From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752445AbaJKXIe (ORCPT ); Sat, 11 Oct 2014 19:08:34 -0400 Received: from shards.monkeyblade.net ([149.20.54.216]:40532 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751717AbaJKXId (ORCPT ); Sat, 11 Oct 2014 19:08:33 -0400 Date: Sat, 11 Oct 2014 19:08:29 -0400 (EDT) Message-Id: <20141011.190829.876705206204533685.davem@davemloft.net> To: tgraf@suug.ch Cc: eric.dumazet@gmail.com, heiko.carstens@de.ibm.com, sasha.levin@oracle.com, paulmck@linux.vnet.ibm.com, nikolay@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, braunu@de.ibm.com Subject: Re: [bisected] e341694e3eb5 netlink_lookup() rcu conversion causes latencies From: David Miller In-Reply-To: <20141011222514.GA14186@casper.infradead.org> References: <20141011083627.GB5074@osiris> <1413055964.9362.50.camel@edumazet-glaptop2.roam.corp.google.com> <20141011222514.GA14186@casper.infradead.org> X-Mailer: Mew version 6.6 on Emacs 24.3 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.7 (shards.monkeyblade.net [149.20.54.216]); Sat, 11 Oct 2014 16:08:32 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Thomas Graf Date: Sat, 11 Oct 2014 23:25:14 +0100 > I think the issue here is obvious and a fix is on the way to move > the insertion and removal to a worker to no longer require the > synchronize_rcu(). > > What bothers me is that the synchronize_rcu() should only occur > on expand/shrink and not for every table update. The default table > size is 64. Not true, every netlink socket release incurs a synchronize_net() now, because we added such a call to netlink_release(). I specifically brought this up to as a possible problem when the changes went in...