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[Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa
From: |
Ming Lei |
Subject: |
[Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa2 |
Date: |
Thu, 26 Jun 2014 23:14:16 +0800 |
Hi Stefan,
I found VM block I/O thoughput is decreased by more than 40%
on my laptop, and looks much worsen in my server environment,
and it is caused by your commit 580b6b2aa2:
dataplane: use the QEMU block layer for I/O
I run fio with below config to test random read:
[global]
direct=1
size=4G
bsrange=4k-4k
timeout=20
numjobs=4
ioengine=libaio
iodepth=64
filename=/dev/vdc
group_reporting=1
[f]
rw=randread
Together with throughput drop, the latency is improved a little.
With this commit, I/O block submitted to fs becomes much smaller
than before, and more io_submit() need to be called to kernel, that
means iodepth may become much less.
I am not surprised with the result since I did compare VM I/O
performance between qemu and lkvm before, which has no big qemu
lock problem and handle I/O in a dedicated thread, but lkvm's block
IO is still much worse than qemu from view of throughput, because
lkvm doesn't submit block I/O at batch like the way of previous
dataplane, IMO.
But now you change the way of submitting I/O, could you share
the motivation about the change? Is the throughput drop you expect?
Thanks,
--
Ming Lei
- [Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa2,
Ming Lei <=
- Re: [Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa2, Paolo Bonzini, 2014/06/26
- Re: [Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa2, Ming Lei, 2014/06/26
- Re: [Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa2, Paolo Bonzini, 2014/06/26
- Re: [Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa2, Ming Lei, 2014/06/26
- Re: [Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa2, Paolo Bonzini, 2014/06/26
- Re: [Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa2, Ming Lei, 2014/06/26
- Re: [Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa2, Paolo Bonzini, 2014/06/27
- Re: [Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa2, Kevin Wolf, 2014/06/27
- Re: [Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa2, Paolo Bonzini, 2014/06/27
- Re: [Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa2, Ming Lei, 2014/06/27