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perf trace: Introduce --show-cpu option to display cpu id

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When tracing system-wide workloads or specific events, it is highly
valuable to know exactly which CPU executed a specific event. Currently,
perf trace output defaults to omitting CPU information.

Introduce a new "--show-cpu" command-line option. When provided, this
flag extracts the CPU from the perf sample and prints it in a "[000]"
format immediately following the timestamp. This mirrors the behaviour of
other tracing tools like ftrace and perf script. For example:

  # perf trace -e sched:sched_switch --max-events 5 --show-cpu
       0.000 [002] :0/0 sched:sched_switch(prev_comm: "swapper/2", prev_prio: 120, next_comm: "rcu_preempt", next_pid: 16 (rcu_preempt), next_prio: 120)
       0.009 [002] rcu_preempt/16 sched:sched_switch(prev_comm: "rcu_preempt", prev_pid: 16 (rcu_preempt), prev_prio: 120, prev_state: 128, next_comm: "swapper/2", next_prio: 120)
       0.033 [002] :0/0 sched:sched_switch(prev_comm: "swapper/2", prev_prio: 120, next_comm: "kworker/u32:48", next_pid: 35840 (kworker/u32:48-), next_prio: 120)
       0.041 [002] kworker/u32:48/35840 sched:sched_switch(prev_comm: "kworker/u32:48", prev_pid: 35840 (kworker/u32:48-), prev_prio: 120, prev_state: 128, next_comm: "swapper/2", next_prio: 120)
       0.045 [002] :0/0 sched:sched_switch(prev_comm: "swapper/2", prev_prio: 120, next_comm: "kworker/u32:48", next_pid: 35840 (kworker/u32:48-), next_prio: 120)

The feature is implemented strictly as an opt-in toggle to prevent
cluttering the standard output and to preserve backwards compatibility
for scripts parsing the default output format.

Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Daniel Vacek <neelx@suse.com>
Cc: Howard Chu <howardchu95@gmail.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sean Ashe <sean@ashe.io>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Aaron Tomlin 2026-04-24 17:29:33 -04:00 committed by Arnaldo Carvalho de Melo
parent 2e2ba7d1ea
commit e445b78ffb
2 changed files with 49 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
tools/perf/Documentation/perf-trace.txt
View File

@ -199,6 +199,9 @@ the thread executes on the designated CPUs. Default is to monitor all CPUs.
--show-on-off-events::
Show the --switch-on/off events too.
--show-cpu::
Show cpu id.
--max-stack::
Set the stack depth limit when parsing the callchain, anything
beyond the specified depth will be ignored. Note that at this point

51
tools/perf/builtin-trace.c
View File

@ -217,6 +217,7 @@ struct trace {
bool kernel_syscallchains;
s16 args_alignment;
bool show_tstamp;
bool show_cpu;
bool show_duration;
bool show_zeros;
bool show_arg_names;
@ -1531,6 +1532,7 @@ static size_t fprintf_duration(unsigned long t, bool calculated, FILE *fp)
*/
struct thread_trace {
u64 entry_time;
u32 entry_cpu;
bool entry_pending;
unsigned long nr_events;
unsigned long pfmaj, pfmin;
@ -1893,6 +1895,27 @@ static size_t trace__fprintf_tstamp(struct trace *trace, u64 tstamp, FILE *fp)
return fprintf(fp, " ? ");
}
/**
* trace__fprintf_cpu - Print the CPU ID to a given file stream
* @cpu: The CPU ID to print
* @fp: The file stream to write to
*
* Formats and prints the specified CPU ID enclosed in brackets
* (e.g., "[003] ") to the provided file pointer. It is used to
* align and display the CPU ID consistently within the trace output.
*
* Return: The number of characters printed.
*/
static size_t trace__fprintf_cpu(u32 cpu, FILE *fp)
{
size_t printed = 0;
if (cpu != (u32)-1)
printed += fprintf(fp, "[%03u] ", cpu);
return printed;
}
static pid_t workload_pid = -1;
static volatile sig_atomic_t done = false;
static volatile sig_atomic_t interrupted = false;
@ -1923,12 +1946,15 @@ static size_t trace__fprintf_comm_tid(struct trace *trace, struct thread *thread
}
static size_t trace__fprintf_entry_head(struct trace *trace, struct thread *thread,
u64 duration, bool duration_calculated, u64 tstamp, FILE *fp)
u64 duration, bool duration_calculated,
u64 tstamp, u32 cpu, FILE *fp)
{
size_t printed = 0;
if (trace->show_tstamp)
printed = trace__fprintf_tstamp(trace, tstamp, fp);
if (trace->show_cpu && cpu != (u32)-1)
printed += trace__fprintf_cpu(cpu, fp);
if (trace->show_duration)
printed += fprintf_duration(duration, duration_calculated, fp);
return printed + trace__fprintf_comm_tid(trace, thread, fp);
@ -2707,7 +2733,9 @@ static int trace__printf_interrupted_entry(struct trace *trace)
if (!ttrace->entry_pending)
return 0;
printed = trace__fprintf_entry_head(trace, trace->current, 0, false, ttrace->entry_time, trace->output);
printed = trace__fprintf_entry_head(trace, trace->current, 0, false,
ttrace->entry_time, ttrace->entry_cpu,
trace->output);
printed += len = fprintf(trace->output, "%s)", ttrace->entry_str);
if (len < trace->args_alignment - 4)
@ -2825,6 +2853,7 @@ static int trace__sys_enter(struct trace *trace, struct evsel *evsel,
if (evsel != trace->syscalls.events.sys_enter)
augmented_args = syscall__augmented_args(sc, sample, &augmented_args_size, trace->raw_augmented_syscalls_args_size);
ttrace->entry_time = sample->time;
ttrace->entry_cpu = sample->cpu;
msg = ttrace->entry_str;
printed += scnprintf(msg + printed, trace__entry_str_size - printed, "%s(", sc->name);
@ -2835,7 +2864,9 @@ static int trace__sys_enter(struct trace *trace, struct evsel *evsel,
if (!(trace->duration_filter || trace->summary_only || trace->failure_only || trace->min_stack)) {
int alignment = 0;
trace__fprintf_entry_head(trace, thread, 0, false, ttrace->entry_time, trace->output);
trace__fprintf_entry_head(trace, thread, 0, false,
ttrace->entry_time,
sample->cpu, trace->output);
printed = fprintf(trace->output, "%s)", ttrace->entry_str);
if (trace->args_alignment > printed)
alignment = trace->args_alignment - printed;
@ -2980,7 +3011,9 @@ static int trace__sys_exit(struct trace *trace, struct evsel *evsel,
if (trace->summary_only || (ret >= 0 && trace->failure_only))
goto out;
trace__fprintf_entry_head(trace, thread, duration, duration_calculated, ttrace->entry_time, trace->output);
trace__fprintf_entry_head(trace, thread, duration,
duration_calculated, ttrace->entry_time,
sample->cpu, trace->output);
if (ttrace->entry_pending) {
printed = fprintf(trace->output, "%s", ttrace->entry_str);
@ -3280,6 +3313,9 @@ static int trace__event_handler(struct trace *trace, struct evsel *evsel,
trace__printf_interrupted_entry(trace);
trace__fprintf_tstamp(trace, sample->time, trace->output);
if (trace->show_cpu)
trace__fprintf_cpu(sample->cpu, trace->output);
if (trace->trace_syscalls && trace->show_duration)
fprintf(trace->output, "( ): ");
@ -3405,7 +3441,8 @@ static int trace__pgfault(struct trace *trace,
thread__find_symbol(thread, sample->cpumode, sample->ip, &al);
trace__fprintf_entry_head(trace, thread, 0, true, sample->time, trace->output);
trace__fprintf_entry_head(trace, thread, 0, true, sample->time,
sample->cpu, trace->output);
fprintf(trace->output, "%sfault [",
evsel->core.attr.config == PERF_COUNT_SW_PAGE_FAULTS_MAJ ?
@ -5432,6 +5469,7 @@ int cmd_trace(int argc, const char **argv)
OPT_CALLBACK('m', "mmap-pages", &trace.opts.mmap_pages, "pages",
"number of mmap data pages", evlist__parse_mmap_pages),
OPT_STRING('u', "uid", &trace.uid_str, "user", "user to profile"),
OPT_BOOLEAN(0, "show-cpu", &trace.show_cpu, "show cpu id"),
OPT_CALLBACK(0, "duration", &trace, "float",
"show only events with duration > N.M ms",
trace__set_duration),
@ -5566,6 +5604,9 @@ int cmd_trace(int argc, const char **argv)
goto out;
}
if (trace.show_cpu)
trace.opts.sample_cpu = true;
if ((nr_cgroups || trace.cgroup) && !trace.opts.target.system_wide) {
usage_with_options_msg(trace_usage, trace_options,
"cgroup monitoring only available in system-wide mode");