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  *   Benoît 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     double bucket_size;   /* I/O before throttling to bkt->avg */
  99     double burst_bucket_size; /* Before throttling to bkt->max */
 100
 101     if (!bkt->avg) {
 102         return 0;
 103     }
 104
 105     if (!bkt->max) {
 106         /* If bkt->max is 0 we still want to allow short bursts of I/O
 107          * from the guest, otherwise every other request will be throttled
 108          * and performance will suffer considerably. */
 109         bucket_size = (double) bkt->avg / 10;
 110         burst_bucket_size = 0;
 111     } else {
 112         /* If we have a burst limit then we have to wait until all I/O
 113          * at burst rate has finished before throttling to bkt->avg */
 114         bucket_size = bkt->max * bkt->burst_length;
 115         burst_bucket_size = (double) bkt->max / 10;
 116     }
 117
 118     /* If the main bucket is full then we have to wait */
 119     extra = bkt->level - bucket_size;
 120     if (extra > 0) {
 121         return throttle_do_compute_wait(bkt->avg, extra);
 122     }
 123
 124     /* If the main bucket is not full yet we still have to check the
 125      * burst bucket in order to enforce the burst limit */
 126     if (bkt->burst_length > 1) {
 127         assert(bkt->max > 0); /* see throttle_is_valid() */
 128         extra = bkt->burst_level - burst_bucket_size;
 129         if (extra > 0) {
 130             return throttle_do_compute_wait(bkt->max, extra);
 131         }
 132     }
 133
 134     return 0;
 135 }
 136
 137 /* This function compute the time that must be waited while this IO
 138  *
 139  * @direction:  throttle direction
 140  * @ret:        time to wait
 141  */
 142 static int64_t throttle_compute_wait_for(ThrottleState *ts,
 143                                          ThrottleDirection direction)
 144 {
 145     BucketType to_check[2][4] = { {THROTTLE_BPS_TOTAL,
 146                                    THROTTLE_OPS_TOTAL,
 147                                    THROTTLE_BPS_READ,
 148                                    THROTTLE_OPS_READ},
 149                                   {THROTTLE_BPS_TOTAL,
 150                                    THROTTLE_OPS_TOTAL,
 151                                    THROTTLE_BPS_WRITE,
 152                                    THROTTLE_OPS_WRITE}, };
 153     int64_t wait, max_wait = 0;
 154     int i;
 155
 156     for (i = 0; i < 4; i++) {
 157         BucketType index = to_check[direction][i];
 158         wait = throttle_compute_wait(&ts->cfg.buckets[index]);
 159         if (wait > max_wait) {
 160             max_wait = wait;
 161         }
 162     }
 163
 164     return max_wait;
 165 }
 166
 167 /* compute the timer for this type of operation
 168  *
 169  * @direction:  throttle direction
 170  * @now:        the current clock timestamp
 171  * @next_timestamp: the resulting timer
 172  * @ret:        true if a timer must be set
 173  */
 174 static bool throttle_compute_timer(ThrottleState *ts,
 175                                    ThrottleDirection direction,
 176                                    int64_t now,
 177                                    int64_t *next_timestamp)
 178 {
 179     int64_t wait;
 180
 181     /* leak proportionally to the time elapsed */
 182     throttle_do_leak(ts, now);
 183
 184     /* compute the wait time if any */
 185     wait = throttle_compute_wait_for(ts, direction);
 186
 187     /* if the code must wait compute when the next timer should fire */
 188     if (wait) {
 189         *next_timestamp = now + wait;
 190         return true;
 191     }
 192
 193     /* else no need to wait at all */
 194     *next_timestamp = now;
 195     return false;
 196 }
 197
 198 /* Add timers to event loop */
 199 void throttle_timers_attach_aio_context(ThrottleTimers *tt,
 200                                         AioContext *new_context)
 201 {
 202     ThrottleDirection dir;
 203
 204     for (dir = THROTTLE_READ; dir < THROTTLE_MAX; dir++) {
 205         if (tt->timer_cb[dir]) {
 206             tt->timers[dir] =
 207                 aio_timer_new(new_context, tt->clock_type, SCALE_NS,
 208                               tt->timer_cb[dir], tt->timer_opaque);
 209         }
 210     }
 211 }
 212
 213 /*
 214  * Initialize the ThrottleConfig structure to a valid state
 215  * @cfg: the config to initialize
 216  */
 217 void throttle_config_init(ThrottleConfig *cfg)
 218 {
 219     unsigned i;
 220     memset(cfg, 0, sizeof(*cfg));
 221     for (i = 0; i < BUCKETS_COUNT; i++) {
 222         cfg->buckets[i].burst_length = 1;
 223     }
 224 }
 225
 226 /* To be called first on the ThrottleState */
 227 void throttle_init(ThrottleState *ts)
 228 {
 229     memset(ts, 0, sizeof(ThrottleState));
 230     throttle_config_init(&ts->cfg);
 231 }
 232
 233 /* To be called first on the ThrottleTimers */
 234 void throttle_timers_init(ThrottleTimers *tt,
 235                           AioContext *aio_context,
 236                           QEMUClockType clock_type,
 237                           QEMUTimerCB *read_timer_cb,
 238                           QEMUTimerCB *write_timer_cb,
 239                           void *timer_opaque)
 240 {
 241     assert(read_timer_cb || write_timer_cb);
 242     memset(tt, 0, sizeof(ThrottleTimers));
 243
 244     tt->clock_type = clock_type;
 245     tt->timer_cb[THROTTLE_READ] = read_timer_cb;
 246     tt->timer_cb[THROTTLE_WRITE] = write_timer_cb;
 247     tt->timer_opaque = timer_opaque;
 248     throttle_timers_attach_aio_context(tt, aio_context);
 249 }
 250
 251 /* destroy a timer */
 252 static void throttle_timer_destroy(QEMUTimer **timer)
 253 {
 254     if (*timer == NULL) {
 255         return;
 256     }
 257
 258     timer_free(*timer);
 259     *timer = NULL;
 260 }
 261
 262 /* Remove timers from event loop */
 263 void throttle_timers_detach_aio_context(ThrottleTimers *tt)
 264 {
 265     ThrottleDirection dir;
 266
 267     for (dir = THROTTLE_READ; dir < THROTTLE_MAX; dir++) {
 268         throttle_timer_destroy(&tt->timers[dir]);
 269     }
 270 }
 271
 272 /* To be called last on the ThrottleTimers */
 273 void throttle_timers_destroy(ThrottleTimers *tt)
 274 {
 275     throttle_timers_detach_aio_context(tt);
 276 }
 277
 278 /* is any throttling timer configured */
 279 bool throttle_timers_are_initialized(ThrottleTimers *tt)
 280 {
 281     ThrottleDirection dir;
 282
 283     for (dir = THROTTLE_READ; dir < THROTTLE_MAX; dir++) {
 284         if (tt->timers[dir]) {
 285             return true;
 286         }
 287     }
 288
 289     return false;
 290 }
 291
 292 /* Does any throttling must be done
 293  *
 294  * @cfg: the throttling configuration to inspect
 295  * @ret: true if throttling must be done else false
 296  */
 297 bool throttle_enabled(ThrottleConfig *cfg)
 298 {
 299     int i;
 300
 301     for (i = 0; i < BUCKETS_COUNT; i++) {
 302         if (cfg->buckets[i].avg > 0) {
 303             return true;
 304         }
 305     }
 306
 307     return false;
 308 }
 309
 310 /* check if a throttling configuration is valid
 311  * @cfg: the throttling configuration to inspect
 312  * @ret: true if valid else false
 313  * @errp: error object
 314  */
 315 bool throttle_is_valid(ThrottleConfig *cfg, Error **errp)
 316 {
 317     int i;
 318     bool bps_flag, ops_flag;
 319     bool bps_max_flag, ops_max_flag;
 320
 321     bps_flag = cfg->buckets[THROTTLE_BPS_TOTAL].avg &&
 322                (cfg->buckets[THROTTLE_BPS_READ].avg ||
 323                 cfg->buckets[THROTTLE_BPS_WRITE].avg);
 324
 325     ops_flag = cfg->buckets[THROTTLE_OPS_TOTAL].avg &&
 326                (cfg->buckets[THROTTLE_OPS_READ].avg ||
 327                 cfg->buckets[THROTTLE_OPS_WRITE].avg);
 328
 329     bps_max_flag = cfg->buckets[THROTTLE_BPS_TOTAL].max &&
 330                   (cfg->buckets[THROTTLE_BPS_READ].max  ||
 331                    cfg->buckets[THROTTLE_BPS_WRITE].max);
 332
 333     ops_max_flag = cfg->buckets[THROTTLE_OPS_TOTAL].max &&
 334                    (cfg->buckets[THROTTLE_OPS_READ].max ||
 335                    cfg->buckets[THROTTLE_OPS_WRITE].max);
 336
 337     if (bps_flag || ops_flag || bps_max_flag || ops_max_flag) {
 338         error_setg(errp, "bps/iops/max total values and read/write values"
 339                    " cannot be used at the same time");
 340         return false;
 341     }
 342
 343     if (cfg->op_size &&
 344         !cfg->buckets[THROTTLE_OPS_TOTAL].avg &&
 345         !cfg->buckets[THROTTLE_OPS_READ].avg &&
 346         !cfg->buckets[THROTTLE_OPS_WRITE].avg) {
 347         error_setg(errp, "iops size requires an iops value to be set");
 348         return false;
 349     }
 350
 351     for (i = 0; i < BUCKETS_COUNT; i++) {
 352         LeakyBucket *bkt = &cfg->buckets[i];
 353         if (bkt->avg > THROTTLE_VALUE_MAX || bkt->max > THROTTLE_VALUE_MAX) {
 354             error_setg(errp, "bps/iops/max values must be within [0, %lld]",
 355                        THROTTLE_VALUE_MAX);
 356             return false;
 357         }
 358
 359         if (!bkt->burst_length) {
 360             error_setg(errp, "the burst length cannot be 0");
 361             return false;
 362         }
 363
 364         if (bkt->burst_length > 1 && !bkt->max) {
 365             error_setg(errp, "burst length set without burst rate");
 366             return false;
 367         }
 368
 369         if (bkt->max && bkt->burst_length > THROTTLE_VALUE_MAX / bkt->max) {
 370             error_setg(errp, "burst length too high for this burst rate");
 371             return false;
 372         }
 373
 374         if (bkt->max && !bkt->avg) {
 375             error_setg(errp, "bps_max/iops_max require corresponding"
 376                        " bps/iops values");
 377             return false;
 378         }
 379
 380         if (bkt->max && bkt->max < bkt->avg) {
 381             error_setg(errp, "bps_max/iops_max cannot be lower than bps/iops");
 382             return false;
 383         }
 384     }
 385
 386     return true;
 387 }
 388
 389 /* Used to configure the throttle
 390  *
 391  * @ts: the throttle state we are working on
 392  * @clock_type: the group's clock_type
 393  * @cfg: the config to set
 394  */
 395 void throttle_config(ThrottleState *ts,
 396                      QEMUClockType clock_type,
 397                      ThrottleConfig *cfg)
 398 {
 399     int i;
 400
 401     ts->cfg = *cfg;
 402
 403     /* Zero bucket level */
 404     for (i = 0; i < BUCKETS_COUNT; i++) {
 405         ts->cfg.buckets[i].level = 0;
 406         ts->cfg.buckets[i].burst_level = 0;
 407     }
 408
 409     ts->previous_leak = qemu_clock_get_ns(clock_type);
 410 }
 411
 412 /* used to get config
 413  *
 414  * @ts:  the throttle state we are working on
 415  * @cfg: the config to write
 416  */
 417 void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg)
 418 {
 419     *cfg = ts->cfg;
 420 }
 421
 422
 423 /* Schedule the read or write timer if needed
 424  *
 425  * NOTE: this function is not unit tested due to it's usage of timer_mod
 426  *
 427  * @tt:       the timers structure
 428  * @direction: throttle direction
 429  * @ret:      true if the timer has been scheduled else false
 430  */
 431 bool throttle_schedule_timer(ThrottleState *ts,
 432                              ThrottleTimers *tt,
 433                              ThrottleDirection direction)
 434 {
 435     int64_t now = qemu_clock_get_ns(tt->clock_type);
 436     int64_t next_timestamp;
 437     QEMUTimer *timer;
 438     bool must_wait;
 439
 440     assert(direction < THROTTLE_MAX);
 441     timer = tt->timers[direction];
 442     assert(timer);
 443
 444     must_wait = throttle_compute_timer(ts,
 445                                        direction,
 446                                        now,
 447                                        &next_timestamp);
 448
 449     /* request not throttled */
 450     if (!must_wait) {
 451         return false;
 452     }
 453
 454     /* request throttled and timer pending -> do nothing */
 455     if (timer_pending(timer)) {
 456         return true;
 457     }
 458
 459     /* request throttled and timer not pending -> arm timer */
 460     timer_mod(timer, next_timestamp);
 461     return true;
 462 }
 463
 464 /* do the accounting for this operation
 465  *
 466  * @direction: throttle direction
 467  * @size:     the size of the operation
 468  */
 469 void throttle_account(ThrottleState *ts, ThrottleDirection direction,
 470                       uint64_t size)
 471 {
 472     const BucketType bucket_types_size[2][2] = {
 473         { THROTTLE_BPS_TOTAL, THROTTLE_BPS_READ },
 474         { THROTTLE_BPS_TOTAL, THROTTLE_BPS_WRITE }
 475     };
 476     const BucketType bucket_types_units[2][2] = {
 477         { THROTTLE_OPS_TOTAL, THROTTLE_OPS_READ },
 478         { THROTTLE_OPS_TOTAL, THROTTLE_OPS_WRITE }
 479     };
 480     double units = 1.0;
 481     unsigned i;
 482
 483     assert(direction < THROTTLE_MAX);
 484     /* if cfg.op_size is defined and smaller than size we compute unit count */
 485     if (ts->cfg.op_size && size > ts->cfg.op_size) {
 486         units = (double) size / ts->cfg.op_size;
 487     }
 488
 489     for (i = 0; i < 2; i++) {
 490         LeakyBucket *bkt;
 491
 492         bkt = &ts->cfg.buckets[bucket_types_size[direction][i]];
 493         bkt->level += size;
 494         if (bkt->burst_length > 1) {
 495             bkt->burst_level += size;
 496         }
 497
 498         bkt = &ts->cfg.buckets[bucket_types_units[direction][i]];
 499         bkt->level += units;
 500         if (bkt->burst_length > 1) {
 501             bkt->burst_level += units;
 502         }
 503     }
 504 }
 505
 506 /* return a ThrottleConfig based on the options in a ThrottleLimits
 507  *
 508  * @arg:    the ThrottleLimits object to read from
 509  * @cfg:    the ThrottleConfig to edit
 510  * @errp:   error object
 511  */
 512 void throttle_limits_to_config(ThrottleLimits *arg, ThrottleConfig *cfg,
 513                                Error **errp)
 514 {
 515     if (arg->has_bps_total) {
 516         cfg->buckets[THROTTLE_BPS_TOTAL].avg = arg->bps_total;
 517     }
 518     if (arg->has_bps_read) {
 519         cfg->buckets[THROTTLE_BPS_READ].avg  = arg->bps_read;
 520     }
 521     if (arg->has_bps_write) {
 522         cfg->buckets[THROTTLE_BPS_WRITE].avg = arg->bps_write;
 523     }
 524
 525     if (arg->has_iops_total) {
 526         cfg->buckets[THROTTLE_OPS_TOTAL].avg = arg->iops_total;
 527     }
 528     if (arg->has_iops_read) {
 529         cfg->buckets[THROTTLE_OPS_READ].avg  = arg->iops_read;
 530     }
 531     if (arg->has_iops_write) {
 532         cfg->buckets[THROTTLE_OPS_WRITE].avg = arg->iops_write;
 533     }
 534
 535     if (arg->has_bps_total_max) {
 536         cfg->buckets[THROTTLE_BPS_TOTAL].max = arg->bps_total_max;
 537     }
 538     if (arg->has_bps_read_max) {
 539         cfg->buckets[THROTTLE_BPS_READ].max = arg->bps_read_max;
 540     }
 541     if (arg->has_bps_write_max) {
 542         cfg->buckets[THROTTLE_BPS_WRITE].max = arg->bps_write_max;
 543     }
 544     if (arg->has_iops_total_max) {
 545         cfg->buckets[THROTTLE_OPS_TOTAL].max = arg->iops_total_max;
 546     }
 547     if (arg->has_iops_read_max) {
 548         cfg->buckets[THROTTLE_OPS_READ].max = arg->iops_read_max;
 549     }
 550     if (arg->has_iops_write_max) {
 551         cfg->buckets[THROTTLE_OPS_WRITE].max = arg->iops_write_max;
 552     }
 553
 554     if (arg->has_bps_total_max_length) {
 555         if (arg->bps_total_max_length > UINT_MAX) {
 556             error_setg(errp, "bps-total-max-length value must be in"
 557                              " the range [0, %u]", UINT_MAX);
 558             return;
 559         }
 560         cfg->buckets[THROTTLE_BPS_TOTAL].burst_length = arg->bps_total_max_length;
 561     }
 562     if (arg->has_bps_read_max_length) {
 563         if (arg->bps_read_max_length > UINT_MAX) {
 564             error_setg(errp, "bps-read-max-length value must be in"
 565                              " the range [0, %u]", UINT_MAX);
 566             return;
 567         }
 568         cfg->buckets[THROTTLE_BPS_READ].burst_length = arg->bps_read_max_length;
 569     }
 570     if (arg->has_bps_write_max_length) {
 571         if (arg->bps_write_max_length > UINT_MAX) {
 572             error_setg(errp, "bps-write-max-length value must be in"
 573                              " the range [0, %u]", UINT_MAX);
 574             return;
 575         }
 576         cfg->buckets[THROTTLE_BPS_WRITE].burst_length = arg->bps_write_max_length;
 577     }
 578     if (arg->has_iops_total_max_length) {
 579         if (arg->iops_total_max_length > UINT_MAX) {
 580             error_setg(errp, "iops-total-max-length value must be in"
 581                              " the range [0, %u]", UINT_MAX);
 582             return;
 583         }
 584         cfg->buckets[THROTTLE_OPS_TOTAL].burst_length = arg->iops_total_max_length;
 585     }
 586     if (arg->has_iops_read_max_length) {
 587         if (arg->iops_read_max_length > UINT_MAX) {
 588             error_setg(errp, "iops-read-max-length value must be in"
 589                              " the range [0, %u]", UINT_MAX);
 590             return;
 591         }
 592         cfg->buckets[THROTTLE_OPS_READ].burst_length = arg->iops_read_max_length;
 593     }
 594     if (arg->has_iops_write_max_length) {
 595         if (arg->iops_write_max_length > UINT_MAX) {
 596             error_setg(errp, "iops-write-max-length value must be in"
 597                              " the range [0, %u]", UINT_MAX);
 598             return;
 599         }
 600         cfg->buckets[THROTTLE_OPS_WRITE].burst_length = arg->iops_write_max_length;
 601     }
 602
 603     if (arg->has_iops_size) {
 604         cfg->op_size = arg->iops_size;
 605     }
 606
 607     throttle_is_valid(cfg, errp);
 608 }
 609
 610 /* write the options of a ThrottleConfig to a ThrottleLimits
 611  *
 612  * @cfg:    the ThrottleConfig to read from
 613  * @var:    the ThrottleLimits to write to
 614  */
 615 void throttle_config_to_limits(ThrottleConfig *cfg, ThrottleLimits *var)
 616 {
 617     var->bps_total               = cfg->buckets[THROTTLE_BPS_TOTAL].avg;
 618     var->bps_read                = cfg->buckets[THROTTLE_BPS_READ].avg;
 619     var->bps_write               = cfg->buckets[THROTTLE_BPS_WRITE].avg;
 620     var->iops_total              = cfg->buckets[THROTTLE_OPS_TOTAL].avg;
 621     var->iops_read               = cfg->buckets[THROTTLE_OPS_READ].avg;
 622     var->iops_write              = cfg->buckets[THROTTLE_OPS_WRITE].avg;
 623     var->bps_total_max           = cfg->buckets[THROTTLE_BPS_TOTAL].max;
 624     var->bps_read_max            = cfg->buckets[THROTTLE_BPS_READ].max;
 625     var->bps_write_max           = cfg->buckets[THROTTLE_BPS_WRITE].max;
 626     var->iops_total_max          = cfg->buckets[THROTTLE_OPS_TOTAL].max;
 627     var->iops_read_max           = cfg->buckets[THROTTLE_OPS_READ].max;
 628     var->iops_write_max          = cfg->buckets[THROTTLE_OPS_WRITE].max;
 629     var->bps_total_max_length    = cfg->buckets[THROTTLE_BPS_TOTAL].burst_length;
 630     var->bps_read_max_length     = cfg->buckets[THROTTLE_BPS_READ].burst_length;
 631     var->bps_write_max_length    = cfg->buckets[THROTTLE_BPS_WRITE].burst_length;
 632     var->iops_total_max_length   = cfg->buckets[THROTTLE_OPS_TOTAL].burst_length;
 633     var->iops_read_max_length    = cfg->buckets[THROTTLE_OPS_READ].burst_length;
 634     var->iops_write_max_length   = cfg->buckets[THROTTLE_OPS_WRITE].burst_length;
 635     var->iops_size               = cfg->op_size;
 636
 637     var->has_bps_total = true;
 638     var->has_bps_read = true;
 639     var->has_bps_write = true;
 640     var->has_iops_total = true;
 641     var->has_iops_read = true;
 642     var->has_iops_write = true;
 643     var->has_bps_total_max = true;
 644     var->has_bps_read_max = true;
 645     var->has_bps_write_max = true;
 646     var->has_iops_total_max = true;
 647     var->has_iops_read_max = true;
 648     var->has_iops_write_max = true;
 649     var->has_bps_read_max_length = true;
 650     var->has_bps_total_max_length = true;
 651     var->has_bps_write_max_length = true;
 652     var->has_iops_total_max_length = true;
 653     var->has_iops_read_max_length = true;
 654     var->has_iops_write_max_length = true;
 655     var->has_iops_size = true;
 656 }