diff options
| -rw-r--r-- | block/commit.c | 13 | ||||
| -rw-r--r-- | block/mirror.c | 4 | ||||
| -rw-r--r-- | block/stream.c | 12 | ||||
| -rw-r--r-- | include/qemu/ratelimit.h | 43 |
4 files changed, 46 insertions, 26 deletions
diff --git a/block/commit.c b/block/commit.c index 5d11eb6103..553e18da52 100644 --- a/block/commit.c +++ b/block/commit.c @@ -113,6 +113,7 @@ static void coroutine_fn commit_run(void *opaque) CommitBlockJob *s = opaque; CommitCompleteData *data; int64_t sector_num, end; + uint64_t delay_ns = 0; int ret = 0; int n = 0; void *buf = NULL; @@ -142,10 +143,8 @@ static void coroutine_fn commit_run(void *opaque) buf = blk_blockalign(s->top, COMMIT_BUFFER_SIZE); for (sector_num = 0; sector_num < end; sector_num += n) { - uint64_t delay_ns = 0; bool copy; -wait: /* Note that even when no rate limit is applied we need to yield * with no pending I/O here so that bdrv_drain_all() returns. */ @@ -161,12 +160,6 @@ wait: copy = (ret == 1); trace_commit_one_iteration(s, sector_num, n, ret); if (copy) { - if (s->common.speed) { - delay_ns = ratelimit_calculate_delay(&s->limit, n); - if (delay_ns > 0) { - goto wait; - } - } ret = commit_populate(s->top, s->base, sector_num, n, buf); bytes_written += n * BDRV_SECTOR_SIZE; } @@ -182,6 +175,10 @@ wait: } /* Publish progress */ s->common.offset += n * BDRV_SECTOR_SIZE; + + if (copy && s->common.speed) { + delay_ns = ratelimit_calculate_delay(&s->limit, n); + } } ret = 0; diff --git a/block/mirror.c b/block/mirror.c index 71e5ad4377..b1e633ecad 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -422,7 +422,9 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s) assert(io_sectors); sector_num += io_sectors; nb_chunks -= DIV_ROUND_UP(io_sectors, sectors_per_chunk); - delay_ns += ratelimit_calculate_delay(&s->limit, io_sectors); + if (s->common.speed) { + delay_ns = ratelimit_calculate_delay(&s->limit, io_sectors); + } } return delay_ns; } diff --git a/block/stream.c b/block/stream.c index 2e7c6547d2..31874817c2 100644 --- a/block/stream.c +++ b/block/stream.c @@ -95,6 +95,7 @@ static void coroutine_fn stream_run(void *opaque) BlockDriverState *base = s->base; int64_t sector_num = 0; int64_t end = -1; + uint64_t delay_ns = 0; int error = 0; int ret = 0; int n = 0; @@ -123,10 +124,8 @@ static void coroutine_fn stream_run(void *opaque) } for (sector_num = 0; sector_num < end; sector_num += n) { - uint64_t delay_ns = 0; bool copy; -wait: /* Note that even when no rate limit is applied we need to yield * with no pending I/O here so that bdrv_drain_all() returns. */ @@ -156,12 +155,6 @@ wait: } trace_stream_one_iteration(s, sector_num, n, ret); if (copy) { - if (s->common.speed) { - delay_ns = ratelimit_calculate_delay(&s->limit, n); - if (delay_ns > 0) { - goto wait; - } - } ret = stream_populate(blk, sector_num, n, buf); } if (ret < 0) { @@ -182,6 +175,9 @@ wait: /* Publish progress */ s->common.offset += n * BDRV_SECTOR_SIZE; + if (copy && s->common.speed) { + delay_ns = ratelimit_calculate_delay(&s->limit, n); + } } if (!base) { diff --git a/include/qemu/ratelimit.h b/include/qemu/ratelimit.h index 1e3cb13b28..8da1232574 100644 --- a/include/qemu/ratelimit.h +++ b/include/qemu/ratelimit.h @@ -15,34 +15,59 @@ #define QEMU_RATELIMIT_H typedef struct { - int64_t next_slice_time; + int64_t slice_start_time; + int64_t slice_end_time; uint64_t slice_quota; uint64_t slice_ns; uint64_t dispatched; } RateLimit; +/** Calculate and return delay for next request in ns + * + * Record that we sent @p n data units. If we may send more data units + * in the current time slice, return 0 (i.e. no delay). Otherwise + * return the amount of time (in ns) until the start of the next time + * slice that will permit sending the next chunk of data. + * + * Recording sent data units even after exceeding the quota is + * permitted; the time slice will be extended accordingly. + */ static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n) { int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); + uint64_t delay_slices; - if (limit->next_slice_time < now) { - limit->next_slice_time = now + limit->slice_ns; + assert(limit->slice_quota && limit->slice_ns); + + if (limit->slice_end_time < now) { + /* Previous, possibly extended, time slice finished; reset the + * accounting. */ + limit->slice_start_time = now; + limit->slice_end_time = now + limit->slice_ns; limit->dispatched = 0; } - if (limit->dispatched == 0 || limit->dispatched + n <= limit->slice_quota) { - limit->dispatched += n; + + limit->dispatched += n; + if (limit->dispatched < limit->slice_quota) { + /* We may send further data within the current time slice, no + * need to delay the next request. */ return 0; - } else { - limit->dispatched = n; - return limit->next_slice_time - now; } + + /* Quota exceeded. Calculate the next time slice we may start + * sending data again. */ + delay_slices = (limit->dispatched + limit->slice_quota - 1) / + limit->slice_quota; + limit->slice_end_time = limit->slice_start_time + + delay_slices * limit->slice_ns; + return limit->slice_end_time - now; } static inline void ratelimit_set_speed(RateLimit *limit, uint64_t speed, uint64_t slice_ns) { limit->slice_ns = slice_ns; - limit->slice_quota = ((double)speed * slice_ns)/1000000000ULL; + limit->slice_quota = MAX(((double)speed * slice_ns) / 1000000000ULL, 1); } #endif |