Commit bcfab08d authored by Ian Rogers's avatar Ian Rogers Committed by Arnaldo Carvalho de Melo
Browse files

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: default avatarIan Rogers <irogers@google.com>
Tested-by: default avatarWeilin 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: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 1c5721ca

tools/perf/util/intel-tpebs.c

+58 −1
Original line number Diff line number Diff line
@@ -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