xref: /openbmc/qemu/migration/dirtyrate.c (revision 1af0006a)
1 /*
2  * Dirtyrate implement code
3  *
4  * Copyright (c) 2020 HUAWEI TECHNOLOGIES CO.,LTD.
5  *
6  * Authors:
7  *  Chuan Zheng <zhengchuan@huawei.com>
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 <zlib.h>
15 #include "qapi/error.h"
16 #include "cpu.h"
17 #include "exec/ramblock.h"
18 #include "exec/ram_addr.h"
19 #include "qemu/rcu_queue.h"
20 #include "qemu/main-loop.h"
21 #include "qapi/qapi-commands-migration.h"
22 #include "ram.h"
23 #include "trace.h"
24 #include "dirtyrate.h"
25 #include "monitor/hmp.h"
26 #include "monitor/monitor.h"
27 #include "qapi/qmp/qdict.h"
28 #include "sysemu/kvm.h"
29 #include "sysemu/runstate.h"
30 #include "exec/memory.h"
31 
32 /*
33  * total_dirty_pages is procted by BQL and is used
34  * to stat dirty pages during the period of two
35  * memory_global_dirty_log_sync
36  */
37 uint64_t total_dirty_pages;
38 
39 typedef struct DirtyPageRecord {
40     uint64_t start_pages;
41     uint64_t end_pages;
42 } DirtyPageRecord;
43 
44 static int CalculatingState = DIRTY_RATE_STATUS_UNSTARTED;
45 static struct DirtyRateStat DirtyStat;
46 static DirtyRateMeasureMode dirtyrate_mode =
47                 DIRTY_RATE_MEASURE_MODE_PAGE_SAMPLING;
48 
49 static int64_t dirty_stat_wait(int64_t msec, int64_t initial_time)
50 {
51     int64_t current_time;
52 
53     current_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
54     if ((current_time - initial_time) >= msec) {
55         msec = current_time - initial_time;
56     } else {
57         g_usleep((msec + initial_time - current_time) * 1000);
58     }
59 
60     return msec;
61 }
62 
63 static inline void record_dirtypages(DirtyPageRecord *dirty_pages,
64                                      CPUState *cpu, bool start)
65 {
66     if (start) {
67         dirty_pages[cpu->cpu_index].start_pages = cpu->dirty_pages;
68     } else {
69         dirty_pages[cpu->cpu_index].end_pages = cpu->dirty_pages;
70     }
71 }
72 
73 static int64_t do_calculate_dirtyrate(DirtyPageRecord dirty_pages,
74                                       int64_t calc_time_ms)
75 {
76     uint64_t memory_size_MB;
77     uint64_t increased_dirty_pages =
78         dirty_pages.end_pages - dirty_pages.start_pages;
79 
80     memory_size_MB = (increased_dirty_pages * TARGET_PAGE_SIZE) >> 20;
81 
82     return memory_size_MB * 1000 / calc_time_ms;
83 }
84 
85 void global_dirty_log_change(unsigned int flag, bool start)
86 {
87     qemu_mutex_lock_iothread();
88     if (start) {
89         memory_global_dirty_log_start(flag);
90     } else {
91         memory_global_dirty_log_stop(flag);
92     }
93     qemu_mutex_unlock_iothread();
94 }
95 
96 /*
97  * global_dirty_log_sync
98  * 1. sync dirty log from kvm
99  * 2. stop dirty tracking if needed.
100  */
101 static void global_dirty_log_sync(unsigned int flag, bool one_shot)
102 {
103     qemu_mutex_lock_iothread();
104     memory_global_dirty_log_sync();
105     if (one_shot) {
106         memory_global_dirty_log_stop(flag);
107     }
108     qemu_mutex_unlock_iothread();
109 }
110 
111 static DirtyPageRecord *vcpu_dirty_stat_alloc(VcpuStat *stat)
112 {
113     CPUState *cpu;
114     DirtyPageRecord *records;
115     int nvcpu = 0;
116 
117     CPU_FOREACH(cpu) {
118         nvcpu++;
119     }
120 
121     stat->nvcpu = nvcpu;
122     stat->rates = g_new0(DirtyRateVcpu, nvcpu);
123 
124     records = g_new0(DirtyPageRecord, nvcpu);
125 
126     return records;
127 }
128 
129 static void vcpu_dirty_stat_collect(VcpuStat *stat,
130                                     DirtyPageRecord *records,
131                                     bool start)
132 {
133     CPUState *cpu;
134 
135     CPU_FOREACH(cpu) {
136         record_dirtypages(records, cpu, start);
137     }
138 }
139 
140 int64_t vcpu_calculate_dirtyrate(int64_t calc_time_ms,
141                                  VcpuStat *stat,
142                                  unsigned int flag,
143                                  bool one_shot)
144 {
145     DirtyPageRecord *records;
146     int64_t init_time_ms;
147     int64_t duration;
148     int64_t dirtyrate;
149     int i = 0;
150     unsigned int gen_id;
151 
152 retry:
153     init_time_ms = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
154 
155     cpu_list_lock();
156     gen_id = cpu_list_generation_id_get();
157     records = vcpu_dirty_stat_alloc(stat);
158     vcpu_dirty_stat_collect(stat, records, true);
159     cpu_list_unlock();
160 
161     duration = dirty_stat_wait(calc_time_ms, init_time_ms);
162 
163     global_dirty_log_sync(flag, one_shot);
164 
165     cpu_list_lock();
166     if (gen_id != cpu_list_generation_id_get()) {
167         g_free(records);
168         g_free(stat->rates);
169         cpu_list_unlock();
170         goto retry;
171     }
172     vcpu_dirty_stat_collect(stat, records, false);
173     cpu_list_unlock();
174 
175     for (i = 0; i < stat->nvcpu; i++) {
176         dirtyrate = do_calculate_dirtyrate(records[i], duration);
177 
178         stat->rates[i].id = i;
179         stat->rates[i].dirty_rate = dirtyrate;
180 
181         trace_dirtyrate_do_calculate_vcpu(i, dirtyrate);
182     }
183 
184     g_free(records);
185 
186     return duration;
187 }
188 
189 static bool is_sample_period_valid(int64_t sec)
190 {
191     if (sec < MIN_FETCH_DIRTYRATE_TIME_SEC ||
192         sec > MAX_FETCH_DIRTYRATE_TIME_SEC) {
193         return false;
194     }
195 
196     return true;
197 }
198 
199 static bool is_sample_pages_valid(int64_t pages)
200 {
201     return pages >= MIN_SAMPLE_PAGE_COUNT &&
202            pages <= MAX_SAMPLE_PAGE_COUNT;
203 }
204 
205 static int dirtyrate_set_state(int *state, int old_state, int new_state)
206 {
207     assert(new_state < DIRTY_RATE_STATUS__MAX);
208     trace_dirtyrate_set_state(DirtyRateStatus_str(new_state));
209     if (qatomic_cmpxchg(state, old_state, new_state) == old_state) {
210         return 0;
211     } else {
212         return -1;
213     }
214 }
215 
216 static struct DirtyRateInfo *query_dirty_rate_info(void)
217 {
218     int i;
219     int64_t dirty_rate = DirtyStat.dirty_rate;
220     struct DirtyRateInfo *info = g_new0(DirtyRateInfo, 1);
221     DirtyRateVcpuList *head = NULL, **tail = &head;
222 
223     info->status = CalculatingState;
224     info->start_time = DirtyStat.start_time;
225     info->calc_time = DirtyStat.calc_time;
226     info->sample_pages = DirtyStat.sample_pages;
227     info->mode = dirtyrate_mode;
228 
229     if (qatomic_read(&CalculatingState) == DIRTY_RATE_STATUS_MEASURED) {
230         info->has_dirty_rate = true;
231         info->dirty_rate = dirty_rate;
232 
233         if (dirtyrate_mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) {
234             /*
235              * set sample_pages with 0 to indicate page sampling
236              * isn't enabled
237              **/
238             info->sample_pages = 0;
239             info->has_vcpu_dirty_rate = true;
240             for (i = 0; i < DirtyStat.dirty_ring.nvcpu; i++) {
241                 DirtyRateVcpu *rate = g_new0(DirtyRateVcpu, 1);
242                 rate->id = DirtyStat.dirty_ring.rates[i].id;
243                 rate->dirty_rate = DirtyStat.dirty_ring.rates[i].dirty_rate;
244                 QAPI_LIST_APPEND(tail, rate);
245             }
246             info->vcpu_dirty_rate = head;
247         }
248 
249         if (dirtyrate_mode == DIRTY_RATE_MEASURE_MODE_DIRTY_BITMAP) {
250             info->sample_pages = 0;
251         }
252     }
253 
254     trace_query_dirty_rate_info(DirtyRateStatus_str(CalculatingState));
255 
256     return info;
257 }
258 
259 static void init_dirtyrate_stat(int64_t start_time,
260                                 struct DirtyRateConfig config)
261 {
262     DirtyStat.dirty_rate = -1;
263     DirtyStat.start_time = start_time;
264     DirtyStat.calc_time = config.sample_period_seconds;
265     DirtyStat.sample_pages = config.sample_pages_per_gigabytes;
266 
267     switch (config.mode) {
268     case DIRTY_RATE_MEASURE_MODE_PAGE_SAMPLING:
269         DirtyStat.page_sampling.total_dirty_samples = 0;
270         DirtyStat.page_sampling.total_sample_count = 0;
271         DirtyStat.page_sampling.total_block_mem_MB = 0;
272         break;
273     case DIRTY_RATE_MEASURE_MODE_DIRTY_RING:
274         DirtyStat.dirty_ring.nvcpu = -1;
275         DirtyStat.dirty_ring.rates = NULL;
276         break;
277     default:
278         break;
279     }
280 }
281 
282 static void cleanup_dirtyrate_stat(struct DirtyRateConfig config)
283 {
284     /* last calc-dirty-rate qmp use dirty ring mode */
285     if (dirtyrate_mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) {
286         free(DirtyStat.dirty_ring.rates);
287         DirtyStat.dirty_ring.rates = NULL;
288     }
289 }
290 
291 static void update_dirtyrate_stat(struct RamblockDirtyInfo *info)
292 {
293     DirtyStat.page_sampling.total_dirty_samples += info->sample_dirty_count;
294     DirtyStat.page_sampling.total_sample_count += info->sample_pages_count;
295     /* size of total pages in MB */
296     DirtyStat.page_sampling.total_block_mem_MB += (info->ramblock_pages *
297                                                    TARGET_PAGE_SIZE) >> 20;
298 }
299 
300 static void update_dirtyrate(uint64_t msec)
301 {
302     uint64_t dirtyrate;
303     uint64_t total_dirty_samples = DirtyStat.page_sampling.total_dirty_samples;
304     uint64_t total_sample_count = DirtyStat.page_sampling.total_sample_count;
305     uint64_t total_block_mem_MB = DirtyStat.page_sampling.total_block_mem_MB;
306 
307     dirtyrate = total_dirty_samples * total_block_mem_MB *
308                 1000 / (total_sample_count * msec);
309 
310     DirtyStat.dirty_rate = dirtyrate;
311 }
312 
313 /*
314  * get hash result for the sampled memory with length of TARGET_PAGE_SIZE
315  * in ramblock, which starts from ramblock base address.
316  */
317 static uint32_t get_ramblock_vfn_hash(struct RamblockDirtyInfo *info,
318                                       uint64_t vfn)
319 {
320     uint32_t crc;
321 
322     crc = crc32(0, (info->ramblock_addr +
323                 vfn * TARGET_PAGE_SIZE), TARGET_PAGE_SIZE);
324 
325     trace_get_ramblock_vfn_hash(info->idstr, vfn, crc);
326     return crc;
327 }
328 
329 static bool save_ramblock_hash(struct RamblockDirtyInfo *info)
330 {
331     unsigned int sample_pages_count;
332     int i;
333     GRand *rand;
334 
335     sample_pages_count = info->sample_pages_count;
336 
337     /* ramblock size less than one page, return success to skip this ramblock */
338     if (unlikely(info->ramblock_pages == 0 || sample_pages_count == 0)) {
339         return true;
340     }
341 
342     info->hash_result = g_try_malloc0_n(sample_pages_count,
343                                         sizeof(uint32_t));
344     if (!info->hash_result) {
345         return false;
346     }
347 
348     info->sample_page_vfn = g_try_malloc0_n(sample_pages_count,
349                                             sizeof(uint64_t));
350     if (!info->sample_page_vfn) {
351         g_free(info->hash_result);
352         return false;
353     }
354 
355     rand  = g_rand_new();
356     for (i = 0; i < sample_pages_count; i++) {
357         info->sample_page_vfn[i] = g_rand_int_range(rand, 0,
358                                                     info->ramblock_pages - 1);
359         info->hash_result[i] = get_ramblock_vfn_hash(info,
360                                                      info->sample_page_vfn[i]);
361     }
362     g_rand_free(rand);
363 
364     return true;
365 }
366 
367 static void get_ramblock_dirty_info(RAMBlock *block,
368                                     struct RamblockDirtyInfo *info,
369                                     struct DirtyRateConfig *config)
370 {
371     uint64_t sample_pages_per_gigabytes = config->sample_pages_per_gigabytes;
372 
373     /* Right shift 30 bits to calc ramblock size in GB */
374     info->sample_pages_count = (qemu_ram_get_used_length(block) *
375                                 sample_pages_per_gigabytes) >> 30;
376     /* Right shift TARGET_PAGE_BITS to calc page count */
377     info->ramblock_pages = qemu_ram_get_used_length(block) >>
378                            TARGET_PAGE_BITS;
379     info->ramblock_addr = qemu_ram_get_host_addr(block);
380     strcpy(info->idstr, qemu_ram_get_idstr(block));
381 }
382 
383 static void free_ramblock_dirty_info(struct RamblockDirtyInfo *infos, int count)
384 {
385     int i;
386 
387     if (!infos) {
388         return;
389     }
390 
391     for (i = 0; i < count; i++) {
392         g_free(infos[i].sample_page_vfn);
393         g_free(infos[i].hash_result);
394     }
395     g_free(infos);
396 }
397 
398 static bool skip_sample_ramblock(RAMBlock *block)
399 {
400     /*
401      * Sample only blocks larger than MIN_RAMBLOCK_SIZE.
402      */
403     if (qemu_ram_get_used_length(block) < (MIN_RAMBLOCK_SIZE << 10)) {
404         trace_skip_sample_ramblock(block->idstr,
405                                    qemu_ram_get_used_length(block));
406         return true;
407     }
408 
409     return false;
410 }
411 
412 static bool record_ramblock_hash_info(struct RamblockDirtyInfo **block_dinfo,
413                                       struct DirtyRateConfig config,
414                                       int *block_count)
415 {
416     struct RamblockDirtyInfo *info = NULL;
417     struct RamblockDirtyInfo *dinfo = NULL;
418     RAMBlock *block = NULL;
419     int total_count = 0;
420     int index = 0;
421     bool ret = false;
422 
423     RAMBLOCK_FOREACH_MIGRATABLE(block) {
424         if (skip_sample_ramblock(block)) {
425             continue;
426         }
427         total_count++;
428     }
429 
430     dinfo = g_try_malloc0_n(total_count, sizeof(struct RamblockDirtyInfo));
431     if (dinfo == NULL) {
432         goto out;
433     }
434 
435     RAMBLOCK_FOREACH_MIGRATABLE(block) {
436         if (skip_sample_ramblock(block)) {
437             continue;
438         }
439         if (index >= total_count) {
440             break;
441         }
442         info = &dinfo[index];
443         get_ramblock_dirty_info(block, info, &config);
444         if (!save_ramblock_hash(info)) {
445             goto out;
446         }
447         index++;
448     }
449     ret = true;
450 
451 out:
452     *block_count = index;
453     *block_dinfo = dinfo;
454     return ret;
455 }
456 
457 static void calc_page_dirty_rate(struct RamblockDirtyInfo *info)
458 {
459     uint32_t crc;
460     int i;
461 
462     for (i = 0; i < info->sample_pages_count; i++) {
463         crc = get_ramblock_vfn_hash(info, info->sample_page_vfn[i]);
464         if (crc != info->hash_result[i]) {
465             trace_calc_page_dirty_rate(info->idstr, crc, info->hash_result[i]);
466             info->sample_dirty_count++;
467         }
468     }
469 }
470 
471 static struct RamblockDirtyInfo *
472 find_block_matched(RAMBlock *block, int count,
473                   struct RamblockDirtyInfo *infos)
474 {
475     int i;
476     struct RamblockDirtyInfo *matched;
477 
478     for (i = 0; i < count; i++) {
479         if (!strcmp(infos[i].idstr, qemu_ram_get_idstr(block))) {
480             break;
481         }
482     }
483 
484     if (i == count) {
485         return NULL;
486     }
487 
488     if (infos[i].ramblock_addr != qemu_ram_get_host_addr(block) ||
489         infos[i].ramblock_pages !=
490             (qemu_ram_get_used_length(block) >> TARGET_PAGE_BITS)) {
491         trace_find_page_matched(block->idstr);
492         return NULL;
493     }
494 
495     matched = &infos[i];
496 
497     return matched;
498 }
499 
500 static bool compare_page_hash_info(struct RamblockDirtyInfo *info,
501                                   int block_count)
502 {
503     struct RamblockDirtyInfo *block_dinfo = NULL;
504     RAMBlock *block = NULL;
505 
506     RAMBLOCK_FOREACH_MIGRATABLE(block) {
507         if (skip_sample_ramblock(block)) {
508             continue;
509         }
510         block_dinfo = find_block_matched(block, block_count, info);
511         if (block_dinfo == NULL) {
512             continue;
513         }
514         calc_page_dirty_rate(block_dinfo);
515         update_dirtyrate_stat(block_dinfo);
516     }
517 
518     if (DirtyStat.page_sampling.total_sample_count == 0) {
519         return false;
520     }
521 
522     return true;
523 }
524 
525 static inline void record_dirtypages_bitmap(DirtyPageRecord *dirty_pages,
526                                             bool start)
527 {
528     if (start) {
529         dirty_pages->start_pages = total_dirty_pages;
530     } else {
531         dirty_pages->end_pages = total_dirty_pages;
532     }
533 }
534 
535 static inline void dirtyrate_manual_reset_protect(void)
536 {
537     RAMBlock *block = NULL;
538 
539     WITH_RCU_READ_LOCK_GUARD() {
540         RAMBLOCK_FOREACH_MIGRATABLE(block) {
541             memory_region_clear_dirty_bitmap(block->mr, 0,
542                                              block->used_length);
543         }
544     }
545 }
546 
547 static void calculate_dirtyrate_dirty_bitmap(struct DirtyRateConfig config)
548 {
549     int64_t msec = 0;
550     int64_t start_time;
551     DirtyPageRecord dirty_pages;
552 
553     qemu_mutex_lock_iothread();
554     memory_global_dirty_log_start(GLOBAL_DIRTY_DIRTY_RATE);
555 
556     /*
557      * 1'round of log sync may return all 1 bits with
558      * KVM_DIRTY_LOG_INITIALLY_SET enable
559      * skip it unconditionally and start dirty tracking
560      * from 2'round of log sync
561      */
562     memory_global_dirty_log_sync();
563 
564     /*
565      * reset page protect manually and unconditionally.
566      * this make sure kvm dirty log be cleared if
567      * KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE cap is enabled.
568      */
569     dirtyrate_manual_reset_protect();
570     qemu_mutex_unlock_iothread();
571 
572     record_dirtypages_bitmap(&dirty_pages, true);
573 
574     start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
575     DirtyStat.start_time = start_time / 1000;
576 
577     msec = config.sample_period_seconds * 1000;
578     msec = dirty_stat_wait(msec, start_time);
579     DirtyStat.calc_time = msec / 1000;
580 
581     /*
582      * do two things.
583      * 1. fetch dirty bitmap from kvm
584      * 2. stop dirty tracking
585      */
586     global_dirty_log_sync(GLOBAL_DIRTY_DIRTY_RATE, true);
587 
588     record_dirtypages_bitmap(&dirty_pages, false);
589 
590     DirtyStat.dirty_rate = do_calculate_dirtyrate(dirty_pages, msec);
591 }
592 
593 static void calculate_dirtyrate_dirty_ring(struct DirtyRateConfig config)
594 {
595     int64_t duration;
596     uint64_t dirtyrate = 0;
597     uint64_t dirtyrate_sum = 0;
598     int i = 0;
599 
600     /* start log sync */
601     global_dirty_log_change(GLOBAL_DIRTY_DIRTY_RATE, true);
602 
603     DirtyStat.start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) / 1000;
604 
605     /* calculate vcpu dirtyrate */
606     duration = vcpu_calculate_dirtyrate(config.sample_period_seconds * 1000,
607                                         &DirtyStat.dirty_ring,
608                                         GLOBAL_DIRTY_DIRTY_RATE,
609                                         true);
610 
611     DirtyStat.calc_time = duration / 1000;
612 
613     /* calculate vm dirtyrate */
614     for (i = 0; i < DirtyStat.dirty_ring.nvcpu; i++) {
615         dirtyrate = DirtyStat.dirty_ring.rates[i].dirty_rate;
616         DirtyStat.dirty_ring.rates[i].dirty_rate = dirtyrate;
617         dirtyrate_sum += dirtyrate;
618     }
619 
620     DirtyStat.dirty_rate = dirtyrate_sum;
621 }
622 
623 static void calculate_dirtyrate_sample_vm(struct DirtyRateConfig config)
624 {
625     struct RamblockDirtyInfo *block_dinfo = NULL;
626     int block_count = 0;
627     int64_t msec = 0;
628     int64_t initial_time;
629 
630     rcu_read_lock();
631     initial_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
632     if (!record_ramblock_hash_info(&block_dinfo, config, &block_count)) {
633         goto out;
634     }
635     rcu_read_unlock();
636 
637     msec = config.sample_period_seconds * 1000;
638     msec = dirty_stat_wait(msec, initial_time);
639     DirtyStat.start_time = initial_time / 1000;
640     DirtyStat.calc_time = msec / 1000;
641 
642     rcu_read_lock();
643     if (!compare_page_hash_info(block_dinfo, block_count)) {
644         goto out;
645     }
646 
647     update_dirtyrate(msec);
648 
649 out:
650     rcu_read_unlock();
651     free_ramblock_dirty_info(block_dinfo, block_count);
652 }
653 
654 static void calculate_dirtyrate(struct DirtyRateConfig config)
655 {
656     if (config.mode == DIRTY_RATE_MEASURE_MODE_DIRTY_BITMAP) {
657         calculate_dirtyrate_dirty_bitmap(config);
658     } else if (config.mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) {
659         calculate_dirtyrate_dirty_ring(config);
660     } else {
661         calculate_dirtyrate_sample_vm(config);
662     }
663 
664     trace_dirtyrate_calculate(DirtyStat.dirty_rate);
665 }
666 
667 void *get_dirtyrate_thread(void *arg)
668 {
669     struct DirtyRateConfig config = *(struct DirtyRateConfig *)arg;
670     int ret;
671     rcu_register_thread();
672 
673     ret = dirtyrate_set_state(&CalculatingState, DIRTY_RATE_STATUS_UNSTARTED,
674                               DIRTY_RATE_STATUS_MEASURING);
675     if (ret == -1) {
676         error_report("change dirtyrate state failed.");
677         return NULL;
678     }
679 
680     calculate_dirtyrate(config);
681 
682     ret = dirtyrate_set_state(&CalculatingState, DIRTY_RATE_STATUS_MEASURING,
683                               DIRTY_RATE_STATUS_MEASURED);
684     if (ret == -1) {
685         error_report("change dirtyrate state failed.");
686     }
687 
688     rcu_unregister_thread();
689     return NULL;
690 }
691 
692 void qmp_calc_dirty_rate(int64_t calc_time,
693                          bool has_sample_pages,
694                          int64_t sample_pages,
695                          bool has_mode,
696                          DirtyRateMeasureMode mode,
697                          Error **errp)
698 {
699     static struct DirtyRateConfig config;
700     QemuThread thread;
701     int ret;
702     int64_t start_time;
703 
704     /*
705      * If the dirty rate is already being measured, don't attempt to start.
706      */
707     if (qatomic_read(&CalculatingState) == DIRTY_RATE_STATUS_MEASURING) {
708         error_setg(errp, "the dirty rate is already being measured.");
709         return;
710     }
711 
712     if (!is_sample_period_valid(calc_time)) {
713         error_setg(errp, "calc-time is out of range[%d, %d].",
714                          MIN_FETCH_DIRTYRATE_TIME_SEC,
715                          MAX_FETCH_DIRTYRATE_TIME_SEC);
716         return;
717     }
718 
719     if (!has_mode) {
720         mode =  DIRTY_RATE_MEASURE_MODE_PAGE_SAMPLING;
721     }
722 
723     if (has_sample_pages && mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) {
724         error_setg(errp, "either sample-pages or dirty-ring can be specified.");
725         return;
726     }
727 
728     if (has_sample_pages) {
729         if (!is_sample_pages_valid(sample_pages)) {
730             error_setg(errp, "sample-pages is out of range[%d, %d].",
731                             MIN_SAMPLE_PAGE_COUNT,
732                             MAX_SAMPLE_PAGE_COUNT);
733             return;
734         }
735     } else {
736         sample_pages = DIRTYRATE_DEFAULT_SAMPLE_PAGES;
737     }
738 
739     /*
740      * dirty ring mode only works when kvm dirty ring is enabled.
741      * on the contrary, dirty bitmap mode is not.
742      */
743     if (((mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) &&
744         !kvm_dirty_ring_enabled()) ||
745         ((mode == DIRTY_RATE_MEASURE_MODE_DIRTY_BITMAP) &&
746          kvm_dirty_ring_enabled())) {
747         error_setg(errp, "mode %s is not enabled, use other method instead.",
748                          DirtyRateMeasureMode_str(mode));
749          return;
750     }
751 
752     /*
753      * Init calculation state as unstarted.
754      */
755     ret = dirtyrate_set_state(&CalculatingState, CalculatingState,
756                               DIRTY_RATE_STATUS_UNSTARTED);
757     if (ret == -1) {
758         error_setg(errp, "init dirty rate calculation state failed.");
759         return;
760     }
761 
762     config.sample_period_seconds = calc_time;
763     config.sample_pages_per_gigabytes = sample_pages;
764     config.mode = mode;
765 
766     cleanup_dirtyrate_stat(config);
767 
768     /*
769      * update dirty rate mode so that we can figure out what mode has
770      * been used in last calculation
771      **/
772     dirtyrate_mode = mode;
773 
774     start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) / 1000;
775     init_dirtyrate_stat(start_time, config);
776 
777     qemu_thread_create(&thread, "get_dirtyrate", get_dirtyrate_thread,
778                        (void *)&config, QEMU_THREAD_DETACHED);
779 }
780 
781 struct DirtyRateInfo *qmp_query_dirty_rate(Error **errp)
782 {
783     return query_dirty_rate_info();
784 }
785 
786 void hmp_info_dirty_rate(Monitor *mon, const QDict *qdict)
787 {
788     DirtyRateInfo *info = query_dirty_rate_info();
789 
790     monitor_printf(mon, "Status: %s\n",
791                    DirtyRateStatus_str(info->status));
792     monitor_printf(mon, "Start Time: %"PRIi64" (ms)\n",
793                    info->start_time);
794     monitor_printf(mon, "Sample Pages: %"PRIu64" (per GB)\n",
795                    info->sample_pages);
796     monitor_printf(mon, "Period: %"PRIi64" (sec)\n",
797                    info->calc_time);
798     monitor_printf(mon, "Mode: %s\n",
799                    DirtyRateMeasureMode_str(info->mode));
800     monitor_printf(mon, "Dirty rate: ");
801     if (info->has_dirty_rate) {
802         monitor_printf(mon, "%"PRIi64" (MB/s)\n", info->dirty_rate);
803         if (info->has_vcpu_dirty_rate) {
804             DirtyRateVcpuList *rate, *head = info->vcpu_dirty_rate;
805             for (rate = head; rate != NULL; rate = rate->next) {
806                 monitor_printf(mon, "vcpu[%"PRIi64"], Dirty rate: %"PRIi64
807                                " (MB/s)\n", rate->value->id,
808                                rate->value->dirty_rate);
809             }
810         }
811     } else {
812         monitor_printf(mon, "(not ready)\n");
813     }
814 
815     qapi_free_DirtyRateVcpuList(info->vcpu_dirty_rate);
816     g_free(info);
817 }
818 
819 void hmp_calc_dirty_rate(Monitor *mon, const QDict *qdict)
820 {
821     int64_t sec = qdict_get_try_int(qdict, "second", 0);
822     int64_t sample_pages = qdict_get_try_int(qdict, "sample_pages_per_GB", -1);
823     bool has_sample_pages = (sample_pages != -1);
824     bool dirty_ring = qdict_get_try_bool(qdict, "dirty_ring", false);
825     bool dirty_bitmap = qdict_get_try_bool(qdict, "dirty_bitmap", false);
826     DirtyRateMeasureMode mode = DIRTY_RATE_MEASURE_MODE_PAGE_SAMPLING;
827     Error *err = NULL;
828 
829     if (!sec) {
830         monitor_printf(mon, "Incorrect period length specified!\n");
831         return;
832     }
833 
834     if (dirty_ring && dirty_bitmap) {
835         monitor_printf(mon, "Either dirty ring or dirty bitmap "
836                        "can be specified!\n");
837         return;
838     }
839 
840     if (dirty_bitmap) {
841         mode = DIRTY_RATE_MEASURE_MODE_DIRTY_BITMAP;
842     } else if (dirty_ring) {
843         mode = DIRTY_RATE_MEASURE_MODE_DIRTY_RING;
844     }
845 
846     qmp_calc_dirty_rate(sec, has_sample_pages, sample_pages, true,
847                         mode, &err);
848     if (err) {
849         hmp_handle_error(mon, err);
850         return;
851     }
852 
853     monitor_printf(mon, "Starting dirty rate measurement with period %"PRIi64
854                    " seconds\n", sec);
855     monitor_printf(mon, "[Please use 'info dirty_rate' to check results]\n");
856 }
857