i];
2631 2631 if (klgrpset_ismember(done, lpl_leaf->lpl_lgrpid))
2632 2632 continue;
2633 2633
2634 2634 klgrpset_add(cur_set, lpl_leaf->lpl_lgrpid);
2635 2635
2636 2636 if (hint->cpu_lpl == lpl_leaf)
2637 2637 cp = cpstart = hint;
2638 2638 else
2639 2639 cp = cpstart = lpl_leaf->lpl_cpus;
2640 2640
2641 2641 do {
2642 2642 if (cp == curcpu)
2643 2643 cpupri = -1;
2644 2644 else if (cp == cpu_inmotion)
2645 2645 cpupri = SHRT_MAX;
2646 2646 else
2647 2647 cpupri = cp->cpu_dispatch_pri;
2648 2648 if (cp->cpu_disp->disp_maxrunpri > cpupri)
2649 2649 cpupri = cp->cpu_disp->disp_maxrunpri;
2650 2650 if (cp->cpu_chosen_level > cpupri)
2651 2651 cpupri = cp->cpu_chosen_level;
2652 2652 if (cpupri < bestpri) {
2653 2653 if (CPU_IDLING(cpupri)) {
2654 2654 ASSERT((cp->cpu_flags &
2655 2655 CPU_QUIESCED) == 0);
2656 2656 return (cp);
2657 2657 }
2658 2658 bestcpu = cp;
2659 2659 bestpri = cpupri;
2660 2660 }
2661 2661 } while ((cp = cp->cpu_next_lpl) != cpstart);
2662 2662 }
2663 2663
2664 2664 if (bestcpu && (tpri > bestpri)) {
2665 2665 ASSERT((bestcpu->cpu_flags & CPU_QUIESCED) == 0);
2666 2666 return (bestcpu);
2667 2667 }
2668 2668 if (besthomecpu == NULL)
2669 2669 besthomecpu = bestcpu;
2670 2670 /*
2671 2671 * Add the lgrps we just considered to the "done" set
2672 2672 */
2673 2673 klgrpset_or(done, cur_set);
2674 2674
2675 2675 } while ((lpl_iter = lpl_iter->lpl_parent) != NULL);
2676 2676
2677 2677 /*
2678 2678 * The specified priority isn't high enough to run immediately
2679 2679 * anywhere, so just return the best CPU from the home lgroup.
2680 2680 */
2681 2681 ASSERT((besthomecpu->cpu_flags & CPU_QUIESCED) == 0);
2682 2682 return (besthomecpu);
2683 2683 }
2684 2684
2685 2685 /*
2686 2686 * This routine provides the generic idle cpu function for all processors.
2687 2687 * If a processor has some specific code to execute when idle (say, to stop
2688 2688 * the pipeline and save power) then that routine should be defined in the
2689 2689 * processors specific code (module_xx.c) and the global variable idle_cpu
2690 2690 * set to that function.
2691 2691 */
2692 2692 static void
2693 2693 generic_idle_cpu(void)
2694 2694 {
2695 2695 }
2696 2696
2697 2697 /*ARGSUSED*/
2698 2698 static void
2699 2699 generic_enq_thread(cpu_t *cpu, int bound)
2700 2700 {
2701 2701 }
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