From: Borislav Petkov <bp@alien8.de>
To: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: tony.luck@intel.com, tglx@linutronix.de, mingo@redhat.com,
hpa@zytor.com, bberg@redhat.com, x86@kernel.org,
linux-edac@vger.kernel.org, linux-kernel@vger.kernel.org,
hdegoede@redhat.com, ckellner@redhat.com
Subject: Re: [PATCH 1/2] x86, mce, therm_throt: Optimize logging of thermal throttle messages
Date: Mon, 14 Oct 2019 23:36:18 +0200 [thread overview]
Message-ID: <20191014213618.GK4715@zn.tnic> (raw)
In-Reply-To: <20191014212101.25719-1-srinivas.pandruvada@linux.intel.com>
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. If the CPU returns to normal before the timeout fires,
> we skip printing any messages. If we reach the timeout, then there may be
> a real thermal issue (e.g. inoperative or blocked fan) and we print the
> message (together with a count of how many thermal events have occurred).
> A rate control method is used to avoid printing repeatedly on these broken
> systems.
>
> Some experimentation with fans enabled showed that temperature returned
> to normal on a laptop in ~4 seconds. With fans disabled it took over 10
> seconds. Default timeout is thus set to 8 seconds, but may be changed
> with kernel boot parameter: "x86_therm_warn_delay". This default interval
> is twice of typical sampling interval for cooling using running average
> power limit from user space thermal control softwares.
>
> In addition a new sysfs attribute is added to show what is the maximum
> amount of time in miili-seconds the system was in throttled state. This
> will allow to change x86_therm_warn_delay, if required.
This description is already *begging* for this delay value to be
automatically set by the kernel. Putting yet another knob in front of
the user who doesn't have a clue most of the time shows one more time
that we haven't done our job properly by asking her to know what we
already do.
IOW, a simple history feedback mechanism which sets the timeout based on
the last couple of values is much smarter. The thing would have a max
value, of course, which, when exceeded should mean an anomaly, etc, but
almost anything else is better than merely asking the user to make an
educated guess.
> Suggested-by: Alan Cox <alan@linux.intel.com>
> Commit-comment-by: Tony Luck <tony.luck@intel.com>
^^^^^^^^^^^^^^^^^^
What's that?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2019-10-14 21:36 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <2c2b65c23be3064504566c5f621c1f37bf7e7326.camel@redhat.com>
2019-10-14 21:21 ` [PATCH 1/2] x86, mce, therm_throt: Optimize logging of thermal throttle messages Srinivas Pandruvada
2019-10-14 21:21 ` [PATCH 2/2] x86, mce: Add additional kernel boot parameter Srinivas Pandruvada
2019-10-14 21:36 ` Borislav Petkov [this message]
2019-10-14 22:27 ` [PATCH 1/2] x86, mce, therm_throt: Optimize logging of thermal throttle messages Luck, Tony
2019-10-15 8:36 ` Borislav Petkov
2019-10-15 8:52 ` Peter Zijlstra
2019-10-15 13:43 ` Srinivas Pandruvada
2019-10-14 22:41 ` Srinivas Pandruvada
2019-10-15 8:46 ` Borislav Petkov
2019-10-15 14:01 ` Srinivas Pandruvada
2019-10-15 8:48 ` Peter Zijlstra
2019-10-15 13:31 ` Srinivas Pandruvada
2019-10-16 8:14 ` Peter Zijlstra
2019-10-16 14:00 ` Borislav Petkov
2019-10-17 21:31 ` Luck, Tony
2019-10-17 21:44 ` Borislav Petkov
2019-10-17 23:53 ` Luck, Tony
2019-10-18 6:46 ` Borislav Petkov
2019-10-18 7:17 ` Peter Zijlstra
2019-10-18 12:26 ` Srinivas Pandruvada
2019-10-18 13:23 ` Borislav Petkov
2019-10-18 15:55 ` Srinivas Pandruvada
2019-10-18 19:40 ` Borislav Petkov
2019-10-18 18:02 ` Luck, Tony
2019-10-18 19:45 ` Borislav Petkov
2019-10-18 20:38 ` Luck, Tony
2019-10-19 8:10 ` Borislav Petkov
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