linux-kernel - Re: [PATCH 3/9] oprofile, perf, x86: introduce new functions to reserve perfctrs by index

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Date:	Sat, 20 Mar 2010 06:45:44 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Robert Richter <robert.richter@....com>
Cc:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	oprofile-list <oprofile-list@...ts.sourceforge.net>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 3/9] oprofile, perf, x86: introduce new functions to reserve perfctrs by index

Robert Richter <robert.richter@....com> writes:

> Current perfctr reservation code allocates single pmu msrs. The msr
> addresses may differ depending on the model and offset calculation is
> necessary. This can be easier implemented by reserving a counter by
> its index only.

Sorry reviewing old patch. This doesn't work for the fixed counters on intel,
which don't have a index (or rather they have a separate number space)

I had a old patch to fix the reservation for them (and a matching
patch to perf to use it).

How to resolve this?

-Andi

---

---
 arch/x86/kernel/cpu/perfctr-watchdog.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Index: linux-2.6.32-ak/arch/x86/kernel/cpu/perfctr-watchdog.c
===================================================================
--- linux-2.6.32-ak.orig/arch/x86/kernel/cpu/perfctr-watchdog.c
+++ linux-2.6.32-ak/arch/x86/kernel/cpu/perfctr-watchdog.c
@@ -70,9 +70,13 @@ static inline unsigned int nmi_perfctr_m
 	case X86_VENDOR_AMD:
 		return msr - MSR_K7_PERFCTR0;
 	case X86_VENDOR_INTEL:
-		if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON))
+		if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON)) {
+			if (msr >= MSR_CORE_PERF_FIXED_CTR0 &&
+			    msr < MSR_CORE_PERF_FIXED_CTR0 + 8)
+				return NMI_MAX_COUNTER_BITS -
+						(msr - MSR_CORE_PERF_FIXED_CTR0);
 			return msr - MSR_ARCH_PERFMON_PERFCTR0;
-
+		}
 		switch (boot_cpu_data.x86) {
 		case 6:
 			return msr - MSR_P6_PERFCTR0;




-- 
ak@...ux.intel.com -- Speaking for myself only.
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