netdev - Re: [net PATCH] mlx4: fix XDP_TX is acting like XDP

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Message-ID: <20160917164650.53e68314@redhat.com>
Date:   Sat, 17 Sep 2016 16:46:50 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Brenden Blanco <bblanco@...mgrid.com>
Cc:     brouer@...hat.com, netdev@...r.kernel.org, tariqt@...lanox.com,
        Eric Dumazet <eric.dumazet@...il.com>, tom@...bertland.com,
        rana.shahot@...il.com, "David S. Miller" <davem@...emloft.net>
Subject: Re: [net PATCH] mlx4: fix XDP_TX is acting like XDP_PASS on TX ring
 full

On Fri, 16 Sep 2016 13:43:50 -0700
Brenden Blanco <bblanco@...mgrid.com> wrote:

> On Fri, Sep 16, 2016 at 10:36:12PM +0200, Jesper Dangaard Brouer wrote:
> > The XDP_TX action can fail transmitting the frame in case the TX ring
> > is full or port is down.  In case of TX failure it should drop the
> > frame, and not as now call 'break' which is the same as XDP_PASS.
> > 
> > Fixes: 9ecc2d86171a ("net/mlx4_en: add xdp forwarding and data write support")
> > Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>  
> 
> You could in theory have also tried to recycle the page instead of
> dropping it, but that's probably not worth optimizing when tx is backed
> up, as you'll only save a handful of page_put's. The code to do so
> wouldn't have been pretty.

Yes, we could (and perhaps should) recycle the page instead. But as you
also mention it would not look pretty. I'll send a V3, as XDPs primary
concern is performance.

> Reviewed-by: Brenden Blanco <bblanco@...mgrid.com>



-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer