From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id D8EA66B004D for ; Wed, 10 Mar 2010 19:43:01 -0500 (EST) Received: from m6.gw.fujitsu.co.jp ([10.0.50.76]) by fgwmail5.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o2B0gxZn022665 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Thu, 11 Mar 2010 09:42:59 +0900 Received: from smail (m6 [127.0.0.1]) by outgoing.m6.gw.fujitsu.co.jp (Postfix) with ESMTP id C914845DE4F for ; Thu, 11 Mar 2010 09:42:58 +0900 (JST) Received: from s6.gw.fujitsu.co.jp (s6.gw.fujitsu.co.jp [10.0.50.96]) by m6.gw.fujitsu.co.jp (Postfix) with ESMTP id 9E75645DE4E for ; Thu, 11 Mar 2010 09:42:58 +0900 (JST) Received: from s6.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s6.gw.fujitsu.co.jp (Postfix) with ESMTP id 782A11DB801A for ; Thu, 11 Mar 2010 09:42:58 +0900 (JST) Received: from m106.s.css.fujitsu.com (m106.s.css.fujitsu.com [10.249.87.106]) by s6.gw.fujitsu.co.jp (Postfix) with ESMTP id 088241DB8012 for ; Thu, 11 Mar 2010 09:42:58 +0900 (JST) Date: Thu, 11 Mar 2010 09:39:13 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH -mmotm 0/5] memcg: per cgroup dirty limit (v6) Message-Id: <20100311093913.07c9ca8a.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <1268175636-4673-1-git-send-email-arighi@develer.com> References: <1268175636-4673-1-git-send-email-arighi@develer.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Andrea Righi Cc: Balbir Singh , 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 List-ID: On Wed, 10 Mar 2010 00:00:31 +0100 Andrea Righi wrote: > 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 (v5 -> v6) > ~~~~~~~~~~~~~~~~~~~~~~ > * always disable/enable IRQs at lock/unlock_page_cgroup(): this allows to drop > the previous complicated locking scheme in favor of a simpler locking, even > if this obviously adds some overhead (see results below) > * drop FUSE and NILFS2 dirty pages accounting for now (this depends on > charging bounce pages per cgroup) > > Results > ~~~~~~~ > I ran some tests using a kernel build (2.6.33 x86_64_defconfig) on a > Intel Core 2 @ 1.2GHz as testcase using different kernels: > - mmotm "vanilla" > - mmotm with cgroup-dirty-memory using the previous "complex" locking scheme > (my previous patchset + the fixes reported by Kame-san and Daisuke-san) > - mmotm with cgroup-dirty-memory using the simple locking scheme > (lock_page_cgroup() with IRQs disabled) > > Following the results: > > - mmotm "vanilla", root cgroup: 11m51.983s > - mmotm "vanilla", child cgroup: 11m56.596s > > > - mmotm, "complex" locking scheme, root cgroup: 11m53.037s > - mmotm, "complex" locking scheme, child cgroup: 11m57.896s > > - mmotm, lock_page_cgroup+irq_disabled, root cgroup: 12m5.499s > - mmotm, lock_page_cgroup+irq_disabled, child cgroup: 12m9.920s > > With the "complex" locking solution, the overhead introduced by the > cgroup dirty memory accounting is minimal (0.14%), compared with the overhead > introduced by the lock_page_cgroup+irq_disabled solution (1.90%). > Hmm....isn't this bigger than expected ? > The performance overhead is not so huge in both solutions, but the impact on > performance is even more reduced using a complicated solution... > > Maybe we can go ahead with the simplest implementation for now and start to > think to an alternative implementation of the page_cgroup locking and > charge/uncharge of pages. > maybe. But in this 2 years, one of our biggest concerns was the performance. So, we do something complex in memcg. But complex-locking is , yes, complex. Hmm..I don't want to bet we can fix locking scheme without something complex. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org