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SubjectRe: CFS review

* Mike Galbraith <efault@gmx.de> wrote:

> > Thanks for the testing and the feedback, it's much appreciated! :-)
> > On what platform did you do your tests, and what .config did you use
> > (and could you please send me your .config)?
> >
> > Please also send me the output of this script:
> >
> > http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh
> >
> > (if the output is too large send it to me privately, or bzip2 -9
> > it.)
> >
> > Could you also please send the source code for the "l.c" and "lt.c"
> > apps you used for your testing so i can have a look. Thanks!
>
> I haven't been able to reproduce this with any combination of
> features, and massive_intr tweaked to his work/sleep cycle. I notice
> he's collecting stats though, and they look funky. Recompiling.

yeah, the posted numbers look most weird, but there's a complete lack of
any identification of test environment - so we'll need some more word
from Roman. Perhaps this was run on some really old box that does not
have a high-accuracy sched_clock()? The patch below should simulate that
scenario on 32-bit x86.

Ingo

Index: linux/arch/i386/kernel/tsc.c
===================================================================
--- linux.orig/arch/i386/kernel/tsc.c
+++ linux/arch/i386/kernel/tsc.c
@@ -110,7 +110,7 @@ unsigned long long native_sched_clock(vo
* very important for it to be as fast as the platform
* can achive it. )
*/
- if (unlikely(!tsc_enabled && !tsc_unstable))
+// if (unlikely(!tsc_enabled && !tsc_unstable))
/* No locking but a rare wrong value is not a big deal: */
return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);

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