netdev - Re: [PATCH v6] net: add Faraday FTMAC100 10/100 Ethernet driver

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Message-ID: <1298959188.2676.32.camel@edumazet-laptop>
Date:	Tue, 01 Mar 2011 06:59:48 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Po-Yu Chuang <ratbert.chuang@...il.com>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	bhutchings@...arflare.com, joe@...ches.com, dilinger@...ued.net,
	mirqus@...il.com, davem@...emloft.net,
	Po-Yu Chuang <ratbert@...aday-tech.com>
Subject: Re: [PATCH v6] net: add Faraday FTMAC100 10/100 Ethernet driver

Le mardi 01 mars 2011 à 13:51 +0800, Po-Yu Chuang a écrit :
> On Tue, Mar 1, 2011 at 1:45 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:

> > I am only wondering then if not using fragments would be faster then
> > (eventually doing copybreaks for small frames like tg3)
> 
> Although not many circumstances are tested.
> iperf shows that it is a little faster to use fragments than memcpy, so...

This might be a side effect of skb->truesize being smaller with
fragments than "regular packets" and socket backlog congestion.

If a full page was really accounted for in skb->truesize, instead of
used length, performance might be the same or lower :(

-	skb->truesize += length;
+	skb->truesize += PAGE_SIZE;

This has nothing to do with your driver, but a core implementation
detail.



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