Re: [Qemu-devel] Greate difference of disk I/O performance for guest on Qemu-2.30 of CentOS.

[cauchy-love]

thanks for your help. I don't think it is the filesystem that causes this 
problem since when I updated the kernel of CentOS6.5 to the CentOS 7.0's 
version and the disk io performance was nearly the same as CentOS 7.0.



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在 2015-06-19 16:37:23，"Paolo Bonzini" <address@hidden> 写道：
>
>
>On 19/06/2015 03:03, cauchy-love wrote:
>> I have tried your qemu cammand line but got no luck (the embedded os
>> have no virtio support but this is not the problem i think). The
>> problem probably lies in the host kernel version as it is the only
>> difference for my tests. I traced the guest kernel and found the ATA
>> drivers always used non-DMA mode (CentOS 7 and CentOS 6.5 are the
>> same at this point).
>
>You can use perf to see what's the difference.
>
>Perhaps CentOS 6.5 used ext4 and 7 uses XFS?  Though in general XFS is
>the faster one...
>
>Paolo
>