linux-kernel - Re: [PATCH 3/3] x86/mce/therm_throt: allow disabling the thermal vector altogether

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Date:   Mon, 13 Apr 2020 20:38:12 -0700
From:   Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>,
        linux-kernel@...r.kernel.org, linux-edac@...r.kernel.org,
        x86@...nel.org, arnd@...db.de, bberg@...hat.com, bp@...e.de
Subject: Re: [PATCH 3/3] x86/mce/therm_throt: allow disabling the thermal
 vector altogether

On Tue, 2020-04-07 at 00:33 -0600, Jason A. Donenfeld wrote:
> The thermal IRQ handler uses 1.21% CPU on my system when it's hot
> from
> compiling things. Indeed looking at /proc/interrupts reveals quite a
> lot
I am curious why you are hitting threshold frequently?
What is rdmsr 0x1a2


> of events coming in. Beyond logging them, the existing drivers on the
> system don't appear to do very much that I'm interested in. So, add a
> way to disable this entirely so that I can regain precious CPU
> cycles.
It is showing amount of time system is running in a constrained
environment. Lots of real time and HPC folks really care about this.

Thanks,
Srinivas

> 
> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
> ---
>  arch/x86/Kconfig                | 4 ++++
>  arch/x86/kernel/cpu/mce/intel.c | 3 ++-
>  2 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 39e7444353af..3125a11932f2 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1157,7 +1157,11 @@ config X86_MCE_INJECT
>  
>  config X86_THERMAL_VECTOR
>  	def_bool y
> +	prompt "Machine check thermal vector"
>  	depends on X86_MCE_INTEL
> +	---help---
> +	  Provide support for capturing thermal events, logging them,
> and
> +	  passing them off to other drivers.
>  
>  config X86_MCE_THERMAL_VERBOSE
>  	bool "Verbose logging for thermal events"
> diff --git a/arch/x86/kernel/cpu/mce/intel.c
> b/arch/x86/kernel/cpu/mce/intel.c
> index f996ffb887bc..d14f1922fb49 100644
> --- a/arch/x86/kernel/cpu/mce/intel.c
> +++ b/arch/x86/kernel/cpu/mce/intel.c
> @@ -511,7 +511,8 @@ static void intel_ppin_init(struct cpuinfo_x86
> *c)
>  
>  void mce_intel_feature_init(struct cpuinfo_x86 *c)
>  {
> -	intel_init_thermal(c);
> +	if (IS_ENABLED(CONFIG_X86_THERMAL_VECTOR))
> +		intel_init_thermal(c);
>  	intel_init_cmci();
>  	intel_init_lmce();
>  	intel_ppin_init(c);