linux-kernel - Re: fio posixaio performance problem

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Date:	Wed, 03 Aug 2011 17:48:54 +0800
From:	Gui Jianfeng <guijianfeng@...fujitsu.com>
To:	Shaohua Li <shli@...nel.org>
CC:	Vivek Goyal <vgoyal@...hat.com>, Jens Axboe <jaxboe@...ionio.com>,
	linux-kernel@...r.kernel.org
Subject: Re: fio posixaio performance problem

On 2011-8-3 16:22, Shaohua Li wrote:
> 2011/8/3 Gui Jianfeng <guijianfeng@...fujitsu.com>:
>> On 2011-8-3 15:38, Shaohua Li wrote:
>>> 2011/8/3 Gui Jianfeng <guijianfeng@...fujitsu.com>:
>>>> Hi,
>>>>
>>>> I ran a fio test to simulate qemu-kvm io behaviour.
>>>> When job number is greater than 2, IO performance is
>>>> really bad.
>>>>
>>>> 1 thread: aggrb=15,129KB/s
>>>> 4 thread: aggrb=1,049KB/s
>>>>
>>>> Kernel: lastest upstream
>>>>
>>>> Any idea?
>>>>
>>>> ---
>>>> [global]
>>>> runtime=30
>>>> time_based=1
>>>> size=1G
>>>> group_reporting=1
>>>> ioengine=posixaio
>>>> exec_prerun='echo 3 > /proc/sys/vm/drop_caches'
>>>> thread=1
>>>>
>>>> [kvmio-1]
>>>> description=kvmio-1
>>>> numjobs=4
>>>> rw=write
>>>> bs=4k
>>>> direct=1
>>>> filename=/mnt/sda4/1G.img
>>> Hmm, the test runs always about 15M/s at my side regardless how many threads.
>>
>> CFQ？
> yes.
> 
>> what's the slice_idle value?
> default value. I didn't change it.

Hmm, I use a sata disk, and can reproduce this bug every time...

Thanks,
Gui

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