Commit eb2eac0c authored by Ian Rogers's avatar Ian Rogers Committed by Arnaldo Carvalho de Melo
Browse files

perf evsel: Fallback to "task-clock" when not system wide 



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.

Signed-off-by: default avatarIan Rogers <irogers@google.com>
Tested-by: default avatarAthira Rajeev <atrajeev@linux.vnet.ibm.com>
Acked-by: default avatarNamhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ajay Kaher <akaher@vmware.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Makhalov <amakhalov@vmware.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Yang Jihong <yangjihong1@huawei.com>
Link: https://lore.kernel.org/r/20231121000420.368075-1-irogers@google.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 018b0424

tools/perf/builtin-record.c

+1 −1
Original line number Diff line number Diff line
@@ -1360,7 +1360,7 @@ 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;

tools/perf/builtin-stat.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

tools/perf/builtin-top.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

tools/perf/util/evsel.c

+10 −8
Original line number Diff line number Diff line
@@ -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;

tools/perf/util/evsel.h

+2 −1
Original line number Diff line number Diff line
@@ -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);