perf intel-tpebs: Filter non-workload samples

If perf is running with a benchmark then we want the retirement
latency samples associated with the benchmark rather than from the
system as a whole.

Use the workload's PID to filter out samples that aren't from the
workload or its children.

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Weilin Wang <weilin.wang@intel.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250430200108.243234-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/intel-tpebs.c b/tools/perf/util/intel-tpebs.c
index 7fd6cae1063e6297bf513fee6f7a0c7ce020bd8e..4ad4bc118ea5f52ba61349fc702c3002fff45b01 100644 (file)
--- a/tools/perf/util/intel-tpebs.c
+++ b/tools/perf/util/intel-tpebs.c
@@ -3,7 +3,7 @@
  * intel_tpebs.c: Intel TPEBS support
  */
 
-
+#include <api/fs/fs.h>
 #include <sys/param.h>
 #include <subcmd/run-command.h>
 #include <thread.h>
@@ -121,6 +121,59 @@ static int evsel__tpebs_start_perf_record(struct evsel *evsel)
        return ret;
 }
 
+static bool is_child_pid(pid_t parent, pid_t child)
+{
+       if (parent < 0 || child < 0)
+               return false;
+
+       while (true) {
+               char path[PATH_MAX];
+               char line[256];
+               FILE *fp;
+
+new_child:
+               if (parent == child)
+                       return true;
+
+               if (child <= 0)
+                       return false;
+
+               scnprintf(path, sizeof(path), "%s/%d/status", procfs__mountpoint(), child);
+               fp = fopen(path, "r");
+               if (!fp) {
+                       /* Presumably the process went away. Assume not a child. */
+                       return false;
+               }
+               while (fgets(line, sizeof(line), fp) != NULL) {
+                       if (strncmp(line, "PPid:", 5) == 0) {
+                               fclose(fp);
+                               if (sscanf(line + 5, "%d", &child) != 1) {
+                                       /* Unexpected error parsing. */
+                                       return false;
+                               }
+                               goto new_child;
+                       }
+               }
+               /* Unexpected EOF. */
+               fclose(fp);
+               return false;
+       }
+}
+
+static bool should_ignore_sample(const struct perf_sample *sample, const struct tpebs_retire_lat *t)
+{
+       pid_t workload_pid = t->evsel->evlist->workload.pid;
+       pid_t sample_pid = sample->pid;
+
+       if (workload_pid < 0 || workload_pid == sample_pid)
+               return false;
+
+       if (!t->evsel->core.attr.inherit)
+               return true;
+
+       return !is_child_pid(workload_pid, sample_pid);
+}
+
 static int process_sample_event(const struct perf_tool *tool __maybe_unused,
                                union perf_event *event __maybe_unused,
                                struct perf_sample *sample,
@@ -140,6 +193,10 @@ static int process_sample_event(const struct perf_tool *tool __maybe_unused,
                mutex_unlock(tpebs_mtx_get());
                return -EINVAL;
        }
+       if (should_ignore_sample(sample, t)) {
+               mutex_unlock(tpebs_mtx_get());
+               return 0;
+       }
        /*
         * Need to handle per core results? We are assuming average retire
         * latency value will be used. Save the number of samples and the sum of