lkml.org 
[lkml]   [2008]   [Nov]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Oprofile : need to adjust PC by 16 bytes
Mikael Pettersson a écrit :
> Eric Dumazet writes:
> > Very strange results on my Intel E5450 CPU
> >
> > I found that I have to bias regs->ip by 16 bytes in order to have
> > correct profiling.
> >
> > Does it rings a bell to anyone ?
>
> The term is "skid". All OO processors are susceptible to it,
> as was known already to the Alpha "continous profiling"
> performance counter folks.

Cool. Maybe this can explain the other bug I have with oprofile.

>
> And no, blindly subtracting 16 from IP is not a fix.

Who mentioned a fix ? I am only giving more fuel to Intel guys so they
hopefully can give us a working oprofile.


>
> >
> > opcontrol --version
> > opcontrol: oprofile 0.9.4 compiled on Nov 3 2008 06:45:57
> >
> > Thank you
> >
> > diff --git a/arch/x86/oprofile/op_model_ppro.c b/arch/x86/oprofile/op_model_ppro.c
> > index 3f1b81a..051fb16 100644
> > --- a/arch/x86/oprofile/op_model_ppro.c
> > +++ b/arch/x86/oprofile/op_model_ppro.c
> > @@ -131,7 +131,9 @@ static int ppro_check_ctrs(struct pt_regs * const regs,
> > continue;
> > rdmsrl(msrs->counters[i].addr, val);
> > if (CTR_OVERFLOWED(val)) {
> > + regs->ip -= 0x10;
> > oprofile_add_sample(regs, i);
> > + regs->ip += 0x10;
> > wrmsrl(msrs->counters[i].addr, -reset_value[i]);
> > }
> > }
> >
> > --


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2008-11-14 18:25    [from the cache]
©2003-2011 Jasper Spaans