From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753424Ab0CQGoO (ORCPT ); Wed, 17 Mar 2010 02:44:14 -0400 Received: from e28smtp01.in.ibm.com ([122.248.162.1]:49325 "EHLO e28smtp01.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753366Ab0CQGoN (ORCPT ); Wed, 17 Mar 2010 02:44:13 -0400 Date: Wed, 17 Mar 2010 12:14:02 +0530 From: Balbir Singh To: Andrea Righi Cc: KAMEZAWA Hiroyuki , Daisuke Nishimura , Vivek Goyal , Peter Zijlstra , Trond Myklebust , Suleiman Souhlal , Greg Thelen , "Kirill A. Shutemov" , Andrew Morton , containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH -mmotm 0/5] memcg: per cgroup dirty limit (v7) Message-ID: <20100317064402.GP18054@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <1268609202-15581-1-git-send-email-arighi@develer.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1268609202-15581-1-git-send-email-arighi@develer.com> User-Agent: Mutt/1.5.20 (2009-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Andrea Righi [2010-03-15 00:26:37]: > Control the maximum amount of dirty pages a cgroup can have at any given time. > > Per cgroup dirty limit is like fixing the max amount of dirty (hard to reclaim) > page cache used by any cgroup. So, in case of multiple cgroup writers, they > will not be able to consume more than their designated share of dirty pages and > will be forced to perform write-out if they cross that limit. > > The overall design is the following: > > - account dirty pages per cgroup > - limit the number of dirty pages via memory.dirty_ratio / memory.dirty_bytes > and memory.dirty_background_ratio / memory.dirty_background_bytes in > cgroupfs > - start to write-out (background or actively) when the cgroup limits are > exceeded > > This feature is supposed to be strictly connected to any underlying IO > controller implementation, so we can stop increasing dirty pages in VM layer > and enforce a write-out before any cgroup will consume the global amount of > dirty pages defined by the /proc/sys/vm/dirty_ratio|dirty_bytes and > /proc/sys/vm/dirty_background_ratio|dirty_background_bytes limits. > > Changelog (v6 -> v7) > ~~~~~~~~~~~~~~~~~~~~~~ > * introduce trylock_page_cgroup() to guarantee that lock_page_cgroup() > is never called under tree_lock (no strict accounting, but better overall > performance) > * do not account file cache statistics for the root cgroup (zero > overhead for the root cgroup) > * fix: evaluate cgroup free pages as at the minimum free pages of all > its parents > > Results > ~~~~~~~ > The testcase is a kernel build (2.6.33 x86_64_defconfig) on a Intel Core 2 @ > 1.2GHz: > > > - root cgroup: 11m51.983s > - child cgroup: 11m56.596s > > > - root cgroup: 11m51.742s > - child cgroup: 12m5.016s > > In the previous version of this patchset, using the "complex" locking scheme > with the _locked and _unlocked version of mem_cgroup_update_page_stat(), the > child cgroup required 11m57.896s and 12m9.920s with lock_page_cgroup()+irq_disabled. > > With this version there's no overhead for the root cgroup (the small difference > is in error range). I expected to see less overhead for the child cgroup, I'll > do more testing and try to figure better what's happening. I like that the root overhead is going away. > > In the while, it would be great if someone could perform some tests on a larger > system... unfortunately at the moment I don't have a big system available for > this kind of tests... > I'll test this, I have a small machine to test on at the moment, I'll revert back with data. -- Three Cheers, Balbir