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: Ian Rogers <irogers@google.com>
Tested-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Acked-by: Namhyung 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: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 9b4f3805ca92f34e8606df12abdb9d2c851ca86d..db814eadc16b968c32638d9f63ea1eaaec2ff42f 100644 (file)
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -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;

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index a3af805a1d572d101b80fefbdddd04b41413629e..d8e5d6f7a87a65d667b1d0741b6225d979235018 100644 (file)
--- 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 ea8c7eca5eeedd7616976139b288b3ff5c8c95d4..1e42bd1c7d5a5fed0aa5db724392bec90af5674b 100644 (file)
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1044,7 +1044,7 @@ try_again:
                            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 a5da74e3a517b52ca90aa47e99b3999b80bdd4a2..532f34d9fcb503aeb17b43561481d4443200ef32 100644 (file)
--- 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 f19ac9f027efc75db438b9f5f1ac9916b7b7f1aa..efbb6e848287f3f6b4f9f0aca779b2a6590ec42f 100644 (file)
--- 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);