Mailing List Archive

On Fri, 2012-09-28 at 18:51 +0100, Ian Jackson wrote:
> Stefano Stabellini writes ("[Xen-devel] [PATCH v2] libxl/qemu-xen: use cache=writeback for IDE and SCSI"):
> > Change caching mode from writethrough to writeback for upstream QEMU.
> >
> > After a lengthy discussion, we came up with the conclusion that
> > WRITEBACK is OK for IDE.
> > See: http://marc.info/?l=xen-devel&m=133311527009773
> >
> > Given that the same reasons apply to SCSI as well, change to writeback
> > for SCSI too.
>
> Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>

Acked + applied.

Are the performance benefits of this patch worthy of a 4.2 backport,
even though qemu-xen is not the default?

Ian.


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On Fri, 5 Oct 2012, Ian Campbell wrote:
> On Fri, 2012-09-28 at 18:51 +0100, Ian Jackson wrote:
> > Stefano Stabellini writes ("[Xen-devel] [PATCH v2] libxl/qemu-xen: use cache=writeback for IDE and SCSI"):
> > > Change caching mode from writethrough to writeback for upstream QEMU.
> > >
> > > After a lengthy discussion, we came up with the conclusion that
> > > WRITEBACK is OK for IDE.
> > > See: http://marc.info/?l=xen-devel&m=133311527009773
> > >
> > > Given that the same reasons apply to SCSI as well, change to writeback
> > > for SCSI too.
> >
> > Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
>
> Acked + applied.
>
> Are the performance benefits of this patch worthy of a 4.2 backport,
> even though qemu-xen is not the default?

I think they are: QEMU should be more than twice as fast with that
patch.

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