From d11ae71ec97aab632df0b1aed20018da7a9db6a9 Mon Sep 17 00:00:00 2001
From: Fam Zheng <famz@redhat.com>
Date: Tue, 16 Jul 2013 06:08:41 +0200
Subject: [PATCH 10/21] block: fix I/O throttling accounting blind spot
RH-Author: Fam Zheng <famz@redhat.com>
Message-id: <1373954921-25694-1-git-send-email-famz@redhat.com>
Patchwork-id: 52511
O-Subject: [PATCH RHEL-6.5 qemu-kvm v4 10/15] block: fix I/O throttling accounting blind spot
Bugzilla: 956825
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
From: Stefan Hajnoczi <stefanha@redhat.com>
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>
(cherry picked from commit 5905fbc9c94ccd744c1b249472eafcc2d827548a)
Signed-off-by: Fam Zheng <famz@redhat.com>
Conflicts:
block.c
include/block/block_int.h
---
v4: zero out bs_new->slice_submitted [Laszlo]
---
block.c | 23 +++++++++++------------
block_int.h | 2 +-
2 files changed, 12 insertions(+), 13 deletions(-)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
block.c | 23 +++++++++++------------
block_int.h | 2 +-
2 files changed, 12 insertions(+), 13 deletions(-)
diff --git a/block.c b/block.c
index 8c2f94b..3e582a8 100644
--- a/block.c
+++ b/block.c
@@ -136,7 +136,6 @@ 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)
@@ -1161,8 +1160,8 @@ void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top)
tmp.slice_time = bs_top->slice_time;
tmp.slice_start = bs_top->slice_start;
tmp.slice_end = bs_top->slice_end;
+ tmp.slice_submitted = bs_top->slice_submitted;
tmp.io_limits = bs_top->io_limits;
- tmp.io_base = bs_top->io_base;
tmp.throttled_reqs = bs_top->throttled_reqs;
tmp.block_timer = bs_top->block_timer;
tmp.io_limits_enabled = bs_top->io_limits_enabled;
@@ -1219,7 +1218,7 @@ void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top)
bs_new->dirty_bitmap = NULL;
qemu_co_queue_init(&bs_new->throttled_reqs);
- memset(&bs_new->io_base, 0, sizeof(bs_new->io_base));
+ memset(&bs_new->slice_submitted, 0, sizeof(bs_new->slice_submitted));
memset(&bs_new->io_limits, 0, sizeof(bs_new->io_limits));
bdrv_iostatus_disable(bs_new);
@@ -3622,9 +3621,9 @@ 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
@@ -3682,9 +3681,9 @@ 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) {
@@ -3729,11 +3728,7 @@ 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;
@@ -3761,6 +3756,10 @@ 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;
}
diff --git a/block_int.h b/block_int.h
index 0e405f5..abf6609 100644
--- a/block_int.h
+++ b/block_int.h
@@ -284,7 +284,7 @@ struct BlockDriverState {
int64_t slice_start;
int64_t slice_end;
BlockIOLimit io_limits;
- BlockIOBaseValue io_base;
+ BlockIOBaseValue slice_submitted;
CoQueue throttled_reqs;
QEMUTimer *block_timer;
bool io_limits_enabled;
--
1.7.1