From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933200AbaLDVTR (ORCPT ); Thu, 4 Dec 2014 16:19:17 -0500 Received: from mail-qc0-f174.google.com ([209.85.216.174]:40794 "EHLO mail-qc0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932752AbaLDVTQ (ORCPT ); Thu, 4 Dec 2014 16:19:16 -0500 Date: Thu, 4 Dec 2014 16:19:12 -0500 From: Tejun Heo To: Christoph Lameter Cc: Al Viro , Leonard Crestez , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sorin Dumitru Subject: Re: [RFC v2] percpu: Add a separate function to merge free areas Message-ID: <20141204211912.GG4080@htj.dyndns.org> References: <547E3E57.3040908@ixiacom.com> <20141204175713.GE2995@htj.dyndns.org> <5480BFAA.2020106@ixiacom.com> <20141204205202.GP29748@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 04, 2014 at 03:15:27PM -0600, Christoph Lameter wrote: > On Thu, 4 Dec 2014, Al Viro wrote: > > > ... except that somebody has not known that and took refcounts on e.g. > > vfsmounts into percpu. With massive amounts of hilarity once docker folks > > started to test the workloads that created/destroyed those in large amounts. > > Well, vfsmounts being a performance issue is a bit weird and unexpected. Docker usage is pretty wide-spread now, making what used to be siberia-cold paths hot enough to cause actual scalability issues. Besides, we're now using percpu_ref for things like aio and cgroup control structures which can be created and destroyed quite frequently. I don't think we can say these are "weird" use cases anymore. Thanks. -- tejun