Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757415AbZFWADE (ORCPT ); Mon, 22 Jun 2009 20:03:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753661AbZFWACz (ORCPT ); Mon, 22 Jun 2009 20:02:55 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:38329 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752337AbZFWACy (ORCPT ); Mon, 22 Jun 2009 20:02:54 -0400 Date: Tue, 23 Jun 2009 09:01:16 +0900 From: KAMEZAWA Hiroyuki To: Andrew Morton Cc: balbir@linux.vnet.ibm.com, 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: <20090623090116.556d4f97.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090622154343.9cdbf23a.akpm@linux-foundation.org> References: <20090615043900.GF23577@balbir.in.ibm.com> <20090622154343.9cdbf23a.akpm@linux-foundation.org> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 2.5.0 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1767 Lines: 63 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, -Kame -- 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/