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    SubjectRe: [PATCH 0/5] mm: support parallel free of memory
    On Fri, 24 Feb 2017 19:40:31 +0800 Aaron Lu <aaron.lu@intel.com> wrote:

    > For regular processes, the time taken in its exit() path to free its
    > used memory is not a problem. But there are heavy ones that consume
    > several Terabytes memory and the time taken to free its memory could
    > last more than ten minutes.
    >
    > To optimize this use case, a parallel free method is proposed here.
    > For detailed explanation, please refer to patch 2/5.
    >
    > I'm not sure if we need patch 4/5 which can avoid page accumulation
    > being interrupted in some case(patch description has more information).
    > My test case, which only deal with anon memory doesn't get any help out
    > of this of course. It can be safely dropped if it is deemed not useful.
    >
    > A test program that did a single malloc() of 320G memory is used to see
    > how useful the proposed parallel free solution is, the time calculated
    > is for the free() call. Test machine is a Haswell EX which has
    > 4nodes/72cores/144threads with 512G memory. All tests are done with THP
    > disabled.
    >
    > kernel time
    > v4.10 10.8s __2.8%
    > this patch(with default setting) 5.795s __5.8%

    Dumb question: why not do this in userspace, presumably as part of the
    malloc() library? malloc knows where all the memory is and should be
    able to kick off N threads to run around munmapping everything?

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