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From: Ming Lei <ming.lei@canonical.com>
Date: Fri,  4 Jul 2014 11:06:39 +0800
Message-Id: <1404443202-14174-1-git-send-email-ming.lei@canonical.com>
Subject: [Qemu-devel] [PATCH v5 0/3] linux-aio: introduce submit I/O as a
	batch
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To: Peter Maydell <peter.maydell@linaro.org>, qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Fam Zheng <famz@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>

Hi,

The commit 580b6b2aa2(dataplane: use the QEMU block layer for I/O)
introduces ~40% throughput regression on virtio-blk dataplane, and
one of causes is that submitting I/O as a batch is removed.

This patchset trys to introduce this mechanism on block, at least,
linux-aio can benefit from that.

With these patches, it is observed that thoughout on virtio-blk
dataplane can be improved a lot, see data in commit log of patch
3/3.

It should be possible to apply the batch mechanism to other devices
(such as virtio-scsi) too.

TODO:
	- support queuing I/O to multi files for scsi devies, which
	need some changes to linux-aio

V5:
	- rebase on v2.1.0-rc0 of qemu.git/master
	- block/linux-aio.c code style fix
    - don't flush io queue before flush, pointed by Paolo

V4:
	- support other non-raw formats with under-optimized performance
	- use reference counter for plug & unplug
	- flush io queue before sending flush command

V3:
	- only support submitting I/O as a batch for raw format, pointed by
    Kevin

V2:
	- define return value of bdrv_io_unplug as void, suggested by Paolo
	- avoid busy-wait for handling io_submit
V1:
	- move queuing io stuff into linux-aio.c as suggested by Paolo


Thanks,
--
Ming Lei