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
