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[Qemu-devel] [PATCH v4 3/3] dataplane: submit I/O as a batch
From: |
Ming Lei |
Subject: |
[Qemu-devel] [PATCH v4 3/3] dataplane: submit I/O as a batch |
Date: |
Wed, 2 Jul 2014 20:18:48 +0800 |
Before commit 580b6b2aa2(dataplane: use the QEMU block
layer for I/O), dataplane for virtio-blk submits block
I/O as a batch.
This commit 580b6b2aa2 replaces the custom linux AIO
implementation(including submit I/O as a batch) with QEMU
block layer, but this commit causes ~40% throughput regression
on virtio-blk performance, and removing submitting I/O
as a batch is one of the causes.
This patch applies the newly introduced bdrv_io_plug() and
bdrv_io_unplug() interfaces to support submitting I/O
at batch for Qemu block layer, and in my test, the change
can improve throughput by ~30% with 'aio=native'.
Following my fio test script:
[global]
direct=1
size=4G
bsrange=4k-4k
timeout=40
numjobs=4
ioengine=libaio
iodepth=64
filename=/dev/vdc
group_reporting=1
[f]
rw=randread
Result on one of my small machine(host: x86_64, 2cores, 4thread, guest: 4cores):
- qemu master: 59K IOPS
- qemu master with these patches: 81K IOPS
- 2.0.0 release(dataplane using custom linux aio): 104K IOPS
Reviewed-by: Paolo Bonzini <address@hidden>
Signed-off-by: Ming Lei <address@hidden>
---
hw/block/dataplane/virtio-blk.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index c10b7b7..82bb276 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -201,6 +201,9 @@ static void do_flush_cmd(VirtIOBlockDataPlane *s,
VirtQueueElement *elem,
req->elem = elem;
req->inhdr = inhdr;
+ /* flush IOs queued first */
+ bdrv_flush_io_queue(s->blk->conf.bs);
+
bdrv_aio_flush(s->blk->conf.bs, complete_flush, req);
}
@@ -289,6 +292,7 @@ static void handle_notify(EventNotifier *e)
int ret;
event_notifier_test_and_clear(&s->host_notifier);
+ bdrv_io_plug(s->blk->conf.bs);
for (;;) {
/* Disable guest->host notifies to avoid unnecessary vmexits */
vring_disable_notification(s->vdev, &s->vring);
@@ -322,6 +326,7 @@ static void handle_notify(EventNotifier *e)
break;
}
}
+ bdrv_io_unplug(s->blk->conf.bs);
}
/* Context: QEMU global mutex held */
--
1.7.9.5
- Re: [Qemu-devel] [PATCH v4 2/3] linux-aio: implement io plug, unplug and flush io queue, (continued)
- Re: [Qemu-devel] [PATCH v4 2/3] linux-aio: implement io plug, unplug and flush io queue, Paolo Bonzini, 2014/07/03
- Re: [Qemu-devel] [PATCH v4 2/3] linux-aio: implement io plug, unplug and flush io queue, Ming Lei, 2014/07/03
- Re: [Qemu-devel] [PATCH v4 2/3] linux-aio: implement io plug, unplug and flush io queue, Paolo Bonzini, 2014/07/03
- Re: [Qemu-devel] [PATCH v4 2/3] linux-aio: implement io plug, unplug and flush io queue, Ming Lei, 2014/07/03
- Re: [Qemu-devel] [PATCH v4 2/3] linux-aio: implement io plug, unplug and flush io queue, Kevin Wolf, 2014/07/03
- Re: [Qemu-devel] [PATCH v4 2/3] linux-aio: implement io plug, unplug and flush io queue, Ming Lei, 2014/07/03
- Re: [Qemu-devel] [PATCH v4 2/3] linux-aio: implement io plug, unplug and flush io queue, Kevin Wolf, 2014/07/03
Re: [Qemu-devel] [PATCH v4 2/3] linux-aio: implement io plug, unplug and flush io queue, Stefan Hajnoczi, 2014/07/03
[Qemu-devel] [PATCH v4 3/3] dataplane: submit I/O as a batch,
Ming Lei <=
Re: [Qemu-devel] [PATCH v4 3/3] dataplane: submit I/O as a batch, Stefan Hajnoczi, 2014/07/03
Re: [Qemu-devel] [PATCH v4 3/3] dataplane: submit I/O as a batch, Stefan Hajnoczi, 2014/07/03
Re: [Qemu-devel] [PATCH v4 0/3] linux-aio: introduce submit I/O as a batch, Kevin Wolf, 2014/07/03
Re: [Qemu-devel] [PATCH v4 0/3] linux-aio: introduce submit I/O as a batch, Stefan Hajnoczi, 2014/07/03