Message ID | 1378053587-12121-2-git-send-email-benoit@irqsave.net |
---|---|
State | New |
Headers | show |
On Sun, 09/01 18:39, Benoît Canet wrote: > Implement the continuous leaky bucket algorithm devised on IRC as a separate > module. > > Signed-off-by: Benoit Canet <benoit@irqsave.net> > --- > include/qemu/throttle.h | 103 ++++++++++++ > util/Makefile.objs | 1 + > util/throttle.c | 396 +++++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 500 insertions(+) > create mode 100644 include/qemu/throttle.h > create mode 100644 util/throttle.c > > diff --git a/include/qemu/throttle.h b/include/qemu/throttle.h > new file mode 100644 > index 0000000..823650d > --- /dev/null > +++ b/include/qemu/throttle.h > @@ -0,0 +1,103 @@ > +/* > + * QEMU throttling infrastructure > + * > + * Copyright (C) Nodalink, SARL. 2013 > + * > + * Author: > + * Benoît Canet <benoit.canet@irqsave.net> > + * > + * 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/>. > + */ > + > +#ifndef THROTTLE_H > +#define THROTTLE_H > + > +#include <stdint.h> > +#include "qemu-common.h" > +#include "qemu/timer.h" > + > +#define NANOSECONDS_PER_SECOND 1000000000.0 > + > +typedef enum { > + THROTTLE_BPS_TOTAL, > + THROTTLE_BPS_READ, > + THROTTLE_BPS_WRITE, > + THROTTLE_OPS_TOTAL, > + THROTTLE_OPS_READ, > + THROTTLE_OPS_WRITE, > + BUCKETS_COUNT, > +} BucketType; > + > +typedef struct LeakyBucket { > + double avg; /* average goal in units per second */ > + double max; /* leaky bucket max burst in units */ > + double level; /* bucket level in units */ > +} LeakyBucket; > + > +/* The following structure is used to configure a ThrottleState > + * It contains a bit of state: the bucket field of the LeakyBucket structure. > + * However it allows to keep the code clean and the bucket field is reset to > + * zero at the right time. > + */ > +typedef struct ThrottleConfig { > + LeakyBucket buckets[BUCKETS_COUNT]; /* leaky buckets */ > + uint64_t op_size; /* size of an operation in bytes */ > +} ThrottleConfig; > + > +typedef struct ThrottleState { > + ThrottleConfig cfg; /* configuration */ > + int64_t previous_leak; /* timestamp of the last leak done */ > + QEMUTimer * timers[2]; /* timers used to do the throttling */ > + QEMUClockType clock_type; /* the clock used */ > +} ThrottleState; > + > +/* operations on single leaky buckets */ > +void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta); > + > +int64_t throttle_compute_wait(LeakyBucket *bkt); > + > +/* expose timer computation function for unit tests */ > +bool throttle_compute_timer(ThrottleState *ts, > + bool is_write, > + int64_t now, > + int64_t *next_timestamp); > + > +/* init/destroy cycle */ > +void throttle_init(ThrottleState *ts, > + QEMUClockType clock_type, > + void (read_timer)(void *), > + void (write_timer)(void *), > + void *timer_opaque); > + > +void throttle_destroy(ThrottleState *ts); > + > +bool throttle_have_timer(ThrottleState *ts); > + > +/* configuration */ > +bool throttle_enabled(ThrottleConfig *cfg); > + > +bool throttle_conflicting(ThrottleConfig *cfg); > + > +bool throttle_is_valid(ThrottleConfig *cfg); > + > +void throttle_config(ThrottleState *ts, ThrottleConfig *cfg); > + > +void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg); > + > +/* usage */ > +bool throttle_schedule_timer(ThrottleState *ts, bool is_write); > + > +void throttle_account(ThrottleState *ts, bool is_write, uint64_t size); > + > +#endif > diff --git a/util/Makefile.objs b/util/Makefile.objs > index dc72ab0..2bb13a2 100644 > --- a/util/Makefile.objs > +++ b/util/Makefile.objs > @@ -11,3 +11,4 @@ util-obj-y += iov.o aes.o qemu-config.o qemu-sockets.o uri.o notify.o > util-obj-y += qemu-option.o qemu-progress.o > util-obj-y += hexdump.o > util-obj-y += crc32c.o > +util-obj-y += throttle.o > diff --git a/util/throttle.c b/util/throttle.c > new file mode 100644 > index 0000000..cf048b9 > --- /dev/null > +++ b/util/throttle.c > @@ -0,0 +1,396 @@ > +/* > + * QEMU throttling infrastructure > + * > + * Copyright (C) Nodalink, SARL. 2013 > + * > + * Author: > + * Benoît Canet <benoit.canet@irqsave.net> > + * > + * 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/throttle.h" > +#include "qemu/timer.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); > +} > + > +/* 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; > + } > + > + extra = bkt->level - bkt->max; > + > + if (extra <= 0) { > + return 0; > + } > + > + return throttle_do_compute_wait(bkt->avg, extra); > +} > + > +/* 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 > + */ > +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; > +} > + > +/* To be called first on the ThrottleState */ > +void throttle_init(ThrottleState *ts, > + QEMUClockType clock_type, > + QEMUTimerCB *read_timer_cb, > + QEMUTimerCB *write_timer_cb, > + void *timer_opaque) > +{ > + memset(ts, 0, sizeof(ThrottleState)); > + > + ts->clock_type = clock_type; > + ts->timers[0] = timer_new_ns(clock_type, read_timer_cb, timer_opaque); > + ts->timers[1] = timer_new_ns(clock_type, write_timer_cb, timer_opaque); > +} > + > +/* destroy a timer */ > +static void throttle_timer_destroy(QEMUTimer **timer) > +{ > + assert(*timer != NULL); > + > + timer_del(*timer); > + timer_free(*timer); > + *timer = NULL; > +} > + > +/* To be called last on the ThrottleState */ > +void throttle_destroy(ThrottleState *ts) > +{ > + int i; > + > + for (i = 0; i < 2; i++) { > + throttle_timer_destroy(&ts->timers[i]); > + } > +} > + > +/* is any throttling timer configured */ > +bool throttle_have_timer(ThrottleState *ts) > +{ > + if (ts->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; > +} > + > +/* return true if any two throttling parameters conflicts > + * > + * @cfg: the throttling configuration to inspect > + * @ret: true if any conflict detected else false > + */ > +bool throttle_conflicting(ThrottleConfig *cfg) > +{ > + 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); > + > + return bps_flag || ops_flag || bps_max_flag || ops_max_flag; > +} > + > +/* check if a throttling configuration is valid > + * @cfg: the throttling configuration to inspect > + * @ret: true if valid else false > + */ > +bool throttle_is_valid(ThrottleConfig *cfg) > +{ > + bool invalid = false; > + int i; > + > + for (i = 0; i < BUCKETS_COUNT; i++) { > + if (cfg->buckets[i].avg < 0) { > + invalid = true; > + } > + } > + > + for (i = 0; i < BUCKETS_COUNT; i++) { > + if (cfg->buckets[i].max < 0) { > + invalid = true; > + } > + } > + > + return !invalid; > +} > + > +/* fix bucket parameters */ > +static void throttle_fix_bucket(LeakyBucket *bkt) > +{ > + double min; > + > + /* zero bucket level */ > + bkt->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 > + * @cfg: the config to set > + */ > +void throttle_config(ThrottleState *ts, 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(ts->clock_type); > + > + for (i = 0; i < 2; i++) { > + throttle_cancel_timer(ts->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 > + * > + * @is_write: the type of operation (read/write) > + * @ret: true if the timer has been scheduled else false > + */ > +bool throttle_schedule_timer(ThrottleState *ts, bool is_write) > +{ > + int64_t now = qemu_clock_get_ns(ts->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(ts->timers[is_write])) { > + return true; > + } > + > + /* request throttled and timer not pending -> arm timer */ > + timer_mod(ts->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) > +{ > + double units = 1.0; > + > + /* if cfg.op_size is not defined we will account exactly 1 operation */ > + if (ts->cfg.op_size) { > + units = (double) size / ts->cfg.op_size; > + } If op_size is non-zero, iops limits are merely a fixed proportion of bps limits, which means the lower set of the two is applied and the higher skipped. I understand the amazon uses op_size like accounting for big IO requests, but we don't do it condionally on io size or anything here, so that once user sets op_size, it simply kicks either bps_{,rd,wr} or iops_{,rd,wr} out the game, is that true? Fam > + > + ts->cfg.buckets[THROTTLE_BPS_TOTAL].level += size; > + ts->cfg.buckets[THROTTLE_OPS_TOTAL].level += units; > + > + if (is_write) { > + ts->cfg.buckets[THROTTLE_BPS_WRITE].level += size; > + ts->cfg.buckets[THROTTLE_OPS_WRITE].level += units; > + } else { > + ts->cfg.buckets[THROTTLE_BPS_READ].level += size; > + ts->cfg.buckets[THROTTLE_OPS_READ].level += units; > + } > +} > + > -- > 1.7.10.4 > >
> If op_size is non-zero, iops limits are merely a fixed proportion of bps > limits, which means the lower set of the two is applied and the higher skipped. > I understand the amazon uses op_size like accounting for big IO requests, but > we don't do it condionally on io size or anything here, so that once user sets > op_size, it simply kicks either bps_{,rd,wr} or iops_{,rd,wr} out the game, is > that true? It will combine with iops_{,rd,wr}. Best regards Benoît
Il 02/09/2013 12:16, Benoît Canet ha scritto: >> If op_size is non-zero, iops limits are merely a fixed proportion of bps >> > limits, which means the lower set of the two is applied and the higher skipped. >> > I understand the amazon uses op_size like accounting for big IO requests, but >> > we don't do it condionally on io size or anything here, so that once user sets >> > op_size, it simply kicks either bps_{,rd,wr} or iops_{,rd,wr} out the game, is >> > that true? > It will combine with iops_{,rd,wr}. I think what Fam asked is this: what is the difference between bps=524288 and iops=1/op_size=524288? And I think the answer should be that bs=524288 will allow many requests up to 524288 bytes, while with iops all requests should be rounded up to the op_size. However, I think this is not what the code is doing right now, isn't it? Paolo
> However, I think this is not what the code is doing right now, isn't it?
Hi Paolo,
I changed the code so it trigger only if the request size is bigger than
op_size.
Best regards
Benoît
diff --git a/include/qemu/throttle.h b/include/qemu/throttle.h new file mode 100644 index 0000000..823650d --- /dev/null +++ b/include/qemu/throttle.h @@ -0,0 +1,103 @@ +/* + * QEMU throttling infrastructure + * + * Copyright (C) Nodalink, SARL. 2013 + * + * Author: + * Benoît Canet <benoit.canet@irqsave.net> + * + * 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/>. + */ + +#ifndef THROTTLE_H +#define THROTTLE_H + +#include <stdint.h> +#include "qemu-common.h" +#include "qemu/timer.h" + +#define NANOSECONDS_PER_SECOND 1000000000.0 + +typedef enum { + THROTTLE_BPS_TOTAL, + THROTTLE_BPS_READ, + THROTTLE_BPS_WRITE, + THROTTLE_OPS_TOTAL, + THROTTLE_OPS_READ, + THROTTLE_OPS_WRITE, + BUCKETS_COUNT, +} BucketType; + +typedef struct LeakyBucket { + double avg; /* average goal in units per second */ + double max; /* leaky bucket max burst in units */ + double level; /* bucket level in units */ +} LeakyBucket; + +/* The following structure is used to configure a ThrottleState + * It contains a bit of state: the bucket field of the LeakyBucket structure. + * However it allows to keep the code clean and the bucket field is reset to + * zero at the right time. + */ +typedef struct ThrottleConfig { + LeakyBucket buckets[BUCKETS_COUNT]; /* leaky buckets */ + uint64_t op_size; /* size of an operation in bytes */ +} ThrottleConfig; + +typedef struct ThrottleState { + ThrottleConfig cfg; /* configuration */ + int64_t previous_leak; /* timestamp of the last leak done */ + QEMUTimer * timers[2]; /* timers used to do the throttling */ + QEMUClockType clock_type; /* the clock used */ +} ThrottleState; + +/* operations on single leaky buckets */ +void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta); + +int64_t throttle_compute_wait(LeakyBucket *bkt); + +/* expose timer computation function for unit tests */ +bool throttle_compute_timer(ThrottleState *ts, + bool is_write, + int64_t now, + int64_t *next_timestamp); + +/* init/destroy cycle */ +void throttle_init(ThrottleState *ts, + QEMUClockType clock_type, + void (read_timer)(void *), + void (write_timer)(void *), + void *timer_opaque); + +void throttle_destroy(ThrottleState *ts); + +bool throttle_have_timer(ThrottleState *ts); + +/* configuration */ +bool throttle_enabled(ThrottleConfig *cfg); + +bool throttle_conflicting(ThrottleConfig *cfg); + +bool throttle_is_valid(ThrottleConfig *cfg); + +void throttle_config(ThrottleState *ts, ThrottleConfig *cfg); + +void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg); + +/* usage */ +bool throttle_schedule_timer(ThrottleState *ts, bool is_write); + +void throttle_account(ThrottleState *ts, bool is_write, uint64_t size); + +#endif diff --git a/util/Makefile.objs b/util/Makefile.objs index dc72ab0..2bb13a2 100644 --- a/util/Makefile.objs +++ b/util/Makefile.objs @@ -11,3 +11,4 @@ util-obj-y += iov.o aes.o qemu-config.o qemu-sockets.o uri.o notify.o util-obj-y += qemu-option.o qemu-progress.o util-obj-y += hexdump.o util-obj-y += crc32c.o +util-obj-y += throttle.o diff --git a/util/throttle.c b/util/throttle.c new file mode 100644 index 0000000..cf048b9 --- /dev/null +++ b/util/throttle.c @@ -0,0 +1,396 @@ +/* + * QEMU throttling infrastructure + * + * Copyright (C) Nodalink, SARL. 2013 + * + * Author: + * Benoît Canet <benoit.canet@irqsave.net> + * + * 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/throttle.h" +#include "qemu/timer.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); +} + +/* 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; + } + + extra = bkt->level - bkt->max; + + if (extra <= 0) { + return 0; + } + + return throttle_do_compute_wait(bkt->avg, extra); +} + +/* 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 + */ +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; +} + +/* To be called first on the ThrottleState */ +void throttle_init(ThrottleState *ts, + QEMUClockType clock_type, + QEMUTimerCB *read_timer_cb, + QEMUTimerCB *write_timer_cb, + void *timer_opaque) +{ + memset(ts, 0, sizeof(ThrottleState)); + + ts->clock_type = clock_type; + ts->timers[0] = timer_new_ns(clock_type, read_timer_cb, timer_opaque); + ts->timers[1] = timer_new_ns(clock_type, write_timer_cb, timer_opaque); +} + +/* destroy a timer */ +static void throttle_timer_destroy(QEMUTimer **timer) +{ + assert(*timer != NULL); + + timer_del(*timer); + timer_free(*timer); + *timer = NULL; +} + +/* To be called last on the ThrottleState */ +void throttle_destroy(ThrottleState *ts) +{ + int i; + + for (i = 0; i < 2; i++) { + throttle_timer_destroy(&ts->timers[i]); + } +} + +/* is any throttling timer configured */ +bool throttle_have_timer(ThrottleState *ts) +{ + if (ts->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; +} + +/* return true if any two throttling parameters conflicts + * + * @cfg: the throttling configuration to inspect + * @ret: true if any conflict detected else false + */ +bool throttle_conflicting(ThrottleConfig *cfg) +{ + 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); + + return bps_flag || ops_flag || bps_max_flag || ops_max_flag; +} + +/* check if a throttling configuration is valid + * @cfg: the throttling configuration to inspect + * @ret: true if valid else false + */ +bool throttle_is_valid(ThrottleConfig *cfg) +{ + bool invalid = false; + int i; + + for (i = 0; i < BUCKETS_COUNT; i++) { + if (cfg->buckets[i].avg < 0) { + invalid = true; + } + } + + for (i = 0; i < BUCKETS_COUNT; i++) { + if (cfg->buckets[i].max < 0) { + invalid = true; + } + } + + return !invalid; +} + +/* fix bucket parameters */ +static void throttle_fix_bucket(LeakyBucket *bkt) +{ + double min; + + /* zero bucket level */ + bkt->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 + * @cfg: the config to set + */ +void throttle_config(ThrottleState *ts, 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(ts->clock_type); + + for (i = 0; i < 2; i++) { + throttle_cancel_timer(ts->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 + * + * @is_write: the type of operation (read/write) + * @ret: true if the timer has been scheduled else false + */ +bool throttle_schedule_timer(ThrottleState *ts, bool is_write) +{ + int64_t now = qemu_clock_get_ns(ts->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(ts->timers[is_write])) { + return true; + } + + /* request throttled and timer not pending -> arm timer */ + timer_mod(ts->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) +{ + double units = 1.0; + + /* if cfg.op_size is not defined we will account exactly 1 operation */ + if (ts->cfg.op_size) { + units = (double) size / ts->cfg.op_size; + } + + ts->cfg.buckets[THROTTLE_BPS_TOTAL].level += size; + ts->cfg.buckets[THROTTLE_OPS_TOTAL].level += units; + + if (is_write) { + ts->cfg.buckets[THROTTLE_BPS_WRITE].level += size; + ts->cfg.buckets[THROTTLE_OPS_WRITE].level += units; + } else { + ts->cfg.buckets[THROTTLE_BPS_READ].level += size; + ts->cfg.buckets[THROTTLE_OPS_READ].level += units; + } +} +
Implement the continuous leaky bucket algorithm devised on IRC as a separate module. Signed-off-by: Benoit Canet <benoit@irqsave.net> --- include/qemu/throttle.h | 103 ++++++++++++ util/Makefile.objs | 1 + util/throttle.c | 396 +++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 500 insertions(+) create mode 100644 include/qemu/throttle.h create mode 100644 util/throttle.c