From: Samuel Wu <wusamuel@google.com>
To: Huang Rui <ray.huang@amd.com>,
"Gautham R. Shenoy" <gautham.shenoy@amd.com>,
Mario Limonciello <mario.limonciello@amd.com>,
Perry Yuan <perry.yuan@amd.com>,
Jonathan Corbet <corbet@lwn.net>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Viresh Kumar <viresh.kumar@linaro.org>,
Steven Rostedt <rostedt@goodmis.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
Len Brown <lenb@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@fomichev.me>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Ian Rogers <irogers@google.com>,
Adrian Hunter <adrian.hunter@intel.com>,
James Clark <james.clark@linaro.org>
Cc: christian.loehle@arm.com, Samuel Wu <wusamuel@google.com>,
kernel-team@android.com, linux-pm@vger.kernel.org,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org,
linux-perf-users@vger.kernel.org
Subject: [PATCH v2 1/2] cpufreq: Replace trace_cpu_frequency with trace_policy_frequency
Date: Mon, 1 Dec 2025 12:13:09 -0800 [thread overview]
Message-ID: <20251201201311.3746338-1-wusamuel@google.com> (raw)
The existing cpu_frequency trace_event can be verbose, emitting a nearly
identical trace event for every CPU in the policy even when their
frequencies are identical.
This patch replaces the cpu_frequency trace event with policy_frequency
trace event, a more efficient alternative. From the kernel's
perspective, emitting a trace event once per policy instead of once per
cpu saves some memory and is less overhead. From the post-processing
perspective, analysis of the trace log is simplified without any loss of
information.
Signed-off-by: Samuel Wu <wusamuel@google.com>
---
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 ++++++------
7 files changed, 41 insertions(+), 31 deletions(-)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 4472bb1ec83c..dd3f08f3b958 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -309,8 +309,6 @@ static void cpufreq_notify_transition(struct cpufreq_policy *policy,
struct cpufreq_freqs *freqs,
unsigned int state)
{
- int cpu;
-
BUG_ON(irqs_disabled());
if (cpufreq_disabled())
@@ -344,10 +342,7 @@ static void cpufreq_notify_transition(struct cpufreq_policy *policy,
adjust_jiffies(CPUFREQ_POSTCHANGE, freqs);
pr_debug("FREQ: %u - CPUs: %*pbl\n", freqs->new,
cpumask_pr_args(policy->cpus));
-
- for_each_cpu(cpu, policy->cpus)
- trace_cpu_frequency(freqs->new, cpu);
-
+ trace_policy_frequency(freqs->new, policy->cpu, policy->cpus);
srcu_notifier_call_chain(&cpufreq_transition_notifier_list,
CPUFREQ_POSTCHANGE, freqs);
@@ -2201,7 +2196,6 @@ unsigned int cpufreq_driver_fast_switch(struct cpufreq_policy *policy,
unsigned int target_freq)
{
unsigned int freq;
- int cpu;
target_freq = clamp_val(target_freq, policy->min, policy->max);
freq = cpufreq_driver->fast_switch(policy, target_freq);
@@ -2213,11 +2207,7 @@ unsigned int cpufreq_driver_fast_switch(struct cpufreq_policy *policy,
arch_set_freq_scale(policy->related_cpus, freq,
arch_scale_freq_ref(policy->cpu));
cpufreq_stats_record_transition(policy, freq);
-
- if (trace_cpu_frequency_enabled()) {
- for_each_cpu(cpu, policy->cpus)
- trace_cpu_frequency(freq, cpu);
- }
+ trace_policy_frequency(freq, policy->cpu, policy->cpus);
return freq;
}
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index ec4abe374573..9724b5d19d83 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2297,7 +2297,8 @@ static int hwp_get_cpu_scaling(int cpu)
static void intel_pstate_set_pstate(struct cpudata *cpu, int pstate)
{
- trace_cpu_frequency(pstate * cpu->pstate.scaling, cpu->cpu);
+ trace_policy_frequency(pstate * cpu->pstate.scaling, cpu->cpu,
+ cpumask_of(cpu->cpu));
cpu->pstate.current_pstate = pstate;
/*
* Generally, there is no guarantee that this code will always run on
@@ -2587,7 +2588,8 @@ static void intel_pstate_adjust_pstate(struct cpudata *cpu)
target_pstate = get_target_pstate(cpu);
target_pstate = intel_pstate_prepare_request(cpu, target_pstate);
- trace_cpu_frequency(target_pstate * cpu->pstate.scaling, cpu->cpu);
+ trace_policy_frequency(target_pstate * cpu->pstate.scaling, cpu->cpu,
+ cpumask_of(cpu->cpu));
intel_pstate_update_pstate(cpu, target_pstate);
sample = &cpu->sample;
diff --git a/include/trace/events/power.h b/include/trace/events/power.h
index 370f8df2fdb4..317098ffdd5f 100644
--- a/include/trace/events/power.h
+++ b/include/trace/events/power.h
@@ -182,11 +182,29 @@ TRACE_EVENT(pstate_sample,
{ PM_EVENT_RECOVER, "recover" }, \
{ PM_EVENT_POWEROFF, "poweroff" })
-DEFINE_EVENT(cpu, cpu_frequency,
+TRACE_EVENT(policy_frequency,
- TP_PROTO(unsigned int frequency, unsigned int cpu_id),
+ TP_PROTO(unsigned int frequency, unsigned int cpu_id,
+ const struct cpumask *policy_cpus),
- TP_ARGS(frequency, cpu_id)
+ TP_ARGS(frequency, cpu_id, policy_cpus),
+
+ TP_STRUCT__entry(
+ __field(u32, state)
+ __field(u32, cpu_id)
+ __cpumask(cpumask)
+ ),
+
+ TP_fast_assign(
+ __entry->state = frequency;
+ __entry->cpu_id = cpu_id;
+ __assign_cpumask(cpumask, policy_cpus);
+ ),
+
+ TP_printk("state=%lu cpu_id=%lu policy_cpus=%*pb",
+ (unsigned long)__entry->state,
+ (unsigned long)__entry->cpu_id,
+ cpumask_pr_args((struct cpumask *)__get_dynamic_array(cpumask)))
);
TRACE_EVENT(cpu_frequency_limits,
diff --git a/kernel/trace/power-traces.c b/kernel/trace/power-traces.c
index f2fe33573e54..a537e68a6878 100644
--- a/kernel/trace/power-traces.c
+++ b/kernel/trace/power-traces.c
@@ -16,5 +16,5 @@
EXPORT_TRACEPOINT_SYMBOL_GPL(suspend_resume);
EXPORT_TRACEPOINT_SYMBOL_GPL(cpu_idle);
-EXPORT_TRACEPOINT_SYMBOL_GPL(cpu_frequency);
+EXPORT_TRACEPOINT_SYMBOL_GPL(policy_frequency);
diff --git a/samples/bpf/cpustat_kern.c b/samples/bpf/cpustat_kern.c
index 7ec7143e2757..f485de0f89b2 100644
--- a/samples/bpf/cpustat_kern.c
+++ b/samples/bpf/cpustat_kern.c
@@ -75,9 +75,9 @@ struct {
} pstate_duration SEC(".maps");
/*
- * The trace events for cpu_idle and cpu_frequency are taken from:
+ * The trace events for cpu_idle and policy_frequency are taken from:
* /sys/kernel/tracing/events/power/cpu_idle/format
- * /sys/kernel/tracing/events/power/cpu_frequency/format
+ * /sys/kernel/tracing/events/power/policy_frequency/format
*
* These two events have same format, so define one common structure.
*/
@@ -162,7 +162,7 @@ int bpf_prog1(struct cpu_args *ctx)
*/
if (ctx->state != (u32)-1) {
- /* record pstate after have first cpu_frequency event */
+ /* record pstate after have first policy_frequency event */
if (!*pts)
return 0;
@@ -208,7 +208,7 @@ int bpf_prog1(struct cpu_args *ctx)
return 0;
}
-SEC("tracepoint/power/cpu_frequency")
+SEC("tracepoint/power/policy_frequency")
int bpf_prog2(struct cpu_args *ctx)
{
u64 *pts, *cstate, *pstate, cur_ts, delta;
diff --git a/samples/bpf/cpustat_user.c b/samples/bpf/cpustat_user.c
index 356f756cba0d..f7e81f702358 100644
--- a/samples/bpf/cpustat_user.c
+++ b/samples/bpf/cpustat_user.c
@@ -143,12 +143,12 @@ static int cpu_stat_inject_cpu_idle_event(void)
/*
* It's possible to have no any frequency change for long time and cannot
- * get ftrace event 'trace_cpu_frequency' for long period, this introduces
+ * get ftrace event 'trace_policy_frequency' for long period, this introduces
* big deviation for pstate statistics.
*
* To solve this issue, below code forces to set 'scaling_max_freq' to 208MHz
- * for triggering ftrace event 'trace_cpu_frequency' and then recovery back to
- * the maximum frequency value 1.2GHz.
+ * for triggering ftrace event 'trace_policy_frequency' and then recovery back
+ * to the maximum frequency value 1.2GHz.
*/
static int cpu_stat_inject_cpu_frequency_event(void)
{
diff --git a/tools/perf/builtin-timechart.c b/tools/perf/builtin-timechart.c
index 22050c640dfa..3ef1a2fd0493 100644
--- a/tools/perf/builtin-timechart.c
+++ b/tools/perf/builtin-timechart.c
@@ -612,10 +612,10 @@ process_sample_cpu_idle(struct timechart *tchart __maybe_unused,
}
static int
-process_sample_cpu_frequency(struct timechart *tchart,
- struct evsel *evsel,
- struct perf_sample *sample,
- const char *backtrace __maybe_unused)
+process_sample_policy_frequency(struct timechart *tchart,
+ struct evsel *evsel,
+ struct perf_sample *sample,
+ const char *backtrace __maybe_unused)
{
u32 state = evsel__intval(evsel, sample, "state");
u32 cpu_id = evsel__intval(evsel, sample, "cpu_id");
@@ -1541,7 +1541,7 @@ static int __cmd_timechart(struct timechart *tchart, const char *output_name)
{
const struct evsel_str_handler power_tracepoints[] = {
{ "power:cpu_idle", process_sample_cpu_idle },
- { "power:cpu_frequency", process_sample_cpu_frequency },
+ { "power:policy_frequency", process_sample_policy_frequency },
{ "sched:sched_wakeup", process_sample_sched_wakeup },
{ "sched:sched_switch", process_sample_sched_switch },
#ifdef SUPPORT_OLD_POWER_EVENTS
@@ -1804,7 +1804,7 @@ static int timechart__record(struct timechart *tchart, int argc, const char **ar
unsigned int backtrace_args_no = ARRAY_SIZE(backtrace_args);
const char * const power_args[] = {
- "-e", "power:cpu_frequency",
+ "-e", "power:policy_frequency",
"-e", "power:cpu_idle",
};
unsigned int power_args_nr = ARRAY_SIZE(power_args);
--
2.52.0.107.ga0afd4fd5b-goog
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