From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net-next] ipv6: reduce percpu needs for icmpv6msg mibs Date: Mon, 14 Nov 2011 00:12:44 -0500 (EST) Message-ID: <20111114.001244.386130843572045582.davem@davemloft.net> References: <1321183444.17837.21.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: eric.dumazet@gmail.com Return-path: Received: from shards.monkeyblade.net ([198.137.202.13]:55041 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750775Ab1KNFMr (ORCPT ); Mon, 14 Nov 2011 00:12:47 -0500 In-Reply-To: <1321183444.17837.21.camel@edumazet-laptop> Sender: netdev-owner@vger.kernel.org List-ID: From: Eric Dumazet 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 Applied, thanks Eric.