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.
-- 发自我的网易邮箱手机智能版 在 2015-06-19 16:37:23，"Paolo Bonzini" <pbonz...@redhat.com> 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 >
