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

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Thu, Sep 13, 2012 at 12:05:35PM +0100, Stefano Stabellini wrote:
> On Thu, 13 Sep 2012, Jan Beulich wrote:
> > >>> On 13.09.12 at 04:28, "Duan, Ronghui" <ronghui.duan@intel.com> 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?

Well for right now I am just using the most simple configuration to
eliminate any extra variables (stacking of components). So my
"testing" has been just on phy:/dev/sda,xvda,w with the sda being
a Corsair SSD.