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    SubjectRe: CONFIG_NO_HZ breaks blktrace timestamps
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    On Thu, 2008-01-10 at 23:44 +0100, Guillaume Chazarain wrote:
    > David Dillow <dillowda@ornl.gov> wrote:
    >
    > > At the moment, I'm not sure how to track this farther, or how to fix it
    > > properly. Any advice would be appreciated.
    >
    > Just out of curiosity, could you try the appended cumulative patch and
    > report .clock_warps, .clock_overflows and .clock_underflows as you did.

    With those patches, CONFIG_NO_HZ works just fine.

    Patched kernel, nohz=off:
    now at 214257.820809 msecs
    .clock : 214212.727559
    .idle_clock : 0.000000
    .prev_clock_raw : 244569.402345
    .clock_warps : 0
    .clock_overflows : 577
    .clock_underflows : 213887
    .clock_deep_idle_events : 4
    .clock_max_delta : 0.999830

    Patched kernel, nohz=on:
    now at 248931.524381 msecs
    .clock : 248745.808465
    .idle_clock : 0.000000
    .prev_clock_raw : 270911.098507
    .clock_warps : 0
    .clock_overflows : 69
    .clock_underflows : 784
    .clock_deep_idle_events : 4
    .clock_max_delta : 100.639397

    Running my disk test, blktrace is getting the proper timestamps now with
    CONFIG_NO_HZ.

    Thanks!
    --
    Dave Dillow
    National Center for Computational Science
    Oak Ridge National Laboratory
    (865) 241-6602 office



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