mirror of https://gitee.com/openkylin/qemu.git
throttle: Add a new throttling API implementing continuous leaky bucket.
Implement the continuous leaky bucket algorithm devised on IRC as a separate module. Signed-off-by: Benoit Canet <benoit@irqsave.net> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Benoît Canet
Stefan Hajnoczi
parent
df7131623d
commit
5ddfffbdc5
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@ -0,0 +1,110 @@
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/*
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* QEMU throttling infrastructure
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*
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* Copyright (C) Nodalink, SARL. 2013
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*
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* Author:
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* Benoît Canet <benoit.canet@irqsave.net>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 or
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* (at your option) version 3 of the License.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef THROTTLE_H
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#define THROTTLE_H
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#include <stdint.h>
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#include "qemu-common.h"
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#include "qemu/timer.h"
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#define NANOSECONDS_PER_SECOND 1000000000.0
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typedef enum {
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THROTTLE_BPS_TOTAL,
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THROTTLE_BPS_READ,
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THROTTLE_BPS_WRITE,
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THROTTLE_OPS_TOTAL,
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THROTTLE_OPS_READ,
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THROTTLE_OPS_WRITE,
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BUCKETS_COUNT,
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} BucketType;
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/*
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* The max parameter of the leaky bucket throttling algorithm can be used to
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* allow the guest to do bursts.
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* The max value is a pool of I/O that the guest can use without being throttled
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* at all. Throttling is triggered once this pool is empty.
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*/
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typedef struct LeakyBucket {
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double avg; /* average goal in units per second */
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double max; /* leaky bucket max burst in units */
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double level; /* bucket level in units */
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} LeakyBucket;
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/* The following structure is used to configure a ThrottleState
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* It contains a bit of state: the bucket field of the LeakyBucket structure.
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* However it allows to keep the code clean and the bucket field is reset to
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* zero at the right time.
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*/
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typedef struct ThrottleConfig {
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LeakyBucket buckets[BUCKETS_COUNT]; /* leaky buckets */
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uint64_t op_size; /* size of an operation in bytes */
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} ThrottleConfig;
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typedef struct ThrottleState {
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ThrottleConfig cfg; /* configuration */
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int64_t previous_leak; /* timestamp of the last leak done */
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QEMUTimer * timers[2]; /* timers used to do the throttling */
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QEMUClockType clock_type; /* the clock used */
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} ThrottleState;
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/* operations on single leaky buckets */
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void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta);
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int64_t throttle_compute_wait(LeakyBucket *bkt);
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/* expose timer computation function for unit tests */
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bool throttle_compute_timer(ThrottleState *ts,
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bool is_write,
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int64_t now,
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int64_t *next_timestamp);
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/* init/destroy cycle */
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void throttle_init(ThrottleState *ts,
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QEMUClockType clock_type,
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void (read_timer)(void *),
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void (write_timer)(void *),
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void *timer_opaque);
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void throttle_destroy(ThrottleState *ts);
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bool throttle_have_timer(ThrottleState *ts);
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/* configuration */
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bool throttle_enabled(ThrottleConfig *cfg);
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bool throttle_conflicting(ThrottleConfig *cfg);
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bool throttle_is_valid(ThrottleConfig *cfg);
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void throttle_config(ThrottleState *ts, ThrottleConfig *cfg);
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void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg);
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/* usage */
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bool throttle_schedule_timer(ThrottleState *ts, bool is_write);
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void throttle_account(ThrottleState *ts, bool is_write, uint64_t size);
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#endif
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@ -11,3 +11,4 @@ util-obj-y += iov.o aes.o qemu-config.o qemu-sockets.o uri.o notify.o
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util-obj-y += qemu-option.o qemu-progress.o
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util-obj-y += hexdump.o
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util-obj-y += crc32c.o
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util-obj-y += throttle.o
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@ -0,0 +1,396 @@
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/*
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* QEMU throttling infrastructure
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*
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* Copyright (C) Nodalink, SARL. 2013
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*
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* Author:
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* Benoît Canet <benoit.canet@irqsave.net>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 or
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* (at your option) version 3 of the License.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include "qemu/throttle.h"
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#include "qemu/timer.h"
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/* This function make a bucket leak
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*
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* @bkt: the bucket to make leak
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* @delta_ns: the time delta
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*/
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void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta_ns)
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{
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double leak;
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/* compute how much to leak */
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leak = (bkt->avg * (double) delta_ns) / NANOSECONDS_PER_SECOND;
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/* make the bucket leak */
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bkt->level = MAX(bkt->level - leak, 0);
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}
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/* Calculate the time delta since last leak and make proportionals leaks
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*
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* @now: the current timestamp in ns
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*/
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static void throttle_do_leak(ThrottleState *ts, int64_t now)
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{
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/* compute the time elapsed since the last leak */
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int64_t delta_ns = now - ts->previous_leak;
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int i;
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ts->previous_leak = now;
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if (delta_ns <= 0) {
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return;
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}
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/* make each bucket leak */
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for (i = 0; i < BUCKETS_COUNT; i++) {
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throttle_leak_bucket(&ts->cfg.buckets[i], delta_ns);
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}
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}
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/* do the real job of computing the time to wait
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*
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* @limit: the throttling limit
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* @extra: the number of operation to delay
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* @ret: the time to wait in ns
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*/
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static int64_t throttle_do_compute_wait(double limit, double extra)
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{
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double wait = extra * NANOSECONDS_PER_SECOND;
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wait /= limit;
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return wait;
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}
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/* This function compute the wait time in ns that a leaky bucket should trigger
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*
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* @bkt: the leaky bucket we operate on
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* @ret: the resulting wait time in ns or 0 if the operation can go through
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*/
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int64_t throttle_compute_wait(LeakyBucket *bkt)
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{
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double extra; /* the number of extra units blocking the io */
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if (!bkt->avg) {
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return 0;
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}
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extra = bkt->level - bkt->max;
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if (extra <= 0) {
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return 0;
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}
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return throttle_do_compute_wait(bkt->avg, extra);
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}
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/* This function compute the time that must be waited while this IO
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*
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* @is_write: true if the current IO is a write, false if it's a read
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* @ret: time to wait
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*/
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static int64_t throttle_compute_wait_for(ThrottleState *ts,
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bool is_write)
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{
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BucketType to_check[2][4] = { {THROTTLE_BPS_TOTAL,
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THROTTLE_OPS_TOTAL,
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THROTTLE_BPS_READ,
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THROTTLE_OPS_READ},
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{THROTTLE_BPS_TOTAL,
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THROTTLE_OPS_TOTAL,
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THROTTLE_BPS_WRITE,
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THROTTLE_OPS_WRITE}, };
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int64_t wait, max_wait = 0;
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int i;
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for (i = 0; i < 4; i++) {
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BucketType index = to_check[is_write][i];
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wait = throttle_compute_wait(&ts->cfg.buckets[index]);
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if (wait > max_wait) {
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max_wait = wait;
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}
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}
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return max_wait;
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}
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/* compute the timer for this type of operation
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*
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* @is_write: the type of operation
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* @now: the current clock timestamp
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* @next_timestamp: the resulting timer
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* @ret: true if a timer must be set
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*/
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bool throttle_compute_timer(ThrottleState *ts,
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bool is_write,
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int64_t now,
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int64_t *next_timestamp)
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{
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int64_t wait;
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/* leak proportionally to the time elapsed */
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throttle_do_leak(ts, now);
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/* compute the wait time if any */
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wait = throttle_compute_wait_for(ts, is_write);
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/* if the code must wait compute when the next timer should fire */
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if (wait) {
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*next_timestamp = now + wait;
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return true;
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}
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/* else no need to wait at all */
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*next_timestamp = now;
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return false;
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}
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/* To be called first on the ThrottleState */
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void throttle_init(ThrottleState *ts,
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QEMUClockType clock_type,
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QEMUTimerCB *read_timer_cb,
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QEMUTimerCB *write_timer_cb,
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void *timer_opaque)
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{
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memset(ts, 0, sizeof(ThrottleState));
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ts->clock_type = clock_type;
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ts->timers[0] = timer_new_ns(clock_type, read_timer_cb, timer_opaque);
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ts->timers[1] = timer_new_ns(clock_type, write_timer_cb, timer_opaque);
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}
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/* destroy a timer */
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static void throttle_timer_destroy(QEMUTimer **timer)
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{
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assert(*timer != NULL);
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timer_del(*timer);
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timer_free(*timer);
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*timer = NULL;
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}
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/* To be called last on the ThrottleState */
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void throttle_destroy(ThrottleState *ts)
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{
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int i;
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for (i = 0; i < 2; i++) {
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throttle_timer_destroy(&ts->timers[i]);
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}
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}
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/* is any throttling timer configured */
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bool throttle_have_timer(ThrottleState *ts)
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{
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if (ts->timers[0]) {
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return true;
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}
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return false;
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}
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/* Does any throttling must be done
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*
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* @cfg: the throttling configuration to inspect
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* @ret: true if throttling must be done else false
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*/
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bool throttle_enabled(ThrottleConfig *cfg)
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{
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int i;
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for (i = 0; i < BUCKETS_COUNT; i++) {
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if (cfg->buckets[i].avg > 0) {
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return true;
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}
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}
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return false;
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}
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/* return true if any two throttling parameters conflicts
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*
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* @cfg: the throttling configuration to inspect
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* @ret: true if any conflict detected else false
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*/
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bool throttle_conflicting(ThrottleConfig *cfg)
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{
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bool bps_flag, ops_flag;
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bool bps_max_flag, ops_max_flag;
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bps_flag = cfg->buckets[THROTTLE_BPS_TOTAL].avg &&
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(cfg->buckets[THROTTLE_BPS_READ].avg ||
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cfg->buckets[THROTTLE_BPS_WRITE].avg);
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ops_flag = cfg->buckets[THROTTLE_OPS_TOTAL].avg &&
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(cfg->buckets[THROTTLE_OPS_READ].avg ||
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cfg->buckets[THROTTLE_OPS_WRITE].avg);
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bps_max_flag = cfg->buckets[THROTTLE_BPS_TOTAL].max &&
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(cfg->buckets[THROTTLE_BPS_READ].max ||
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cfg->buckets[THROTTLE_BPS_WRITE].max);
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ops_max_flag = cfg->buckets[THROTTLE_OPS_TOTAL].max &&
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(cfg->buckets[THROTTLE_OPS_READ].max ||
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cfg->buckets[THROTTLE_OPS_WRITE].max);
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return bps_flag || ops_flag || bps_max_flag || ops_max_flag;
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}
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/* check if a throttling configuration is valid
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* @cfg: the throttling configuration to inspect
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* @ret: true if valid else false
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*/
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bool throttle_is_valid(ThrottleConfig *cfg)
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{
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bool invalid = false;
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int i;
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for (i = 0; i < BUCKETS_COUNT; i++) {
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if (cfg->buckets[i].avg < 0) {
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invalid = true;
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}
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}
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for (i = 0; i < BUCKETS_COUNT; i++) {
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if (cfg->buckets[i].max < 0) {
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invalid = true;
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}
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}
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return !invalid;
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}
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/* fix bucket parameters */
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static void throttle_fix_bucket(LeakyBucket *bkt)
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{
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double min;
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/* zero bucket level */
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bkt->level = 0;
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/* The following is done to cope with the Linux CFQ block scheduler
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* which regroup reads and writes by block of 100ms in the guest.
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* When they are two process one making reads and one making writes cfq
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* make a pattern looking like the following:
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* WWWWWWWWWWWRRRRRRRRRRRRRRWWWWWWWWWWWWWwRRRRRRRRRRRRRRRRR
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* Having a max burst value of 100ms of the average will help smooth the
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* throttling
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*/
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min = bkt->avg / 10;
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if (bkt->avg && !bkt->max) {
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bkt->max = min;
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}
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}
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/* take care of canceling a timer */
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static void throttle_cancel_timer(QEMUTimer *timer)
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{
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assert(timer != NULL);
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timer_del(timer);
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}
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/* Used to configure the throttle
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*
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* @ts: the throttle state we are working on
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* @cfg: the config to set
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*/
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void throttle_config(ThrottleState *ts, ThrottleConfig *cfg)
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{
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int i;
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ts->cfg = *cfg;
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for (i = 0; i < BUCKETS_COUNT; i++) {
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throttle_fix_bucket(&ts->cfg.buckets[i]);
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}
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ts->previous_leak = qemu_clock_get_ns(ts->clock_type);
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for (i = 0; i < 2; i++) {
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throttle_cancel_timer(ts->timers[i]);
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}
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}
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/* used to get config
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*
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* @ts: the throttle state we are working on
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* @cfg: the config to write
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*/
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void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg)
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{
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*cfg = ts->cfg;
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}
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/* Schedule the read or write timer if needed
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*
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* NOTE: this function is not unit tested due to it's usage of timer_mod
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*
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* @is_write: the type of operation (read/write)
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* @ret: true if the timer has been scheduled else false
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*/
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bool throttle_schedule_timer(ThrottleState *ts, bool is_write)
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{
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int64_t now = qemu_clock_get_ns(ts->clock_type);
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int64_t next_timestamp;
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bool must_wait;
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must_wait = throttle_compute_timer(ts,
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is_write,
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now,
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&next_timestamp);
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/* request not throttled */
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if (!must_wait) {
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return false;
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}
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/* request throttled and timer pending -> do nothing */
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if (timer_pending(ts->timers[is_write])) {
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return true;
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}
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/* request throttled and timer not pending -> arm timer */
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timer_mod(ts->timers[is_write], next_timestamp);
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return true;
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}
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/* do the accounting for this operation
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*
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* @is_write: the type of operation (read/write)
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* @size: the size of the operation
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*/
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void throttle_account(ThrottleState *ts, bool is_write, uint64_t size)
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{
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double units = 1.0;
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/* 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;
|
||||
}
|
||||
|
||||
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;
|
||||
}
|
||||
}
|
||||
|
||||
Loading…
Reference in New Issue