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Message-ID: <aXJFYpY8_oL2GMhV@x1>
Date: Thu, 22 Jan 2026 12:42:26 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Swapnil Sapkal <swapnil.sapkal@....com>
Cc: peterz@...radead.org, mingo@...hat.com, namhyung@...nel.org,
irogers@...gle.com, james.clark@....com, ravi.bangoria@....com,
yu.c.chen@...el.com, mark.rutland@....com,
alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
rostedt@...dmis.org, vincent.guittot@...aro.org,
adrian.hunter@...el.com, kan.liang@...ux.intel.com,
gautham.shenoy@....com, kprateek.nayak@....com,
juri.lelli@...hat.com, yangjihong@...edance.com, void@...ifault.com,
tj@...nel.org, sshegde@...ux.ibm.com, ctshao@...gle.com,
quic_zhonhan@...cinc.com, thomas.falcon@...el.com,
blakejones@...gle.com, ashelat@...hat.com, leo.yan@....com,
dvyukov@...gle.com, ak@...ux.intel.com, yujie.liu@...el.com,
graham.woodward@....com, ben.gainey@....com, vineethr@...ux.ibm.com,
tim.c.chen@...ux.intel.com, linux@...blig.org,
santosh.shukla@....com, sandipan.das@....com,
linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
James Clark <james.clark@...aro.org>
Subject: Re: [PATCH v5 07/10] perf sched stats: Add support for live mode
On Wed, Jan 21, 2026 at 09:54:16PM -0300, Arnaldo Carvalho de Melo wrote:
> On Mon, Jan 19, 2026 at 05:58:29PM +0000, Swapnil Sapkal wrote:
> > The live mode works similar to simple `perf stat` command, by profiling
> > the target and printing results on the terminal as soon as the target
> > finishes.
> >
> > Example usage:
> >
> > # perf sched stats -- true
> > Description
> > ----------------------------------------------------------------------------------------------------
> > DESC -> Description of the field
> > COUNT -> Value of the field
> > PCT_CHANGE -> Percent change with corresponding base value
> > AVG_JIFFIES -> Avg time in jiffies between two consecutive occurrence of event
> > ----------------------------------------------------------------------------------------------------
> >
> > Time elapsed (in jiffies) : 1
> > ----------------------------------------------------------------------------------------------------
> > CPU: <ALL CPUS SUMMARY>
> > ----------------------------------------------------------------------------------------------------
> > DESC COUNT PCT_CHANGE
> > ----------------------------------------------------------------------------------------------------
> > yld_count : 0
> > array_exp : 0
> > sched_count : 0
> > sched_goidle : 0 ( 0.00% )
> > ttwu_count : 0
> > ttwu_local : 0 ( 0.00% )
> > rq_cpu_time : 27875
> > run_delay : 0 ( 0.00% )
> > pcount : 0
> > ----------------------------------------------------------------------------------------------------
> > CPU: <ALL CPUS SUMMARY> | DOMAIN: SMT
> > ----------------------------------------------------------------------------------------------------
> > DESC COUNT AVG_JIFFIES
> > ----------------------------------------- <Category busy> ------------------------------------------
> > busy_lb_count : 0 $ 0.00 $
> > busy_lb_balanced : 0 $ 0.00 $
> > busy_lb_failed : 0 $ 0.00 $
> > busy_lb_imbalance_load : 0
> > busy_lb_imbalance_util : 0
> > busy_lb_imbalance_task : 0
> > busy_lb_imbalance_misfit : 0
> > busy_lb_gained : 0
> > busy_lb_hot_gained : 0
> > busy_lb_nobusyq : 0 $ 0.00 $
> > busy_lb_nobusyg : 0 $ 0.00 $
> > *busy_lb_success_count : 0
> > *busy_lb_avg_pulled : 0.00
> >
> > ... and so on. Output will show similar data for all the cpus in the
> > system.
> >
> > Co-developed-by: Ravi Bangoria <ravi.bangoria@....com>
> > Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
> > Tested-by: James Clark <james.clark@...aro.org>
> > Signed-off-by: Swapnil Sapkal <swapnil.sapkal@....com>
> > ---
> > tools/perf/builtin-sched.c | 99 +++++++++++++++++++++++++++++++++++++-
> > tools/perf/util/header.c | 3 +-
> > tools/perf/util/header.h | 3 ++
> > 3 files changed, 102 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> > index c6b054b9b12a..8993308439bc 100644
> > --- a/tools/perf/builtin-sched.c
> > +++ b/tools/perf/builtin-sched.c
> > @@ -4426,6 +4426,103 @@ static int perf_sched__schedstat_report(struct perf_sched *sched)
> > return err;
> > }
> >
> > +static int process_synthesized_event_live(const struct perf_tool *tool __maybe_unused,
> > + union perf_event *event,
> > + struct perf_sample *sample __maybe_unused,
> > + struct machine *machine __maybe_unused)
> > +{
> > + return perf_sched__process_schedstat(tool, NULL, event);
> > +}
> > +
> > +static int perf_sched__schedstat_live(struct perf_sched *sched,
> > + int argc, const char **argv)
> > +{
> > + struct cpu_domain_map **cd_map = NULL;
> > + struct target target = {};
> > + u32 __maybe_unused md;
> > + struct evlist *evlist;
> > + u32 nr = 0, sv;
> > + int reset = 0;
> > + int err = 0;
> > +
> > + signal(SIGINT, sighandler);
> > + signal(SIGCHLD, sighandler);
> > + signal(SIGTERM, sighandler);
> > +
> > + evlist = evlist__new();
> > + if (!evlist)
> > + return -ENOMEM;
> > +
> > + /*
> > + * `perf sched schedstat` does not support workload profiling (-p pid)
> > + * since /proc/schedstat file contains cpu specific data only. Hence, a
> > + * profile target is either set of cpus or systemwide, never a process.
> > + * Note that, although `-- <workload>` is supported, profile data are
> > + * still cpu/systemwide.
> > + */
> > + if (cpu_list)
> > + target.cpu_list = cpu_list;
> > + else
> > + target.system_wide = true;
> > +
> > + if (argc) {
> > + err = evlist__prepare_workload(evlist, &target, argv, false, NULL);
> > + if (err)
> > + goto out;
> > + }
> > +
> > + err = evlist__create_maps(evlist, &target);
> > + if (err < 0)
> > + goto out;
> > +
> > + user_requested_cpus = evlist->core.user_requested_cpus;
> > +
> > + err = perf_event__synthesize_schedstat(&(sched->tool),
> > + process_synthesized_event_live,
> > + user_requested_cpus);
> > + if (err < 0)
> > + goto out;
> > +
> > + err = enable_sched_schedstats(&reset);
> > + if (err < 0)
> > + goto out;
> > +
> > + if (argc)
> > + evlist__start_workload(evlist);
> > +
> > + /* wait for signal */
> > + pause();
> > +
> > + if (reset) {
> > + err = disable_sched_schedstat();
> > + if (err < 0)
> > + goto out;
> > + }
> > +
> > + err = perf_event__synthesize_schedstat(&(sched->tool),
> > + process_synthesized_event_live,
> > + user_requested_cpus);
> > + if (err)
> > + goto out;
> > +
> > + setup_pager();
> > +
> > + if (list_empty(&cpu_head)) {
> > + pr_err("Data is not available\n");
> > + err = -1;
> > + goto out;
> > + }
> > +
> > + nr = cpu__max_present_cpu().cpu;
> > + cd_map = build_cpu_domain_map(&sv, &md, nr);
> > + show_schedstat_data(&cpu_head, cd_map);
> > +out:
>
> With clang on almalinux 10:
>
> + make ARCH= CROSS_COMPILE= EXTRA_CFLAGS= -C tools/perf O=/tmp/build/perf CC=clang
> make: Entering directory '/git/perf-6.19.0-rc4/tools/perf'
> GEN /tmp/build/perf/pmu-events/arch/powerpc/power8/memory.json
> builtin-sched.c:4709:6: error: variable 'sv' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
> 4709 | if (list_empty(&cpu_head)) {
> | ^~~~~~~~~~~~~~~~~~~~~
> GEN /tmp/build/perf/pmu-events/arch/powerpc/power8/metrics.json
> GEN /tmp/build/perf/pmu-events/arch/powerpc/power8/other.json
> CC /tmp/build/perf/tests/kmod-path.o
> builtin-sched.c:4719:31: note: uninitialized use occurs here
> GEN /tmp/build/perf/pmu-events/arch/powerpc/power8/pipeline.json
> 4719 | free_cpu_domain_info(cd_map, sv, nr);
> | ^~
>
Moving the label does the trick as free_cpu_domain_info() only needs to
be called if build_cpu_domain_map() was called.
- Arnaldo
diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 8993308439bc5998..ec9fa29196b24f5a 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -4516,8 +4516,8 @@ static int perf_sched__schedstat_live(struct perf_sched *sched,
nr = cpu__max_present_cpu().cpu;
cd_map = build_cpu_domain_map(&sv, &md, nr);
show_schedstat_data(&cpu_head, cd_map);
-out:
free_cpu_domain_info(cd_map, sv, nr);
+out:
free_schedstat(&cpu_head);
evlist__delete(evlist);
return err;
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