netdev - Re: [PATCH] Enhance AF_PACKET implementation to not require high order contiguous memory allocation

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Message-Id: <20101025.164646.104054845.davem@davemloft.net>
Date:	Mon, 25 Oct 2010 16:46:46 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	nhorman@...driver.com
Cc:	eric.dumazet@...il.com, netdev@...r.kernel.org, jpirko@...hat.com
Subject: Re: [PATCH] Enhance AF_PACKET implementation to not require high
 order contiguous memory allocation

From: Neil Horman <nhorman@...driver.com>
Date: Mon, 25 Oct 2010 19:35:58 -0400

> On Tue, Oct 26, 2010 at 12:30:56AM +0200, Eric Dumazet wrote:
>> I would try a two level thing : Try to get high order pages, and
>> fallback on low order pages, but normally libpcap does this for us ?
>> 
>> 
> It does, but it tries them in that order, which causes the problem I'm
> describing, which is to say that attempting to get a large high order allocation
> causes the system to dig into swap and become unresponsive while it tries to
> assemble those allocations.  I would suggest a vmalloc, with a backoff to high
> order allocation if that fails.

I think that logic should be maintained, except that one of the GFP_*
flags should be specified so that it doesn't go all swap crazy on us,
and instead fails a high order allocation earlier.
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