block: fix I/O throttling accounting blind spot
I/O throttling relies on bdrv_acct_done() which is called when a request completes. This leaves a blind spot since we only charge for completed requests, not submitted requests. For example, if there is 1 operation remaining in this time slice the guest could submit 3 operations and they will all be submitted successfully since they don't actually get accounted for until they complete. Originally we probably thought this is okay since the requests will be accounted when the time slice is extended. In practice it causes fluctuations since the guest can exceed its I/O limit and it will be punished for this later on. Account for I/O upon submission so that I/O limits are enforced properly. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Tested-By: Benoit Canet <benoit@irqsave.net> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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parent
76534da749
commit
5905fbc9c9
21
block.c
21
block.c
@ -141,7 +141,6 @@ void bdrv_io_limits_disable(BlockDriverState *bs)
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bs->slice_start = 0;
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bs->slice_start = 0;
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bs->slice_end = 0;
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bs->slice_end = 0;
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bs->slice_time = 0;
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bs->slice_time = 0;
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memset(&bs->io_base, 0, sizeof(bs->io_base));
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}
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}
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static void bdrv_block_timer(void *opaque)
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static void bdrv_block_timer(void *opaque)
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@ -1436,8 +1435,8 @@ static void bdrv_move_feature_fields(BlockDriverState *bs_dest,
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bs_dest->slice_time = bs_src->slice_time;
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bs_dest->slice_time = bs_src->slice_time;
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bs_dest->slice_start = bs_src->slice_start;
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bs_dest->slice_start = bs_src->slice_start;
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bs_dest->slice_end = bs_src->slice_end;
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bs_dest->slice_end = bs_src->slice_end;
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bs_dest->slice_submitted = bs_src->slice_submitted;
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bs_dest->io_limits = bs_src->io_limits;
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bs_dest->io_limits = bs_src->io_limits;
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bs_dest->io_base = bs_src->io_base;
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bs_dest->throttled_reqs = bs_src->throttled_reqs;
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bs_dest->throttled_reqs = bs_src->throttled_reqs;
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bs_dest->block_timer = bs_src->block_timer;
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bs_dest->block_timer = bs_src->block_timer;
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bs_dest->io_limits_enabled = bs_src->io_limits_enabled;
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bs_dest->io_limits_enabled = bs_src->io_limits_enabled;
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@ -3768,9 +3767,9 @@ static bool bdrv_exceed_bps_limits(BlockDriverState *bs, int nb_sectors,
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slice_time = bs->slice_end - bs->slice_start;
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slice_time = bs->slice_end - bs->slice_start;
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slice_time /= (NANOSECONDS_PER_SECOND);
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slice_time /= (NANOSECONDS_PER_SECOND);
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bytes_limit = bps_limit * slice_time;
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bytes_limit = bps_limit * slice_time;
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bytes_base = bs->nr_bytes[is_write] - bs->io_base.bytes[is_write];
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bytes_base = bs->slice_submitted.bytes[is_write];
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if (bs->io_limits.bps[BLOCK_IO_LIMIT_TOTAL]) {
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if (bs->io_limits.bps[BLOCK_IO_LIMIT_TOTAL]) {
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bytes_base += bs->nr_bytes[!is_write] - bs->io_base.bytes[!is_write];
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bytes_base += bs->slice_submitted.bytes[!is_write];
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}
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}
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/* bytes_base: the bytes of data which have been read/written; and
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/* bytes_base: the bytes of data which have been read/written; and
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@ -3828,9 +3827,9 @@ static bool bdrv_exceed_iops_limits(BlockDriverState *bs, bool is_write,
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slice_time = bs->slice_end - bs->slice_start;
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slice_time = bs->slice_end - bs->slice_start;
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slice_time /= (NANOSECONDS_PER_SECOND);
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slice_time /= (NANOSECONDS_PER_SECOND);
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ios_limit = iops_limit * slice_time;
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ios_limit = iops_limit * slice_time;
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ios_base = bs->nr_ops[is_write] - bs->io_base.ios[is_write];
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ios_base = bs->slice_submitted.ios[is_write];
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if (bs->io_limits.iops[BLOCK_IO_LIMIT_TOTAL]) {
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if (bs->io_limits.iops[BLOCK_IO_LIMIT_TOTAL]) {
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ios_base += bs->nr_ops[!is_write] - bs->io_base.ios[!is_write];
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ios_base += bs->slice_submitted.ios[!is_write];
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}
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}
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if (ios_base + 1 <= ios_limit) {
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if (ios_base + 1 <= ios_limit) {
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@ -3875,11 +3874,7 @@ static bool bdrv_exceed_io_limits(BlockDriverState *bs, int nb_sectors,
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bs->slice_start = now;
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bs->slice_start = now;
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bs->slice_end = now + bs->slice_time;
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bs->slice_end = now + bs->slice_time;
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bs->io_base.bytes[is_write] = bs->nr_bytes[is_write];
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memset(&bs->slice_submitted, 0, sizeof(bs->slice_submitted));
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bs->io_base.bytes[!is_write] = bs->nr_bytes[!is_write];
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bs->io_base.ios[is_write] = bs->nr_ops[is_write];
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bs->io_base.ios[!is_write] = bs->nr_ops[!is_write];
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}
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}
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elapsed_time = now - bs->slice_start;
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elapsed_time = now - bs->slice_start;
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@ -3907,6 +3902,10 @@ static bool bdrv_exceed_io_limits(BlockDriverState *bs, int nb_sectors,
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*wait = 0;
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*wait = 0;
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}
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}
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bs->slice_submitted.bytes[is_write] += (int64_t)nb_sectors *
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BDRV_SECTOR_SIZE;
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bs->slice_submitted.ios[is_write]++;
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return false;
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return false;
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}
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}
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@ -256,7 +256,7 @@ struct BlockDriverState {
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int64_t slice_start;
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int64_t slice_start;
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int64_t slice_end;
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int64_t slice_end;
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BlockIOLimit io_limits;
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BlockIOLimit io_limits;
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BlockIOBaseValue io_base;
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BlockIOBaseValue slice_submitted;
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CoQueue throttled_reqs;
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CoQueue throttled_reqs;
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QEMUTimer *block_timer;
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QEMUTimer *block_timer;
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bool io_limits_enabled;
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bool io_limits_enabled;
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