Re: [tip:perfcounters/core] perfcounters: IRQ and NMI support onAMD CPUs

[Robert Richter]

On 05.03.09 17:27:29, Peter Zijlstra wrote:
> Commit-ID:  b0f3f28e0f14eb335f67bfaae33ce8b8d74fd58b
> Gitweb:     http://git.kernel.org/tip/b0f3f28e0f14eb335f67bfaae33ce8b8d74fd58b
> Author:     "Peter Zijlstra" <a.p.zijlstra@xxxxxxxxx>
> AuthorDate: Thu, 5 Mar 2009 18:08:27 +0100
> Commit:     Ingo Molnar <mingo@xxxxxxx>
> CommitDate: Thu, 5 Mar 2009 18:25:16 +0100
> 
> perfcounters: IRQ and NMI support on AMD CPUs
> 
> The below completes the K7+ performance counter support:
> 
>  - IRQ support
>  - NMI support
> 
> KernelTop output works now as well.
> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> Cc: Jaswinder Singh Rajput <jaswinder@xxxxxxxxxx>
> Cc: Paul Mackerras <paulus@xxxxxxxxx>
> LKML-Reference: <1236273633.5187.286.camel@laptop>
> Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
> 
> 
> ---
>  arch/x86/kernel/cpu/perf_counter.c |  272 ++++++++++++++++++++++++++++++------
>  1 files changed, 228 insertions(+), 44 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
> index 3b65f19..6ebe9ab 100644
> --- a/arch/x86/kernel/cpu/perf_counter.c
> +++ b/arch/x86/kernel/cpu/perf_counter.c

[...]

> @@ -205,18 +243,24 @@ static u64 pmc_intel_save_disable_all(void)
>  
>  static u64 pmc_amd_save_disable_all(void)
>  {
> -	int idx;
> -	u64 val, ctrl = 0;
> +	struct cpu_hw_counters *cpuc = &__get_cpu_var(cpu_hw_counters);
> +	int enabled, idx;
> +
> +	enabled = cpuc->enabled;
> +	cpuc->enabled = 0;
> +	barrier();

Peter,

please add comments to all barrier()s you added to this file. Is it
sufficient in hw_perf_save_disable() to stop NMI's only on the current
core?

-Robert

>  
>  	for (idx = 0; idx < nr_counters_generic; idx++) {
> +		u64 val;
> +
>  		rdmsrl(MSR_K7_EVNTSEL0 + idx, val);
> -		if (val & ARCH_PERFMON_EVENTSEL0_ENABLE)
> -			ctrl |= (1 << idx);
> -		val &= ~ARCH_PERFMON_EVENTSEL0_ENABLE;
> -		wrmsrl(MSR_K7_EVNTSEL0 + idx, val);
> +		if (val & ARCH_PERFMON_EVENTSEL0_ENABLE) {
> +			val &= ~ARCH_PERFMON_EVENTSEL0_ENABLE;
> +			wrmsrl(MSR_K7_EVNTSEL0 + idx, val);
> +		}
>  	}
>  
> -	return ctrl;
> +	return enabled;
>  }
>  
>  u64 hw_perf_save_disable(void)

[...]

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

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