netdev - Re: [PATCH net-next] ipv6: reduce percpu needs for icmpv6msg mibs

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Message-Id: <20111114.001244.386130843572045582.davem@davemloft.net>
Date:	Mon, 14 Nov 2011 00:12:44 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net-next] ipv6: reduce percpu needs for icmpv6msg mibs

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Sun, 13 Nov 2011 12:24:04 +0100

> Reading /proc/net/snmp6 on a machine with a lot of cpus is very
> expensive (can be ~88000 us).
> 
> This is because ICMPV6MSG MIB uses 4096 bytes per cpu, and folding
> values for all possible cpus can read 16 Mbytes of memory (32MBytes on
> non x86 arches)
> 
> ICMP messages are not considered as fast path on a typical server, and
> eventually few cpus handle them anyway. We can afford an atomic
> operation instead of using percpu data.
> 
> This saves 4096 bytes per cpu and per network namespace.
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>

Applied, thanks Eric.
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