x86, mce, therm_throt: Optimize notifications of thermal throttle

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.

This issue became worse starting with the Ivy Bridge generation of
CPUs because they include a TCC activation offset in the MSR
IA32_TEMPERATURE_TARGET. OEMs use this to provide alerts long before
critical temperatures are reached.

A test run on a laptop with Intel 8th Gen i5 core for two hours with a
workload resulted in 20K+ thermal interrupts per CPU for core level and
another 20K+ interrupts at package level. The kernel logs were full of
throttling messages.

The real value of these threshold interrupts, is to debug problems with
the external cooling solutions and performance issues due to excessive
throttling.

So the solution here is the following:
- In the current thermal_throttle folder, show the maximum time for one
throttling event and total amount of time, the system was in throttling
state.
- Do not log short excursions.
- Log only when, in spite of thermal throttling the temperature is rising.
On the high threshold interrupt trigger a delayed workqueue, that
monitors the threshold violation log bit (THERM_STATUS_PROCHOT_LOG). When
the log bit is set, this workqueue callback calculates three point moving
average and logs warning message when the temperature trend is rising.
When this log bit is clear and temperature is below threshold temperature,
then the workqueue callback logs "Normal" message". Once a high threshold
event is logged, the logging is rate limited.

With this patch, on the same test laptop, no warnings are printed in logs
as the max time the processor could bring the temperature under control is
only 280 ms.

This implementation is done with the inputs from Alan Cox and Tony Luck.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
---

Version History:
v1:
Changes compared to RFC PATCH:
	Addressed comments from Boris
	Rebased to tip/master
	Added kenrel doc for struct
	Edits to the commit description
	Optimize storage for _thermal_state
	Ignore invalid sample for threshold high

 arch/x86/kernel/cpu/mce/therm_throt.c | 251 +++++++++++++++++++++++---
 1 file changed, 227 insertions(+), 24 deletions(-)

Message ID	20191111214312.81365-1-srinivas.pandruvada@linux.intel.com (mailing list archive)
State	New, archived
Headers	show Return-Path: <SRS0=Epe3=ZD=vger.kernel.org=linux-edac-owner@kernel.org> Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id CDF1415AB for <patchwork-linux-edac@patchwork.kernel.org>; Mon, 11 Nov 2019 21:43:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A40262184C for <patchwork-linux-edac@patchwork.kernel.org>; Mon, 11 Nov 2019 21:43:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727012AbfKKVni (ORCPT <rfc822;patchwork-linux-edac@patchwork.kernel.org>); Mon, 11 Nov 2019 16:43:38 -0500 Received: from mga07.intel.com ([134.134.136.100]:33174 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727001AbfKKVni (ORCPT <rfc822;linux-edac@vger.kernel.org>); Mon, 11 Nov 2019 16:43:38 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 11 Nov 2019 13:43:36 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,293,1569308400"; d="scan'208";a="202186945" Received: from spandruv-desk.jf.intel.com ([10.54.75.31]) by fmsmga008.fm.intel.com with ESMTP; 11 Nov 2019 13:43:35 -0800 From: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> To: tony.luck@intel.com, bp@alien8.de, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, bberg@redhat.com Cc: x86@kernel.org, linux-edac@vger.kernel.org, linux-kernel@vger.kernel.org, hdegoede@redhat.com, ckellner@redhat.com, Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Subject: [PATCH] x86, mce, therm_throt: Optimize notifications of thermal throttle Date: Mon, 11 Nov 2019 13:43:12 -0800 Message-Id: <20191111214312.81365-1-srinivas.pandruvada@linux.intel.com> X-Mailer: git-send-email 2.17.2 Sender: linux-edac-owner@vger.kernel.org Precedence: bulk List-ID: <linux-edac.vger.kernel.org> X-Mailing-List: linux-edac@vger.kernel.org
Series	x86, mce, therm_throt: Optimize notifications of thermal throttle \| expand x86, mce, therm_throt: Optimize notifications of thermal throttle

x86, mce, therm_throt: Optimize notifications of thermal throttle

Commit Message

Comments

Patch