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    SubjectRe: [patch 2/3] mm, oom: remove unnecessary check for NULL zonelist
    On Fri, 1 Aug 2014, Johannes Weiner wrote:

    > > > out_of_memory() wants the zonelist that was used during allocation,
    > > > not just the random first node's zonelist that's simply picked to
    > > > serialize page fault OOM kills system-wide.
    > > >
    > > > This would even change how panic_on_oom behaves for page fault OOMs
    > > > (in a completely unpredictable way) if we get CONSTRAINED_CPUSET.
    > > >
    > > > This change makes no sense to me.
    > > >
    > >
    > > Allocations during fault will be constrained by the cpuset's mems, if we
    > > are oom then why would we panic when panic_on_oom == 1?
    >
    > Can you please address the concerns I raised?
    >

    I see one concern: that panic_on_oom == 1 will not trigger on pagefault
    when constrained by cpusets. To address that, I'll state that, since
    cpuset-constrained allocations are the allocation context for pagefaults,
    panic_on_oom == 1 should not trigger on pagefault when constrained by
    cpusets.

    > And please describe user-visible changes in the changelog.
    >

    Ok, Andrew please annotate the changelog for
    mm-oom-remove-unnecessary-check-for-null-zonelist.patch by including:

    This also causes panic_on_oom == 1 to not panic the machine when the
    pagefault is constrained by the mems of current's cpuset. That behavior
    agrees with the semantics of the sysctl in Documentation/sysctl/vm.txt.


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