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    SubjectRe: [Bug #14141] order 2 page allocation failures in iwlagn
    On Monday 26 October 2009, Frans Pop wrote:
    > On Tuesday 20 October 2009, Mel Gorman wrote:
    > > I've attached a patch below that should allow us to cheat. When it's
    > > applied, it outputs who called congestion_wait(), how long the timeout
    > > was and how long it waited for. By comparing before and after sleep
    > > times, we should be able to see which of the callers has significantly
    > > changed and if it's something easily addressable.
    > The results from this look fairly interesting (although I may be a bad
    > judge as I don't really know what I'm looking at ;-).
    > I've tested with two kernels:
    > 1) 1 test run
    > 2) + congestion_wait() reverts: 2 test runs

    I've taken another look at the data from this debug patch, resulting in
    these graphs:

    I think the graph may show the reason for the congestion_wait() regression.
    Horizontal axis shows time, vertical axis shows number of logged
    congestion_wait calls per type.

    The top chart is without the revert, the bottom one after the revert.

    Note how before the revert the graph shows distinct steps: first you get
    almost exclusively kwapd, followed by almost exclusively alloc_pages and
    try_to_free. I suspect the periods where kswapd is almost horizontal
    correspond to the freezes.

    With the revert the lines for the different functions are almost straight
    and everything happens much better interspersed.


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      Last update: 2009-11-05 21:17    [W:0.019 / U:12.588 seconds]
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