From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759286AbaDJXYR (ORCPT ); Thu, 10 Apr 2014 19:24:17 -0400 Received: from merlin.infradead.org ([205.233.59.134]:58780 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753823AbaDJXYO (ORCPT ); Thu, 10 Apr 2014 19:24:14 -0400 Message-ID: <5347280B.3000303@infradead.org> Date: Thu, 10 Apr 2014 16:23:55 -0700 From: Randy Dunlap User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: Tang Chen , hannes@cmpxchg.org, mhocko@suse.cz, bsingharora@gmail.com, kamezawa.hiroyu@jp.fujitsu.com CC: cgroups@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, guz.fnst@cn.fujitsu.com, Andrew Morton Subject: Re: [PATCH 1/1] doc, mempolicy: Fix wrong document in numa_memory_policy.txt References: <1396410782-26208-1-git-send-email-tangchen@cn.fujitsu.com> In-Reply-To: <1396410782-26208-1-git-send-email-tangchen@cn.fujitsu.com> 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 04/01/2014 08:53 PM, Tang Chen wrote: > In document numa_memory_policy.txt, the following examples for flag > MPOL_F_RELATIVE_NODES are incorrect. > > For example, consider a task that is attached to a cpuset with > mems 2-5 that sets an Interleave policy over the same set with > MPOL_F_RELATIVE_NODES. If the cpuset's mems change to 3-7, the > interleave now occurs over nodes 3,5-6. If the cpuset's mems > then change to 0,2-3,5, then the interleave occurs over nodes > 0,3,5. > > According to the comment of the patch adding flag MPOL_F_RELATIVE_NODES, > the nodemasks the user specifies should be considered relative to the > current task's mems_allowed. > (https://lkml.org/lkml/2008/2/29/428) > > And according to numa_memory_policy.txt, if the user's nodemask includes > nodes that are outside the range of the new set of allowed nodes, then > the remap wraps around to the beginning of the nodemask and, if not already > set, sets the node in the mempolicy nodemask. > > So in the example, if the user specifies 2-5, for a task whose mems_allowed > is 3-7, the nodemasks should be remapped the third, fourth, fifth, sixth > node in mems_allowed. like the following: > > mems_allowed: 3 4 5 6 7 > > relative index: 0 1 2 3 4 > 5 > > So the nodemasks should be remapped to 3,5-7, but not 3,5-6. > > And for a task whose mems_allowed is 0,2-3,5, the nodemasks should be > remapped to 0,2-3,5, but not 0,3,5. > > mems_allowed: 0 2 3 5 > > relative index: 0 1 2 3 > 4 5 > > > Signed-off-by: Tang Chen Wow. This was not an April fools joke, right? Have there been any acks of this? I haven't seen any responses to it. Andrew, do you want to merge it? > --- > Documentation/vm/numa_memory_policy.txt | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/Documentation/vm/numa_memory_policy.txt b/Documentation/vm/numa_memory_policy.txt > index 4e7da65..badb050 100644 > --- a/Documentation/vm/numa_memory_policy.txt > +++ b/Documentation/vm/numa_memory_policy.txt > @@ -174,7 +174,6 @@ Components of Memory Policies > allocation fails, the kernel will search other nodes, in order of > increasing distance from the preferred node based on information > provided by the platform firmware. > - containing the cpu where the allocation takes place. > > Internally, the Preferred policy uses a single node--the > preferred_node member of struct mempolicy. When the internal > @@ -275,9 +274,9 @@ Components of Memory Policies > For example, consider a task that is attached to a cpuset with > mems 2-5 that sets an Interleave policy over the same set with > MPOL_F_RELATIVE_NODES. If the cpuset's mems change to 3-7, the > - interleave now occurs over nodes 3,5-6. If the cpuset's mems > + interleave now occurs over nodes 3,5-7. If the cpuset's mems > then change to 0,2-3,5, then the interleave occurs over nodes > - 0,3,5. > + 0,2-3,5. > > Thanks to the consistent remapping, applications preparing > nodemasks to specify memory policies using this flag should > -- ~Randy