Re: [Xen-devel] [PATCH v2] blkif.h: document blkif multi-queue/ring extension

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Nov 03, 2015 at 12:58:42PM -0500, Konrad Rzeszutek Wilk wrote:
> On Fri, Oct 30, 2015 at 07:24:27AM +0800, Bob Liu wrote:
> > Document the multi-queue/ring feature in terms of XenStore keys to be 
> > written
> > by the backend and by the frontend.
> > 
> > Signed-off-by: Bob Liu <bob.liu@xxxxxxxxxx>
> 
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

xen]$ scripts/get_maintainer.pl -f `find . -name blkif.h`
Ian Campbell <ian.campbell@xxxxxxxxxx>
Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Jan Beulich <jbeulich@xxxxxxxx>
Keir Fraser <keir@xxxxxxx>
Tim Deegan <tim@xxxxxxx>
xen-devel@xxxxxxxxxxxxx

So adding those folks on the 'To:' list.


> > --
> > v2: Comments from Konrad
> > ---
> >  xen/include/public/io/blkif.h |   48 
> > +++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 48 insertions(+)
> > 
> > diff --git a/xen/include/public/io/blkif.h b/xen/include/public/io/blkif.h
> > index 8f0f9a6..fbc9ddb 100644
> > --- a/xen/include/public/io/blkif.h
> > +++ b/xen/include/public/io/blkif.h
> > @@ -394,6 +394,54 @@
> >   */
> >  
> >  /*
> > + * Multiple hardware queues/rings:
> > + * If supported, the backend will write the key "multi-queue-max-queues" to
> > + * the directory for that vbd, and set its value to the maximum supported
> > + * number of queues.
> > + * Frontends that are aware of this feature and wish to use it can write 
> > the
> > + * key "multi-queue-num-queues" with the number they wish to use, which 
> > must be
> > + * greater than zero, and no more than the value reported by the backend in
> > + * "multi-queue-max-queues".
> > + *
> > + * For frontends requesting just one queue, the usual event-channel and
> > + * ring-ref keys are written as before, simplifying the backend processing
> > + * to avoid distinguishing between a frontend that doesn't understand the
> > + * multi-queue feature, and one that does, but requested only one queue.
> > + *
> > + * Frontends requesting two or more queues must not write the toplevel
> > + * event-channel and ring-ref keys, instead writing those keys under 
> > sub-keys
> > + * having the name "queue-N" where N is the integer ID of the queue/ring 
> > for
> > + * which those keys belong. Queues are indexed from zero.
> > + * For example, a frontend with two queues must write the following set of
> > + * queue-related keys:
> > + *
> > + * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2"
> > + * /local/domain/1/device/vbd/0/queue-0 = ""
> > + * /local/domain/1/device/vbd/0/queue-0/ring-ref = "<ring-ref#0>"
> > + * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>"
> > + * /local/domain/1/device/vbd/0/queue-1 = ""
> > + * /local/domain/1/device/vbd/0/queue-1/ring-ref = "<ring-ref#1>"
> > + * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>"
> > + *
> > + * It is also possible to use multiple queues/rings together with
> > + * feature multi-page ring buffer.
> > + * For example, a frontend requests two queues/rings and the size of each 
> > ring
> > + * buffer is two pages must write the following set of related keys:
> > + *
> > + * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2"
> > + * /local/domain/1/device/vbd/0/ring-page-order = "1"
> > + * /local/domain/1/device/vbd/0/queue-0 = ""
> > + * /local/domain/1/device/vbd/0/queue-0/ring-ref0 = "<ring-ref#0>"
> > + * /local/domain/1/device/vbd/0/queue-0/ring-ref1 = "<ring-ref#1>"
> > + * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>"
> > + * /local/domain/1/device/vbd/0/queue-1 = ""
> > + * /local/domain/1/device/vbd/0/queue-1/ring-ref0 = "<ring-ref#2>"
> > + * /local/domain/1/device/vbd/0/queue-1/ring-ref1 = "<ring-ref#3>"
> > + * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>"
> > + *
> > + */
> > +
> > +/*
> >   * STATE DIAGRAMS
> >   *
> >   
> > *****************************************************************************
> > -- 
> > 1.7.10.4
> > 

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