netdev - Re: [PATCH 4/4] udp: memory accounting in IPv4

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Date:	Tue, 4 Dec 2007 11:26:45 +1100
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Hideo AOKI <haoki@...hat.com>
Cc:	Eric Dumazet <dada1@...mosbay.com>,
	netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Satoshi Oshima <satoshi.oshima.fk@...achi.com>,
	Bill Fink <billfink@...dspring.com>,
	Andi Kleen <andi@...stfloor.org>,
	Evgeniy Polyakov <johnpol@....mipt.ru>,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	yoshfuji@...ux-ipv6.org,
	Yumiko Sugita <yumiko.sugita.yf@...achi.com>
Subject: Re: [PATCH 4/4] udp: memory accounting in IPv4

On Mon, Dec 03, 2007 at 07:14:26PM -0500, Hideo AOKI wrote:
>
> Let me try to use sk_forward_alloc at first, while percpu storage
> is an interesting idea.

Actually I don't think sk_forward_alloc would work for UDP because
it runs lockless (unlike TCP which is run under a the socket lock).

So it's either going to be the atomic op or per-cpu counters.  For
me the atomic op isn't the issue, it's the SMP cache-line bouncing
that's more important so having something that did atomic ops on a
socket counter which then feeds into the global counter would solve
my concerns.

But let's wait and see what Dave has to say about this too.

Thanks,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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