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 11:23:13 +0100
From:	Tim Blechmann <tim@...ngt.org>
To:	Robert Richter <robert.richter@....com>
Cc:	oprofile-list@...ts.sf.net, linux-kernel@...r.kernel.org
Subject: Re: 2.6.29-rc4 regression (was: Re: 2.6.28-rc9: oprofile
 regression)

> 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


this tweak did not work on later kernels, that i tested, though, and i 
haven't had time to look into it in more detail.

tim

-- 
tim@...ngt.org
http://tim.klingt.org

Linux is like a wigwam: no windows, no gates, apache inside, stable.
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