linux-kernel - Re: 2.6.29-rc4 regression (was: Re: 2.6.28-rc9: oprofile regression)

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Date:	Mon, 16 Feb 2009 12:40:10 +0100
From:	Robert Richter <robert.richter@....com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	oprofile-list@...ts.sf.net, linux-kernel@...r.kernel.org,
	Tim Blechmann <tim@...ngt.org>
Subject: Re: 2.6.29-rc4 regression (was: Re: 2.6.28-rc9: oprofile
	regression)

On 16.02.09 11:23:13, Tim Blechmann wrote:
> > still, I can not reproduce this with my tests with v2.6.29-rc4. The
> > regression on the systems I have runs fine on rc4. On the system you
> > have, is commit b99170288421c79f0c2efa8b33e26e65f4bb7fb8 the first bad
> > one? If so, I will split the patch into smaller pieces to find the
> > change that introduces the bug.
> 
> i got revision df13b31c286b3e91c556167954eda088d90a4295 working, by not
> resetting the counter width:
> 
> diff --git a/arch/x86/oprofile/op_model_ppro.c b/arch/x86/oprofile/op_model_ppro.c
> index 12e207a..f0e019d 100644
> --- a/arch/x86/oprofile/op_model_ppro.c
> +++ b/arch/x86/oprofile/op_model_ppro.c
> @@ -76,12 +76,14 @@ static void ppro_setup_ctrs(struct op_msrs const * const msrs)
>  			return;
>  	}
>  
> +#if 0
>  	if (cpu_has_arch_perfmon) {
>  		union cpuid10_eax eax;
>  		eax.full = cpuid_eax(0xa);
>  		if (counter_width < eax.split.bit_width)
>  			counter_width = eax.split.bit_width;
>  	}
> +#endif

Andi,

do you suggest a fix for this (disable arch_perfmon for already
implemented cpus, for all, or for this certain cpu)?

-Robert

-- 
Advanced Micro Devices, Inc.
Operating System Research Center
email: robert.richter@....com

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