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    SubjectRe: REGRESSION: Performance regressions from switching anon_vma->lock to mutex
    On Wed, 2011-06-15 at 18:50 -0700, Linus Torvalds wrote:

    > Tim, have you tried running your bigger load with that patch? You
    > could try my patch on top too just to match Peter's tree, but I doubt
    > that's the big first-order issue.
    > Linus

    I ran exim with different kernel versions. Using 2.6.39-vanilla
    kernel as a baseline, the results are as follow:

    2.6.39(vanilla) 100.0%
    2.6.39+ra-patch 166.7% (+66.7%) (note: tmpfs readahead patchset is merged in 3.0-rc2)
    3.0-rc2(vanilla) 68.0% (-32%)
    3.0-rc2+linus 115.7% (+15.7%)
    3.0-rc2+linus+softirq 86.2% (-17.3%)

    So Linus' patch certainly helped things over vanilla 3.0-rc2, but throughput is still
    less than the 2.6.39 with the readahead patch set. The softirq patch I used was from Ingo's
    combined patch from Shaohua and Paul. It seems odd that it makes things worse. I will
    recheck this data probably just this patch and without Linus' patch later.

    I also notice that the run to run variations have increased quite a bit for 3.0-rc2.
    I'm using 6 runs per kernel. Perhaps a side effect of converting the anon_vma->lock to mutex?

    2.6.39(vanilla) 3%
    2.6.39+ra-patch 3%
    3.0-rc2(vanilla) 20%
    3.0-rc2+linus 36%
    3.0-rc2+linus+softirq 40%



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