perf pmu: Add perf_pmu__{open,scan}_file_at()

These two helpers will also use openat() to reduce the overhead with
relative pathnames.  Convert other functions in pmu_lookup() to use
the new helpers.

Committer testing:

Before:

  ⬢[acme@toolbox perf-tools-next]$ perf bench internals pmu-scan
  # Running 'internals/pmu-scan' benchmark:
  Computing performance of sysfs PMU event scan for 100 times
    Average PMU scanning took: 2729.040 usec (+- 7.117 usec)
  ⬢[acme@toolbox perf-tools-next]$

After:

  ⬢[acme@toolbox perf-tools-next]$ perf bench internals pmu-scan
  # Running 'internals/pmu-scan' benchmark:
  Computing performance of sysfs PMU event scan for 100 times
    Average PMU scanning took: 2419.870 usec (+- 9.057 usec)
  ⬢[acme@toolbox perf-tools-next]$

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230331202949.810326-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index 751c7016e7b6..32c3a75bca0e 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -220,7 +220,12 @@ bool is_pmu_core(const char *name);
 void print_pmu_events(const struct print_callbacks *print_cb, void *print_state);
 bool pmu_have_event(const char *pname, const char *name);
 
+FILE *perf_pmu__open_file(struct perf_pmu *pmu, const char *name);
+FILE *perf_pmu__open_file_at(struct perf_pmu *pmu, int dirfd, const char *name);
+
 int perf_pmu__scan_file(struct perf_pmu *pmu, const char *name, const char *fmt, ...) __scanf(3, 4);
+int perf_pmu__scan_file_at(struct perf_pmu *pmu, int dirfd, const char *name,
+			   const char *fmt, ...) __scanf(4, 5);
 
 bool perf_pmu__file_exists(struct perf_pmu *pmu, const char *name);
 
@@ -259,7 +264,6 @@ int perf_pmu__pathname_scnprintf(char *buf, size_t size,
 				 const char *pmu_name, const char *filename);
 int perf_pmu__event_source_devices_fd(void);
 int perf_pmu__pathname_fd(int dirfd, const char *pmu_name, const char *filename, int flags);
-FILE *perf_pmu__open_file(struct perf_pmu *pmu, const char *name);
 
 void perf_pmu__destroy(void);