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block: rate-limit streaming operations

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This patch implements rate-limiting for image streaming.  If we've
exceeded the bandwidth quota for a 100 ms time slice we sleep the
coroutine until the next slice begins.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2012-01-18 14:40:45 +00:00 committed by Kevin Wolf
parent 4f1043b4ff
commit 5094a6c016
1 changed files with 59 additions and 6 deletions
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65
block/stream.c
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@ -23,8 +23,39 @@ enum {
STREAM_BUFFER_SIZE = 512 * 1024, /* in bytes */
};
#define SLICE_TIME 100000000ULL /* ns */
typedef struct {
int64_t next_slice_time;
uint64_t slice_quota;
uint64_t dispatched;
} RateLimit;
static int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)
{
int64_t delay_ns = 0;
int64_t now = qemu_get_clock_ns(rt_clock);
if (limit->next_slice_time < now) {
limit->next_slice_time = now + SLICE_TIME;
limit->dispatched = 0;
}
if (limit->dispatched + n > limit->slice_quota) {
delay_ns = limit->next_slice_time - now;
} else {
limit->dispatched += n;
}
return delay_ns;
}
static void ratelimit_set_speed(RateLimit *limit, uint64_t speed)
{
limit->slice_quota = speed / (1000000000ULL / SLICE_TIME);
}
typedef struct StreamBlockJob {
BlockJob common;
RateLimit limit;
BlockDriverState *base;
} StreamBlockJob;
@ -72,20 +103,24 @@ static void coroutine_fn stream_run(void *opaque)
}
for (sector_num = 0; sector_num < end; sector_num += n) {
retry:
if (block_job_is_cancelled(&s->common)) {
break;
}
/* TODO rate-limit */
/* Note that even when no rate limit is applied we need to yield with
* no pending I/O here so that qemu_aio_flush() is able to return.
*/
co_sleep_ns(rt_clock, 0);
ret = bdrv_co_is_allocated(bs, sector_num,
STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n);
trace_stream_one_iteration(s, sector_num, n, ret);
if (ret == 0) {
if (s->common.speed) {
uint64_t delay_ns = ratelimit_calculate_delay(&s->limit, n);
if (delay_ns > 0) {
co_sleep_ns(rt_clock, delay_ns);
/* Recheck cancellation and that sectors are unallocated */
goto retry;
}
}
ret = stream_populate(bs, sector_num, n, buf);
}
if (ret < 0) {
@ -94,6 +129,11 @@ static void coroutine_fn stream_run(void *opaque)
/* Publish progress */
s->common.offset += n * BDRV_SECTOR_SIZE;
/* Note that even when no rate limit is applied we need to yield
* with no pending I/O here so that qemu_aio_flush() returns.
*/
co_sleep_ns(rt_clock, 0);
}
if (!base) {
@ -108,9 +148,22 @@ static void coroutine_fn stream_run(void *opaque)
block_job_complete(&s->common, ret);
}
static int stream_set_speed(BlockJob *job, int64_t value)
{
StreamBlockJob *s = container_of(job, StreamBlockJob, common);
if (value < 0) {
return -EINVAL;
}
job->speed = value;
ratelimit_set_speed(&s->limit, value / BDRV_SECTOR_SIZE);
return 0;
}
static BlockJobType stream_job_type = {
.instance_size = sizeof(StreamBlockJob),
.job_type = "stream",
.set_speed = stream_set_speed,
};
int stream_start(BlockDriverState *bs, BlockDriverState *base,