* along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
+#include "qemu/osdep.h"
+#include "sysemu/block-backend.h"
#include "block/throttle-groups.h"
+#include "qemu/queue.h"
+#include "qemu/thread.h"
+#include "sysemu/qtest.h"
/* The ThrottleGroup structure (with its ThrottleState) is shared
- * among different BlockDriverState and it's independent from
+ * among different BlockBackends and it's independent from
* AioContext, so in order to use it from different threads it needs
* its own locking.
*
* The whole ThrottleGroup structure is private and invisible to
* outside users, that only use it through its ThrottleState.
*
- * In addition to the ThrottleGroup structure, BlockDriverState has
+ * In addition to the ThrottleGroup structure, BlockBackendPublic has
* fields that need to be accessed by other members of the group and
- * therefore also need to be protected by this lock. Once a BDS is
- * registered in a group those fields can be accessed by other threads
- * any time.
+ * therefore also need to be protected by this lock. Once a
+ * BlockBackend is registered in a group those fields can be accessed
+ * by other threads any time.
*
* Again, all this is handled internally and is mostly transparent to
* the outside. The 'throttle_timers' field however has an additional
* constraint because it may be temporarily invalid (see for example
* bdrv_set_aio_context()). Therefore in this file a thread will
- * access some other BDS's timers only after verifying that that BDS
- * has throttled requests in the queue.
+ * access some other BlockBackend's timers only after verifying that
+ * that BlockBackend has throttled requests in the queue.
*/
typedef struct ThrottleGroup {
char *name; /* This is constant during the lifetime of the group */
QemuMutex lock; /* This lock protects the following four fields */
ThrottleState ts;
- QLIST_HEAD(, BlockDriverState) head;
- BlockDriverState *tokens[2];
+ QLIST_HEAD(, BlockBackendPublic) head;
+ BlockBackend *tokens[2];
bool any_timer_armed[2];
/* These two are protected by the global throttle_groups_lock */
* created.
*
* @name: the name of the ThrottleGroup
- * @ret: the ThrottleGroup
+ * @ret: the ThrottleState member of the ThrottleGroup
*/
-static ThrottleGroup *throttle_group_incref(const char *name)
+ThrottleState *throttle_group_incref(const char *name)
{
ThrottleGroup *tg = NULL;
ThrottleGroup *iter;
qemu_mutex_unlock(&throttle_groups_lock);
- return tg;
+ return &tg->ts;
}
/* Decrease the reference count of a ThrottleGroup.
* When the reference count reaches zero the ThrottleGroup is
* destroyed.
*
- * @tg: The ThrottleGroup to unref
+ * @ts: The ThrottleGroup to unref, given by its ThrottleState member
*/
-static void throttle_group_unref(ThrottleGroup *tg)
+void throttle_group_unref(ThrottleState *ts)
{
+ ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
+
qemu_mutex_lock(&throttle_groups_lock);
if (--tg->refcount == 0) {
QTAILQ_REMOVE(&throttle_groups, tg, list);
qemu_mutex_unlock(&throttle_groups_lock);
}
-/* Get the name from a BlockDriverState's ThrottleGroup. The name (and
- * the pointer) is guaranteed to remain constant during the lifetime
- * of the group.
+/* Get the name from a BlockBackend's ThrottleGroup. The name (and the pointer)
+ * is guaranteed to remain constant during the lifetime of the group.
*
- * @bs: a BlockDriverState that is member of a throttling group
+ * @blk: a BlockBackend that is member of a throttling group
* @ret: the name of the group.
*/
-const char *throttle_group_get_name(BlockDriverState *bs)
+const char *throttle_group_get_name(BlockBackend *blk)
{
- ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
+ BlockBackendPublic *blkp = blk_get_public(blk);
+ ThrottleGroup *tg = container_of(blkp->throttle_state, ThrottleGroup, ts);
return tg->name;
}
-/* Return the next BlockDriverState in the round-robin sequence,
- * simulating a circular list.
+/* Return the next BlockBackend in the round-robin sequence, simulating a
+ * circular list.
*
* This assumes that tg->lock is held.
*
- * @bs: the current BlockDriverState
- * @ret: the next BlockDriverState in the sequence
+ * @blk: the current BlockBackend
+ * @ret: the next BlockBackend in the sequence
*/
-static BlockDriverState *throttle_group_next_bs(BlockDriverState *bs)
+static BlockBackend *throttle_group_next_blk(BlockBackend *blk)
{
- ThrottleState *ts = bs->throttle_state;
+ BlockBackendPublic *blkp = blk_get_public(blk);
+ ThrottleState *ts = blkp->throttle_state;
ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
- BlockDriverState *next = QLIST_NEXT(bs, round_robin);
+ BlockBackendPublic *next = QLIST_NEXT(blkp, round_robin);
if (!next) {
- return QLIST_FIRST(&tg->head);
+ next = QLIST_FIRST(&tg->head);
}
- return next;
+ return blk_by_public(next);
+}
+
+/*
+ * Return whether a BlockBackend has pending requests.
+ *
+ * This assumes that tg->lock is held.
+ *
+ * @blk: the BlockBackend
+ * @is_write: the type of operation (read/write)
+ * @ret: whether the BlockBackend has pending requests.
+ */
+static inline bool blk_has_pending_reqs(BlockBackend *blk,
+ bool is_write)
+{
+ const BlockBackendPublic *blkp = blk_get_public(blk);
+ return blkp->pending_reqs[is_write];
+}
+
+/* Return the next BlockBackend in the round-robin sequence with pending I/O
+ * requests.
+ *
+ * This assumes that tg->lock is held.
+ *
+ * @blk: the current BlockBackend
+ * @is_write: the type of operation (read/write)
+ * @ret: the next BlockBackend with pending requests, or blk if there is
+ * none.
+ */
+static BlockBackend *next_throttle_token(BlockBackend *blk, bool is_write)
+{
+ BlockBackendPublic *blkp = blk_get_public(blk);
+ ThrottleGroup *tg = container_of(blkp->throttle_state, ThrottleGroup, ts);
+ BlockBackend *token, *start;
+
+ start = token = tg->tokens[is_write];
+
+ /* get next bs round in round robin style */
+ token = throttle_group_next_blk(token);
+ while (token != start && !blk_has_pending_reqs(token, is_write)) {
+ token = throttle_group_next_blk(token);
+ }
+
+ /* If no IO are queued for scheduling on the next round robin token
+ * then decide the token is the current bs because chances are
+ * the current bs get the current request queued.
+ */
+ if (token == start && !blk_has_pending_reqs(token, is_write)) {
+ token = blk;
+ }
+
+ /* Either we return the original BB, or one with pending requests */
+ assert(token == blk || blk_has_pending_reqs(token, is_write));
+
+ return token;
+}
+
+/* Check if the next I/O request for a BlockBackend needs to be throttled or
+ * not. If there's no timer set in this group, set one and update the token
+ * accordingly.
+ *
+ * This assumes that tg->lock is held.
+ *
+ * @blk: the current BlockBackend
+ * @is_write: the type of operation (read/write)
+ * @ret: whether the I/O request needs to be throttled or not
+ */
+static bool throttle_group_schedule_timer(BlockBackend *blk, bool is_write)
+{
+ BlockBackendPublic *blkp = blk_get_public(blk);
+ ThrottleState *ts = blkp->throttle_state;
+ ThrottleTimers *tt = &blkp->throttle_timers;
+ ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
+ bool must_wait;
+
+ if (blkp->io_limits_disabled) {
+ return false;
+ }
+
+ /* Check if any of the timers in this group is already armed */
+ if (tg->any_timer_armed[is_write]) {
+ return true;
+ }
+
+ must_wait = throttle_schedule_timer(ts, tt, is_write);
+
+ /* If a timer just got armed, set blk as the current token */
+ if (must_wait) {
+ tg->tokens[is_write] = blk;
+ tg->any_timer_armed[is_write] = true;
+ }
+
+ return must_wait;
+}
+
+/* Look for the next pending I/O request and schedule it.
+ *
+ * This assumes that tg->lock is held.
+ *
+ * @blk: the current BlockBackend
+ * @is_write: the type of operation (read/write)
+ */
+static void schedule_next_request(BlockBackend *blk, bool is_write)
+{
+ BlockBackendPublic *blkp = blk_get_public(blk);
+ ThrottleGroup *tg = container_of(blkp->throttle_state, ThrottleGroup, ts);
+ bool must_wait;
+ BlockBackend *token;
+
+ /* Check if there's any pending request to schedule next */
+ token = next_throttle_token(blk, is_write);
+ if (!blk_has_pending_reqs(token, is_write)) {
+ return;
+ }
+
+ /* Set a timer for the request if it needs to be throttled */
+ must_wait = throttle_group_schedule_timer(token, is_write);
+
+ /* If it doesn't have to wait, queue it for immediate execution */
+ if (!must_wait) {
+ /* Give preference to requests from the current blk */
+ if (qemu_in_coroutine() &&
+ qemu_co_queue_next(&blkp->throttled_reqs[is_write])) {
+ token = blk;
+ } else {
+ ThrottleTimers *tt = &blk_get_public(token)->throttle_timers;
+ int64_t now = qemu_clock_get_ns(tt->clock_type);
+ timer_mod(tt->timers[is_write], now + 1);
+ tg->any_timer_armed[is_write] = true;
+ }
+ tg->tokens[is_write] = token;
+ }
+}
+
+/* Check if an I/O request needs to be throttled, wait and set a timer
+ * if necessary, and schedule the next request using a round robin
+ * algorithm.
+ *
+ * @blk: the current BlockBackend
+ * @bytes: the number of bytes for this I/O
+ * @is_write: the type of operation (read/write)
+ */
+void coroutine_fn throttle_group_co_io_limits_intercept(BlockBackend *blk,
+ unsigned int bytes,
+ bool is_write)
+{
+ bool must_wait;
+ BlockBackend *token;
+
+ BlockBackendPublic *blkp = blk_get_public(blk);
+ ThrottleGroup *tg = container_of(blkp->throttle_state, ThrottleGroup, ts);
+ qemu_mutex_lock(&tg->lock);
+
+ /* First we check if this I/O has to be throttled. */
+ token = next_throttle_token(blk, is_write);
+ must_wait = throttle_group_schedule_timer(token, is_write);
+
+ /* Wait if there's a timer set or queued requests of this type */
+ if (must_wait || blkp->pending_reqs[is_write]) {
+ blkp->pending_reqs[is_write]++;
+ qemu_mutex_unlock(&tg->lock);
+ qemu_co_queue_wait(&blkp->throttled_reqs[is_write], NULL);
+ qemu_mutex_lock(&tg->lock);
+ blkp->pending_reqs[is_write]--;
+ }
+
+ /* The I/O will be executed, so do the accounting */
+ throttle_account(blkp->throttle_state, is_write, bytes);
+
+ /* Schedule the next request */
+ schedule_next_request(blk, is_write);
+
+ qemu_mutex_unlock(&tg->lock);
+}
+
+void throttle_group_restart_blk(BlockBackend *blk)
+{
+ BlockBackendPublic *blkp = blk_get_public(blk);
+ int i;
+
+ for (i = 0; i < 2; i++) {
+ while (qemu_co_enter_next(&blkp->throttled_reqs[i])) {
+ ;
+ }
+ }
}
/* Update the throttle configuration for a particular group. Similar
* to throttle_config(), but guarantees atomicity within the
* throttling group.
*
- * @bs: a BlockDriverState that is member of the group
+ * @blk: a BlockBackend that is a member of the group
* @cfg: the configuration to set
*/
-void throttle_group_config(BlockDriverState *bs, ThrottleConfig *cfg)
+void throttle_group_config(BlockBackend *blk, ThrottleConfig *cfg)
{
- ThrottleTimers *tt = &bs->throttle_timers;
- ThrottleState *ts = bs->throttle_state;
+ BlockBackendPublic *blkp = blk_get_public(blk);
+ ThrottleTimers *tt = &blkp->throttle_timers;
+ ThrottleState *ts = blkp->throttle_state;
ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
qemu_mutex_lock(&tg->lock);
- throttle_config(ts, tt, cfg);
/* throttle_config() cancels the timers */
- tg->any_timer_armed[0] = tg->any_timer_armed[1] = false;
+ if (timer_pending(tt->timers[0])) {
+ tg->any_timer_armed[0] = false;
+ }
+ if (timer_pending(tt->timers[1])) {
+ tg->any_timer_armed[1] = false;
+ }
+ throttle_config(ts, tt, cfg);
qemu_mutex_unlock(&tg->lock);
+
+ qemu_co_enter_next(&blkp->throttled_reqs[0]);
+ qemu_co_enter_next(&blkp->throttled_reqs[1]);
}
/* Get the throttle configuration from a particular group. Similar to
* throttle_get_config(), but guarantees atomicity within the
* throttling group.
*
- * @bs: a BlockDriverState that is member of the group
+ * @blk: a BlockBackend that is a member of the group
* @cfg: the configuration will be written here
*/
-void throttle_group_get_config(BlockDriverState *bs, ThrottleConfig *cfg)
+void throttle_group_get_config(BlockBackend *blk, ThrottleConfig *cfg)
{
- ThrottleState *ts = bs->throttle_state;
+ BlockBackendPublic *blkp = blk_get_public(blk);
+ ThrottleState *ts = blkp->throttle_state;
ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
qemu_mutex_lock(&tg->lock);
throttle_get_config(ts, cfg);
qemu_mutex_unlock(&tg->lock);
}
-/* Register a BlockDriverState in the throttling group, also updating
- * its throttle_state pointer to point to it. If a throttling group
- * with that name does not exist yet, it will be created.
+/* ThrottleTimers callback. This wakes up a request that was waiting
+ * because it had been throttled.
+ *
+ * @blk: the BlockBackend whose request had been throttled
+ * @is_write: the type of operation (read/write)
+ */
+static void timer_cb(BlockBackend *blk, bool is_write)
+{
+ BlockBackendPublic *blkp = blk_get_public(blk);
+ ThrottleState *ts = blkp->throttle_state;
+ 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 */
+ aio_context_acquire(blk_get_aio_context(blk));
+ empty_queue = !qemu_co_enter_next(&blkp->throttled_reqs[is_write]);
+ aio_context_release(blk_get_aio_context(blk));
+
+ /* 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(blk, 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 BlockBackend 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.
*
- * @bs: the BlockDriverState to insert
+ * @blk: the BlockBackend to insert
* @groupname: the name of the group
*/
-void throttle_group_register_bs(BlockDriverState *bs, const char *groupname)
+void throttle_group_register_blk(BlockBackend *blk, const char *groupname)
{
int i;
- ThrottleGroup *tg = throttle_group_incref(groupname);
+ BlockBackendPublic *blkp = blk_get_public(blk);
+ ThrottleState *ts = throttle_group_incref(groupname);
+ ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
+ int clock_type = QEMU_CLOCK_REALTIME;
- bs->throttle_state = &tg->ts;
+ if (qtest_enabled()) {
+ /* For testing block IO throttling only */
+ clock_type = QEMU_CLOCK_VIRTUAL;
+ }
+
+ blkp->throttle_state = ts;
qemu_mutex_lock(&tg->lock);
- /* If the ThrottleGroup is new set this BlockDriverState as the token */
+ /* If the ThrottleGroup is new set this BlockBackend as the token */
for (i = 0; i < 2; i++) {
if (!tg->tokens[i]) {
- tg->tokens[i] = bs;
+ tg->tokens[i] = blk;
}
}
- QLIST_INSERT_HEAD(&tg->head, bs, round_robin);
+ QLIST_INSERT_HEAD(&tg->head, blkp, round_robin);
+
+ throttle_timers_init(&blkp->throttle_timers,
+ blk_get_aio_context(blk),
+ clock_type,
+ read_timer_cb,
+ write_timer_cb,
+ blk);
+
qemu_mutex_unlock(&tg->lock);
}
-/* Unregister a BlockDriverState from its group, removing it from the
- * list and setting the throttle_state pointer to NULL.
+/* Unregister a BlockBackend from its group, removing it from the list,
+ * destroying the timers and setting the throttle_state pointer to NULL.
+ *
+ * The BlockBackend 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.
*
- * @bs: the BlockDriverState to remove
+ * @blk: the BlockBackend to remove
*/
-void throttle_group_unregister_bs(BlockDriverState *bs)
+void throttle_group_unregister_blk(BlockBackend *blk)
{
- ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
+ BlockBackendPublic *blkp = blk_get_public(blk);
+ ThrottleGroup *tg = container_of(blkp->throttle_state, ThrottleGroup, ts);
int i;
+ assert(blkp->pending_reqs[0] == 0 && blkp->pending_reqs[1] == 0);
+ assert(qemu_co_queue_empty(&blkp->throttled_reqs[0]));
+ assert(qemu_co_queue_empty(&blkp->throttled_reqs[1]));
+
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) {
+ if (tg->tokens[i] == blk) {
+ BlockBackend *token = throttle_group_next_blk(blk);
+ /* Take care of the case where this is the last blk in the group */
+ if (token == blk) {
token = NULL;
}
tg->tokens[i] = token;
}
}
- /* remove the current bs from the list */
- QLIST_REMOVE(bs, round_robin);
+ /* remove the current blk from the list */
+ QLIST_REMOVE(blkp, round_robin);
+ throttle_timers_destroy(&blkp->throttle_timers);
qemu_mutex_unlock(&tg->lock);
- throttle_group_unref(tg);
- bs->throttle_state = NULL;
+ throttle_group_unref(&tg->ts);
+ blkp->throttle_state = NULL;
}
static void throttle_groups_init(void)
projects / mirror_qemu.git / blobdiff