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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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