netdev - Re: [PATCH 0/2] Get rid of ndo_xmit

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Message-ID: <1409142672.26515.24.camel@localhost>
Date:	Wed, 27 Aug 2014 14:31:12 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, therbert@...gle.com, jhs@...atatu.com,
	edumazet@...gle.com, jeffrey.t.kirsher@...el.com,
	rusty@...tcorp.com.au, dborkman@...hat.com, brouer@...hat.com
Subject: Re: [PATCH 0/2] Get rid of ndo_xmit_flush

On Mo, 2014-08-25 at 16:34 -0700, David Miller wrote:
> Given Jesper's performance numbers, it's not the way to go.
> 
> Instead, go with a signalling scheme via new boolean skb->xmit_more.
> 
> This has several advantages:
> 
> 1) Nearly trivial driver support, just protect the tail pointer
>    update with the skb->xmit_more check.

One thing one should keep in mind is, that there must be a skb available
to trigger the flush, maybe this will hurt us one day.

Thinking more about it should we go with a coccinelle script and
replace/extend ndo_start_xmit with an additional argument?

We can also add a new function pointer and call that instead of
ndo_start_xmit. I think only the callq *%rax hurts performance.

Bye,
Hannes



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