linux-kernel - Re: [PATCH v3 0/2] Replace trace_cpu_frequency with trace_policy

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Message-ID: <inifvm4pxifvdazsfyi2ppzfwum6ukzujx5sfiux4s2iv55z4p@otoaj35vr47c>
Date: Tue, 2 Dec 2025 12:13:37 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Samuel Wu <wusamuel@...gle.com>
Cc: Huang Rui <ray.huang@....com>, 
	"Gautham R. Shenoy" <gautham.shenoy@....com>, Mario Limonciello <mario.limonciello@....com>, 
	Perry Yuan <perry.yuan@....com>, Jonathan Corbet <corbet@....net>, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Steven Rostedt <rostedt@...dmis.org>, 
	Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>, Len Brown <lenb@...nel.org>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, 
	Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	James Clark <james.clark@...aro.org>, christian.loehle@....com, kernel-team@...roid.com, 
	linux-pm@...r.kernel.org, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org, bpf@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v3 0/2] Replace trace_cpu_frequency with
 trace_policy_frequency

On 01-12-25, 12:24, Samuel Wu wrote:
> This series replaces the cpu_frequency trace event with a new trace event,
> policy_frequency. Since by definition all CPUs in a policy are of the same
> frequency, we can emit a frequency change per policy instead of per CPU.
> This saves some compute and memory from the kernel side, while simplifying
> analysis from the post-processing of the trace log side.
> 
> Any process that relied on cpu_frequency trace event needs to switch to the
> new policy_frequency trace event in order to maintain functionality. The
> decision of replacing instead of adding the trace event is intentional. Since
> emitting once per policy instead of once per CPU is anyways a semantics change
> that would require a tooling update, the trace event was also appropriately
> renamed. The presence of the policy_frequency event in a trace log is a clear
> and obvious signal for tooling to determine kernel version and which trace
> event to parse.
> 
> 1/2: Replaces trace_cpu_frequency with trace_policy_frequency
> 2/2: Corresponding documentation patch that updates references to
>      cpu_frequency with policy_frequency
> 
> Changes in v3:
> - Resending v2 properly (accidentally ommited cover letter in v2)
> 
> Changes in v2:
> - Replaced trace_cpu_frequency with trace_policy_frequency (per Christian
>   and Viresh)
> - Updated references to cpu_frequency in documentation with
>   policy_frequency
> - v1 link: https://lore.kernel.org/all/20251112235154.2974902-1-wusamuel@google.com
> 
> Samuel Wu (2):
>   cpufreq: Replace trace_cpu_frequency with trace_policy_frequency
>   cpufreq: Documentation update for trace_policy_frequency
> 
>  Documentation/admin-guide/pm/amd-pstate.rst   | 10 ++++----
>  Documentation/admin-guide/pm/intel_pstate.rst | 14 +++++------
>  Documentation/trace/events-power.rst          |  2 +-
>  drivers/cpufreq/cpufreq.c                     | 14 ++---------
>  drivers/cpufreq/intel_pstate.c                |  6 +++--
>  include/trace/events/power.h                  | 24 ++++++++++++++++---
>  kernel/trace/power-traces.c                   |  2 +-
>  samples/bpf/cpustat_kern.c                    |  8 +++----
>  samples/bpf/cpustat_user.c                    |  6 ++---
>  tools/perf/builtin-timechart.c                | 12 +++++-----
>  10 files changed, 54 insertions(+), 44 deletions(-)

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh