From: Aaron Tomlin Date: Fri, 24 Apr 2026 21:29:33 +0000 (-0400) Subject: perf trace: Introduce --show-cpu option to display cpu id X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e445b78ffb8d43440b9f417d6701826746114a0d;p=thirdparty%2Fkernel%2Flinux.git perf trace: Introduce --show-cpu option to display cpu id 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 Cc: Adrian Hunter Cc: Alexander Shishkin Cc: Daniel Vacek Cc: Howard Chu Cc: Ian Rogers Cc: Ingo Molnar Cc: James Clark Cc: Jiri Olsa Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Sean Ashe Signed-off-by: Arnaldo Carvalho de Melo --- diff --git a/tools/perf/Documentation/perf-trace.txt b/tools/perf/Documentation/perf-trace.txt index 892c82a9bf402..d0b6c771a1b92 100644 --- a/tools/perf/Documentation/perf-trace.txt +++ b/tools/perf/Documentation/perf-trace.txt @@ -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 diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c index e58c49d047a29..e9cc870a5acda 100644 --- a/tools/perf/builtin-trace.c +++ b/tools/perf/builtin-trace.c @@ -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");