Messages in this thread | | | Date | Fri, 14 Nov 2008 18:21:21 +0100 | From | Eric Dumazet <> | Subject | Re: Oprofile : need to adjust PC by 16 bytes |
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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]); > > } > > } > > > > --
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