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

[Paul Durrant <Paul.Durrant@citrix.com>]

> -----Original Message-----
> From: Stefan Hajnoczi [mailto:stefanha@gmail.com]
> Sent: 08 November 2017 17:42
> To: Paul Durrant <Paul.Durrant@citrix.com>
> Cc: qemu-devel@nongnu.org; xen-devel@lists.xenproject.org; Anthony
> Perard <anthony.perard@citrix.com>; Kevin Wolf <kwolf@redhat.com>;
> Stefano Stabellini <sstabellini@kernel.org>; Max Reitz <mreitz@redhat.com>
> 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.

  Cheers,

    Paul