From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755330AbYDTXmR (ORCPT ); Sun, 20 Apr 2008 19:42:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751399AbYDTXmG (ORCPT ); Sun, 20 Apr 2008 19:42:06 -0400 Received: from extu-mxob-2.symantec.com ([216.10.194.135]:47328 "EHLO extu-mxob-2.symantec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750931AbYDTXmF (ORCPT ); Sun, 20 Apr 2008 19:42:05 -0400 Date: Mon, 21 Apr 2008 00:51:30 +0100 (BST) From: Hugh Dickins X-X-Sender: hugh@blonde.site To: Andrew Morton cc: Paul Menage , Balbir Singh , Pavel Emelianov , KAMEZAWA Hiroyuki , Shi Weihua , Mel Gorman , linux-kernel@vger.kernel.org Subject: Re: -mm merge plans for 2.6.26 (memcgroup) In-Reply-To: <20080420072053.6bcb7884.akpm@linux-foundation.org> Message-ID: References: <20080420072053.6bcb7884.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 20 Apr 2008, Andrew Morton wrote: > > These can be found at > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.25/2.6.25-mm1 A couple of comments on memcgroup patches in your high-priority initial section (I've not studied further yet) > Merge, and backport to 2.6.25.x > disable-the-memory-controller-by-default-v3.patch > disable-the-memory-controller-by-default-v3-fix.patch If those are to go in, then the sooner the better, yes. But though I argued for cgroup_disable=memory (or some such), I think myself that taking it even further now (requiring an additional cgroup_enable=memory at boottime to get the memcg stuff you chose with CGROUP_MEM_RES_CTLR=y at build time) is confusing overkill, just messing around. Others think differently. A compromise would be to improve the helptext for CGROUP_MEM_RES_CTLR (some of it is presently nonsense, isn't it? Certainly there's a significant overhead, but it's the 32-bit struct page not the 64-bit which then suffers from crossing cacheline boundaries). Not much point in mentioning cgroup_disable=memory if those patches go in, but needs to say cgroup_enable=memory bootoption also needed. > memcgroup-check-and-initialize-page-cgroup-in-memmap_init_zone.patch No, it was a good find from Shi, but you were right to think the patch fishy, and Kame put in lots of work (thank you!) to identify the actual culprit: he and Mel are discussing what the actual fix should be; and we might want to choose a different fix for stable than for 2.6.26. I think you should drop that memmap_init_zone patch: the cgroup pointer is not the only field we assume is zeroed, both flags and mapping can cause trouble if they were not originally zeroed. Re-zero the whole struct page? No, far better to fix the root of the corruption, that Kame and Mel are working on. Hugh