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    SubjectRe: [PATCH] anobjrmap 9 priority mjb tree
    On Fri, 9 Apr 2004, Martin J. Bligh wrote:
    > >> This slows down kernel compile a little, but worse, it slows down SDET
    > >> by about 25% (on the 16x). I think you did something horrible to sem
    > >> contention ... presumably i_shared_sem, which SDET was fighting with
    > >> as it was anyway ;-(
    > >>
    > >> Diffprofile shows:
    > >>
    > >> 122626 15.7% total
    > >> 44129 790.0% __down
    > >> 20988 4.1% default_idle
    >
    > I applied Andrew's high sophisticated proprietary semtrace technology.

    Thanks a lot, Martin, this seems pretty important.

    So, i_shared_sem, as you supposed.

    Do you still have the two profiles input to diffprofile?
    I wonder if they'd have clues to help us understand it better.

    Any chance of you doing the same comparison between 2.6.5-aa5
    2.6.5-aa5 minus prio-tree? (Well, needn't be -aa5, whatever comes to
    hand. Looks like "patch -p1 -R < prio-tree" mostly works, just some
    rejects in mm/mmap.c itself, let me know if I can help out on that.)

    If -aa is okay, I hope so, then it's surely some stupidity from me.

    We're not at all surprised that vma linking and unlinking should take
    rather longer; but the rise in __down, __wake_up, finish_task_switch
    is horrifying. Or is that how it usually looks, when a semaphore is
    well contended - thundering herd?

    Hugh

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