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2ed982b6a9
xemu/hw/block
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Ming Lei dd67c1d7e7 dataplane: submit I/O as a batch 
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: 65K IOPS
	- qemu master with these patches: 92K IOPS
	- 2.0.0 release(dataplane using custom linux aio): 104K IOPS

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-07-07 11:05:17 +02:00
..
dataplane dataplane: submit I/O as a batch 2014-07-07 11:05:17 +02:00
block.c
cdrom.c bswap.h: Remove cpu_to_be32wu() 2013-11-05 19:57:47 -08:00
ecc.c savevm: Remove all the unneeded version_minimum_id_old (arm) 2014-05-13 16:09:35 +01:00
fdc.c savevm: Remove all the unneeded version_minimum_id_old (x86) 2014-06-16 04:55:26 +02:00
hd-geometry.c
m25p80.c block: m25p80: Support read only bdrvs. 2014-06-21 16:40:14 +08:00
Makefile.objs
nand.c savevm: Remove all the unneeded version_minimum_id_old (arm) 2014-05-13 16:09:35 +01:00
nvme.c nvme: Permit zero-length block devices 2014-03-31 22:35:03 +02:00
nvme.h
onenand.c block: Drop superfluous conditionals around g_free() 2014-06-16 17:23:19 +08:00
pflash_cfi01.c hw/block/pflash_cfi01: Report correct size info for parallel configs 2014-06-19 18:06:25 +01:00
pflash_cfi02.c
tc58128.c shix: Don't require firmware presence for qtest 2013-11-05 17:47:29 +01:00
virtio-blk.c virtio-blk: replace x-iothread with iothread link property 2014-07-01 09:15:02 +02:00
xen_blkif.h xen_disk: add discard support 2014-05-07 16:18:04 +00:00
xen_disk.c xen_disk: add discard support 2014-05-07 16:18:04 +00:00