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[Qemu-devel] [PULL 09/12] block/io: optimize bdrv_co_pwritev for small r
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PULL 09/12] block/io: optimize bdrv_co_pwritev for small requests |
Date: |
Tue, 7 Jun 2016 15:26:22 +0100 |
From: Peter Lieven <address@hidden>
in a read-modify-write cycle a small request might cause
head and tail to fall into the same aligned block. Currently
QEMU reads the same block twice in this case which is
not necessary.
Signed-off-by: Peter Lieven <address@hidden>
Message-id: address@hidden
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
block/io.c | 8 ++++++++
tests/qemu-iotests/077 | 12 +-----------
tests/qemu-iotests/077.out | 26 --------------------------
3 files changed, 9 insertions(+), 37 deletions(-)
diff --git a/block/io.c b/block/io.c
index 7ac9897..e12f303 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1427,6 +1427,14 @@ int coroutine_fn bdrv_co_pwritev(BlockDriverState *bs,
bytes += offset & (align - 1);
offset = offset & ~(align - 1);
+
+ /* We have read the tail already if the request is smaller
+ * than one aligned block.
+ */
+ if (bytes < align) {
+ qemu_iovec_add(&local_qiov, head_buf + bytes, align - bytes);
+ bytes = align;
+ }
}
if ((offset + bytes) & (align - 1)) {
diff --git a/tests/qemu-iotests/077 b/tests/qemu-iotests/077
index 4dc680b..d2d2a2d 100755
--- a/tests/qemu-iotests/077
+++ b/tests/qemu-iotests/077
@@ -60,7 +60,7 @@ EOF
# Sequential RMW requests on the same physical sector
off=0x1000
-for ev in "head" "after_head" "tail" "after_tail"; do
+for ev in "head" "after_head"; do
cat <<EOF
break pwritev_rmw_$ev A
aio_write -P 10 $((off + 0x200)) 0x200
@@ -211,16 +211,6 @@ function verify_io()
echo read -P 11 0x2400 0x200
echo read -P 0 0x2600 0xa00
- echo read -P 0 0x3000 0x200
- echo read -P 10 0x3200 0x200
- echo read -P 11 0x3400 0x200
- echo read -P 0 0x3600 0xa00
-
- echo read -P 0 0x4000 0x200
- echo read -P 10 0x4200 0x200
- echo read -P 11 0x4400 0x200
- echo read -P 0 0x4600 0xa00
-
# Chained dependencies
echo read -P 10 0x5000 0x200
echo read -P 11 0x5200 0x200
diff --git a/tests/qemu-iotests/077.out b/tests/qemu-iotests/077.out
index eab14ae..16f951f 100644
--- a/tests/qemu-iotests/077.out
+++ b/tests/qemu-iotests/077.out
@@ -19,16 +19,6 @@ wrote XXX/XXX bytes at offset XXX
XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
wrote XXX/XXX bytes at offset XXX
XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-blkdebug: Resuming request 'A'
-wrote XXX/XXX bytes at offset XXX
-XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-wrote XXX/XXX bytes at offset XXX
-XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-blkdebug: Resuming request 'A'
-wrote XXX/XXX bytes at offset XXX
-XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-wrote XXX/XXX bytes at offset XXX
-XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
wrote XXX/XXX bytes at offset XXX
XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
wrote XXX/XXX bytes at offset XXX
@@ -114,22 +104,6 @@ read 512/512 bytes at offset 9216
512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
read 2560/2560 bytes at offset 9728
2.500 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-read 512/512 bytes at offset 12288
-512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-read 512/512 bytes at offset 12800
-512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-read 512/512 bytes at offset 13312
-512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-read 2560/2560 bytes at offset 13824
-2.500 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-read 512/512 bytes at offset 16384
-512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-read 512/512 bytes at offset 16896
-512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-read 512/512 bytes at offset 17408
-512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-read 2560/2560 bytes at offset 17920
-2.500 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
read 512/512 bytes at offset 20480
512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
read 512/512 bytes at offset 20992
--
2.5.5
- [Qemu-devel] [PULL 00/12] Block patches, Stefan Hajnoczi, 2016/06/07
- [Qemu-devel] [PULL 03/12] blockdev-backup: Don't move target AioContext if it's attached, Stefan Hajnoczi, 2016/06/07
- [Qemu-devel] [PULL 01/12] tests: avoid coroutine pool test crash, Stefan Hajnoczi, 2016/06/07
- [Qemu-devel] [PULL 02/12] blockdev-backup: Use bdrv_lookup_bs on target, Stefan Hajnoczi, 2016/06/07
- [Qemu-devel] [PULL 04/12] virtio-blk: Remove op blocker for dataplane, Stefan Hajnoczi, 2016/06/07
- [Qemu-devel] [PULL 05/12] virtio-scsi: Remove op blocker for dataplane, Stefan Hajnoczi, 2016/06/07
- [Qemu-devel] [PULL 07/12] block/io: Remove unused bdrv_aio_write_zeroes(), Stefan Hajnoczi, 2016/06/07
- [Qemu-devel] [PULL 08/12] iostatus: fix comments for block_job_iostatus_reset, Stefan Hajnoczi, 2016/06/07
- [Qemu-devel] [PULL 06/12] virtio: drop duplicate virtio_queue_get_id() function, Stefan Hajnoczi, 2016/06/07
- [Qemu-devel] [PULL 11/12] block: Drop bdrv_ioctl_bh_cb, Stefan Hajnoczi, 2016/06/07
- [Qemu-devel] [PULL 09/12] block/io: optimize bdrv_co_pwritev for small requests,
Stefan Hajnoczi <=
- [Qemu-devel] [PULL 10/12] block: Move BlockRequest type to io.c, Stefan Hajnoczi, 2016/06/07
- [Qemu-devel] [PULL 12/12] throttle: refuse iops-size without iops-total/read/write, Stefan Hajnoczi, 2016/06/07
- Re: [Qemu-devel] [PULL 00/12] Block patches, Peter Maydell, 2016/06/07