Messages in this thread | | | Date | Wed, 03 Aug 2011 17:48:54 +0800 | From | Gui Jianfeng <> | Subject | Re: fio posixaio performance problem |
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On 2011-8-3 16:22, Shaohua Li wrote: > 2011/8/3 Gui Jianfeng <guijianfeng@cn.fujitsu.com>: >> 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? > 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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