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    SubjectRe: [PATCHv2 0/9] split page table lock for PMD tables
    On Mon, Sep 16, 2013 at 02:25:31PM +0300, Kirill A. Shutemov wrote:
    > Alex Thorlton noticed that some massivly threaded workloads work poorly,
    > if THP enabled. This patchset fixes this by introducing split page table
    > lock for PMD tables. hugetlbfs is not covered yet.
    >
    > This patchset is based on work by Naoya Horiguchi.
    >
    > Changes:
    > v2:
    > - reuse CONFIG_SPLIT_PTLOCK_CPUS for PMD split lock;
    > - s/huge_pmd_lock/pmd_lock/g;
    > - assume pgtable_pmd_page_ctor() can fail;
    > - fix format line in task_mem() for VmPTE;
    >
    > Benchmark (from Alex): ftp://shell.sgi.com/collect/appsx_test/pthread_test.tar.gz
    > Run on 4 socket Westmere with 128 GiB of RAM.

    Kirill,

    I'm hitting some performance issues with these patches on our larger
    machines (>=128 cores/256 threads). I've managed to livelock larger
    systems with one of our tests (I'll publish this one soon), and I'm
    actually seeing a performance hit on some of the smaller ones. I'm
    currently collecting some results to show the problems I'm hitting,
    and trying to research what's causing the livelock. For now I just
    wanted to let you know that I'm seeing some issues. I'll be in touch
    with more details.

    Sorry for the delayed response, I wanted to be really sure that I was
    seeing problems before I put up a red flag.

    - Alex


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