netdev - Re: [PATCH net-next] ipv4: reduce percpu needs for icmpmsg mibs

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Message-Id: <20111109.160438.1236405221658994935.davem@davemloft.net>
Date:	Wed, 09 Nov 2011 16:04:38 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net-next] ipv4: reduce percpu needs for icmpmsg mibs

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Wed, 09 Nov 2011 00:04:43 +0100

> Reading /proc/net/snmp on a machine with a lot of cpus is very expensive
> (can be ~88000 us).
> 
> This is because ICMPMSG MIB uses 4096 bytes per cpu, and folding values
> for all possible cpus can read 16 Mbytes of memory.
> 
> 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>
> ---
> If this patch is accepted, I'll submit the IPv6 part as well.

Looks good, applied, thanks Eric.
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