From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754086AbZBDJFt (ORCPT ); Wed, 4 Feb 2009 04:05:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751664AbZBDJFf (ORCPT ); Wed, 4 Feb 2009 04:05:35 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:50570 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751234AbZBDJFd (ORCPT ); Wed, 4 Feb 2009 04:05:33 -0500 Message-ID: <498959C6.2090509@cn.fujitsu.com> Date: Wed, 04 Feb 2009 17:03:02 +0800 From: Miao Xie Reply-To: miaox@cn.fujitsu.com User-Agent: Thunderbird 2.0.0.6 (Windows/20070728) MIME-Version: 1.0 To: Andrew Morton CC: mingo@elte.hu, menage@google.com, linux-kernel@vger.kernel.org, cl@linux-foundation.org, nickpiggin@yahoo.com.au Subject: Re: [PATCH] cpuset: fix allocating page cache/slab object on the unallowed node when memory spread is set References: <4976D77C.3020107@cn.fujitsu.com> <20090127144233.18cf9b3f.akpm@linux-foundation.org> <4987B925.1010405@cn.fujitsu.com> <20090203141645.91c7ea18.akpm@linux-foundation.org> In-Reply-To: <20090203141645.91c7ea18.akpm@linux-foundation.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org on 2009-2-4 6:16 Andrew Morton wrote: > On Tue, 03 Feb 2009 11:25:25 +0800 > Miao Xie wrote: > >> on 2009-1-28 6:42 Andrew Morton wrote: >>> On Wed, 21 Jan 2009 16:06:20 +0800 >>> Miao Xie wrote: >>> >>>> The task still allocated the page caches on old node after modifying its >>>> cpuset's mems when 'memory_spread_page' was set, it is caused by the old >>>> mem_allowed_list of the task, the current kernel doesn't updates it unless some >>>> function invokes cpuset_update_task_memory_state(), it is too late sometimes. >>>> We must update the mem_allowed_list of the tasks in time. >>>> >>>> Slab has the same problem. >>>> >>>> We fixes the bug by updating tasks' mem_allowed_list and spread flag after >>>> its cpuset's mems or spread flag is changed. >>>> >>>> >>>> ... >>>> >>>> --- a/kernel/kthread.c >>>> +++ b/kernel/kthread.c >>>> @@ -242,6 +242,7 @@ int kthreadd(void *unused) >>>> set_user_nice(tsk, KTHREAD_NICE_LEVEL); >>>> set_cpus_allowed_ptr(tsk, CPU_MASK_ALL_PTR); >>>> >>>> + current->mems_allowed = node_possible_map; >>>> current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG; >>> Why this change? kthreadd() is called from rest_init(), before anyone >>> has had a chance to alter ->mems_allowed? >> I found that after mems_allowed of kthreadd was not initialized applying this patch, >> every bit of it is 1, so... >> Maybe it is redundant. > > I think it is redundant. kthreadd's mems_allowed _should_ be all-ones. > Or at least, all-nodes-allowed. > > I wasn't able to find out where the setting of init'smems_allowed > happens, after a bit of grepping and hunting. It should be done within > INIT_TASK, but isn't. I found it. Call trace is following: start_kernel() ->build_all_zonelists() ->cpuset_init_current_mems_allowed() ->nodes_setall(current->mems_allowed); then, it is inherited by kthreadd. > > Still, kthreadd is reliably parented by swapper, and there shold be no > need to alter its mems_allowed. but it is strange to users because there are not so many nodes in the system in fact, so I think using node_possible_map to set init's mems_allowed is better. > Similarly, what was the reason for setting current->mems_allowed in > kernel_init()? That also should be unneeded. The same as above. > > Finally, I've somewhat lost track of where we are with this patch. > Paul, do you see any other remaining issues? > > > >