On Tue, Jun 19, 2012 at 5:24 AM, Asias He [off-list ref] wrote:

On 06/18/2012 06:58 PM, Stefan Hajnoczi wrote:

quoted

As long as the latency is decreasing that's good.  But It's worth
keeping in mind that these percentages are probably wildly different
on real storage devices and/or qemu-kvm.  What we don't know here is
whether this bottleneck matters in real environments - results with
real storage and with qemu-kvm would be interesting.

Yes. Here is the performance data on a Fusion-IO SSD device.

Fio test is performed in a 8 vcpu guest with Fusion-IO based guest using kvm
tool.

   Short version:
    With bio-based IO path, sequential read/write, random read/write
    IOPS boost         : 11%, 11%, 13%, 10%
    Latency improvement: 10%, 10%, 12%, 10%

Nice, I'm glad the improvement shows on real hardware.

Stefan