Re: [Xen-devel] [PATCH V4 net-next 5/5] xen-net{back, front}: Document multi-queue feature in netif.h

[Andrew Bennieston <andrew.bennieston@xxxxxxxxxx>]

On 21/02/14 12:22, Paul Durrant wrote:
> > -----Original Message-----
> > From: Andrew J. Bennieston [mailto:andrew.bennieston@xxxxxxxxxx]
> > Sent: 17 February 2014 17:58
> > To: xen-devel@xxxxxxxxxxxxxxxxxxxx
> > Cc: Ian Campbell; Wei Liu; Paul Durrant; netdev@xxxxxxxxxxxxxxx; David
> > Vrabel; Andrew Bennieston
> > Subject: [PATCH V4 net-next 5/5] xen-net{back,front}: Document multi-
> > queue feature in netif.h
> >
> > From: "Andrew J. Bennieston" <andrew.bennieston@xxxxxxxxxx>
> >
> > Document the multi-queue feature in terms of XenStore keys to be written
> > by the backend and by the frontend.
> >
> > Signed-off-by: Andrew J. Bennieston <andrew.bennieston@xxxxxxxxxx>
> > ---
> >   include/xen/interface/io/netif.h |   21 +++++++++++++++++++++
> >   1 file changed, 21 insertions(+)
> >
> > diff --git a/include/xen/interface/io/netif.h
> > b/include/xen/interface/io/netif.h
> > index c50061d..8868c51 100644
> > --- a/include/xen/interface/io/netif.h
> > +++ b/include/xen/interface/io/netif.h
> > @@ -51,6 +51,27 @@
> >    */
> >
> >   /*
> > + * Multiple transmit and receive queues:
> > + * If supported, the backend will write "multi-queue-max-queues" 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", set to the number they wish to use.
> > + *
> > + * Queues replicate the shared rings and event channels, and
> > + * "feature-split-event-channels" is required when using multiple queues.
> > + *
> Is it? The code in patch 2 appears to cope with the "event-channel" key as well 
> as the split variants regardless of the number of queues being used. Am I missing some 
> other restriction?
Hmm, perhaps I just assumed that limitation. I'll check and update the 
doc accordingly.
Andrew

>    Paul
>
> > + * 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 them under sub-keys
> > having
> > + * the name "queue-N" where N is the integer ID of the queue for which
> > those
> > + * keys belong. Queues are indexed from zero.
> > + */
> > +
> > +/*
> >    * "feature-no-csum-offload" should be used to turn IPv4 TCP/UDP
> > checksum
> >    * offload off or on. If it is missing then the feature is assumed to be on.
> >    * "feature-ipv6-csum-offload" should be used to turn IPv6 TCP/UDP
> > checksum
> > --
> > 1.7.10.4

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