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Groups > linux.kernel > #1561435

Re: [RFC 3/4] mm, page_alloc: move cpuset seqcount checking to slowpath

From Vlastimil Babka <vbabka@suse.cz>
Newsgroups linux.kernel
Subject Re: [RFC 3/4] mm, page_alloc: move cpuset seqcount checking to slowpath
Date 2017-01-18 11:10 +0100
Message-ID <t0VlN-2Ex-23@gated-at.bofh.it> (permalink)
References <t0LZ8-5nf-33@gated-at.bofh.it> <t0M8O-5qs-7@gated-at.bofh.it> <t0VlM-2Ex-13@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On 01/18/2017 10:40 AM, Michal Hocko wrote:
> On Tue 17-01-17 23:16:09, Vlastimil Babka wrote:
>> This is a preparation for the following patch to make review simpler. While
>> the primary motivation is a bug fix, this could also save some cycles in the
>> fast path.
>
> I cannot say I would be happy about this patch :/ The code is still very
> confusing and subtle. I really think we should get rid of
> synchronization with the concurrent cpuset/mempolicy updates instead.
> Have you considered that instead?

Not so thoroughly yet, but I already suspect it would be intrusive for stable. 
We could make copies of nodemask and mems_allowed and protect just the copying 
with seqcount, but that would mean overhead and stack space. Also we might try 
revert 682a3385e773 ("mm, page_alloc: inline the fast path of the zonelist 
iterator") ...

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Thread

[RFC 0/4] fix premature OOM due to cpuset races Vlastimil Babka <vbabka@suse.cz> - 2017-01-18 01:10 +0100
  [RFC 4/4] mm, page_alloc: fix premature OOM when racing with cpuset mems update Vlastimil Babka <vbabka@suse.cz> - 2017-01-18 01:10 +0100
    Re: [RFC 4/4] mm, page_alloc: fix premature OOM when racing with cpuset mems update "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2017-01-18 08:20 +0100
      Re: [RFC 4/4] mm, page_alloc: fix premature OOM when racing with  cpuset mems update Vlastimil Babka <vbabka@suse.cz> - 2017-01-18 10:40 +0100
    Re: [RFC 4/4] mm, page_alloc: fix premature OOM when racing with  cpuset mems update Mel Gorman <mgorman@techsingularity.net> - 2017-01-18 11:20 +0100
  [RFC 3/4] mm, page_alloc: move cpuset seqcount checking to slowpath Vlastimil Babka <vbabka@suse.cz> - 2017-01-18 01:20 +0100
    Re: [RFC 3/4] mm, page_alloc: move cpuset seqcount checking to slowpath "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2017-01-18 08:40 +0100
      Re: [RFC 3/4] mm, page_alloc: move cpuset seqcount checking to  slowpath Vlastimil Babka <vbabka@suse.cz> - 2017-01-18 10:30 +0100
    Re: [RFC 3/4] mm, page_alloc: move cpuset seqcount checking to  slowpath Mel Gorman <mgorman@techsingularity.net> - 2017-01-18 11:10 +0100
    Re: [RFC 3/4] mm, page_alloc: move cpuset seqcount checking to  slowpath Michal Hocko <mhocko@kernel.org> - 2017-01-18 11:10 +0100
      Re: [RFC 3/4] mm, page_alloc: move cpuset seqcount checking to  slowpath Vlastimil Babka <vbabka@suse.cz> - 2017-01-18 11:10 +0100
        Re: [RFC 3/4] mm, page_alloc: move cpuset seqcount checking to  slowpath Michal Hocko <mhocko@kernel.org> - 2017-01-18 11:20 +0100
  [RFC 2/4] mm, page_alloc: fix fast-path race with cpuset update or removal Vlastimil Babka <vbabka@suse.cz> - 2017-01-18 01:20 +0100
    Re: [RFC 2/4] mm, page_alloc: fix fast-path race with cpuset update  or removal Michal Hocko <mhocko@kernel.org> - 2017-01-18 10:40 +0100
    Re: [RFC 2/4] mm, page_alloc: fix fast-path race with cpuset update  or removal Mel Gorman <mgorman@techsingularity.net> - 2017-01-18 10:50 +0100
  Re: [RFC 0/4] fix premature OOM due to cpuset races Michal Hocko <mhocko@kernel.org> - 2017-01-18 10:40 +0100
  [RFC 5/4] mm, page_alloc: fix premature OOM due to vma mempolicy  update Vlastimil Babka <vbabka@suse.cz> - 2017-01-18 17:30 +0100
    Re: [RFC 5/4] mm, page_alloc: fix premature OOM due to vma mempolicy  update Vlastimil Babka <vbabka@suse.cz> - 2017-01-18 17:30 +0100

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