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

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Date:   Tue, 14 Apr 2020 13:41:08 -0600
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, linux-edac@...r.kernel.org,
        X86 ML <x86@...nel.org>, Arnd Bergmann <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, Apr 14, 2020 at 8:45 AM Srinivas Pandruvada
<srinivas.pandruvada@...ux.intel.com> wrote:
>
> On Mon, 2020-04-13 at 22:21 -0600, Jason A. Donenfeld wrote:
> > On Mon, Apr 13, 2020 at 9:38 PM Srinivas Pandruvada
> > <srinivas.pandruvada@...ux.intel.com> wrote:
> > > 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
> >
> > 5640000
> You are getting too many interrupts at 95C. You should look at your
> cooling system.
>
> >
> > > > 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.
> >
> > Which is why this patch adds an option, not a full removal or
> > something. Real time and HPC people can keep their expensive
> > interrupt. Other people with different varieties of system
> > disable
> > it.
> Generally compile time flag is not desirable. If it is what required
> then we should have boot time flag something in lines of existing
> "int_pln_enable" option.

Generally it is desirable, and extremely common too. This thermal code
-- which mostly functions to print some messages into kmsg -- is very
verbose. This is not something I want to compile into smaller systems.
This is the reason why kconfig has options in the first place. I'm not
sure yet-another boottime flag makes sense for this.