| /* |
| * QEMU throttling infrastructure |
| * |
| * Copyright (C) Nodalink, EURL. 2013-2014 |
| * Copyright (C) Igalia, S.L. 2015 |
| * |
| * Authors: |
| * Benoît Canet <benoit.canet@nodalink.com> |
| * Alberto Garcia <berto@igalia.com> |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public License as |
| * published by the Free Software Foundation; either version 2 or |
| * (at your option) version 3 of the License. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, see <http://www.gnu.org/licenses/>. |
| */ |
| |
| #include "qemu/osdep.h" |
| #include "qapi/error.h" |
| #include "qemu/throttle.h" |
| #include "qemu/timer.h" |
| #include "block/aio.h" |
| |
| /* This function make a bucket leak |
| * |
| * @bkt: the bucket to make leak |
| * @delta_ns: the time delta |
| */ |
| void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta_ns) |
| { |
| double leak; |
| |
| /* compute how much to leak */ |
| leak = (bkt->avg * (double) delta_ns) / NANOSECONDS_PER_SECOND; |
| |
| /* make the bucket leak */ |
| bkt->level = MAX(bkt->level - leak, 0); |
| |
| /* if we allow bursts for more than one second we also need to |
| * keep track of bkt->burst_level so the bkt->max goal per second |
| * is attained */ |
| if (bkt->burst_length > 1) { |
| leak = (bkt->max * (double) delta_ns) / NANOSECONDS_PER_SECOND; |
| bkt->burst_level = MAX(bkt->burst_level - leak, 0); |
| } |
| } |
| |
| /* Calculate the time delta since last leak and make proportionals leaks |
| * |
| * @now: the current timestamp in ns |
| */ |
| static void throttle_do_leak(ThrottleState *ts, int64_t now) |
| { |
| /* compute the time elapsed since the last leak */ |
| int64_t delta_ns = now - ts->previous_leak; |
| int i; |
| |
| ts->previous_leak = now; |
| |
| if (delta_ns <= 0) { |
| return; |
| } |
| |
| /* make each bucket leak */ |
| for (i = 0; i < BUCKETS_COUNT; i++) { |
| throttle_leak_bucket(&ts->cfg.buckets[i], delta_ns); |
| } |
| } |
| |
| /* do the real job of computing the time to wait |
| * |
| * @limit: the throttling limit |
| * @extra: the number of operation to delay |
| * @ret: the time to wait in ns |
| */ |
| static int64_t throttle_do_compute_wait(double limit, double extra) |
| { |
| double wait = extra * NANOSECONDS_PER_SECOND; |
| wait /= limit; |
| return wait; |
| } |
| |
| /* This function compute the wait time in ns that a leaky bucket should trigger |
| * |
| * @bkt: the leaky bucket we operate on |
| * @ret: the resulting wait time in ns or 0 if the operation can go through |
| */ |
| int64_t throttle_compute_wait(LeakyBucket *bkt) |
| { |
| double extra; /* the number of extra units blocking the io */ |
| |
| if (!bkt->avg) { |
| return 0; |
| } |
| |
| /* If the bucket is full then we have to wait */ |
| extra = bkt->level - bkt->max * bkt->burst_length; |
| if (extra > 0) { |
| return throttle_do_compute_wait(bkt->avg, extra); |
| } |
| |
| /* If the bucket is not full yet we have to make sure that we |
| * fulfill the goal of bkt->max units per second. */ |
| if (bkt->burst_length > 1) { |
| /* We use 1/10 of the max value to smooth the throttling. |
| * See throttle_fix_bucket() for more details. */ |
| extra = bkt->burst_level - bkt->max / 10; |
| if (extra > 0) { |
| return throttle_do_compute_wait(bkt->max, extra); |
| } |
| } |
| |
| return 0; |
| } |
| |
| /* This function compute the time that must be waited while this IO |
| * |
| * @is_write: true if the current IO is a write, false if it's a read |
| * @ret: time to wait |
| */ |
| static int64_t throttle_compute_wait_for(ThrottleState *ts, |
| bool is_write) |
| { |
| BucketType to_check[2][4] = { {THROTTLE_BPS_TOTAL, |
| THROTTLE_OPS_TOTAL, |
| THROTTLE_BPS_READ, |
| THROTTLE_OPS_READ}, |
| {THROTTLE_BPS_TOTAL, |
| THROTTLE_OPS_TOTAL, |
| THROTTLE_BPS_WRITE, |
| THROTTLE_OPS_WRITE}, }; |
| int64_t wait, max_wait = 0; |
| int i; |
| |
| for (i = 0; i < 4; i++) { |
| BucketType index = to_check[is_write][i]; |
| wait = throttle_compute_wait(&ts->cfg.buckets[index]); |
| if (wait > max_wait) { |
| max_wait = wait; |
| } |
| } |
| |
| return max_wait; |
| } |
| |
| /* compute the timer for this type of operation |
| * |
| * @is_write: the type of operation |
| * @now: the current clock timestamp |
| * @next_timestamp: the resulting timer |
| * @ret: true if a timer must be set |
| */ |
| static bool throttle_compute_timer(ThrottleState *ts, |
| bool is_write, |
| int64_t now, |
| int64_t *next_timestamp) |
| { |
| int64_t wait; |
| |
| /* leak proportionally to the time elapsed */ |
| throttle_do_leak(ts, now); |
| |
| /* compute the wait time if any */ |
| wait = throttle_compute_wait_for(ts, is_write); |
| |
| /* if the code must wait compute when the next timer should fire */ |
| if (wait) { |
| *next_timestamp = now + wait; |
| return true; |
| } |
| |
| /* else no need to wait at all */ |
| *next_timestamp = now; |
| return false; |
| } |
| |
| /* Add timers to event loop */ |
| void throttle_timers_attach_aio_context(ThrottleTimers *tt, |
| AioContext *new_context) |
| { |
| tt->timers[0] = aio_timer_new(new_context, tt->clock_type, SCALE_NS, |
| tt->read_timer_cb, tt->timer_opaque); |
| tt->timers[1] = aio_timer_new(new_context, tt->clock_type, SCALE_NS, |
| tt->write_timer_cb, tt->timer_opaque); |
| } |
| |
| /* |
| * Initialize the ThrottleConfig structure to a valid state |
| * @cfg: the config to initialize |
| */ |
| void throttle_config_init(ThrottleConfig *cfg) |
| { |
| unsigned i; |
| memset(cfg, 0, sizeof(*cfg)); |
| for (i = 0; i < BUCKETS_COUNT; i++) { |
| cfg->buckets[i].burst_length = 1; |
| } |
| } |
| |
| /* To be called first on the ThrottleState */ |
| void throttle_init(ThrottleState *ts) |
| { |
| memset(ts, 0, sizeof(ThrottleState)); |
| throttle_config_init(&ts->cfg); |
| } |
| |
| /* To be called first on the ThrottleTimers */ |
| void throttle_timers_init(ThrottleTimers *tt, |
| AioContext *aio_context, |
| QEMUClockType clock_type, |
| QEMUTimerCB *read_timer_cb, |
| QEMUTimerCB *write_timer_cb, |
| void *timer_opaque) |
| { |
| memset(tt, 0, sizeof(ThrottleTimers)); |
| |
| tt->clock_type = clock_type; |
| tt->read_timer_cb = read_timer_cb; |
| tt->write_timer_cb = write_timer_cb; |
| tt->timer_opaque = timer_opaque; |
| throttle_timers_attach_aio_context(tt, aio_context); |
| } |
| |
| /* destroy a timer */ |
| static void throttle_timer_destroy(QEMUTimer **timer) |
| { |
| assert(*timer != NULL); |
| |
| timer_del(*timer); |
| timer_free(*timer); |
| *timer = NULL; |
| } |
| |
| /* Remove timers from event loop */ |
| void throttle_timers_detach_aio_context(ThrottleTimers *tt) |
| { |
| int i; |
| |
| for (i = 0; i < 2; i++) { |
| throttle_timer_destroy(&tt->timers[i]); |
| } |
| } |
| |
| /* To be called last on the ThrottleTimers */ |
| void throttle_timers_destroy(ThrottleTimers *tt) |
| { |
| throttle_timers_detach_aio_context(tt); |
| } |
| |
| /* is any throttling timer configured */ |
| bool throttle_timers_are_initialized(ThrottleTimers *tt) |
| { |
| if (tt->timers[0]) { |
| return true; |
| } |
| |
| return false; |
| } |
| |
| /* Does any throttling must be done |
| * |
| * @cfg: the throttling configuration to inspect |
| * @ret: true if throttling must be done else false |
| */ |
| bool throttle_enabled(ThrottleConfig *cfg) |
| { |
| int i; |
| |
| for (i = 0; i < BUCKETS_COUNT; i++) { |
| if (cfg->buckets[i].avg > 0) { |
| return true; |
| } |
| } |
| |
| return false; |
| } |
| |
| /* check if a throttling configuration is valid |
| * @cfg: the throttling configuration to inspect |
| * @ret: true if valid else false |
| * @errp: error object |
| */ |
| bool throttle_is_valid(ThrottleConfig *cfg, Error **errp) |
| { |
| int i; |
| bool bps_flag, ops_flag; |
| bool bps_max_flag, ops_max_flag; |
| |
| bps_flag = cfg->buckets[THROTTLE_BPS_TOTAL].avg && |
| (cfg->buckets[THROTTLE_BPS_READ].avg || |
| cfg->buckets[THROTTLE_BPS_WRITE].avg); |
| |
| ops_flag = cfg->buckets[THROTTLE_OPS_TOTAL].avg && |
| (cfg->buckets[THROTTLE_OPS_READ].avg || |
| cfg->buckets[THROTTLE_OPS_WRITE].avg); |
| |
| bps_max_flag = cfg->buckets[THROTTLE_BPS_TOTAL].max && |
| (cfg->buckets[THROTTLE_BPS_READ].max || |
| cfg->buckets[THROTTLE_BPS_WRITE].max); |
| |
| ops_max_flag = cfg->buckets[THROTTLE_OPS_TOTAL].max && |
| (cfg->buckets[THROTTLE_OPS_READ].max || |
| cfg->buckets[THROTTLE_OPS_WRITE].max); |
| |
| if (bps_flag || ops_flag || bps_max_flag || ops_max_flag) { |
| error_setg(errp, "bps/iops/max total values and read/write values" |
| " cannot be used at the same time"); |
| return false; |
| } |
| |
| if (cfg->op_size && |
| !cfg->buckets[THROTTLE_OPS_TOTAL].avg && |
| !cfg->buckets[THROTTLE_OPS_READ].avg && |
| !cfg->buckets[THROTTLE_OPS_WRITE].avg) { |
| error_setg(errp, "iops size requires an iops value to be set"); |
| return false; |
| } |
| |
| for (i = 0; i < BUCKETS_COUNT; i++) { |
| if (cfg->buckets[i].avg < 0 || |
| cfg->buckets[i].max < 0 || |
| cfg->buckets[i].avg > THROTTLE_VALUE_MAX || |
| cfg->buckets[i].max > THROTTLE_VALUE_MAX) { |
| error_setg(errp, "bps/iops/max values must be within [0, %lld]", |
| THROTTLE_VALUE_MAX); |
| return false; |
| } |
| |
| if (!cfg->buckets[i].burst_length) { |
| error_setg(errp, "the burst length cannot be 0"); |
| return false; |
| } |
| |
| if (cfg->buckets[i].burst_length > 1 && !cfg->buckets[i].max) { |
| error_setg(errp, "burst length set without burst rate"); |
| return false; |
| } |
| |
| if (cfg->buckets[i].max && !cfg->buckets[i].avg) { |
| error_setg(errp, "bps_max/iops_max require corresponding" |
| " bps/iops values"); |
| return false; |
| } |
| |
| if (cfg->buckets[i].max && cfg->buckets[i].max < cfg->buckets[i].avg) { |
| error_setg(errp, "bps_max/iops_max cannot be lower than bps/iops"); |
| return false; |
| } |
| } |
| |
| return true; |
| } |
| |
| /* fix bucket parameters */ |
| static void throttle_fix_bucket(LeakyBucket *bkt) |
| { |
| double min; |
| |
| /* zero bucket level */ |
| bkt->level = bkt->burst_level = 0; |
| |
| /* The following is done to cope with the Linux CFQ block scheduler |
| * which regroup reads and writes by block of 100ms in the guest. |
| * When they are two process one making reads and one making writes cfq |
| * make a pattern looking like the following: |
| * WWWWWWWWWWWRRRRRRRRRRRRRRWWWWWWWWWWWWWwRRRRRRRRRRRRRRRRR |
| * Having a max burst value of 100ms of the average will help smooth the |
| * throttling |
| */ |
| min = bkt->avg / 10; |
| if (bkt->avg && !bkt->max) { |
| bkt->max = min; |
| } |
| } |
| |
| /* take care of canceling a timer */ |
| static void throttle_cancel_timer(QEMUTimer *timer) |
| { |
| assert(timer != NULL); |
| |
| timer_del(timer); |
| } |
| |
| /* Used to configure the throttle |
| * |
| * @ts: the throttle state we are working on |
| * @tt: the throttle timers we use in this aio context |
| * @cfg: the config to set |
| */ |
| void throttle_config(ThrottleState *ts, |
| ThrottleTimers *tt, |
| ThrottleConfig *cfg) |
| { |
| int i; |
| |
| ts->cfg = *cfg; |
| |
| for (i = 0; i < BUCKETS_COUNT; i++) { |
| throttle_fix_bucket(&ts->cfg.buckets[i]); |
| } |
| |
| ts->previous_leak = qemu_clock_get_ns(tt->clock_type); |
| |
| for (i = 0; i < 2; i++) { |
| throttle_cancel_timer(tt->timers[i]); |
| } |
| } |
| |
| /* used to get config |
| * |
| * @ts: the throttle state we are working on |
| * @cfg: the config to write |
| */ |
| void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg) |
| { |
| *cfg = ts->cfg; |
| } |
| |
| |
| /* Schedule the read or write timer if needed |
| * |
| * NOTE: this function is not unit tested due to it's usage of timer_mod |
| * |
| * @tt: the timers structure |
| * @is_write: the type of operation (read/write) |
| * @ret: true if the timer has been scheduled else false |
| */ |
| bool throttle_schedule_timer(ThrottleState *ts, |
| ThrottleTimers *tt, |
| bool is_write) |
| { |
| int64_t now = qemu_clock_get_ns(tt->clock_type); |
| int64_t next_timestamp; |
| bool must_wait; |
| |
| must_wait = throttle_compute_timer(ts, |
| is_write, |
| now, |
| &next_timestamp); |
| |
| /* request not throttled */ |
| if (!must_wait) { |
| return false; |
| } |
| |
| /* request throttled and timer pending -> do nothing */ |
| if (timer_pending(tt->timers[is_write])) { |
| return true; |
| } |
| |
| /* request throttled and timer not pending -> arm timer */ |
| timer_mod(tt->timers[is_write], next_timestamp); |
| return true; |
| } |
| |
| /* do the accounting for this operation |
| * |
| * @is_write: the type of operation (read/write) |
| * @size: the size of the operation |
| */ |
| void throttle_account(ThrottleState *ts, bool is_write, uint64_t size) |
| { |
| const BucketType bucket_types_size[2][2] = { |
| { THROTTLE_BPS_TOTAL, THROTTLE_BPS_READ }, |
| { THROTTLE_BPS_TOTAL, THROTTLE_BPS_WRITE } |
| }; |
| const BucketType bucket_types_units[2][2] = { |
| { THROTTLE_OPS_TOTAL, THROTTLE_OPS_READ }, |
| { THROTTLE_OPS_TOTAL, THROTTLE_OPS_WRITE } |
| }; |
| double units = 1.0; |
| unsigned i; |
| |
| /* if cfg.op_size is defined and smaller than size we compute unit count */ |
| if (ts->cfg.op_size && size > ts->cfg.op_size) { |
| units = (double) size / ts->cfg.op_size; |
| } |
| |
| for (i = 0; i < 2; i++) { |
| LeakyBucket *bkt; |
| |
| bkt = &ts->cfg.buckets[bucket_types_size[is_write][i]]; |
| bkt->level += size; |
| if (bkt->burst_length > 1) { |
| bkt->burst_level += size; |
| } |
| |
| bkt = &ts->cfg.buckets[bucket_types_units[is_write][i]]; |
| bkt->level += units; |
| if (bkt->burst_length > 1) { |
| bkt->burst_level += units; |
| } |
| } |
| } |
| |
