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authorStefan Hajnoczi <stefanha@redhat.com>2013-04-05 11:32:19 +0200
committerKevin Wolf <kwolf@redhat.com>2013-04-05 18:58:05 +0200
commit5905fbc9c94ccd744c1b249472eafcc2d827548a (patch)
tree71685e79fabea4499032719f71671420dec26a6b /block.c
parent76534da749ceb3b4c13ec09b173bcf6d6c2e36d4 (diff)
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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>
Diffstat (limited to 'block.c')
-rw-r--r--block.c21
1 files changed, 10 insertions, 11 deletions
diff --git a/block.c b/block.c
index 0ae2e93..25976b5 100644
--- a/block.c
+++ b/block.c
@@ -141,7 +141,6 @@ void bdrv_io_limits_disable(BlockDriverState *bs)
bs->slice_start = 0;
bs->slice_end = 0;
bs->slice_time = 0;
- memset(&bs->io_base, 0, sizeof(bs->io_base));
}
static void bdrv_block_timer(void *opaque)
@@ -1436,8 +1435,8 @@ static void bdrv_move_feature_fields(BlockDriverState *bs_dest,
bs_dest->slice_time = bs_src->slice_time;
bs_dest->slice_start = bs_src->slice_start;
bs_dest->slice_end = bs_src->slice_end;
+ bs_dest->slice_submitted = bs_src->slice_submitted;
bs_dest->io_limits = bs_src->io_limits;
- bs_dest->io_base = bs_src->io_base;
bs_dest->throttled_reqs = bs_src->throttled_reqs;
bs_dest->block_timer = bs_src->block_timer;
bs_dest->io_limits_enabled = bs_src->io_limits_enabled;
@@ -3768,9 +3767,9 @@ static bool bdrv_exceed_bps_limits(BlockDriverState *bs, int nb_sectors,
slice_time = bs->slice_end - bs->slice_start;
slice_time /= (NANOSECONDS_PER_SECOND);
bytes_limit = bps_limit * slice_time;
- bytes_base = bs->nr_bytes[is_write] - bs->io_base.bytes[is_write];
+ bytes_base = bs->slice_submitted.bytes[is_write];
if (bs->io_limits.bps[BLOCK_IO_LIMIT_TOTAL]) {
- bytes_base += bs->nr_bytes[!is_write] - bs->io_base.bytes[!is_write];
+ bytes_base += bs->slice_submitted.bytes[!is_write];
}
/* bytes_base: the bytes of data which have been read/written; and
@@ -3828,9 +3827,9 @@ static bool bdrv_exceed_iops_limits(BlockDriverState *bs, bool is_write,
slice_time = bs->slice_end - bs->slice_start;
slice_time /= (NANOSECONDS_PER_SECOND);
ios_limit = iops_limit * slice_time;
- ios_base = bs->nr_ops[is_write] - bs->io_base.ios[is_write];
+ ios_base = bs->slice_submitted.ios[is_write];
if (bs->io_limits.iops[BLOCK_IO_LIMIT_TOTAL]) {
- ios_base += bs->nr_ops[!is_write] - bs->io_base.ios[!is_write];
+ ios_base += bs->slice_submitted.ios[!is_write];
}
if (ios_base + 1 <= ios_limit) {
@@ -3875,11 +3874,7 @@ static bool bdrv_exceed_io_limits(BlockDriverState *bs, int nb_sectors,
bs->slice_start = now;
bs->slice_end = now + bs->slice_time;
- bs->io_base.bytes[is_write] = bs->nr_bytes[is_write];
- bs->io_base.bytes[!is_write] = bs->nr_bytes[!is_write];
-
- bs->io_base.ios[is_write] = bs->nr_ops[is_write];
- bs->io_base.ios[!is_write] = bs->nr_ops[!is_write];
+ memset(&bs->slice_submitted, 0, sizeof(bs->slice_submitted));
}
elapsed_time = now - bs->slice_start;
@@ -3907,6 +3902,10 @@ static bool bdrv_exceed_io_limits(BlockDriverState *bs, int nb_sectors,
*wait = 0;
}
+ bs->slice_submitted.bytes[is_write] += (int64_t)nb_sectors *
+ BDRV_SECTOR_SIZE;
+ bs->slice_submitted.ios[is_write]++;
+
return false;
}