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[PULL 20/32] qcow2: handle_dependencies(): relax conflict detection
From: |
Hanna Reitz |
Subject: |
[PULL 20/32] qcow2: handle_dependencies(): relax conflict detection |
Date: |
Wed, 15 Sep 2021 19:53:06 +0200 |
From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
There is no conflict and no dependency if we have parallel writes to
different subclusters of one cluster when the cluster itself is already
allocated. So, relax extra dependency.
Measure performance:
First, prepare build/qemu-img-old and build/qemu-img-new images.
cd scripts/simplebench
./img_bench_templater.py
Paste the following to stdin of running script:
qemu_img=../../build/qemu-img-{old|new}
$qemu_img create -f qcow2 -o extended_l2=on /ssd/x.qcow2 1G
$qemu_img bench -c 100000 -d 8 [-s 2K|-s 2K -o 512|-s $((1024*2+512))] \
-w -t none -n /ssd/x.qcow2
The result:
All results are in seconds
------------------ --------- ---------
old new
-s 2K 6.7 ± 15% 6.2 ± 12%
-7%
-s 2K -o 512 13 ± 3% 11 ± 5%
-16%
-s $((1024*2+512)) 9.5 ± 4% 8.4
-12%
------------------ --------- ---------
So small writes are more independent now and that helps to keep deeper
io queue which improves performance.
271 iotest output becomes racy for three allocation in one cluster.
Second and third writes may finish in different order. Second and
third requests don't depend on each other any more. Still they both
depend on first request anyway. Filter out second and third write
offsets to cover both possible outputs.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210824101517.59802-4-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
[hreitz: s/ an / and /]
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
---
block/qcow2-cluster.c | 11 +++++++++++
tests/qemu-iotests/271 | 5 ++++-
tests/qemu-iotests/271.out | 4 ++--
3 files changed, 17 insertions(+), 3 deletions(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 9917e5c28c..c1c43a891b 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1403,6 +1403,17 @@ static int handle_dependencies(BlockDriverState *bs,
uint64_t guest_offset,
continue;
}
+ if (old_alloc->keep_old_clusters &&
+ (end <= l2meta_cow_start(old_alloc) ||
+ start >= l2meta_cow_end(old_alloc)))
+ {
+ /*
+ * Clusters intersect but COW areas don't. And cluster itself is
+ * already allocated. So, there is no actual conflict.
+ */
+ continue;
+ }
+
/* Conflict */
if (start < old_start) {
diff --git a/tests/qemu-iotests/271 b/tests/qemu-iotests/271
index 599b849cc6..2775b4d130 100755
--- a/tests/qemu-iotests/271
+++ b/tests/qemu-iotests/271
@@ -893,7 +893,10 @@ EOF
}
_make_test_img -o extended_l2=on 1M
-_concurrent_io | $QEMU_IO | _filter_qemu_io
+# Second and third writes in _concurrent_io() are independent and may finish in
+# different order. So, filter offset out to match both possible variants.
+_concurrent_io | $QEMU_IO | _filter_qemu_io | \
+ $SED -e 's/\(20480\|40960\)/OFFSET/'
_concurrent_verify | $QEMU_IO | _filter_qemu_io
# success, all done
diff --git a/tests/qemu-iotests/271.out b/tests/qemu-iotests/271.out
index 81043ba4d7..5be780de76 100644
--- a/tests/qemu-iotests/271.out
+++ b/tests/qemu-iotests/271.out
@@ -719,8 +719,8 @@ blkdebug: Suspended request 'A'
blkdebug: Resuming request 'A'
wrote 2048/2048 bytes at offset 30720
2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-wrote 2048/2048 bytes at offset 20480
+wrote 2048/2048 bytes at offset OFFSET
2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-wrote 2048/2048 bytes at offset 40960
+wrote 2048/2048 bytes at offset OFFSET
2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
*** done
--
2.31.1
- [PULL 17/32] block: bdrv_inactivate_recurse(): check for permissions and fix crash, (continued)
- [PULL 17/32] block: bdrv_inactivate_recurse(): check for permissions and fix crash, Hanna Reitz, 2021/09/15
- [PULL 09/32] iotests: Fix use-{list,dict}-literal warnings, Hanna Reitz, 2021/09/15
- [PULL 11/32] migrate-bitmaps-postcopy-test: Fix pylint warnings, Hanna Reitz, 2021/09/15
- [PULL 12/32] migrate-bitmaps-test: Fix pylint warnings, Hanna Reitz, 2021/09/15
- [PULL 16/32] tests: add migrate-during-backup, Hanna Reitz, 2021/09/15
- [PULL 14/32] iotests/297: Cover tests/, Hanna Reitz, 2021/09/15
- [PULL 08/32] iotests: Fix unspecified-encoding pylint warnings, Hanna Reitz, 2021/09/15
- [PULL 19/32] qcow2: refactor handle_dependencies() loop body, Hanna Reitz, 2021/09/15
- [PULL 18/32] simplebench: add img_bench_templater.py, Hanna Reitz, 2021/09/15
- [PULL 21/32] qemu-img: Allow target be aligned to sector size, Hanna Reitz, 2021/09/15
- [PULL 20/32] qcow2: handle_dependencies(): relax conflict detection,
Hanna Reitz <=
- [PULL 22/32] qcow2-refcount: improve style of check_refcounts_l2(), Hanna Reitz, 2021/09/15
- [PULL 23/32] qcow2: compressed read: simplify cluster descriptor passing, Hanna Reitz, 2021/09/15
- [PULL 24/32] qcow2: introduce qcow2_parse_compressed_l2_entry() helper, Hanna Reitz, 2021/09/15
- [PULL 25/32] qcow2-refcount: introduce fix_l2_entry_by_zero(), Hanna Reitz, 2021/09/15
- [PULL 26/32] qcow2-refcount: fix_l2_entry_by_zero(): also zero L2 entry bitmap, Hanna Reitz, 2021/09/15
- [PULL 27/32] qcow2-refcount: check_refcounts_l2(): check l2_bitmap, Hanna Reitz, 2021/09/15
- [PULL 28/32] qcow2-refcount: check_refcounts_l2(): check reserved bits, Hanna Reitz, 2021/09/15
- [PULL 29/32] qcow2-refcount: improve style of check_refcounts_l1(), Hanna Reitz, 2021/09/15
- [PULL 30/32] qcow2-refcount: check_refcounts_l1(): check reserved bits, Hanna Reitz, 2021/09/15
- [PULL 31/32] qcow2-refcount: check_refblocks(): add separate message for reserved, Hanna Reitz, 2021/09/15