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    SubjectRe: [patch 00/19] VM pageout scalability improvements
    Rik van Riel wrote:

    >On Fri, 04 Jan 2008 17:34:00 +0100
    >Andi Kleen <andi@firstfloor.org> wrote:
    >
    >
    >>Lee Schermerhorn <Lee.Schermerhorn@hp.com> writes:
    >>
    >>
    >>
    >>>We can easily [he says, glibly] reproduce the hang on the anon_vma lock
    >>>
    >>>
    >>Is that a NUMA platform? On non x86? Perhaps you just need queued spinlocks?
    >>
    >>
    >
    >I really think that the anon_vma and i_mmap_lock spinlock hangs are
    >due to the lack of queued spinlocks. Not because I have seen your
    >system hang, but because I've seen one of Larry's test systems here
    >hang in scary/amusing ways :)
    >
    Changing the anon_vma->lock into a rwlock_t helps because
    page_lock_anon_vma()
    can take it for read and thats where the contention is. However its the
    fact that under
    some tests, most of the pages are in vmas queued to one anon_vma that
    causes so much
    lock contention.


    >
    >With queued spinlocks the system should just slow down, not hang.
    >
    >
    >




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