From mboxrd@z Thu Jan 1 00:00:00 1970 From: Randy Dunlap Subject: Re: [PATCH 1/1] doc, mempolicy: Fix wrong document in numa_memory_policy.txt Date: Thu, 10 Apr 2014 16:23:55 -0700 Message-ID: <5347280B.3000303@infradead.org> References: <1396410782-26208-1-git-send-email-tangchen@cn.fujitsu.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1396410782-26208-1-git-send-email-tangchen-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Tang Chen , hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, mhocko-AlSwsSmVLrQ@public.gmane.org, bsingharora-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, guz.fnst-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org, Andrew Morton 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