Messages in this thread | | | Date | Fri, 11 Apr 2014 16:13:33 +0800 | From | Tang Chen <> | Subject | Re: [PATCH 1/1] doc, mempolicy: Fix wrong document in numa_memory_policy.txt |
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Hi Randy,
On 04/11/2014 07:23 AM, Randy Dunlap wrote: > 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<tangchen@cn.fujitsu.com> > > Wow. This was not an April fools joke, right? > > Have there been any acks of this? I haven't seen any responses to it.
Thanks for the reply. I found this problem when I was reading the doc. I think it is wrong. And according to the original patch:
https://lkml.org/lkml/2008/2/29/428
I think it should be fixed in the above way. But if I was wrong, please let me know, and I think we can at least improve the doc since it is not that easy to understand.
Thanks. :)
> > 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 >> > >
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