Move the CoMutex and CoQueue inits inside throttle_group_register_tgm() which is called whenever a ThrottleGroupMember is initialized. There's no need for them to be separate. Reviewed-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
581 lines
18 KiB
C
581 lines
18 KiB
C
/*
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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 "qemu/osdep.h"
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#include "sysemu/block-backend.h"
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#include "block/throttle-groups.h"
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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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/* The ThrottleGroup structure (with its ThrottleState) is shared
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* among different ThrottleGroupMembers 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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* transparent to outside users.
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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, ThrottleGroupMember 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
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* ThrottleGroupMember is registered in a group those fields can be accessed
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* by other threads 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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* blk_set_aio_context()). Therefore in this file a thread will
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* access some other ThrottleGroupMember's timers only after verifying that
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* that ThrottleGroupMember 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(, ThrottleGroupMember) head;
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ThrottleGroupMember *tokens[2];
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bool any_timer_armed[2];
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QEMUClockType clock_type;
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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 ThrottleState member of the ThrottleGroup
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*/
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ThrottleState *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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tg->clock_type = QEMU_CLOCK_REALTIME;
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if (qtest_enabled()) {
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/* For testing block IO throttling only */
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tg->clock_type = QEMU_CLOCK_VIRTUAL;
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}
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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->ts;
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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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* @ts: The ThrottleGroup to unref, given by its ThrottleState member
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*/
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void throttle_group_unref(ThrottleState *ts)
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{
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ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
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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 ThrottleGroupMember's group. The name (and the pointer)
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* is guaranteed to remain constant during the lifetime of the group.
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*
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* @tgm: a ThrottleGroupMember
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* @ret: the name of the group.
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*/
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const char *throttle_group_get_name(ThrottleGroupMember *tgm)
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{
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ThrottleGroup *tg = container_of(tgm->throttle_state, ThrottleGroup, ts);
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return tg->name;
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}
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/* Return the next ThrottleGroupMember in the round-robin sequence, simulating
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* 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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* @tgm: the current ThrottleGroupMember
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* @ret: the next ThrottleGroupMember in the sequence
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*/
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static ThrottleGroupMember *throttle_group_next_tgm(ThrottleGroupMember *tgm)
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{
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ThrottleState *ts = tgm->throttle_state;
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ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
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ThrottleGroupMember *next = QLIST_NEXT(tgm, round_robin);
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if (!next) {
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next = QLIST_FIRST(&tg->head);
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}
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return next;
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}
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/*
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* Return whether a ThrottleGroupMember has pending requests.
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*
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* This assumes that tg->lock is held.
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*
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* @tgm: the ThrottleGroupMember
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* @is_write: the type of operation (read/write)
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* @ret: whether the ThrottleGroupMember has pending requests.
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*/
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static inline bool tgm_has_pending_reqs(ThrottleGroupMember *tgm,
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bool is_write)
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{
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return tgm->pending_reqs[is_write];
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}
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/* Return the next ThrottleGroupMember in the round-robin sequence with pending
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* 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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* @tgm: the current ThrottleGroupMember
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* @is_write: the type of operation (read/write)
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* @ret: the next ThrottleGroupMember with pending requests, or tgm if
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* there is none.
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*/
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static ThrottleGroupMember *next_throttle_token(ThrottleGroupMember *tgm,
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bool is_write)
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{
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ThrottleState *ts = tgm->throttle_state;
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ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
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ThrottleGroupMember *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_tgm(token);
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while (token != start && !tgm_has_pending_reqs(token, is_write)) {
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token = throttle_group_next_tgm(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 tgm because chances are
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* the current tgm got the current request queued.
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*/
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if (token == start && !tgm_has_pending_reqs(token, is_write)) {
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token = tgm;
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}
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/* Either we return the original TGM, or one with pending requests */
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assert(token == tgm || tgm_has_pending_reqs(token, is_write));
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return token;
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}
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/* Check if the next I/O request for a ThrottleGroupMember needs to be
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* throttled or not. If there's no timer set in this group, set one and update
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* 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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* @tgm: the current ThrottleGroupMember
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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(ThrottleGroupMember *tgm,
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bool is_write)
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{
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ThrottleState *ts = tgm->throttle_state;
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ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
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ThrottleTimers *tt = &tgm->throttle_timers;
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bool must_wait;
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if (atomic_read(&tgm->io_limits_disabled)) {
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return false;
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}
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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 tgm as the current token */
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if (must_wait) {
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tg->tokens[is_write] = tgm;
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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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/* Start the next pending I/O request for a ThrottleGroupMember. Return whether
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* any request was actually pending.
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*
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* @tgm: the current ThrottleGroupMember
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* @is_write: the type of operation (read/write)
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*/
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static bool coroutine_fn throttle_group_co_restart_queue(ThrottleGroupMember *tgm,
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bool is_write)
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{
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bool ret;
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qemu_co_mutex_lock(&tgm->throttled_reqs_lock);
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ret = qemu_co_queue_next(&tgm->throttled_reqs[is_write]);
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qemu_co_mutex_unlock(&tgm->throttled_reqs_lock);
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return ret;
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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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* @tgm: the current ThrottleGroupMember
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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(ThrottleGroupMember *tgm, bool is_write)
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{
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ThrottleState *ts = tgm->throttle_state;
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ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
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bool must_wait;
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ThrottleGroupMember *token;
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/* Check if there's any pending request to schedule next */
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token = next_throttle_token(tgm, is_write);
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if (!tgm_has_pending_reqs(token, 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 tgm */
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if (qemu_in_coroutine() &&
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throttle_group_co_restart_queue(tgm, is_write)) {
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token = tgm;
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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(tg->clock_type);
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timer_mod(tt->timers[is_write], now);
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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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* @tgm: the current ThrottleGroupMember
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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(ThrottleGroupMember *tgm,
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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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ThrottleGroupMember *token;
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ThrottleGroup *tg = container_of(tgm->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(tgm, 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 || tgm->pending_reqs[is_write]) {
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tgm->pending_reqs[is_write]++;
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qemu_mutex_unlock(&tg->lock);
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qemu_co_mutex_lock(&tgm->throttled_reqs_lock);
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qemu_co_queue_wait(&tgm->throttled_reqs[is_write],
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&tgm->throttled_reqs_lock);
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qemu_co_mutex_unlock(&tgm->throttled_reqs_lock);
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qemu_mutex_lock(&tg->lock);
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tgm->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(tgm->throttle_state, is_write, bytes);
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/* Schedule the next request */
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schedule_next_request(tgm, is_write);
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qemu_mutex_unlock(&tg->lock);
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}
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typedef struct {
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ThrottleGroupMember *tgm;
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bool is_write;
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} RestartData;
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static void coroutine_fn throttle_group_restart_queue_entry(void *opaque)
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{
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RestartData *data = opaque;
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ThrottleGroupMember *tgm = data->tgm;
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ThrottleState *ts = tgm->throttle_state;
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ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
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bool is_write = data->is_write;
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bool empty_queue;
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empty_queue = !throttle_group_co_restart_queue(tgm, is_write);
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/* If the request queue was empty then we have to take care of
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* scheduling the next one */
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if (empty_queue) {
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qemu_mutex_lock(&tg->lock);
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schedule_next_request(tgm, is_write);
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qemu_mutex_unlock(&tg->lock);
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}
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}
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static void throttle_group_restart_queue(ThrottleGroupMember *tgm, bool is_write)
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{
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Coroutine *co;
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RestartData rd = {
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.tgm = tgm,
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.is_write = is_write
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};
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co = qemu_coroutine_create(throttle_group_restart_queue_entry, &rd);
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aio_co_enter(tgm->aio_context, co);
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}
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void throttle_group_restart_tgm(ThrottleGroupMember *tgm)
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{
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if (tgm->throttle_state) {
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throttle_group_restart_queue(tgm, 0);
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throttle_group_restart_queue(tgm, 1);
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}
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}
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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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* @tgm: a ThrottleGroupMember that is a 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(ThrottleGroupMember *tgm, ThrottleConfig *cfg)
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{
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ThrottleState *ts = tgm->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, tg->clock_type, cfg);
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qemu_mutex_unlock(&tg->lock);
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throttle_group_restart_tgm(tgm);
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}
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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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* @tgm: a ThrottleGroupMember that is a 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(ThrottleGroupMember *tgm, ThrottleConfig *cfg)
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{
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ThrottleState *ts = tgm->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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/* 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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* @tgm: the ThrottleGroupMember 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(ThrottleGroupMember *tgm, bool is_write)
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{
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ThrottleState *ts = tgm->throttle_state;
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ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
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/* The timer has just been fired, so we can update the flag */
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qemu_mutex_lock(&tg->lock);
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tg->any_timer_armed[is_write] = false;
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qemu_mutex_unlock(&tg->lock);
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|
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/* Run the request that was waiting for this timer */
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throttle_group_restart_queue(tgm, is_write);
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}
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|
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static void read_timer_cb(void *opaque)
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{
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timer_cb(opaque, false);
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}
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|
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static void write_timer_cb(void *opaque)
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{
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timer_cb(opaque, true);
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}
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|
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/* Register a ThrottleGroupMember from 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.
|
|
*
|
|
* @tgm: the ThrottleGroupMember to insert
|
|
* @groupname: the name of the group
|
|
* @ctx: the AioContext to use
|
|
*/
|
|
void throttle_group_register_tgm(ThrottleGroupMember *tgm,
|
|
const char *groupname,
|
|
AioContext *ctx)
|
|
{
|
|
int i;
|
|
ThrottleState *ts = throttle_group_incref(groupname);
|
|
ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
|
|
|
|
tgm->throttle_state = ts;
|
|
tgm->aio_context = ctx;
|
|
|
|
qemu_mutex_lock(&tg->lock);
|
|
/* If the ThrottleGroup is new set this ThrottleGroupMember as the token */
|
|
for (i = 0; i < 2; i++) {
|
|
if (!tg->tokens[i]) {
|
|
tg->tokens[i] = tgm;
|
|
}
|
|
}
|
|
|
|
QLIST_INSERT_HEAD(&tg->head, tgm, round_robin);
|
|
|
|
throttle_timers_init(&tgm->throttle_timers,
|
|
tgm->aio_context,
|
|
tg->clock_type,
|
|
read_timer_cb,
|
|
write_timer_cb,
|
|
tgm);
|
|
qemu_co_mutex_init(&tgm->throttled_reqs_lock);
|
|
qemu_co_queue_init(&tgm->throttled_reqs[0]);
|
|
qemu_co_queue_init(&tgm->throttled_reqs[1]);
|
|
|
|
qemu_mutex_unlock(&tg->lock);
|
|
}
|
|
|
|
/* Unregister a ThrottleGroupMember from its group, removing it from the list,
|
|
* destroying the timers and setting the throttle_state pointer to NULL.
|
|
*
|
|
* The ThrottleGroupMember must not have pending throttled requests, so the
|
|
* caller has to drain them first.
|
|
*
|
|
* The group will be destroyed if it's empty after this operation.
|
|
*
|
|
* @tgm the ThrottleGroupMember to remove
|
|
*/
|
|
void throttle_group_unregister_tgm(ThrottleGroupMember *tgm)
|
|
{
|
|
ThrottleState *ts = tgm->throttle_state;
|
|
ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
|
|
ThrottleGroupMember *token;
|
|
int i;
|
|
|
|
assert(tgm->pending_reqs[0] == 0 && tgm->pending_reqs[1] == 0);
|
|
assert(qemu_co_queue_empty(&tgm->throttled_reqs[0]));
|
|
assert(qemu_co_queue_empty(&tgm->throttled_reqs[1]));
|
|
|
|
qemu_mutex_lock(&tg->lock);
|
|
for (i = 0; i < 2; i++) {
|
|
if (tg->tokens[i] == tgm) {
|
|
token = throttle_group_next_tgm(tgm);
|
|
/* Take care of the case where this is the last tgm in the group */
|
|
if (token == tgm) {
|
|
token = NULL;
|
|
}
|
|
tg->tokens[i] = token;
|
|
}
|
|
}
|
|
|
|
/* remove the current tgm from the list */
|
|
QLIST_REMOVE(tgm, round_robin);
|
|
throttle_timers_destroy(&tgm->throttle_timers);
|
|
qemu_mutex_unlock(&tg->lock);
|
|
|
|
throttle_group_unref(&tg->ts);
|
|
tgm->throttle_state = NULL;
|
|
}
|
|
|
|
void throttle_group_attach_aio_context(ThrottleGroupMember *tgm,
|
|
AioContext *new_context)
|
|
{
|
|
ThrottleTimers *tt = &tgm->throttle_timers;
|
|
throttle_timers_attach_aio_context(tt, new_context);
|
|
tgm->aio_context = new_context;
|
|
}
|
|
|
|
void throttle_group_detach_aio_context(ThrottleGroupMember *tgm)
|
|
{
|
|
ThrottleTimers *tt = &tgm->throttle_timers;
|
|
throttle_timers_detach_aio_context(tt);
|
|
tgm->aio_context = NULL;
|
|
}
|
|
|
|
static void throttle_groups_init(void)
|
|
{
|
|
qemu_mutex_init(&throttle_groups_lock);
|
|
}
|
|
|
|
block_init(throttle_groups_init);
|