Re: fio posixaio performance problem

[Shaohua Li]

2011/8/3 Gui Jianfeng <guijianfeng@xxxxxxxxxxxxxx>:
> On 2011-8-3 15:38, Shaohua Li wrote:
>> 2011/8/3 Gui Jianfeng <guijianfeng@xxxxxxxxxxxxxx>:
>>> 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.
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