netdev - RE: [Xen-devel] [PATCH v2 net-next 5/7] xen-netback: process guest rx packets in batches

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Date:   Tue, 4 Oct 2016 14:02:21 +0000
From:   Paul Durrant <Paul.Durrant@...rix.com>
To:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        Wei Liu <wei.liu2@...rix.com>,
        David Vrabel <david.vrabel@...rix.com>
Subject: RE: [Xen-devel] [PATCH v2 net-next 5/7] xen-netback: process guest rx
 packets in batches

> -----Original Message-----
> From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@...cle.com]
> Sent: 04 October 2016 13:48
> To: Paul Durrant <Paul.Durrant@...rix.com>
> Cc: netdev@...r.kernel.org; xen-devel@...ts.xenproject.org; Wei Liu
> <wei.liu2@...rix.com>; David Vrabel <david.vrabel@...rix.com>
> Subject: Re: [Xen-devel] [PATCH v2 net-next 5/7] xen-netback: process
> guest rx packets in batches
> 
> On Tue, Oct 04, 2016 at 10:29:16AM +0100, Paul Durrant wrote:
> > From: David Vrabel <david.vrabel@...rix.com>
> >
> > Instead of only placing one skb on the guest rx ring at a time,
> > process a batch of up-to 64.  This improves performance by ~10% in some
> tests.

I believe the tests are mainly throughput tests, but David would know the specifics.

> 
> And does it regress latency workloads?
> 

It shouldn't, although I have not run ping-pong tests to verify. If packets are only placed on the vif queue singly though then the batching should have no effect, since rx_action will complete and do the push as before.

  Paul

> What are those 'some tests' you speak off?
> 
> Thanks.
> >
> > Signed-off-by: David Vrabel <david.vrabel@...rix.com> [re-based]
> > Signed-off-by: Paul Durrant <paul.durrant@...rix.com>
> > ---
> > Cc: Wei Liu <wei.liu2@...rix.com>
> > ---
> >  drivers/net/xen-netback/rx.c | 15 ++++++++++++++-
> >  1 file changed, 14 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/xen-netback/rx.c
> > b/drivers/net/xen-netback/rx.c index 9548709..ae822b8 100644
> > --- a/drivers/net/xen-netback/rx.c
> > +++ b/drivers/net/xen-netback/rx.c
> > @@ -399,7 +399,7 @@ static void xenvif_rx_extra_slot(struct
> xenvif_queue *queue,
> >  	BUG();
> >  }
> >
> > -void xenvif_rx_action(struct xenvif_queue *queue)
> > +void xenvif_rx_skb(struct xenvif_queue *queue)
> >  {
> >  	struct xenvif_pkt_state pkt;
> >
> > @@ -425,6 +425,19 @@ void xenvif_rx_action(struct xenvif_queue
> *queue)
> >  	xenvif_rx_complete(queue, &pkt);
> >  }
> >
> > +#define RX_BATCH_SIZE 64
> > +
> > +void xenvif_rx_action(struct xenvif_queue *queue) {
> > +	unsigned int work_done = 0;
> > +
> > +	while (xenvif_rx_ring_slots_available(queue) &&
> > +	       work_done < RX_BATCH_SIZE) {
> > +		xenvif_rx_skb(queue);
> > +		work_done++;
> > +	}
> > +}
> > +
> >  static bool xenvif_rx_queue_stalled(struct xenvif_queue *queue)  {
> >  	RING_IDX prod, cons;
> > --
> > 2.1.4
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@...ts.xen.org
> > https://lists.xen.org/xen-devel