Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754865AbZFWEyH (ORCPT ); Tue, 23 Jun 2009 00:54:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751312AbZFWEx4 (ORCPT ); Tue, 23 Jun 2009 00:53:56 -0400 Received: from e34.co.us.ibm.com ([32.97.110.152]:47903 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751164AbZFWExz (ORCPT ); Tue, 23 Jun 2009 00:53:55 -0400 Date: Tue, 23 Jun 2009 10:23:16 +0530 From: Balbir Singh To: KAMEZAWA Hiroyuki Cc: Andrew Morton , kamezawa.hiroyuki@jp.fujitsu.com, nishimura@mxp.nes.nec.co.jp, lizf@cn.fujitsu.com, menage@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: Low overhead patches for the memory cgroup controller (v5) Message-ID: <20090623045316.GF8642@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20090615043900.GF23577@balbir.in.ibm.com> <20090622154343.9cdbf23a.akpm@linux-foundation.org> <20090623090116.556d4f97.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20090623090116.556d4f97.kamezawa.hiroyu@jp.fujitsu.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2092 Lines: 66 * KAMEZAWA Hiroyuki [2009-06-23 09:01:16]: > On Mon, 22 Jun 2009 15:43:43 -0700 > Andrew Morton wrote: > > > On Mon, 15 Jun 2009 10:09:00 +0530 > > Balbir Singh wrote: > > > > > > > > ... > > > > > > This patch changes the memory cgroup and removes the overhead associated > > > with accounting all pages in the root cgroup. As a side-effect, we can > > > no longer set a memory hard limit in the root cgroup. > > > > > > A new flag to track whether the page has been accounted or not > > > has been added as well. Flags are now set atomically for page_cgroup, > > > pcg_default_flags is now obsolete and removed. > > > > > > ... > > > > > > @@ -1114,9 +1121,22 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem, > > > css_put(&mem->css); > > > return; > > > } > > > + > > > pc->mem_cgroup = mem; > > > smp_wmb(); > > > - pc->flags = pcg_default_flags[ctype]; > > > + switch (ctype) { > > > + case MEM_CGROUP_CHARGE_TYPE_CACHE: > > > + case MEM_CGROUP_CHARGE_TYPE_SHMEM: > > > + SetPageCgroupCache(pc); > > > + SetPageCgroupUsed(pc); > > > + break; > > > + case MEM_CGROUP_CHARGE_TYPE_MAPPED: > > > + ClearPageCgroupCache(pc); > > > + SetPageCgroupUsed(pc); > > > + break; > > > + default: > > > + break; > > > + } > > > > Do we still need the smp_wmb()? > > > > It's hard to say, because we forgot to document it :( > > > Sorry for lack of documentation. > > pc->mem_cgroup should be visible before SetPageCgroupUsed(). Othrewise, > A routine believes USED bit will see bad pc->mem_cgroup. > > I'd like to add a comment later (againt new mmotm.) > Thanks Kamezawa! We do use the barrier Andrew, an easy way to find affected code is to look at the smp_rmb()'s we have. But it is better documented. -- Balbir -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/