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Message-ID: <aXF1OECUByl0kgCF@x1>
Date: Wed, 21 Jan 2026 21:54:16 -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 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);
| ^~
But then it doesn't build on 32-bit arches with:
20.64 almalinux:9-i386 : FAIL gcc version 11.4.1 20231218 (Red Hat 11.4.1-3) (GCC)
| ^~~
/tmp/build/perf/libperf/include/perf/schedstat-v15.h:4:1: note: in expansion of macro ‘CPU_FIELD’
4 | CPU_FIELD(__u32, yld_count, "sched_yield() count",
| ^~~~~~~~~
In file included from util/event.c:3:
/usr/include/inttypes.h:105:41: note: format string is defined here
105 | # define PRIu64 __PRI64_PREFIX "u"
util/event.c:583:29: error: format ‘%llu’ expects argument of type ‘long long unsigned int’, but argument 3 has type ‘long unsigned int’ [-Werror=format=]
583 | size += fprintf(fp, "%" PRIu64 " ", (unsigned long)cs->_ver._name)
| ^~~
/tmp/build/perf/libperf/include/perf/schedstat-v15.h:6:1: note: in expansion of macro ‘CPU_FIELD’
6 | CPU_FIELD(__u32, array_exp, "Legacy counter can be ignored",
| ^~~~~~~~~
In file included from util/event.c:3:
/usr/include/inttypes.h:105:41: note: format string is defined here
105 | # define PRIu64 __PRI64_PREFIX "u"
util/event.c:583:29: error: format ‘%llu’ expects argument of type ‘long long unsigned int’, but argument 3 has type ‘long unsigned int’ [-Werror=format=]
583 | size += fprintf(fp, "%" PRIu64 " ", (unsigned long)cs->_ver._name)
| ^~~
/tmp/build/perf/libperf/include/perf/schedstat-v15.h:8:1: note: in expansion of macro ‘CPU_FIELD’
8 | CPU_FIELD(__u32, sched_count, "schedule() called",
So continuing to test build up to:
⬢ [acme@...lbx perf-tools-next]$ git log --oneline -5
139b45df27c05531 (HEAD -> perf-tools-next) perf sched stats: Add schedstat v17 support
e092c5d4541da7f0 perf sched stats: Add schedstat v16 support
e659d5e11000b7ff perf sched stats: Add record and rawdump support
900884770020691c perf header: Support CPU DOMAIN relation info
a02829a0e6c65b12 tools/lib: Add list_is_first()
⬢ [acme@...lbx perf-tools-next]$
- Arnaldo
> + free_cpu_domain_info(cd_map, sv, nr);
> + free_schedstat(&cpu_head);
> + evlist__delete(evlist);
> + return err;
> +}
> +
> static bool schedstat_events_exposed(void)
> {
> /*
> @@ -4751,7 +4848,7 @@ int cmd_sched(int argc, const char **argv)
> stats_usage, 0);
> return perf_sched__schedstat_report(&sched);
> }
> - usage_with_options(stats_usage, stats_options);
> + return perf_sched__schedstat_live(&sched, argc, argv);
> } else {
> usage_with_options(sched_usage, sched_options);
> }
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index 673d53bb2a2c..9a15dd4b7640 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -1614,8 +1614,7 @@ static int write_pmu_caps(struct feat_fd *ff,
> return 0;
> }
>
> -static struct cpu_domain_map **build_cpu_domain_map(u32 *schedstat_version, u32 *max_sched_domains,
> - u32 nr)
> +struct cpu_domain_map **build_cpu_domain_map(u32 *schedstat_version, u32 *max_sched_domains, u32 nr)
> {
> struct domain_info *domain_info;
> struct cpu_domain_map **cd_map;
> diff --git a/tools/perf/util/header.h b/tools/perf/util/header.h
> index c62f3275a80f..36cc74e2d14d 100644
> --- a/tools/perf/util/header.h
> +++ b/tools/perf/util/header.h
> @@ -211,4 +211,7 @@ char *get_cpuid_str(struct perf_cpu cpu);
> char *get_cpuid_allow_env_override(struct perf_cpu cpu);
>
> int strcmp_cpuid_str(const char *s1, const char *s2);
> +
> +struct cpu_domain_map **build_cpu_domain_map(u32 *schedstat_version, u32 *max_sched_domains,
> + u32 nr);
> #endif /* __PERF_HEADER_H */
> --
> 2.43.0
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