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[qemu.git] / util / throttle.c
1 /*
2 * QEMU throttling infrastructure
3 *
4 * Copyright (C) Nodalink, EURL. 2013-2014
5 * Copyright (C) Igalia, S.L. 2015
6 *
7 * Authors:
8 * BenoƮt Canet <benoit.canet@nodalink.com>
9 * Alberto Garcia <berto@igalia.com>
10 *
11 * This program is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU General Public License as
13 * published by the Free Software Foundation; either version 2 or
14 * (at your option) version 3 of the License.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
20 *
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, see <http://www.gnu.org/licenses/>.
23 */
24
25 #include "qemu/osdep.h"
26 #include "qapi/error.h"
27 #include "qemu/throttle.h"
28 #include "qemu/timer.h"
29 #include "block/aio.h"
30
31 /* This function make a bucket leak
32 *
33 * @bkt: the bucket to make leak
34 * @delta_ns: the time delta
35 */
36 void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta_ns)
37 {
38 double leak;
39
40 /* compute how much to leak */
41 leak = (bkt->avg * (double) delta_ns) / NANOSECONDS_PER_SECOND;
42
43 /* make the bucket leak */
44 bkt->level = MAX(bkt->level - leak, 0);
45
46 /* if we allow bursts for more than one second we also need to
47 * keep track of bkt->burst_level so the bkt->max goal per second
48 * is attained */
49 if (bkt->burst_length > 1) {
50 leak = (bkt->max * (double) delta_ns) / NANOSECONDS_PER_SECOND;
51 bkt->burst_level = MAX(bkt->burst_level - leak, 0);
52 }
53 }
54
55 /* Calculate the time delta since last leak and make proportionals leaks
56 *
57 * @now: the current timestamp in ns
58 */
59 static void throttle_do_leak(ThrottleState *ts, int64_t now)
60 {
61 /* compute the time elapsed since the last leak */
62 int64_t delta_ns = now - ts->previous_leak;
63 int i;
64
65 ts->previous_leak = now;
66
67 if (delta_ns <= 0) {
68 return;
69 }
70
71 /* make each bucket leak */
72 for (i = 0; i < BUCKETS_COUNT; i++) {
73 throttle_leak_bucket(&ts->cfg.buckets[i], delta_ns);
74 }
75 }
76
77 /* do the real job of computing the time to wait
78 *
79 * @limit: the throttling limit
80 * @extra: the number of operation to delay
81 * @ret: the time to wait in ns
82 */
83 static int64_t throttle_do_compute_wait(double limit, double extra)
84 {
85 double wait = extra * NANOSECONDS_PER_SECOND;
86 wait /= limit;
87 return wait;
88 }
89
90 /* This function compute the wait time in ns that a leaky bucket should trigger
91 *
92 * @bkt: the leaky bucket we operate on
93 * @ret: the resulting wait time in ns or 0 if the operation can go through
94 */
95 int64_t throttle_compute_wait(LeakyBucket *bkt)
96 {
97 double extra; /* the number of extra units blocking the io */
98
99 if (!bkt->avg) {
100 return 0;
101 }
102
103 /* If the bucket is full then we have to wait */
104 extra = bkt->level - bkt->max * bkt->burst_length;
105 if (extra > 0) {
106 return throttle_do_compute_wait(bkt->avg, extra);
107 }
108
109 /* If the bucket is not full yet we have to make sure that we
110 * fulfill the goal of bkt->max units per second. */
111 if (bkt->burst_length > 1) {
112 /* We use 1/10 of the max value to smooth the throttling.
113 * See throttle_fix_bucket() for more details. */
114 extra = bkt->burst_level - bkt->max / 10;
115 if (extra > 0) {
116 return throttle_do_compute_wait(bkt->max, extra);
117 }
118 }
119
120 return 0;
121 }
122
123 /* This function compute the time that must be waited while this IO
124 *
125 * @is_write: true if the current IO is a write, false if it's a read
126 * @ret: time to wait
127 */
128 static int64_t throttle_compute_wait_for(ThrottleState *ts,
129 bool is_write)
130 {
131 BucketType to_check[2][4] = { {THROTTLE_BPS_TOTAL,
132 THROTTLE_OPS_TOTAL,
133 THROTTLE_BPS_READ,
134 THROTTLE_OPS_READ},
135 {THROTTLE_BPS_TOTAL,
136 THROTTLE_OPS_TOTAL,
137 THROTTLE_BPS_WRITE,
138 THROTTLE_OPS_WRITE}, };
139 int64_t wait, max_wait = 0;
140 int i;
141
142 for (i = 0; i < 4; i++) {
143 BucketType index = to_check[is_write][i];
144 wait = throttle_compute_wait(&ts->cfg.buckets[index]);
145 if (wait > max_wait) {
146 max_wait = wait;
147 }
148 }
149
150 return max_wait;
151 }
152
153 /* compute the timer for this type of operation
154 *
155 * @is_write: the type of operation
156 * @now: the current clock timestamp
157 * @next_timestamp: the resulting timer
158 * @ret: true if a timer must be set
159 */
160 static bool throttle_compute_timer(ThrottleState *ts,
161 bool is_write,
162 int64_t now,
163 int64_t *next_timestamp)
164 {
165 int64_t wait;
166
167 /* leak proportionally to the time elapsed */
168 throttle_do_leak(ts, now);
169
170 /* compute the wait time if any */
171 wait = throttle_compute_wait_for(ts, is_write);
172
173 /* if the code must wait compute when the next timer should fire */
174 if (wait) {
175 *next_timestamp = now + wait;
176 return true;
177 }
178
179 /* else no need to wait at all */
180 *next_timestamp = now;
181 return false;
182 }
183
184 /* Add timers to event loop */
185 void throttle_timers_attach_aio_context(ThrottleTimers *tt,
186 AioContext *new_context)
187 {
188 tt->timers[0] = aio_timer_new(new_context, tt->clock_type, SCALE_NS,
189 tt->read_timer_cb, tt->timer_opaque);
190 tt->timers[1] = aio_timer_new(new_context, tt->clock_type, SCALE_NS,
191 tt->write_timer_cb, tt->timer_opaque);
192 }
193
194 /*
195 * Initialize the ThrottleConfig structure to a valid state
196 * @cfg: the config to initialize
197 */
198 void throttle_config_init(ThrottleConfig *cfg)
199 {
200 unsigned i;
201 memset(cfg, 0, sizeof(*cfg));
202 for (i = 0; i < BUCKETS_COUNT; i++) {
203 cfg->buckets[i].burst_length = 1;
204 }
205 }
206
207 /* To be called first on the ThrottleState */
208 void throttle_init(ThrottleState *ts)
209 {
210 memset(ts, 0, sizeof(ThrottleState));
211 throttle_config_init(&ts->cfg);
212 }
213
214 /* To be called first on the ThrottleTimers */
215 void throttle_timers_init(ThrottleTimers *tt,
216 AioContext *aio_context,
217 QEMUClockType clock_type,
218 QEMUTimerCB *read_timer_cb,
219 QEMUTimerCB *write_timer_cb,
220 void *timer_opaque)
221 {
222 memset(tt, 0, sizeof(ThrottleTimers));
223
224 tt->clock_type = clock_type;
225 tt->read_timer_cb = read_timer_cb;
226 tt->write_timer_cb = write_timer_cb;
227 tt->timer_opaque = timer_opaque;
228 throttle_timers_attach_aio_context(tt, aio_context);
229 }
230
231 /* destroy a timer */
232 static void throttle_timer_destroy(QEMUTimer **timer)
233 {
234 assert(*timer != NULL);
235
236 timer_del(*timer);
237 timer_free(*timer);
238 *timer = NULL;
239 }
240
241 /* Remove timers from event loop */
242 void throttle_timers_detach_aio_context(ThrottleTimers *tt)
243 {
244 int i;
245
246 for (i = 0; i < 2; i++) {
247 throttle_timer_destroy(&tt->timers[i]);
248 }
249 }
250
251 /* To be called last on the ThrottleTimers */
252 void throttle_timers_destroy(ThrottleTimers *tt)
253 {
254 throttle_timers_detach_aio_context(tt);
255 }
256
257 /* is any throttling timer configured */
258 bool throttle_timers_are_initialized(ThrottleTimers *tt)
259 {
260 if (tt->timers[0]) {
261 return true;
262 }
263
264 return false;
265 }
266
267 /* Does any throttling must be done
268 *
269 * @cfg: the throttling configuration to inspect
270 * @ret: true if throttling must be done else false
271 */
272 bool throttle_enabled(ThrottleConfig *cfg)
273 {
274 int i;
275
276 for (i = 0; i < BUCKETS_COUNT; i++) {
277 if (cfg->buckets[i].avg > 0) {
278 return true;
279 }
280 }
281
282 return false;
283 }
284
285 /* check if a throttling configuration is valid
286 * @cfg: the throttling configuration to inspect
287 * @ret: true if valid else false
288 * @errp: error object
289 */
290 bool throttle_is_valid(ThrottleConfig *cfg, Error **errp)
291 {
292 int i;
293 bool bps_flag, ops_flag;
294 bool bps_max_flag, ops_max_flag;
295
296 bps_flag = cfg->buckets[THROTTLE_BPS_TOTAL].avg &&
297 (cfg->buckets[THROTTLE_BPS_READ].avg ||
298 cfg->buckets[THROTTLE_BPS_WRITE].avg);
299
300 ops_flag = cfg->buckets[THROTTLE_OPS_TOTAL].avg &&
301 (cfg->buckets[THROTTLE_OPS_READ].avg ||
302 cfg->buckets[THROTTLE_OPS_WRITE].avg);
303
304 bps_max_flag = cfg->buckets[THROTTLE_BPS_TOTAL].max &&
305 (cfg->buckets[THROTTLE_BPS_READ].max ||
306 cfg->buckets[THROTTLE_BPS_WRITE].max);
307
308 ops_max_flag = cfg->buckets[THROTTLE_OPS_TOTAL].max &&
309 (cfg->buckets[THROTTLE_OPS_READ].max ||
310 cfg->buckets[THROTTLE_OPS_WRITE].max);
311
312 if (bps_flag || ops_flag || bps_max_flag || ops_max_flag) {
313 error_setg(errp, "bps/iops/max total values and read/write values"
314 " cannot be used at the same time");
315 return false;
316 }
317
318 if (cfg->op_size &&
319 !cfg->buckets[THROTTLE_OPS_TOTAL].avg &&
320 !cfg->buckets[THROTTLE_OPS_READ].avg &&
321 !cfg->buckets[THROTTLE_OPS_WRITE].avg) {
322 error_setg(errp, "iops size requires an iops value to be set");
323 return false;
324 }
325
326 for (i = 0; i < BUCKETS_COUNT; i++) {
327 if (cfg->buckets[i].avg < 0 ||
328 cfg->buckets[i].max < 0 ||
329 cfg->buckets[i].avg > THROTTLE_VALUE_MAX ||
330 cfg->buckets[i].max > THROTTLE_VALUE_MAX) {
331 error_setg(errp, "bps/iops/max values must be within [0, %lld]",
332 THROTTLE_VALUE_MAX);
333 return false;
334 }
335
336 if (!cfg->buckets[i].burst_length) {
337 error_setg(errp, "the burst length cannot be 0");
338 return false;
339 }
340
341 if (cfg->buckets[i].burst_length > 1 && !cfg->buckets[i].max) {
342 error_setg(errp, "burst length set without burst rate");
343 return false;
344 }
345
346 if (cfg->buckets[i].max && !cfg->buckets[i].avg) {
347 error_setg(errp, "bps_max/iops_max require corresponding"
348 " bps/iops values");
349 return false;
350 }
351 }
352
353 return true;
354 }
355
356 /* fix bucket parameters */
357 static void throttle_fix_bucket(LeakyBucket *bkt)
358 {
359 double min;
360
361 /* zero bucket level */
362 bkt->level = bkt->burst_level = 0;
363
364 /* The following is done to cope with the Linux CFQ block scheduler
365 * which regroup reads and writes by block of 100ms in the guest.
366 * When they are two process one making reads and one making writes cfq
367 * make a pattern looking like the following:
368 * WWWWWWWWWWWRRRRRRRRRRRRRRWWWWWWWWWWWWWwRRRRRRRRRRRRRRRRR
369 * Having a max burst value of 100ms of the average will help smooth the
370 * throttling
371 */
372 min = bkt->avg / 10;
373 if (bkt->avg && !bkt->max) {
374 bkt->max = min;
375 }
376 }
377
378 /* take care of canceling a timer */
379 static void throttle_cancel_timer(QEMUTimer *timer)
380 {
381 assert(timer != NULL);
382
383 timer_del(timer);
384 }
385
386 /* Used to configure the throttle
387 *
388 * @ts: the throttle state we are working on
389 * @tt: the throttle timers we use in this aio context
390 * @cfg: the config to set
391 */
392 void throttle_config(ThrottleState *ts,
393 ThrottleTimers *tt,
394 ThrottleConfig *cfg)
395 {
396 int i;
397
398 ts->cfg = *cfg;
399
400 for (i = 0; i < BUCKETS_COUNT; i++) {
401 throttle_fix_bucket(&ts->cfg.buckets[i]);
402 }
403
404 ts->previous_leak = qemu_clock_get_ns(tt->clock_type);
405
406 for (i = 0; i < 2; i++) {
407 throttle_cancel_timer(tt->timers[i]);
408 }
409 }
410
411 /* used to get config
412 *
413 * @ts: the throttle state we are working on
414 * @cfg: the config to write
415 */
416 void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg)
417 {
418 *cfg = ts->cfg;
419 }
420
421
422 /* Schedule the read or write timer if needed
423 *
424 * NOTE: this function is not unit tested due to it's usage of timer_mod
425 *
426 * @tt: the timers structure
427 * @is_write: the type of operation (read/write)
428 * @ret: true if the timer has been scheduled else false
429 */
430 bool throttle_schedule_timer(ThrottleState *ts,
431 ThrottleTimers *tt,
432 bool is_write)
433 {
434 int64_t now = qemu_clock_get_ns(tt->clock_type);
435 int64_t next_timestamp;
436 bool must_wait;
437
438 must_wait = throttle_compute_timer(ts,
439 is_write,
440 now,
441 &next_timestamp);
442
443 /* request not throttled */
444 if (!must_wait) {
445 return false;
446 }
447
448 /* request throttled and timer pending -> do nothing */
449 if (timer_pending(tt->timers[is_write])) {
450 return true;
451 }
452
453 /* request throttled and timer not pending -> arm timer */
454 timer_mod(tt->timers[is_write], next_timestamp);
455 return true;
456 }
457
458 /* do the accounting for this operation
459 *
460 * @is_write: the type of operation (read/write)
461 * @size: the size of the operation
462 */
463 void throttle_account(ThrottleState *ts, bool is_write, uint64_t size)
464 {
465 const BucketType bucket_types_size[2][2] = {
466 { THROTTLE_BPS_TOTAL, THROTTLE_BPS_READ },
467 { THROTTLE_BPS_TOTAL, THROTTLE_BPS_WRITE }
468 };
469 const BucketType bucket_types_units[2][2] = {
470 { THROTTLE_OPS_TOTAL, THROTTLE_OPS_READ },
471 { THROTTLE_OPS_TOTAL, THROTTLE_OPS_WRITE }
472 };
473 double units = 1.0;
474 unsigned i;
475
476 /* if cfg.op_size is defined and smaller than size we compute unit count */
477 if (ts->cfg.op_size && size > ts->cfg.op_size) {
478 units = (double) size / ts->cfg.op_size;
479 }
480
481 for (i = 0; i < 2; i++) {
482 LeakyBucket *bkt;
483
484 bkt = &ts->cfg.buckets[bucket_types_size[is_write][i]];
485 bkt->level += size;
486 if (bkt->burst_length > 1) {
487 bkt->burst_level += size;
488 }
489
490 bkt = &ts->cfg.buckets[bucket_types_units[is_write][i]];
491 bkt->level += units;
492 if (bkt->burst_length > 1) {
493 bkt->burst_level += units;
494 }
495 }
496 }
497