2015-06-08 19:17:42 +03:00
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/*
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* QEMU block throttling group infrastructure
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*
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* Copyright (C) Nodalink, EURL. 2014
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* Copyright (C) Igalia, S.L. 2015
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*
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* Authors:
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* Benoît Canet <benoit.canet@nodalink.com>
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* Alberto Garcia <berto@igalia.com>
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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 "block/throttle-groups.h"
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2015-06-08 19:17:44 +03:00
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#include "qemu/queue.h"
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#include "qemu/thread.h"
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#include "sysemu/qtest.h"
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2015-06-08 19:17:42 +03:00
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/* The ThrottleGroup structure (with its ThrottleState) is shared
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* among different BlockDriverState and it's independent from
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* AioContext, so in order to use it from different threads it needs
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* its own locking.
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*
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* This locking is however handled internally in this file, so it's
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2015-06-08 19:17:45 +03:00
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* mostly transparent to outside users (but see the documentation in
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* throttle_groups_lock()).
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2015-06-08 19:17:42 +03:00
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*
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* The whole ThrottleGroup structure is private and invisible to
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* outside users, that only use it through its ThrottleState.
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*
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* In addition to the ThrottleGroup structure, BlockDriverState has
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* fields that need to be accessed by other members of the group and
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* therefore also need to be protected by this lock. Once a BDS is
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* registered in a group those fields can be accessed by other threads
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* any time.
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*
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* Again, all this is handled internally and is mostly transparent to
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* the outside. The 'throttle_timers' field however has an additional
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* constraint because it may be temporarily invalid (see for example
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* bdrv_set_aio_context()). Therefore in this file a thread will
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* access some other BDS's timers only after verifying that that BDS
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* has throttled requests in the queue.
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*/
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typedef struct ThrottleGroup {
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char *name; /* This is constant during the lifetime of the group */
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QemuMutex lock; /* This lock protects the following four fields */
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ThrottleState ts;
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QLIST_HEAD(, BlockDriverState) head;
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BlockDriverState *tokens[2];
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bool any_timer_armed[2];
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/* These two are protected by the global throttle_groups_lock */
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unsigned refcount;
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QTAILQ_ENTRY(ThrottleGroup) list;
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} ThrottleGroup;
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static QemuMutex throttle_groups_lock;
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static QTAILQ_HEAD(, ThrottleGroup) throttle_groups =
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QTAILQ_HEAD_INITIALIZER(throttle_groups);
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/* Increments the reference count of a ThrottleGroup given its name.
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*
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* If no ThrottleGroup is found with the given name a new one is
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* created.
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*
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* @name: the name of the ThrottleGroup
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* @ret: the ThrottleGroup
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*/
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static ThrottleGroup *throttle_group_incref(const char *name)
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{
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ThrottleGroup *tg = NULL;
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ThrottleGroup *iter;
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qemu_mutex_lock(&throttle_groups_lock);
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/* Look for an existing group with that name */
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QTAILQ_FOREACH(iter, &throttle_groups, list) {
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if (!strcmp(name, iter->name)) {
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tg = iter;
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break;
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}
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}
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/* Create a new one if not found */
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if (!tg) {
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tg = g_new0(ThrottleGroup, 1);
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tg->name = g_strdup(name);
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qemu_mutex_init(&tg->lock);
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throttle_init(&tg->ts);
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QLIST_INIT(&tg->head);
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QTAILQ_INSERT_TAIL(&throttle_groups, tg, list);
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}
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tg->refcount++;
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qemu_mutex_unlock(&throttle_groups_lock);
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return tg;
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}
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/* Decrease the reference count of a ThrottleGroup.
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*
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* When the reference count reaches zero the ThrottleGroup is
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* destroyed.
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*
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* @tg: The ThrottleGroup to unref
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*/
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static void throttle_group_unref(ThrottleGroup *tg)
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{
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qemu_mutex_lock(&throttle_groups_lock);
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if (--tg->refcount == 0) {
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QTAILQ_REMOVE(&throttle_groups, tg, list);
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qemu_mutex_destroy(&tg->lock);
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g_free(tg->name);
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g_free(tg);
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}
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qemu_mutex_unlock(&throttle_groups_lock);
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}
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/* Get the name from a BlockDriverState's ThrottleGroup. The name (and
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* the pointer) is guaranteed to remain constant during the lifetime
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* of the group.
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*
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* @bs: a BlockDriverState that is member of a throttling group
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* @ret: the name of the group.
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*/
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const char *throttle_group_get_name(BlockDriverState *bs)
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{
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ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
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return tg->name;
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}
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/* Return the next BlockDriverState in the round-robin sequence,
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* simulating a circular list.
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*
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* This assumes that tg->lock is held.
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*
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* @bs: the current BlockDriverState
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* @ret: the next BlockDriverState in the sequence
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*/
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static BlockDriverState *throttle_group_next_bs(BlockDriverState *bs)
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{
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ThrottleState *ts = bs->throttle_state;
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ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
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BlockDriverState *next = QLIST_NEXT(bs, round_robin);
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if (!next) {
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return QLIST_FIRST(&tg->head);
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}
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return next;
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}
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2015-06-08 19:17:44 +03:00
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/* Return the next BlockDriverState in the round-robin sequence with
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* pending I/O requests.
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*
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* This assumes that tg->lock is held.
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*
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* @bs: the current BlockDriverState
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* @is_write: the type of operation (read/write)
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* @ret: the next BlockDriverState with pending requests, or bs
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* if there is none.
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*/
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static BlockDriverState *next_throttle_token(BlockDriverState *bs,
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bool is_write)
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{
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ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
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BlockDriverState *token, *start;
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start = token = tg->tokens[is_write];
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/* get next bs round in round robin style */
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token = throttle_group_next_bs(token);
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while (token != start && !token->pending_reqs[is_write]) {
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token = throttle_group_next_bs(token);
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}
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/* If no IO are queued for scheduling on the next round robin token
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* then decide the token is the current bs because chances are
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* the current bs get the current request queued.
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*/
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if (token == start && !token->pending_reqs[is_write]) {
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token = bs;
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}
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return token;
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}
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/* Check if the next I/O request for a BlockDriverState needs to be
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* throttled or not. If there's no timer set in this group, set one
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* and update the token accordingly.
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*
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* This assumes that tg->lock is held.
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*
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* @bs: the current BlockDriverState
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* @is_write: the type of operation (read/write)
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* @ret: whether the I/O request needs to be throttled or not
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*/
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static bool throttle_group_schedule_timer(BlockDriverState *bs,
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bool is_write)
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{
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ThrottleState *ts = bs->throttle_state;
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ThrottleTimers *tt = &bs->throttle_timers;
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ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
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bool must_wait;
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/* Check if any of the timers in this group is already armed */
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if (tg->any_timer_armed[is_write]) {
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return true;
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}
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must_wait = throttle_schedule_timer(ts, tt, is_write);
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/* If a timer just got armed, set bs as the current token */
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if (must_wait) {
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tg->tokens[is_write] = bs;
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tg->any_timer_armed[is_write] = true;
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}
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return must_wait;
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}
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/* Look for the next pending I/O request and schedule it.
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*
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* This assumes that tg->lock is held.
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*
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* @bs: the current BlockDriverState
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* @is_write: the type of operation (read/write)
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*/
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static void schedule_next_request(BlockDriverState *bs, bool is_write)
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{
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ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
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bool must_wait;
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BlockDriverState *token;
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/* Check if there's any pending request to schedule next */
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token = next_throttle_token(bs, is_write);
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if (!token->pending_reqs[is_write]) {
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return;
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}
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/* Set a timer for the request if it needs to be throttled */
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must_wait = throttle_group_schedule_timer(token, is_write);
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/* If it doesn't have to wait, queue it for immediate execution */
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if (!must_wait) {
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/* Give preference to requests from the current bs */
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if (qemu_in_coroutine() &&
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qemu_co_queue_next(&bs->throttled_reqs[is_write])) {
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token = bs;
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} else {
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ThrottleTimers *tt = &token->throttle_timers;
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int64_t now = qemu_clock_get_ns(tt->clock_type);
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timer_mod(tt->timers[is_write], now + 1);
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tg->any_timer_armed[is_write] = true;
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}
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tg->tokens[is_write] = token;
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}
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}
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/* Check if an I/O request needs to be throttled, wait and set a timer
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* if necessary, and schedule the next request using a round robin
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* algorithm.
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*
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* @bs: the current BlockDriverState
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* @bytes: the number of bytes for this I/O
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* @is_write: the type of operation (read/write)
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*/
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void coroutine_fn throttle_group_co_io_limits_intercept(BlockDriverState *bs,
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unsigned int bytes,
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bool is_write)
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{
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bool must_wait;
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BlockDriverState *token;
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ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
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qemu_mutex_lock(&tg->lock);
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/* First we check if this I/O has to be throttled. */
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token = next_throttle_token(bs, is_write);
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must_wait = throttle_group_schedule_timer(token, is_write);
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/* Wait if there's a timer set or queued requests of this type */
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if (must_wait || bs->pending_reqs[is_write]) {
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bs->pending_reqs[is_write]++;
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qemu_mutex_unlock(&tg->lock);
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qemu_co_queue_wait(&bs->throttled_reqs[is_write]);
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qemu_mutex_lock(&tg->lock);
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bs->pending_reqs[is_write]--;
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}
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/* The I/O will be executed, so do the accounting */
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throttle_account(bs->throttle_state, is_write, bytes);
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/* Schedule the next request */
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schedule_next_request(bs, is_write);
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qemu_mutex_unlock(&tg->lock);
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}
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2015-06-08 19:17:42 +03:00
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/* Update the throttle configuration for a particular group. Similar
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* to throttle_config(), but guarantees atomicity within the
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* throttling group.
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*
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* @bs: a BlockDriverState that is member of the group
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* @cfg: the configuration to set
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*/
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void throttle_group_config(BlockDriverState *bs, ThrottleConfig *cfg)
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{
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ThrottleTimers *tt = &bs->throttle_timers;
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ThrottleState *ts = bs->throttle_state;
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ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
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qemu_mutex_lock(&tg->lock);
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throttle_config(ts, tt, cfg);
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/* throttle_config() cancels the timers */
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tg->any_timer_armed[0] = tg->any_timer_armed[1] = false;
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qemu_mutex_unlock(&tg->lock);
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}
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/* Get the throttle configuration from a particular group. Similar to
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* throttle_get_config(), but guarantees atomicity within the
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* throttling group.
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*
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* @bs: a BlockDriverState that is member of the group
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* @cfg: the configuration will be written here
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*/
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void throttle_group_get_config(BlockDriverState *bs, ThrottleConfig *cfg)
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{
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ThrottleState *ts = bs->throttle_state;
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ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
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qemu_mutex_lock(&tg->lock);
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throttle_get_config(ts, cfg);
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qemu_mutex_unlock(&tg->lock);
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}
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2015-06-08 19:17:44 +03:00
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/* ThrottleTimers callback. This wakes up a request that was waiting
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* because it had been throttled.
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*
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* @bs: the BlockDriverState whose request had been throttled
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* @is_write: the type of operation (read/write)
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*/
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static void timer_cb(BlockDriverState *bs, bool is_write)
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{
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ThrottleState *ts = bs->throttle_state;
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ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
|
|
|
|
bool empty_queue;
|
|
|
|
|
|
|
|
/* The timer has just been fired, so we can update the flag */
|
|
|
|
qemu_mutex_lock(&tg->lock);
|
|
|
|
tg->any_timer_armed[is_write] = false;
|
|
|
|
qemu_mutex_unlock(&tg->lock);
|
|
|
|
|
|
|
|
/* Run the request that was waiting for this timer */
|
|
|
|
empty_queue = !qemu_co_enter_next(&bs->throttled_reqs[is_write]);
|
|
|
|
|
|
|
|
/* If the request queue was empty then we have to take care of
|
|
|
|
* scheduling the next one */
|
|
|
|
if (empty_queue) {
|
|
|
|
qemu_mutex_lock(&tg->lock);
|
|
|
|
schedule_next_request(bs, is_write);
|
|
|
|
qemu_mutex_unlock(&tg->lock);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
static void read_timer_cb(void *opaque)
|
|
|
|
{
|
|
|
|
timer_cb(opaque, false);
|
|
|
|
}
|
|
|
|
|
|
|
|
static void write_timer_cb(void *opaque)
|
|
|
|
{
|
|
|
|
timer_cb(opaque, true);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Register a BlockDriverState in the throttling group, also
|
|
|
|
* initializing its timers and updating its throttle_state pointer to
|
|
|
|
* point to it. If a throttling group with that name does not exist
|
|
|
|
* yet, it will be created.
|
2015-06-08 19:17:42 +03:00
|
|
|
*
|
|
|
|
* @bs: the BlockDriverState to insert
|
|
|
|
* @groupname: the name of the group
|
|
|
|
*/
|
|
|
|
void throttle_group_register_bs(BlockDriverState *bs, const char *groupname)
|
|
|
|
{
|
|
|
|
int i;
|
|
|
|
ThrottleGroup *tg = throttle_group_incref(groupname);
|
2015-06-08 19:17:44 +03:00
|
|
|
int clock_type = QEMU_CLOCK_REALTIME;
|
|
|
|
|
|
|
|
if (qtest_enabled()) {
|
|
|
|
/* For testing block IO throttling only */
|
|
|
|
clock_type = QEMU_CLOCK_VIRTUAL;
|
|
|
|
}
|
2015-06-08 19:17:42 +03:00
|
|
|
|
|
|
|
bs->throttle_state = &tg->ts;
|
|
|
|
|
|
|
|
qemu_mutex_lock(&tg->lock);
|
|
|
|
/* If the ThrottleGroup is new set this BlockDriverState as the token */
|
|
|
|
for (i = 0; i < 2; i++) {
|
|
|
|
if (!tg->tokens[i]) {
|
|
|
|
tg->tokens[i] = bs;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
QLIST_INSERT_HEAD(&tg->head, bs, round_robin);
|
2015-06-08 19:17:44 +03:00
|
|
|
|
|
|
|
throttle_timers_init(&bs->throttle_timers,
|
|
|
|
bdrv_get_aio_context(bs),
|
|
|
|
clock_type,
|
|
|
|
read_timer_cb,
|
|
|
|
write_timer_cb,
|
|
|
|
bs);
|
|
|
|
|
2015-06-08 19:17:42 +03:00
|
|
|
qemu_mutex_unlock(&tg->lock);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Unregister a BlockDriverState from its group, removing it from the
|
2015-06-08 19:17:44 +03:00
|
|
|
* list, destroying the timers and setting the throttle_state pointer
|
|
|
|
* to NULL.
|
2015-06-08 19:17:42 +03:00
|
|
|
*
|
|
|
|
* The group will be destroyed if it's empty after this operation.
|
|
|
|
*
|
|
|
|
* @bs: the BlockDriverState to remove
|
|
|
|
*/
|
|
|
|
void throttle_group_unregister_bs(BlockDriverState *bs)
|
|
|
|
{
|
|
|
|
ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
|
|
|
|
int i;
|
|
|
|
|
|
|
|
qemu_mutex_lock(&tg->lock);
|
|
|
|
for (i = 0; i < 2; i++) {
|
|
|
|
if (tg->tokens[i] == bs) {
|
|
|
|
BlockDriverState *token = throttle_group_next_bs(bs);
|
|
|
|
/* Take care of the case where this is the last bs in the group */
|
|
|
|
if (token == bs) {
|
|
|
|
token = NULL;
|
|
|
|
}
|
|
|
|
tg->tokens[i] = token;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/* remove the current bs from the list */
|
|
|
|
QLIST_REMOVE(bs, round_robin);
|
2015-06-08 19:17:44 +03:00
|
|
|
throttle_timers_destroy(&bs->throttle_timers);
|
2015-06-08 19:17:42 +03:00
|
|
|
qemu_mutex_unlock(&tg->lock);
|
|
|
|
|
|
|
|
throttle_group_unref(tg);
|
|
|
|
bs->throttle_state = NULL;
|
|
|
|
}
|
|
|
|
|
2015-06-08 19:17:45 +03:00
|
|
|
/* Acquire the lock of this throttling group.
|
|
|
|
*
|
|
|
|
* You won't normally need to use this. None of the functions from the
|
|
|
|
* ThrottleGroup API require you to acquire the lock since all of them
|
|
|
|
* deal with it internally.
|
|
|
|
*
|
|
|
|
* This should only be used in exceptional cases when you want to
|
|
|
|
* access the protected fields of a BlockDriverState directly
|
|
|
|
* (e.g. bdrv_swap()).
|
|
|
|
*
|
|
|
|
* @bs: a BlockDriverState that is member of the group
|
|
|
|
*/
|
|
|
|
void throttle_group_lock(BlockDriverState *bs)
|
|
|
|
{
|
|
|
|
ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
|
|
|
|
qemu_mutex_lock(&tg->lock);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Release the lock of this throttling group.
|
|
|
|
*
|
|
|
|
* See the comments in throttle_group_lock().
|
|
|
|
*/
|
|
|
|
void throttle_group_unlock(BlockDriverState *bs)
|
|
|
|
{
|
|
|
|
ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
|
|
|
|
qemu_mutex_unlock(&tg->lock);
|
|
|
|
}
|
|
|
|
|
2015-06-08 19:17:42 +03:00
|
|
|
static void throttle_groups_init(void)
|
|
|
|
{
|
|
|
|
qemu_mutex_init(&throttle_groups_lock);
|
|
|
|
}
|
|
|
|
|
|
|
|
block_init(throttle_groups_init);
|