netdev - Re: net: more accurate skb truesize

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Date:	Tue, 10 Apr 2012 13:50:25 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	monstr@...str.eu
Cc:	netdev@...r.kernel.org,
	John Williams <john.williams@...alogix.com>,
	David Miller <davem@...emloft.net>
Subject: Re: net: more accurate skb truesize - regression on Microblaze

On Tue, 2012-04-10 at 13:38 +0200, Michal Simek wrote:
> On 04/10/2012 01:32 PM, Eric Dumazet wrote:
> >
> > ll_temac allocates XTE_MAX_JUMBO_FRAME_SIZE frames, even for MTU=1500 ?
> 
> yes.
> 
> >
> > Trying to allocate smaller packets would definitely help your tcp
> > receiver performance and overall reliability  (order-0 allocations
> > instead of order-2)
> 
> There is long history for ll_temac and axi emac drivers. and if you compare
> them they are very similar with similar bugs.
> In our distribution we are using older ll_temac driver where this is fixed.
> Performance is much higher if you allocate buffers for actual mtu.
> 
> Thanks,
> Michal
> 
> P.S.: Our plan is to start to use mainline drivers and fixing them to get
> the same performance as we have with old one. It is one my todo list.

Ah good, because this 9000+pad versus 1500+pad allocation is way more
problematic than the (small) change on skb->truesize you bisected ;)



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