netdev - RE: [PATCH net v3 2/2] xen-netback: napi: don't prematurely request a tx event

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Message-ID: <9AAE0902D5BC7E449B7C8E4E778ABCD01AEA51@AMSPEX01CL01.citrite.net>
Date:	Wed, 11 Dec 2013 10:29:03 +0000
From:	Paul Durrant <Paul.Durrant@...rix.com>
To:	Ian Campbell <Ian.Campbell@...rix.com>
CC:	"xen-devel@...ts.xen.org" <xen-devel@...ts.xen.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Wei Liu <wei.liu2@...rix.com>,
	David Vrabel <david.vrabel@...rix.com>
Subject: RE: [PATCH net v3 2/2] xen-netback: napi: don't prematurely request
 a tx event

> -----Original Message-----
> From: Ian Campbell
> Sent: 11 December 2013 09:44
> To: Paul Durrant
> Cc: xen-devel@...ts.xen.org; netdev@...r.kernel.org; Wei Liu; David Vrabel
> Subject: Re: [PATCH net v3 2/2] xen-netback: napi: don't prematurely
> request a tx event
> 
> On Tue, 2013-12-10 at 13:39 +0000, Paul Durrant wrote:
> > This patch changes the RING_FINAL_CHECK_FOR_REQUESTS in
> > xenvif_build_tx_gops to a check for RING_HAS_UNCONSUMED_REQUESTS
> as the
> > former call has the side effect of advancing the ring event pointer and
> > therefore inviting another interrupt from the frontend before the napi
> > poll has actually finished, thereby defeating the point of napi.
> 
> Like I said last time:
> 
> Can you add a reminder of when/where the ring event pointer is
> eventually advanced now please.
> 

Sorry, I missed that. Will do.

  Paul