netdev - RE: [Xen-devel] [RFC PATCH 3/6] netback: switch to NAPI + kthread model

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 16 Jan 2012 10:56:53 +0000
From:	Paul Durrant <Paul.Durrant@...rix.com>
To:	Ian Campbell <Ian.Campbell@...rix.com>,
	"Wei Liu (Intern)" <wei.liu2@...rix.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	David Vrabel <david.vrabel@...rix.com>,
	"konrad.wilk@...cle.com" <konrad.wilk@...cle.com>
Subject: RE: [Xen-devel] [RFC PATCH 3/6] netback: switch to NAPI + kthread
 model

> -----Original Message-----
> From: xen-devel-bounces@...ts.xensource.com [mailto:xen-devel-
> bounces@...ts.xensource.com] On Behalf Of Ian Campbell
> Sent: 16 January 2012 10:45
> To: Wei Liu (Intern)
> Cc: netdev@...r.kernel.org; xen-devel@...ts.xensource.com; David Vrabel;
> konrad.wilk@...cle.com
> Subject: Re: [Xen-devel] [RFC PATCH 3/6] netback: switch to NAPI + kthread
> model
> 
> On Mon, 2012-01-16 at 09:33 +0000, Wei Liu (Intern) wrote:
> > On Fri, 2012-01-13 at 18:21 +0000, David Vrabel wrote:
> > > On 13/01/12 16:59, Wei Liu wrote:
> > > > This patch implements 1:1 model netback. We utilizes NAPI and
> > > > kthread to do the weight-lifting job:
> > > >
> > > >   - NAPI is used for guest side TX (host side RX)
> > > >   - kthread is used for guest side RX (host side TX)
> > > >
> > > > This model provides better scheduling fairness among vifs. It also
> > > > lays the foundation for future work.
> > > >
> > > > The major defect for the current implementation is that in the
> > > > NAPI poll handler we don't actually disable interrupt. Xen stuff
> > > > is different from real hardware, it requires some other tuning of
> > > > ring macros.
> > >
> > > RING_FINAL_CHECK_FOR_REQUESTS() looks it does the correct thing to
> me.
> > >
> > > David
> >
> > I need to stop the other end from generating events, so
> > RING_FINAL_CHECK_FOR_REQUESTS is not the right answer I think.
> 
> What you need is a variant which sets req_event some large distance into
> the future instead of to just req_cons + 1. Or possibly it should be set to just
> in the past (e.g. req_cons - 1). Call it something like
> RING_POLL_FOR_REQUESTS().
> 

Can you just simply avoid calling RING_FINAL_CHECK_FOR_REQUESTS() unless you actually want to re-enable 'interrupts'? All it does is manipulate the event pointer and tell you whether there are still unconsumed requests.

  Paul
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html