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Message-ID: <CAP-5=fUTuBjF8HJZAvXHkM4FjL05gjDcevKUruEXJHYRUhXygA@mail.gmail.com>
Date: Mon, 4 Dec 2023 08:02:13 -0800
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Kan Liang <kan.liang@...ux.intel.com>,
Yang Jihong <yangjihong1@...wei.com>,
Leo Yan <leo.yan@...aro.org>,
Sandipan Das <sandipan.das@....com>,
Ravi Bangoria <ravi.bangoria@....com>,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
Ajay Kaher <akaher@...are.com>,
Alexey Makhalov <amakhalov@...are.com>
Subject: Re: [RFC PATCH v2] perf evsel: Fallback to task-clock when not system wide
On Mon, Nov 20, 2023 at 4:04 PM Ian Rogers <irogers@...gle.com> wrote:
>
> When the cycles event isn't available evsel will fallback to the
> cpu-clock software event. task-clock is similar to cpu-clock but only
> runs when the process is running. Falling back to cpu-clock when not
> system wide leads to confusion, by falling back to task-clock it is
> hoped the confusion is less.
>
> Pass the target to determine if task-clock is more appropriate. Update
> a nearby comment and debug string for the change.
>
> ---
> v2. Use target__has_cpu as suggested by Namhyung.
> https://lpc.events/event/17/contributions/1556/
>
> Signed-off-by: Ian Rogers <irogers@...gle.com>
Ping.
Thanks,
Ian
> ---
> tools/perf/builtin-record.c | 2 +-
> tools/perf/builtin-stat.c | 2 +-
> tools/perf/builtin-top.c | 2 +-
> tools/perf/util/evsel.c | 18 ++++++++++--------
> tools/perf/util/evsel.h | 3 ++-
> 5 files changed, 15 insertions(+), 12 deletions(-)
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 8ec818568662..d8bb59511fdd 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1350,7 +1350,7 @@ static int record__open(struct record *rec)
> evlist__for_each_entry(evlist, pos) {
> try_again:
> if (evsel__open(pos, pos->core.cpus, pos->core.threads) < 0) {
> - if (evsel__fallback(pos, errno, msg, sizeof(msg))) {
> + if (evsel__fallback(pos, &opts->target, errno, msg, sizeof(msg))) {
> if (verbose > 0)
> ui__warning("%s\n", msg);
> goto try_again;
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index a3af805a1d57..d8e5d6f7a87a 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -653,7 +653,7 @@ static enum counter_recovery stat_handle_error(struct evsel *counter)
> if ((evsel__leader(counter) != counter) ||
> !(counter->core.leader->nr_members > 1))
> return COUNTER_SKIP;
> - } else if (evsel__fallback(counter, errno, msg, sizeof(msg))) {
> + } else if (evsel__fallback(counter, &target, errno, msg, sizeof(msg))) {
> if (verbose > 0)
> ui__warning("%s\n", msg);
> return COUNTER_RETRY;
> diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
> index ea8c7eca5eee..1e42bd1c7d5a 100644
> --- a/tools/perf/builtin-top.c
> +++ b/tools/perf/builtin-top.c
> @@ -1044,7 +1044,7 @@ static int perf_top__start_counters(struct perf_top *top)
> perf_top_overwrite_fallback(top, counter))
> goto try_again;
>
> - if (evsel__fallback(counter, errno, msg, sizeof(msg))) {
> + if (evsel__fallback(counter, &opts->target, errno, msg, sizeof(msg))) {
> if (verbose > 0)
> ui__warning("%s\n", msg);
> goto try_again;
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index a5da74e3a517..532f34d9fcb5 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -2853,7 +2853,8 @@ u64 evsel__intval_common(struct evsel *evsel, struct perf_sample *sample, const
>
> #endif
>
> -bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize)
> +bool evsel__fallback(struct evsel *evsel, struct target *target, int err,
> + char *msg, size_t msgsize)
> {
> int paranoid;
>
> @@ -2861,18 +2862,19 @@ bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize)
> evsel->core.attr.type == PERF_TYPE_HARDWARE &&
> evsel->core.attr.config == PERF_COUNT_HW_CPU_CYCLES) {
> /*
> - * If it's cycles then fall back to hrtimer based
> - * cpu-clock-tick sw counter, which is always available even if
> - * no PMU support.
> + * If it's cycles then fall back to hrtimer based cpu-clock sw
> + * counter, which is always available even if no PMU support.
> *
> * PPC returns ENXIO until 2.6.37 (behavior changed with commit
> * b0a873e).
> */
> - scnprintf(msg, msgsize, "%s",
> -"The cycles event is not supported, trying to fall back to cpu-clock-ticks");
> -
> evsel->core.attr.type = PERF_TYPE_SOFTWARE;
> - evsel->core.attr.config = PERF_COUNT_SW_CPU_CLOCK;
> + evsel->core.attr.config = target__has_cpu(target)
> + ? PERF_COUNT_SW_CPU_CLOCK
> + : PERF_COUNT_SW_TASK_CLOCK;
> + scnprintf(msg, msgsize,
> + "The cycles event is not supported, trying to fall back to %s",
> + target__has_cpu(target) ? "cpu-clock" : "task-clock");
>
> zfree(&evsel->name);
> return true;
> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> index f19ac9f027ef..efbb6e848287 100644
> --- a/tools/perf/util/evsel.h
> +++ b/tools/perf/util/evsel.h
> @@ -460,7 +460,8 @@ static inline bool evsel__is_clock(const struct evsel *evsel)
> evsel__match(evsel, SOFTWARE, SW_TASK_CLOCK);
> }
>
> -bool evsel__fallback(struct evsel *evsel, int err, char *msg, size_t msgsize);
> +bool evsel__fallback(struct evsel *evsel, struct target *target, int err,
> + char *msg, size_t msgsize);
> int evsel__open_strerror(struct evsel *evsel, struct target *target,
> int err, char *msg, size_t size);
>
> --
> 2.43.0.rc1.413.gea7ed67945-goog
>
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