From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 0BC156B004D for ; Wed, 30 Sep 2009 20:32:27 -0400 (EDT) Date: Thu, 1 Oct 2009 09:45:14 +0900 From: Daisuke Nishimura Subject: Re: [RFC][PATCH 0/2] memcg: replace memcg's per cpu status counter with array counter like vmstat Message-Id: <20091001094514.c9d2b3d9.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20090930190417.8823fa44.kamezawa.hiroyu@jp.fujitsu.com> References: <20090930190417.8823fa44.kamezawa.hiroyu@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: nishimura@mxp.nes.nec.co.jp, "linux-mm@kvack.org" , "balbir@linux.vnet.ibm.com" , "linux-kernel@vger.kernel.org" List-ID: On Wed, 30 Sep 2009 19:04:17 +0900, KAMEZAWA Hiroyuki wrote: > Hi, > > In current implementation, memcg uses its own percpu counters for counting > evetns and # of RSS, CACHES. Now, counter is maintainer per cpu without > any synchronization as vm_stat[] or percpu_counter. So, this is > update-is-fast-but-read-is-slow conter. > > Because "read" for these counter was only done by memory.stat file, I thought > read-side-slowness was acceptable. Amount of memory usage, which affects > memory limit check, can be read by memory.usage_in_bytes. It's maintained > by res_counter. > > But in current -rc, root memcg's memory usage is calcualted by this per cpu > counter and read side slowness may be trouble if it's frequently read. > > And, in recent discusstion, I wonder we should maintain NR_DIRTY etc... > in memcg. So, slow-read-counter will not match our requirements, I guess. > I want some counter like vm_stat[] in memcg. > I see your concern. But IMHO, it would be better to explain why we need a new percpu array counter instead of using array of percpu_counter(size or consolidation of related counters ?), IOW, what the benefit of percpu array counter is. Thanks, Daisuke Nishimura. > This 2 patches are for using counter like vm_stat[] in memcg. > Just an idea level implementaion but I think this is not so bad. > > I confirmed this patch works well. I'm now thinking how to test performance... > > Any comments are welcome. > This patch is onto mmotm + some myown patches...so...this is just an RFC. > > Regards, > -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