Re: [Xen-devel] [Qemu-devel] [PATCH v3] xen-disk: use an IOThread per instance

[Stefan Hajnoczi <stefanha@xxxxxxxxx>]

On Thu, Nov 09, 2017 at 09:30:45AM +0000, Paul Durrant wrote:
> > -----Original Message-----
> > From: Stefan Hajnoczi [mailto:stefanha@xxxxxxxxx]
> > Sent: 08 November 2017 17:42
> > To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> > Cc: qemu-devel@xxxxxxxxxx; xen-devel@xxxxxxxxxxxxxxxxxxxx; Anthony
> > Perard <anthony.perard@xxxxxxxxxx>; Kevin Wolf <kwolf@xxxxxxxxxx>;
> > Stefano Stabellini <sstabellini@xxxxxxxxxx>; Max Reitz <mreitz@xxxxxxxxxx>
> > Subject: Re: [Qemu-devel] [PATCH v3] xen-disk: use an IOThread per
> > instance
> > 
> > On Tue, Nov 07, 2017 at 05:46:53AM -0500, Paul Durrant wrote:
> > > This patch allocates an IOThread object for each xen_disk instance and
> > > sets the AIO context appropriately on connect. This allows processing
> > > of I/O to proceed in parallel.
> > >
> > > The patch also adds tracepoints into xen_disk to make it possible to
> > > follow the state transtions of an instance in the log.
> > 
> > virtio-blk and virtio-scsi allow the user to specify an IOThread object.
> > This allows users to configure the device<->IOThread mapping any way
> > they like (e.g. 1:1, M:N).  Are you sure you want to hard-code the
> > IOThread mapping?
> 
> Stefan,
> 
>   Realistically it's the only option at the moment. Xen PV backends are not 
> configured bu QAPI... so no ability to control them from the command line or 
> QMP. This is something I seriously intend to address in the near future but, 
> for now, I simply want to unlock the performance boost that IOThread can 
> provide.

Okay.

Stefan

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