From nobody Sun May 10 18:33:28 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 25017C433EF for ; Wed, 27 Apr 2022 07:36:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1358929AbiD0Hj3 (ORCPT ); Wed, 27 Apr 2022 03:39:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46532 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1358913AbiD0HjW (ORCPT ); Wed, 27 Apr 2022 03:39:22 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id C66C59AE65 for ; Wed, 27 Apr 2022 00:36:09 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9E8D4ED1; Wed, 27 Apr 2022 00:36:08 -0700 (PDT) Received: from e123648.arm.com (unknown [10.57.7.196]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 80B7F3F774; Wed, 27 Apr 2022 00:36:06 -0700 (PDT) From: Lukasz Luba To: linux-kernel@vger.kernel.org Cc: sudeep.holla@arm.com, dietmar.eggemann@arm.com, vincent.guittot@linaro.org, gregkh@linuxfoundation.org, rafael@kernel.org, rostedt@goodmis.org, mingo@redhat.com, lukasz.luba@arm.com Subject: [PATCH v3] arch_topology: Trace the update thermal pressure Date: Wed, 27 Apr 2022 08:35:51 +0100 Message-Id: <20220427073551.19032-1-lukasz.luba@arm.com> X-Mailer: git-send-email 2.17.1 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Add trace event to capture the moment of the call for updating the thermal pressure value. It's helpful to investigate how often those events occur in a system dealing with throttling. This trace event is needed since the old 'cdev_update' might not be used by some drivers. The old 'cdev_update' trace event only provides a cooling state value: [0, n]. That state value then needs additional tools to translate it: state -> freq -> capacity -> thermal pressure. This new trace event just stores proper thermal pressure value in the trace buffer, no need for additional logic. This is helpful for cooperation when someone can simply sends to the list the trace buffer output from the platform (no need from additional information from other subsystems). There are also platforms which due to some design reasons don't use cooling devices and thus don't trigger old 'cdev_update' trace event. They are also important and measuring latency for the thermal signal raising/decaying characteristics is in scope. This new trace event would cover them as well. We already have a trace point 'pelt_thermal_tp' which after a change to trace event can be paired with this new 'thermal_pressure_update' and derive more insight what is going on in the system under thermal pressure (and why). Reported-by: kernel test robot Signed-off-by: Lukasz Luba --- Changes in v3: - extended explanation in the changelog following Greg's comment The v2 is here: https://lore.kernel.org/lkml/20220425135317.5880-1-lukasz.luba@arm.com/ The v1 and discussion can be found here at: https://lore.kernel.org/lkml/20220419164801.29078-1-lukasz.luba@arm.com/ Regards, Lukasz drivers/base/arch_topology.c | 5 +++++ include/trace/events/thermal_pressure.h | 29 +++++++++++++++++++++++++ 2 files changed, 34 insertions(+) create mode 100644 include/trace/events/thermal_pressure.h diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c index f73b836047cf..579c851a2bd7 100644 --- a/drivers/base/arch_topology.c +++ b/drivers/base/arch_topology.c @@ -19,6 +19,9 @@ #include #include =20 +#define CREATE_TRACE_POINTS +#include + static DEFINE_PER_CPU(struct scale_freq_data __rcu *, sft_data); static struct cpumask scale_freq_counters_mask; static bool scale_freq_invariant; @@ -195,6 +198,8 @@ void topology_update_thermal_pressure(const struct cpum= ask *cpus, =20 th_pressure =3D max_capacity - capacity; =20 + trace_thermal_pressure_update(cpu, th_pressure); + for_each_cpu(cpu, cpus) WRITE_ONCE(per_cpu(thermal_pressure, cpu), th_pressure); } diff --git a/include/trace/events/thermal_pressure.h b/include/trace/events= /thermal_pressure.h new file mode 100644 index 000000000000..b68680201360 --- /dev/null +++ b/include/trace/events/thermal_pressure.h @@ -0,0 +1,29 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM thermal_pressure + +#if !defined(_TRACE_THERMAL_PRESSURE_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_THERMAL_PRESSURE_H + +#include + +TRACE_EVENT(thermal_pressure_update, + TP_PROTO(int cpu, unsigned long thermal_pressure), + TP_ARGS(cpu, thermal_pressure), + + TP_STRUCT__entry( + __field(unsigned long, thermal_pressure) + __field(int, cpu) + ), + + TP_fast_assign( + __entry->thermal_pressure =3D thermal_pressure; + __entry->cpu =3D cpu; + ), + + TP_printk("cpu=3D%d thermal_pressure=3D%lu", __entry->cpu, __entry->therm= al_pressure) +); +#endif /* _TRACE_THERMAL_PRESSURE_H */ + +/* This part must be outside protection */ +#include --=20 2.17.1