[Qemu-devel] [PULL 09/12] block/io: optimize bdrv_co_pwritev for small requests

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From: Stefan Hajnoczi <stefanha@redhat.com>
To: qemu-devel@nongnu.org
Cc: Peter Maydell <peter.maydell@linaro.org>,
	Peter Lieven <pl@kamp.de>, Stefan Hajnoczi <stefanha@redhat.com>
Subject: [Qemu-devel] [PULL 09/12] block/io: optimize bdrv_co_pwritev for small requests
Date: Tue,  7 Jun 2016 15:26:22 +0100	[thread overview]
Message-ID: <1465309585-31551-10-git-send-email-stefanha@redhat.com> (raw)
In-Reply-To: <1465309585-31551-1-git-send-email-stefanha@redhat.com>

From: Peter Lieven <pl@kamp.de>

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 <pl@kamp.de>
Message-id: 1464607873-28206-1-git-send-email-pl@kamp.de
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 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

next prev parent reply	other threads:[~2016-06-07 14:26 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-07 14:26 [Qemu-devel] [PULL 00/12] Block patches Stefan Hajnoczi
2016-06-07 14:26 ` [Qemu-devel] [PULL 01/12] tests: avoid coroutine pool test crash Stefan Hajnoczi
2016-06-07 14:26 ` [Qemu-devel] [PULL 02/12] blockdev-backup: Use bdrv_lookup_bs on target Stefan Hajnoczi
2016-06-07 14:26 ` [Qemu-devel] [PULL 03/12] blockdev-backup: Don't move target AioContext if it's attached Stefan Hajnoczi
2016-06-07 14:26 ` [Qemu-devel] [PULL 04/12] virtio-blk: Remove op blocker for dataplane Stefan Hajnoczi
2016-06-07 14:26 ` [Qemu-devel] [PULL 05/12] virtio-scsi: " Stefan Hajnoczi
2016-06-07 14:26 ` [Qemu-devel] [PULL 06/12] virtio: drop duplicate virtio_queue_get_id() function Stefan Hajnoczi
2016-06-07 14:26 ` [Qemu-devel] [PULL 07/12] block/io: Remove unused bdrv_aio_write_zeroes() Stefan Hajnoczi
2016-06-07 14:26 ` [Qemu-devel] [PULL 08/12] iostatus: fix comments for block_job_iostatus_reset Stefan Hajnoczi
2016-06-07 14:26 ` Stefan Hajnoczi [this message]
2016-06-07 14:26 ` [Qemu-devel] [PULL 10/12] block: Move BlockRequest type to io.c Stefan Hajnoczi
2016-06-07 14:26 ` [Qemu-devel] [PULL 11/12] block: Drop bdrv_ioctl_bh_cb Stefan Hajnoczi
2016-06-07 14:26 ` [Qemu-devel] [PULL 12/12] throttle: refuse iops-size without iops-total/read/write Stefan Hajnoczi
2016-06-07 15:34 ` [Qemu-devel] [PULL 00/12] Block patches Peter Maydell

find likely ancestor, descendant, or conflicting patches for this message:
( dfblob:7ac9897 dfblob:e12f303 dfblob:4dc680b dfblob:d2d2a2d
dfblob:eab14ae dfblob:16f951f )
 OR (
bs:"[Qemu-devel] [PULL 09/12] block/io: optimize bdrv_co_pwritev for small requests" )
	(help)

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