Re: [Xen-devel] [RFC v1 0/5] VBD: enlarge max segment per request in blkfront

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 13 Sep 2012, Jan Beulich wrote:
> >>> On 13.09.12 at 04:28, "Duan, Ronghui" <ronghui.duan@xxxxxxxxx> wrote:
> >> And with your patch got:
> >>   read : io=4096.0MB, bw=92606KB/s, iops=23151 , runt= 45292msec
> >> 
> >> without:
> >>   read : io=4096.0MB, bw=145187KB/s, iops=36296 , runt= 28889msec
> >> 
> > What type of backend file you are using? In order to remove the influence 
> > of 
> > cache in Dom0, I use a physical partition as backend.
> 
> But you certainly shouldn't be proposing features getting used
> unconditionally or by default that benefit one class of backing
> devices and severely penalize others.

Right.
I am wondering.. Considering that the in-kernel blkback is mainly used
with physical partitions, is it possible that your patches cause a
regression with unmodified backends that don't support the new protocol,
like QEMU for example?

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