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Date: Wed, 03 Aug 2011 16:11:51 +0800
From: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
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To: Shaohua Li <shli@kernel.org>
CC: Vivek Goyal <vgoyal@redhat.com>, Jens Axboe <jaxboe@fusionio.com>,
        linux-kernel@vger.kernel.org
Subject: Re: fio posixaio performance problem
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On 2011-8-3 15:38, Shaohua Li wrote:
> 2011/8/3 Gui Jianfeng <guijianfeng@cn.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？
what's the slice_idle value?

Thanks,
Gui

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