The throttle group support use a cooperative round robin scheduling
algorithm.
The principles of the algorithm are simple:
- Each BDS of the group is used as a token in a circular way.
- The active BDS computes if a wait must be done and arms the right
timer.
- If a wait must be done the token timer will be armed so the token
will become the next active BDS.
Signed-off-by: Alberto Garcia <be...@igalia.com>
---
block.c | 65 ++++++++++----------
block/qapi.c | 5 +-
block/throttle-groups.c | 127 ++++++++++++++++++++++++++++++++++++++++
blockdev.c | 19 +++++-
hmp.c | 4 +-
include/block/block.h | 3 +-
include/block/block_int.h | 9 +--
include/block/throttle-groups.h | 4 ++
qapi/block-core.json | 4 +-
qemu-options.hx | 1 +
qmp-commands.hx | 3 +-
11 files changed, 198 insertions(+), 46 deletions(-)
diff --git a/block.c b/block.c
index da0cb48..cd8582f 100644
--- a/block.c
+++ b/block.c
@@ -36,6 +36,7 @@
#include "qmp-commands.h"
#include "qemu/timer.h"
#include "qapi-event.h"
+#include "block/throttle-groups.h"
#ifdef CONFIG_BSD
#include <sys/types.h>
@@ -130,7 +131,7 @@ void bdrv_set_io_limits(BlockDriverState *bs,
{
int i;
- throttle_config(&bs->throttle_state, &bs->throttle_timers, cfg);
+ throttle_group_config(bs->throttle_state, &bs->throttle_timers, cfg);
for (i = 0; i < 2; i++) {
qemu_co_enter_next(&bs->throttled_reqs[i]);
@@ -160,9 +161,8 @@ static bool bdrv_start_throttled_reqs(BlockDriverState *bs)
void bdrv_io_limits_disable(BlockDriverState *bs)
{
bs->io_limits_enabled = false;
-
bdrv_start_throttled_reqs(bs);
-
+ throttle_group_unregister_bs(bs);
throttle_timers_destroy(&bs->throttle_timers);
}
@@ -179,10 +179,11 @@ static void bdrv_throttle_write_timer_cb(void *opaque)
}
/* should be called before bdrv_set_io_limits if a limit is set */
-void bdrv_io_limits_enable(BlockDriverState *bs)
+void bdrv_io_limits_enable(BlockDriverState *bs, const char *group)
{
assert(!bs->io_limits_enabled);
- throttle_init(&bs->throttle_state);
+
+ throttle_group_register_bs(bs, group ? group : bdrv_get_device_name(bs));
throttle_timers_init(&bs->throttle_timers,
bdrv_get_aio_context(bs),
QEMU_CLOCK_VIRTUAL,
@@ -192,6 +193,23 @@ void bdrv_io_limits_enable(BlockDriverState *bs)
bs->io_limits_enabled = true;
}
+void bdrv_io_limits_update_group(BlockDriverState *bs, const char *group)
+{
+ /* this bs is not part of any group */
+ if (!bs->throttle_state) {
+ return;
+ }
+
+ /* this bs is a part of the same group than the one we want */
+ if (!g_strcmp0(throttle_group_get_name(bs->throttle_state), group)) {
+ return;
+ }
+
+ /* need to change the group this bs belong to */
+ bdrv_io_limits_disable(bs);
+ bdrv_io_limits_enable(bs, group);
+}
+
/* This function makes an IO wait if needed
*
* @nb_sectors: the number of sectors of the IO
@@ -201,29 +219,7 @@ static void bdrv_io_limits_intercept(BlockDriverState *bs,
unsigned int bytes,
bool is_write)
{
- /* does this io must wait */
- bool must_wait = throttle_schedule_timer(&bs->throttle_state,
- &bs->throttle_timers,
- is_write);
-
- /* if must wait or any request of this type throttled queue the IO */
- if (must_wait ||
- !qemu_co_queue_empty(&bs->throttled_reqs[is_write])) {
- qemu_co_queue_wait(&bs->throttled_reqs[is_write]);
- }
-
- /* the IO will be executed, do the accounting */
- throttle_account(&bs->throttle_state, is_write, bytes);
-
-
- /* if the next request must wait -> do nothing */
- if (throttle_schedule_timer(&bs->throttle_state, &bs->throttle_timers,
- is_write)) {
- return;
- }
-
- /* else queue next request for execution */
- qemu_co_queue_next(&bs->throttled_reqs[is_write]);
+ throttle_group_io_limits_intercept(bs, bytes, is_write);
}
size_t bdrv_opt_mem_align(BlockDriverState *bs)
@@ -2050,15 +2046,16 @@ static void bdrv_move_feature_fields(BlockDriverState
*bs_dest,
bs_dest->enable_write_cache = bs_src->enable_write_cache;
/* i/o throttled req */
- memcpy(&bs_dest->throttle_state,
- &bs_src->throttle_state,
- sizeof(ThrottleState));
+ bs_dest->throttle_state = bs_src->throttle_state,
+ bs_dest->io_limits_enabled = bs_src->io_limits_enabled;
+ bs_dest->throttled_reqs[0] = bs_src->throttled_reqs[0];
+ bs_dest->throttled_reqs[1] = bs_src->throttled_reqs[1];
+ memcpy(&bs_dest->round_robin,
+ &bs_src->round_robin,
+ sizeof(bs_dest->round_robin));
memcpy(&bs_dest->throttle_timers,
&bs_src->throttle_timers,
sizeof(ThrottleTimers));
- bs_dest->throttled_reqs[0] = bs_src->throttled_reqs[0];
- bs_dest->throttled_reqs[1] = bs_src->throttled_reqs[1];
- bs_dest->io_limits_enabled = bs_src->io_limits_enabled;
/* r/w error */
bs_dest->on_read_error = bs_src->on_read_error;
diff --git a/block/qapi.c b/block/qapi.c
index 1808e67..abeeb38 100644
--- a/block/qapi.c
+++ b/block/qapi.c
@@ -24,6 +24,7 @@
#include "block/qapi.h"
#include "block/block_int.h"
+#include "block/throttle-groups.h"
#include "block/write-threshold.h"
#include "qmp-commands.h"
#include "qapi-visit.h"
@@ -63,7 +64,9 @@ BlockDeviceInfo *bdrv_block_device_info(BlockDriverState *bs)
if (bs->io_limits_enabled) {
ThrottleConfig cfg;
- throttle_get_config(&bs->throttle_state, &cfg);
+
+ throttle_group_get_config(bs->throttle_state, &cfg);
+
info->bps = cfg.buckets[THROTTLE_BPS_TOTAL].avg;
info->bps_rd = cfg.buckets[THROTTLE_BPS_READ].avg;
info->bps_wr = cfg.buckets[THROTTLE_BPS_WRITE].avg;
diff --git a/block/throttle-groups.c b/block/throttle-groups.c
index e355fed..9075c46 100644
--- a/block/throttle-groups.c
+++ b/block/throttle-groups.c
@@ -23,6 +23,8 @@
*/
#include "block/throttle-groups.h"
+#include "qemu/queue.h"
+#include "qemu/thread.h"
/* The ThrottleGroup structure (with its ThrottleState) is shared
* among different BlockDriverState and it's independent from
@@ -145,6 +147,131 @@ static BlockDriverState
*throttle_group_next_bs(BlockDriverState *bs)
return next;
}
+/* Return the next BlockDriverState in the round-robin sequence with
+ * pending I/O requests.
+ *
+ * @bs: the current BlockDriverState
+ * @is_write: the type of operation (read/write)
+ * @ret: the next BlockDriverState with pending requests, or bs
+ * if there is none.
+ */
+static BlockDriverState *next_throttle_token(BlockDriverState *bs,
+ bool is_write)
+{
+ ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
+ BlockDriverState *token, *start;
+
+ start = token = tg->tokens[is_write];
+
+ /* get next bs round in round robin style */
+ token = throttle_group_next_bs(token);
+ while (token != start &&
+ qemu_co_queue_empty(&token->throttled_reqs[is_write])) {
+ token = throttle_group_next_bs(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 &&
+ qemu_co_queue_empty(&token->throttled_reqs[is_write])) {
+ token = bs;
+ }
+
+ return token;
+}
+
+/* Check if the next I/O request for a BlockDriverState needs to be
+ * throttled or not. If there's no timer set in this group, set one
+ * and update the token accordingly.
+ *
+ * @bs: the current BlockDriverState
+ * @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(BlockDriverState *bs,
+ bool is_write)
+{
+ ThrottleState *ts = bs->throttle_state;
+ ThrottleTimers *tt = &bs->throttle_timers;
+ ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
+ bool must_wait;
+ BlockDriverState *iter;
+
+ /* Check if any of the timers in this group is already armed */
+ QLIST_FOREACH(iter, &tg->head, round_robin) {
+ if (timer_pending(iter->throttle_timers.timers[is_write])) {
+ return true;
+ }
+ }
+
+ must_wait = throttle_schedule_timer(ts, tt, is_write);
+
+ /* If a timer just got armed, set bs as the current token */
+ if (must_wait) {
+ tg->tokens[is_write] = bs;
+ }
+
+ return must_wait;
+}
+
+/* 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.
+ *
+ * @bs: the current BlockDriverState
+ * @bytes: the number of bytes for this I/O
+ * @is_write: the type of operation (read/write)
+ */
+void throttle_group_io_limits_intercept(BlockDriverState *bs,
+ unsigned int bytes,
+ bool is_write)
+{
+ bool must_wait;
+ BlockDriverState *token;
+
+ ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
+ qemu_mutex_lock(&tg->lock);
+
+ /* First we check if this I/O has to be throttled. */
+ token = next_throttle_token(bs, 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 || !qemu_co_queue_empty(&bs->throttled_reqs[is_write])) {
+ qemu_mutex_unlock(&tg->lock);
+ qemu_co_queue_wait(&bs->throttled_reqs[is_write]);
+ qemu_mutex_lock(&tg->lock);
+ }
+
+ /* The I/O will be executed, so do the accounting */
+ throttle_account(bs->throttle_state, is_write, bytes);
+
+ /* Now we check if there's any pending request to schedule next */
+ token = next_throttle_token(bs, is_write);
+ if (!qemu_co_queue_empty(&token->throttled_reqs[is_write])) {
+
+ /* If it doesn't have to wait, queue it for immediate execution */
+ must_wait = throttle_group_schedule_timer(token, is_write);
+
+ if (!must_wait) {
+ /* Give preference to requests from the current bs */
+ if (!qemu_co_queue_empty(&bs->throttled_reqs[is_write])) {
+ token = bs;
+ qemu_co_queue_next(&bs->throttled_reqs[is_write]);
+ } else {
+ ThrottleTimers *tt = &token->throttle_timers;
+ int64_t now = qemu_clock_get_ns(tt->clock_type);
+ timer_mod(tt->timers[is_write], now + 1);
+ }
+ tg->tokens[is_write] = token;
+ }
+ }
+
+ qemu_mutex_unlock(&tg->lock);
+}
+
/* Update the throttle configuration for a particular group. Similar
* to throttle_config(), but guarantees atomicity within the
* throttling group.
diff --git a/blockdev.c b/blockdev.c
index b9c1c0c..89fc7a8 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -357,6 +357,7 @@ static BlockBackend *blockdev_init(const char *file, QDict
*bs_opts,
const char *id;
bool has_driver_specific_opts;
BlockdevDetectZeroesOptions detect_zeroes;
+ const char *throttling_group;
/* Check common options by copying from bs_opts to opts, all other options
* stay in bs_opts for processing by bdrv_open(). */
@@ -459,6 +460,8 @@ static BlockBackend *blockdev_init(const char *file, QDict
*bs_opts,
cfg.op_size = qemu_opt_get_number(opts, "throttling.iops-size", 0);
+ throttling_group = qemu_opt_get(opts, "throttling.group");
+
if (!check_throttle_config(&cfg, &error)) {
error_propagate(errp, error);
goto early_err;
@@ -547,7 +550,7 @@ static BlockBackend *blockdev_init(const char *file, QDict
*bs_opts,
/* disk I/O throttling */
if (throttle_enabled(&cfg)) {
- bdrv_io_limits_enable(bs);
+ bdrv_io_limits_enable(bs, throttling_group);
bdrv_set_io_limits(bs, &cfg);
}
@@ -711,6 +714,8 @@ DriveInfo *drive_new(QemuOpts *all_opts, BlockInterfaceType
block_default_type)
{ "iops_size", "throttling.iops-size" },
+ { "group", "throttling.group" },
+
{ "readonly", "read-only" },
};
@@ -1877,7 +1882,9 @@ void qmp_block_set_io_throttle(const char *device,
int64_t bps, int64_t bps_rd,
bool has_iops_wr_max,
int64_t iops_wr_max,
bool has_iops_size,
- int64_t iops_size, Error **errp)
+ int64_t iops_size,
+ bool has_group,
+ const char *group, Error **errp)
{
ThrottleConfig cfg;
BlockDriverState *bs;
@@ -1929,9 +1936,11 @@ void qmp_block_set_io_throttle(const char *device,
int64_t bps, int64_t bps_rd,
aio_context_acquire(aio_context);
if (!bs->io_limits_enabled && throttle_enabled(&cfg)) {
- bdrv_io_limits_enable(bs);
+ bdrv_io_limits_enable(bs, has_group ? group : NULL);
} else if (bs->io_limits_enabled && !throttle_enabled(&cfg)) {
bdrv_io_limits_disable(bs);
+ } else if (bs->io_limits_enabled && throttle_enabled(&cfg)) {
+ bdrv_io_limits_update_group(bs, has_group ? group : NULL);
}
if (bs->io_limits_enabled) {
@@ -2991,6 +3000,10 @@ QemuOptsList qemu_common_drive_opts = {
.type = QEMU_OPT_NUMBER,
.help = "when limiting by iops max size of an I/O in bytes",
},{
+ .name = "throttling.group",
+ .type = QEMU_OPT_STRING,
+ .help = "name of the block throttling group",
+ },{
.name = "copy-on-read",
.type = QEMU_OPT_BOOL,
.help = "copy read data from backing file into image file",
diff --git a/hmp.c b/hmp.c
index 71c28bc..b81e4ba 100644
--- a/hmp.c
+++ b/hmp.c
@@ -1261,7 +1261,9 @@ void hmp_block_set_io_throttle(Monitor *mon, const QDict
*qdict)
false,
0,
false, /* No default I/O size */
- 0, &err);
+ 0,
+ false,
+ NULL, &err);
hmp_handle_error(mon, &err);
}
diff --git a/include/block/block.h b/include/block/block.h
index 649c269..2bb6222 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -162,8 +162,9 @@ void bdrv_stats_print(Monitor *mon, const QObject *data);
void bdrv_info_stats(Monitor *mon, QObject **ret_data);
/* disk I/O throttling */
-void bdrv_io_limits_enable(BlockDriverState *bs);
+void bdrv_io_limits_enable(BlockDriverState *bs, const char *group);
void bdrv_io_limits_disable(BlockDriverState *bs);
+void bdrv_io_limits_update_group(BlockDriverState *bs, const char *group);
void bdrv_init(void);
void bdrv_init_with_whitelist(void);
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 1314fd3..c02e963 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -358,12 +358,13 @@ struct BlockDriverState {
/* number of in-flight serialising requests */
unsigned int serialising_in_flight;
- /* I/O throttling */
- ThrottleState throttle_state;
- ThrottleTimers throttle_timers;
- CoQueue throttled_reqs[2];
+ /* I/O throttling - following elements protected by ThrottleGroup lock */
+ ThrottleState *throttle_state;
bool io_limits_enabled;
+ CoQueue throttled_reqs[2];
QLIST_ENTRY(BlockDriverState) round_robin;
+ /* timers have their own locking */
+ ThrottleTimers throttle_timers;
/* I/O stats (display with "info blockstats"). */
BlockAcctStats stats;
diff --git a/include/block/throttle-groups.h b/include/block/throttle-groups.h
index 23a172f..ddb962b 100644
--- a/include/block/throttle-groups.h
+++ b/include/block/throttle-groups.h
@@ -38,4 +38,8 @@ void throttle_group_get_config(ThrottleState *ts,
ThrottleConfig *cfg);
void throttle_group_register_bs(BlockDriverState *bs, const char *groupname);
void throttle_group_unregister_bs(BlockDriverState *bs);
+void throttle_group_io_limits_intercept(BlockDriverState *bs,
+ unsigned int bytes,
+ bool is_write);
+
#endif
diff --git a/qapi/block-core.json b/qapi/block-core.json
index a3fdaf0..487b147 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -989,6 +989,8 @@
#
# @iops_size: #optional an I/O size in bytes (Since 1.7)
#
+# @group: #optional throttle group name (Since 2.3)
+#
# Returns: Nothing on success
# If @device is not a valid block device, DeviceNotFound
#
@@ -1000,7 +1002,7 @@
'*bps_max': 'int', '*bps_rd_max': 'int',
'*bps_wr_max': 'int', '*iops_max': 'int',
'*iops_rd_max': 'int', '*iops_wr_max': 'int',
- '*iops_size': 'int' } }
+ '*iops_size': 'int', '*group': 'str' } }
##
# @block-stream:
diff --git a/qemu-options.hx b/qemu-options.hx
index 837624d..6db0613 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -454,6 +454,7 @@ DEF("drive", HAS_ARG, QEMU_OPTION_drive,
" [[,bps_max=bm]|[[,bps_rd_max=rm][,bps_wr_max=wm]]]\n"
" [[,iops_max=im]|[[,iops_rd_max=irm][,iops_wr_max=iwm]]]\n"
" [[,iops_size=is]]\n"
+ " [[,group=g]]\n"
" use 'file' as a drive image\n", QEMU_ARCH_ALL)
STEXI
@item -drive @var{option}[,@var{option}[,@var{option}[,...]]]
diff --git a/qmp-commands.hx b/qmp-commands.hx
index c12334a..d866d57 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1704,7 +1704,7 @@ EQMP
{
.name = "block_set_io_throttle",
- .args_type =
"device:B,bps:l,bps_rd:l,bps_wr:l,iops:l,iops_rd:l,iops_wr:l,bps_max:l?,bps_rd_max:l?,bps_wr_max:l?,iops_max:l?,iops_rd_max:l?,iops_wr_max:l?,iops_size:l?",
+ .args_type =
"device:B,bps:l,bps_rd:l,bps_wr:l,iops:l,iops_rd:l,iops_wr:l,bps_max:l?,bps_rd_max:l?,bps_wr_max:l?,iops_max:l?,iops_rd_max:l?,iops_wr_max:l?,iops_size:l?,group:s?",
.mhandler.cmd_new = qmp_marshal_input_block_set_io_throttle,
},
@@ -1730,6 +1730,7 @@ Arguments:
- "iops_rd_max": read I/O operations max (json-int)
- "iops_wr_max": write I/O operations max (json-int)
- "iops_size": I/O size in bytes when limiting (json-int)
+- "group": throttle group name (json-string)
Example:
--
2.1.4
