/* * QEMU throttling infrastructure * * Copyright (C) Nodalink, EURL. 2013-2014 * Copyright (C) Igalia, S.L. 2015 * * Authors: * BenoƮt 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; } } /* undo internal bucket parameter changes (see throttle_fix_bucket()) */ static void throttle_unfix_bucket(LeakyBucket *bkt) { if (bkt->max < bkt->avg) { bkt->max = 0; } } /* 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) { int i; *cfg = ts->cfg; for (i = 0; i < BUCKETS_COUNT; i++) { throttle_unfix_bucket(&cfg->buckets[i]); } } /* 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; } } }