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block: rate-limit streaming operations
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>
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@ -23,8 +23,39 @@ enum {
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STREAM_BUFFER_SIZE = 512 * 1024, /* in bytes */
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};
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#define SLICE_TIME 100000000ULL /* ns */
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typedef struct {
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int64_t next_slice_time;
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uint64_t slice_quota;
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uint64_t dispatched;
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} RateLimit;
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static int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)
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{
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int64_t delay_ns = 0;
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int64_t now = qemu_get_clock_ns(rt_clock);
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if (limit->next_slice_time < now) {
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limit->next_slice_time = now + SLICE_TIME;
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limit->dispatched = 0;
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}
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if (limit->dispatched + n > limit->slice_quota) {
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delay_ns = limit->next_slice_time - now;
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} else {
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limit->dispatched += n;
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}
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return delay_ns;
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}
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static void ratelimit_set_speed(RateLimit *limit, uint64_t speed)
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{
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limit->slice_quota = speed / (1000000000ULL / SLICE_TIME);
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}
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typedef struct StreamBlockJob {
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BlockJob common;
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RateLimit limit;
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BlockDriverState *base;
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} StreamBlockJob;
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@ -72,20 +103,24 @@ static void coroutine_fn stream_run(void *opaque)
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}
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for (sector_num = 0; sector_num < end; sector_num += n) {
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retry:
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if (block_job_is_cancelled(&s->common)) {
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break;
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}
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/* TODO rate-limit */
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/* Note that even when no rate limit is applied we need to yield with
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* no pending I/O here so that qemu_aio_flush() is able to return.
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*/
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co_sleep_ns(rt_clock, 0);
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ret = bdrv_co_is_allocated(bs, sector_num,
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STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n);
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trace_stream_one_iteration(s, sector_num, n, ret);
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if (ret == 0) {
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if (s->common.speed) {
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uint64_t delay_ns = ratelimit_calculate_delay(&s->limit, n);
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if (delay_ns > 0) {
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co_sleep_ns(rt_clock, delay_ns);
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/* Recheck cancellation and that sectors are unallocated */
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goto retry;
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}
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}
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ret = stream_populate(bs, sector_num, n, buf);
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}
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if (ret < 0) {
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@ -94,6 +129,11 @@ static void coroutine_fn stream_run(void *opaque)
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/* Publish progress */
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s->common.offset += n * BDRV_SECTOR_SIZE;
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/* Note that even when no rate limit is applied we need to yield
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* with no pending I/O here so that qemu_aio_flush() returns.
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*/
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co_sleep_ns(rt_clock, 0);
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}
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if (!base) {
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@ -108,9 +148,22 @@ static void coroutine_fn stream_run(void *opaque)
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block_job_complete(&s->common, ret);
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}
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static int stream_set_speed(BlockJob *job, int64_t value)
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{
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StreamBlockJob *s = container_of(job, StreamBlockJob, common);
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if (value < 0) {
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return -EINVAL;
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}
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job->speed = value;
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ratelimit_set_speed(&s->limit, value / BDRV_SECTOR_SIZE);
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return 0;
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}
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static BlockJobType stream_job_type = {
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.instance_size = sizeof(StreamBlockJob),
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.job_type = "stream",
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.set_speed = stream_set_speed,
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};
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int stream_start(BlockDriverState *bs, BlockDriverState *base,
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