netdev - Re: [PATCH 1/2 -next] r8169: allocate with GFP

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Message-ID: <1285405945.2478.255.camel@edumazet-laptop>
Date:	Sat, 25 Sep 2010 11:12:25 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	romieu@...zoreil.com, sgruszka@...hat.com, netdev@...r.kernel.org
Subject: Re: [PATCH 1/2 -next] r8169: allocate with GFP_KERNEL flag when
 able to sleep

Le samedi 25 septembre 2010 à 00:13 -0700, David Miller a écrit :
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Sat, 25 Sep 2010 08:06:37 +0200
> 
> > Patch solves the suspend/resume, probably, but as soon as we receive
> > trafic, we can hit the allocation error anyway...
> 
> It allocates 1536 + N, where N can be NET_IP_ALIGN, or some small
> value like 8.
> 
> This is in the same ballpark as what tg3 allocates for RX buffers.
> 
> SLAB/SLUB/whatever just wants multi-order page allocations even
> for SKBs which are about this size.
> 
> Furthermore, the sleeping allocations we do at ->open() time to
> allocate the entire RX ring all at once will buddy up a lot of
> pages and make 1-order allocs more likely.

Yes, I forgot this problem about SLUB (I ended using SLAB on servers
because of this order-3 problem on kmalloc(2048))

bnx2 uses GFP_KERNEL allocations at init time, but tg3 uses GFP_ATOMIC
(because tp->lock is held).

The r8169 current problem is its currently copying all incoming frames.
I guess nobody cares or noticed the performance drop.
(But commit c0cd884a is recent (2.6.34), this is not yet in
production...)




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