linux-kernel - Re: [PATCH 1/2] x86, mce, therm_throt: Optimize logging of thermal throttle messages

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Message-ID: <20191015084833.GD2311@hirez.programming.kicks-ass.net>
Date:   Tue, 15 Oct 2019 10:48:33 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     tony.luck@...el.com, bp@...en8.de, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, bberg@...hat.com, x86@...nel.org,
        linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
        hdegoede@...hat.com, ckellner@...hat.com
Subject: Re: [PATCH 1/2] x86, mce, therm_throt: Optimize logging of thermal
 throttle messages

On Mon, Oct 14, 2019 at 02:21:00PM -0700, Srinivas Pandruvada wrote:
> Some modern systems have very tight thermal tolerances. Because of this
> they may cross thermal thresholds when running normal workloads (even
> during boot). The CPU hardware will react by limiting power/frequency
> and using duty cycles to bring the temperature back into normal range.
> 
> Thus users may see a "critical" message about the "temperature above
> threshold" which is soon followed by "temperature/speed normal". These
> messages are rate limited, but still may repeat every few minutes.
> 
> The solution here is to set a timeout when the temperature first exceeds
> the threshold.

Why can we even reach critical thresholds when the fans are working? I
always thought it was BAD to ever reach the critical temps and have the
hardware throttle.