linux-kernel - [RFC PATCH v1 33/37] perf record: pin threads to monitored cpus if enough threads available

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Message-Id: <d2218d8fc69eb7c9e85454af5065523f86c37ff1.1629490974.git.rickyman7@gmail.com>
Date:   Sat, 21 Aug 2021 11:19:39 +0200
From:   Riccardo Mancini <rickyman7@...il.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Ian Rogers <irogers@...gle.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org,
        Riccardo Mancini <rickyman7@...il.com>
Subject: [RFC PATCH v1 33/37] perf record: pin threads to monitored cpus if enough threads available

This patch sets the affinity of the workqueue threads to pin them to
each monitored CPU in case the --threads option is set with enough
threads and evlist multithreading is enabled.

This yields a better performance for the evlist operations, since
affinity need not be sent by each thread everytime.

Signed-off-by: Riccardo Mancini <rickyman7@...il.com>
---
 tools/perf/builtin-record.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 7802a0e25f631fac..e2d2445e05d7c07a 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -2945,6 +2945,16 @@ int cmd_record(int argc, const char **argv)
 			pr_err("setup_global_workqueue: %s\n", errbuf);
 			goto out;
 		}
+
+		if ((int)rec->opts.nr_threads >= rec->evlist->core.all_cpus->nr
+				&& rec->opts.multithreaded_evlist) {
+			err = workqueue_set_affinities_cpu(global_wq, rec->evlist->core.all_cpus);
+			if (err) {
+				workqueue_strerror(global_wq, err, errbuf, sizeof(errbuf));
+				pr_err("workqueue_set_affinities_cpu: %s\n", errbuf);
+				goto out;
+			}
+		}
 	}
 
 	err = __cmd_record(&record, argc, argv);
-- 
2.31.1