xref: /qemu/system/dirtylimit.c (revision fe1a3ace13a8b53fc20c74fb7e3337f754396e6b) 
1 /*
2  * Dirty page rate limit implementation code
3  *
4  * Copyright (c) 2022 CHINA TELECOM CO.,LTD.
5  *
6  * Authors:
7  *  Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
8  *
9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
10  * See the COPYING file in the top-level directory.
11  */
12 
13 #include "qemu/osdep.h"
14 #include "qemu/main-loop.h"
15 #include "qapi/qapi-commands-migration.h"
16 #include "qobject/qdict.h"
17 #include "qapi/error.h"
18 #include "system/dirtyrate.h"
19 #include "system/dirtylimit.h"
20 #include "monitor/hmp.h"
21 #include "monitor/monitor.h"
22 #include "system/memory.h"
23 #include "exec/target_page.h"
24 #include "hw/boards.h"
25 #include "system/kvm.h"
26 #include "trace.h"
27 #include "migration/misc.h"
28 
29 /*
30  * Dirtylimit stop working if dirty page rate error
31  * value less than DIRTYLIMIT_TOLERANCE_RANGE
32  */
33 #define DIRTYLIMIT_TOLERANCE_RANGE  25  /* MB/s */
34 /*
35  * Plus or minus vcpu sleep time linearly if dirty
36  * page rate error value percentage over
37  * DIRTYLIMIT_LINEAR_ADJUSTMENT_PCT.
38  * Otherwise, plus or minus a fixed vcpu sleep time.
39  */
40 #define DIRTYLIMIT_LINEAR_ADJUSTMENT_PCT     50
41 /*
42  * Max vcpu sleep time percentage during a cycle
43  * composed of dirty ring full and sleep time.
44  */
45 #define DIRTYLIMIT_THROTTLE_PCT_MAX 99
46 
47 struct {
48     VcpuStat stat;
49     bool running;
50     QemuThread thread;
51 } *vcpu_dirty_rate_stat;
52 
53 typedef struct VcpuDirtyLimitState {
54     int cpu_index;
55     bool enabled;
56     /*
57      * Quota dirty page rate, unit is MB/s
58      * zero if not enabled.
59      */
60     uint64_t quota;
61 } VcpuDirtyLimitState;
62 
63 struct {
64     VcpuDirtyLimitState *states;
65     /* Max cpus number configured by user */
66     int max_cpus;
67     /* Number of vcpu under dirtylimit */
68     int limited_nvcpu;
69 } *dirtylimit_state;
70 
71 /* protect dirtylimit_state */
72 static QemuMutex dirtylimit_mutex;
73 
74 /* dirtylimit thread quit if dirtylimit_quit is true */
75 static bool dirtylimit_quit;
76 
77 static void vcpu_dirty_rate_stat_collect(void)
78 {
79     VcpuStat stat;
80     int i = 0;
81     int64_t period = DIRTYLIMIT_CALC_TIME_MS;
82 
83     if (migrate_dirty_limit() && migration_is_running()) {
84         period = migrate_vcpu_dirty_limit_period();
85     }
86 
87     /* calculate vcpu dirtyrate */
88     vcpu_calculate_dirtyrate(period,
89                               &stat,
90                               GLOBAL_DIRTY_LIMIT,
91                               false);
92 
93     for (i = 0; i < stat.nvcpu; i++) {
94         vcpu_dirty_rate_stat->stat.rates[i].id = i;
95         vcpu_dirty_rate_stat->stat.rates[i].dirty_rate =
96             stat.rates[i].dirty_rate;
97     }
98 
99     g_free(stat.rates);
100 }
101 
102 static void *vcpu_dirty_rate_stat_thread(void *opaque)
103 {
104     rcu_register_thread();
105 
106     /* start log sync */
107     global_dirty_log_change(GLOBAL_DIRTY_LIMIT, true);
108 
109     while (qatomic_read(&vcpu_dirty_rate_stat->running)) {
110         vcpu_dirty_rate_stat_collect();
111         if (dirtylimit_in_service()) {
112             dirtylimit_process();
113         }
114     }
115 
116     /* stop log sync */
117     global_dirty_log_change(GLOBAL_DIRTY_LIMIT, false);
118 
119     rcu_unregister_thread();
120     return NULL;
121 }
122 
123 int64_t vcpu_dirty_rate_get(int cpu_index)
124 {
125     DirtyRateVcpu *rates = vcpu_dirty_rate_stat->stat.rates;
126     return qatomic_read_i64(&rates[cpu_index].dirty_rate);
127 }
128 
129 void vcpu_dirty_rate_stat_start(void)
130 {
131     if (qatomic_read(&vcpu_dirty_rate_stat->running)) {
132         return;
133     }
134 
135     qatomic_set(&vcpu_dirty_rate_stat->running, 1);
136     qemu_thread_create(&vcpu_dirty_rate_stat->thread,
137                        "dirtyrate-stat",
138                        vcpu_dirty_rate_stat_thread,
139                        NULL,
140                        QEMU_THREAD_JOINABLE);
141 }
142 
143 void vcpu_dirty_rate_stat_stop(void)
144 {
145     qatomic_set(&vcpu_dirty_rate_stat->running, 0);
146     dirtylimit_state_unlock();
147     bql_unlock();
148     qemu_thread_join(&vcpu_dirty_rate_stat->thread);
149     bql_lock();
150     dirtylimit_state_lock();
151 }
152 
153 void vcpu_dirty_rate_stat_initialize(void)
154 {
155     MachineState *ms = MACHINE(qdev_get_machine());
156     int max_cpus = ms->smp.max_cpus;
157 
158     vcpu_dirty_rate_stat =
159         g_malloc0(sizeof(*vcpu_dirty_rate_stat));
160 
161     vcpu_dirty_rate_stat->stat.nvcpu = max_cpus;
162     vcpu_dirty_rate_stat->stat.rates =
163         g_new0(DirtyRateVcpu, max_cpus);
164 
165     vcpu_dirty_rate_stat->running = false;
166 }
167 
168 void vcpu_dirty_rate_stat_finalize(void)
169 {
170     g_free(vcpu_dirty_rate_stat->stat.rates);
171     vcpu_dirty_rate_stat->stat.rates = NULL;
172 
173     g_free(vcpu_dirty_rate_stat);
174     vcpu_dirty_rate_stat = NULL;
175 }
176 
177 void dirtylimit_state_lock(void)
178 {
179     qemu_mutex_lock(&dirtylimit_mutex);
180 }
181 
182 void dirtylimit_state_unlock(void)
183 {
184     qemu_mutex_unlock(&dirtylimit_mutex);
185 }
186 
187 static void
188 __attribute__((__constructor__)) dirtylimit_mutex_init(void)
189 {
190     qemu_mutex_init(&dirtylimit_mutex);
191 }
192 
193 static inline VcpuDirtyLimitState *dirtylimit_vcpu_get_state(int cpu_index)
194 {
195     return &dirtylimit_state->states[cpu_index];
196 }
197 
198 void dirtylimit_state_initialize(void)
199 {
200     MachineState *ms = MACHINE(qdev_get_machine());
201     int max_cpus = ms->smp.max_cpus;
202     int i;
203 
204     dirtylimit_state = g_malloc0(sizeof(*dirtylimit_state));
205 
206     dirtylimit_state->states =
207             g_new0(VcpuDirtyLimitState, max_cpus);
208 
209     for (i = 0; i < max_cpus; i++) {
210         dirtylimit_state->states[i].cpu_index = i;
211     }
212 
213     dirtylimit_state->max_cpus = max_cpus;
214     trace_dirtylimit_state_initialize(max_cpus);
215 }
216 
217 void dirtylimit_state_finalize(void)
218 {
219     g_free(dirtylimit_state->states);
220     dirtylimit_state->states = NULL;
221 
222     g_free(dirtylimit_state);
223     dirtylimit_state = NULL;
224 
225     trace_dirtylimit_state_finalize();
226 }
227 
228 bool dirtylimit_in_service(void)
229 {
230     return !!dirtylimit_state;
231 }
232 
233 bool dirtylimit_vcpu_index_valid(int cpu_index)
234 {
235     MachineState *ms = MACHINE(qdev_get_machine());
236 
237     return !(cpu_index < 0 ||
238              cpu_index >= ms->smp.max_cpus);
239 }
240 
241 static uint64_t dirtylimit_dirty_ring_full_time(uint64_t dirtyrate)
242 {
243     static uint64_t max_dirtyrate;
244     uint64_t dirty_ring_size_MiB;
245 
246     dirty_ring_size_MiB = qemu_target_pages_to_MiB(kvm_dirty_ring_size());
247 
248     if (max_dirtyrate < dirtyrate) {
249         max_dirtyrate = dirtyrate;
250     }
251 
252     return dirty_ring_size_MiB * 1000000 / max_dirtyrate;
253 }
254 
255 static inline bool dirtylimit_done(uint64_t quota,
256                                    uint64_t current)
257 {
258     uint64_t min, max;
259 
260     min = MIN(quota, current);
261     max = MAX(quota, current);
262 
263     return ((max - min) <= DIRTYLIMIT_TOLERANCE_RANGE) ? true : false;
264 }
265 
266 static inline bool
267 dirtylimit_need_linear_adjustment(uint64_t quota,
268                                   uint64_t current)
269 {
270     uint64_t min, max;
271 
272     min = MIN(quota, current);
273     max = MAX(quota, current);
274 
275     return ((max - min) * 100 / max) > DIRTYLIMIT_LINEAR_ADJUSTMENT_PCT;
276 }
277 
278 static void dirtylimit_set_throttle(CPUState *cpu,
279                                     uint64_t quota,
280                                     uint64_t current)
281 {
282     int64_t ring_full_time_us = 0;
283     uint64_t sleep_pct = 0;
284     uint64_t throttle_us = 0;
285 
286     if (current == 0) {
287         cpu->throttle_us_per_full = 0;
288         return;
289     }
290 
291     ring_full_time_us = dirtylimit_dirty_ring_full_time(current);
292 
293     if (dirtylimit_need_linear_adjustment(quota, current)) {
294         if (quota < current) {
295             sleep_pct = (current - quota) * 100 / current;
296             throttle_us =
297                 ring_full_time_us * sleep_pct / (double)(100 - sleep_pct);
298             cpu->throttle_us_per_full += throttle_us;
299         } else {
300             sleep_pct = (quota - current) * 100 / quota;
301             throttle_us =
302                 ring_full_time_us * sleep_pct / (double)(100 - sleep_pct);
303             cpu->throttle_us_per_full -= throttle_us;
304         }
305 
306         trace_dirtylimit_throttle_pct(cpu->cpu_index,
307                                       sleep_pct,
308                                       throttle_us);
309     } else {
310         if (quota < current) {
311             cpu->throttle_us_per_full += ring_full_time_us / 10;
312         } else {
313             cpu->throttle_us_per_full -= ring_full_time_us / 10;
314         }
315     }
316 
317     /*
318      * TODO: in the big kvm_dirty_ring_size case (eg: 65536, or other scenario),
319      *       current dirty page rate may never reach the quota, we should stop
320      *       increasing sleep time?
321      */
322     cpu->throttle_us_per_full = MIN(cpu->throttle_us_per_full,
323         ring_full_time_us * DIRTYLIMIT_THROTTLE_PCT_MAX);
324 
325     cpu->throttle_us_per_full = MAX(cpu->throttle_us_per_full, 0);
326 }
327 
328 static void dirtylimit_adjust_throttle(CPUState *cpu)
329 {
330     uint64_t quota = 0;
331     uint64_t current = 0;
332     int cpu_index = cpu->cpu_index;
333 
334     quota = dirtylimit_vcpu_get_state(cpu_index)->quota;
335     current = vcpu_dirty_rate_get(cpu_index);
336 
337     if (!dirtylimit_done(quota, current)) {
338         dirtylimit_set_throttle(cpu, quota, current);
339     }
340 }
341 
342 void dirtylimit_process(void)
343 {
344     CPUState *cpu;
345 
346     if (!qatomic_read(&dirtylimit_quit)) {
347         dirtylimit_state_lock();
348 
349         if (!dirtylimit_in_service()) {
350             dirtylimit_state_unlock();
351             return;
352         }
353 
354         CPU_FOREACH(cpu) {
355             if (!dirtylimit_vcpu_get_state(cpu->cpu_index)->enabled) {
356                 continue;
357             }
358             dirtylimit_adjust_throttle(cpu);
359         }
360         dirtylimit_state_unlock();
361     }
362 }
363 
364 void dirtylimit_change(bool start)
365 {
366     if (start) {
367         qatomic_set(&dirtylimit_quit, 0);
368     } else {
369         qatomic_set(&dirtylimit_quit, 1);
370     }
371 }
372 
373 void dirtylimit_set_vcpu(int cpu_index,
374                          uint64_t quota,
375                          bool enable)
376 {
377     trace_dirtylimit_set_vcpu(cpu_index, quota);
378 
379     if (enable) {
380         dirtylimit_state->states[cpu_index].quota = quota;
381         if (!dirtylimit_vcpu_get_state(cpu_index)->enabled) {
382             dirtylimit_state->limited_nvcpu++;
383         }
384     } else {
385         dirtylimit_state->states[cpu_index].quota = 0;
386         if (dirtylimit_state->states[cpu_index].enabled) {
387             dirtylimit_state->limited_nvcpu--;
388         }
389     }
390 
391     dirtylimit_state->states[cpu_index].enabled = enable;
392 }
393 
394 void dirtylimit_set_all(uint64_t quota,
395                         bool enable)
396 {
397     MachineState *ms = MACHINE(qdev_get_machine());
398     int max_cpus = ms->smp.max_cpus;
399     int i;
400 
401     for (i = 0; i < max_cpus; i++) {
402         dirtylimit_set_vcpu(i, quota, enable);
403     }
404 }
405 
406 void dirtylimit_vcpu_execute(CPUState *cpu)
407 {
408     if (cpu->throttle_us_per_full) {
409         dirtylimit_state_lock();
410 
411         if (dirtylimit_in_service() &&
412             dirtylimit_vcpu_get_state(cpu->cpu_index)->enabled) {
413             dirtylimit_state_unlock();
414             trace_dirtylimit_vcpu_execute(cpu->cpu_index,
415                     cpu->throttle_us_per_full);
416 
417             g_usleep(cpu->throttle_us_per_full);
418             return;
419         }
420 
421         dirtylimit_state_unlock();
422     }
423 }
424 
425 static void dirtylimit_init(void)
426 {
427     dirtylimit_state_initialize();
428     dirtylimit_change(true);
429     vcpu_dirty_rate_stat_initialize();
430     vcpu_dirty_rate_stat_start();
431 }
432 
433 static void dirtylimit_cleanup(void)
434 {
435     vcpu_dirty_rate_stat_stop();
436     vcpu_dirty_rate_stat_finalize();
437     dirtylimit_change(false);
438     dirtylimit_state_finalize();
439 }
440 
441 /*
442  * dirty page rate limit is not allowed to set if migration
443  * is running with dirty-limit capability enabled.
444  */
445 static bool dirtylimit_is_allowed(void)
446 {
447     if (migration_is_running() &&
448         !migration_thread_is_self() &&
449         migrate_dirty_limit() &&
450         dirtylimit_in_service()) {
451         return false;
452     }
453     return true;
454 }
455 
456 void qmp_cancel_vcpu_dirty_limit(bool has_cpu_index,
457                                  int64_t cpu_index,
458                                  Error **errp)
459 {
460     if (!kvm_enabled() || !kvm_dirty_ring_enabled()) {
461         return;
462     }
463 
464     if (has_cpu_index && !dirtylimit_vcpu_index_valid(cpu_index)) {
465         error_setg(errp, "incorrect cpu index specified");
466         return;
467     }
468 
469     if (!dirtylimit_is_allowed()) {
470         error_setg(errp, "can't cancel dirty page rate limit while"
471                    " migration is running");
472         return;
473     }
474 
475     if (!dirtylimit_in_service()) {
476         return;
477     }
478 
479     dirtylimit_state_lock();
480 
481     if (has_cpu_index) {
482         dirtylimit_set_vcpu(cpu_index, 0, false);
483     } else {
484         dirtylimit_set_all(0, false);
485     }
486 
487     if (!dirtylimit_state->limited_nvcpu) {
488         dirtylimit_cleanup();
489     }
490 
491     dirtylimit_state_unlock();
492 }
493 
494 void hmp_cancel_vcpu_dirty_limit(Monitor *mon, const QDict *qdict)
495 {
496     int64_t cpu_index = qdict_get_try_int(qdict, "cpu_index", -1);
497     Error *err = NULL;
498 
499     qmp_cancel_vcpu_dirty_limit(!!(cpu_index != -1), cpu_index, &err);
500     if (err) {
501         hmp_handle_error(mon, err);
502         return;
503     }
504 
505     monitor_printf(mon, "[Please use 'info vcpu_dirty_limit' to query "
506                    "dirty limit for virtual CPU]\n");
507 }
508 
509 void qmp_set_vcpu_dirty_limit(bool has_cpu_index,
510                               int64_t cpu_index,
511                               uint64_t dirty_rate,
512                               Error **errp)
513 {
514     if (!kvm_enabled() || !kvm_dirty_ring_enabled()) {
515         error_setg(errp, "dirty page limit feature requires KVM with"
516                    " accelerator property 'dirty-ring-size' set'");
517         return;
518     }
519 
520     if (has_cpu_index && !dirtylimit_vcpu_index_valid(cpu_index)) {
521         error_setg(errp, "incorrect cpu index specified");
522         return;
523     }
524 
525     if (!dirtylimit_is_allowed()) {
526         error_setg(errp, "can't set dirty page rate limit while"
527                    " migration is running");
528         return;
529     }
530 
531     if (!dirty_rate) {
532         qmp_cancel_vcpu_dirty_limit(has_cpu_index, cpu_index, errp);
533         return;
534     }
535 
536     dirtylimit_state_lock();
537 
538     if (!dirtylimit_in_service()) {
539         dirtylimit_init();
540     }
541 
542     if (has_cpu_index) {
543         dirtylimit_set_vcpu(cpu_index, dirty_rate, true);
544     } else {
545         dirtylimit_set_all(dirty_rate, true);
546     }
547 
548     dirtylimit_state_unlock();
549 }
550 
551 void hmp_set_vcpu_dirty_limit(Monitor *mon, const QDict *qdict)
552 {
553     int64_t dirty_rate = qdict_get_int(qdict, "dirty_rate");
554     int64_t cpu_index = qdict_get_try_int(qdict, "cpu_index", -1);
555     Error *err = NULL;
556 
557     if (dirty_rate < 0) {
558         error_setg(&err, "invalid dirty page limit %" PRId64, dirty_rate);
559         goto out;
560     }
561 
562     qmp_set_vcpu_dirty_limit(!!(cpu_index != -1), cpu_index, dirty_rate, &err);
563 
564 out:
565     hmp_handle_error(mon, err);
566 }
567 
568 /* Return the max throttle time of each virtual CPU */
569 uint64_t dirtylimit_throttle_time_per_round(void)
570 {
571     CPUState *cpu;
572     int64_t max = 0;
573 
574     CPU_FOREACH(cpu) {
575         if (cpu->throttle_us_per_full > max) {
576             max = cpu->throttle_us_per_full;
577         }
578     }
579 
580     return max;
581 }
582 
583 /*
584  * Estimate average dirty ring full time of each virtaul CPU.
585  * Return 0 if guest doesn't dirty memory.
586  */
587 uint64_t dirtylimit_ring_full_time(void)
588 {
589     CPUState *cpu;
590     uint64_t curr_rate = 0;
591     int nvcpus = 0;
592 
593     CPU_FOREACH(cpu) {
594         if (cpu->running) {
595             nvcpus++;
596             curr_rate += vcpu_dirty_rate_get(cpu->cpu_index);
597         }
598     }
599 
600     if (!curr_rate || !nvcpus) {
601         return 0;
602     }
603 
604     return dirtylimit_dirty_ring_full_time(curr_rate / nvcpus);
605 }
606 
607 static struct DirtyLimitInfo *dirtylimit_query_vcpu(int cpu_index)
608 {
609     DirtyLimitInfo *info = NULL;
610 
611     info = g_malloc0(sizeof(*info));
612     info->cpu_index = cpu_index;
613     info->limit_rate = dirtylimit_vcpu_get_state(cpu_index)->quota;
614     info->current_rate = vcpu_dirty_rate_get(cpu_index);
615 
616     return info;
617 }
618 
619 static struct DirtyLimitInfoList *dirtylimit_query_all(void)
620 {
621     int i, index;
622     DirtyLimitInfo *info = NULL;
623     DirtyLimitInfoList *head = NULL, **tail = &head;
624 
625     dirtylimit_state_lock();
626 
627     if (!dirtylimit_in_service()) {
628         dirtylimit_state_unlock();
629         return NULL;
630     }
631 
632     for (i = 0; i < dirtylimit_state->max_cpus; i++) {
633         index = dirtylimit_state->states[i].cpu_index;
634         if (dirtylimit_vcpu_get_state(index)->enabled) {
635             info = dirtylimit_query_vcpu(index);
636             QAPI_LIST_APPEND(tail, info);
637         }
638     }
639 
640     dirtylimit_state_unlock();
641 
642     return head;
643 }
644 
645 struct DirtyLimitInfoList *qmp_query_vcpu_dirty_limit(Error **errp)
646 {
647     return dirtylimit_query_all();
648 }
649 
650 void hmp_info_vcpu_dirty_limit(Monitor *mon, const QDict *qdict)
651 {
652     DirtyLimitInfoList *info;
653     g_autoptr(DirtyLimitInfoList) head = NULL;
654     Error *err = NULL;
655 
656     if (!dirtylimit_in_service()) {
657         monitor_printf(mon, "Dirty page limit not enabled!\n");
658         return;
659     }
660 
661     head = qmp_query_vcpu_dirty_limit(&err);
662     if (err) {
663         hmp_handle_error(mon, err);
664         return;
665     }
666 
667     for (info = head; info != NULL; info = info->next) {
668         monitor_printf(mon, "vcpu[%"PRIi64"], limit rate %"PRIi64 " (MB/s),"
669                             " current rate %"PRIi64 " (MB/s)\n",
670                             info->value->cpu_index,
671                             info->value->limit_rate,
672                             info->value->current_rate);
673     }
674 }
675