From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net-next v2 0/3] ipv6: per netns FIB6 walkers and garbage collector Date: Tue, 08 Mar 2016 15:17:13 -0500 (EST) Message-ID: <20160308.151713.644429771194150736.davem@davemloft.net> References: Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kuznet@ms2.inr.ac.ru, jmorris@namei.org, yoshfuji@linux-ipv6.org, kaber@trash.net, hannes@stressinduktion.org, kafai@fb.com, xiyou.wangcong@gmail.com To: mkubecek@suse.cz Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:44295 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751186AbcCHURR (ORCPT ); Tue, 8 Mar 2016 15:17:17 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: From: Michal Kubecek Date: Tue, 8 Mar 2016 14:44:15 +0100 (CET) > Commit 2ac3ac8f86f2 ("ipv6: prevent fib6_run_gc() contention") reduced > the risk of contention on FIB6 garbage collector lock on systems with > many CPUs. However, one of our customers can still observe heavy > contention on fib6_gc_lock which can even trigger the soft lockup > detector. > > This is caused by garbage collector running in forced mode from a timer. > While there is one timer per network namespace, the instances of > fib6_run_gc() running from them are protected by one global spinlock so > that only one garbage collector can run at any moment and other > namespaces have to wait. As most relevant data structures are separated > per netns, there is little reason for garbage collectors blocking each > other. > > Similar problem exists for walkers: changes in one tree do not need to > adjust (and block) walkers traversing FIB trees in other namespaces. > > This series separates both the walkers infrastructure and garbage > collector so that they work independently in network namespaces. > > v2: get rid of ifdef in ipv6_route_seq_setup_walk(), pass net from > callers instead Series applied, thanks.