linux-kernel - [PATCH v1 8/8] libperf cpumap: Grow array of read CPUs in smaller increments

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Message-Id: <20241206044035.1062032-9-irogers@google.com>
Date: Thu,  5 Dec 2024 20:40:35 -0800
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, James Clark <james.clark@...aro.org>, 
	Kyle Meyer <kyle.meyer@....com>, Ben Gainey <ben.gainey@....com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1 8/8] libperf cpumap: Grow array of read CPUs in smaller increments

Instead of growing the array by 2048, grow by the larger of the
current range or 16. As ranges are typical for things like the online
CPUs this will mean a single allocation happens. While uncore CPU maps
will grow 16 at a time which is a value that is generous except say on
large servers.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/lib/perf/cpumap.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/tools/lib/perf/cpumap.c b/tools/lib/perf/cpumap.c
index 17413d3a2221..2237505f8f5f 100644
--- a/tools/lib/perf/cpumap.c
+++ b/tools/lib/perf/cpumap.c
@@ -212,7 +212,7 @@ struct perf_cpu_map *perf_cpu_map__new(const char *cpu_list)
 					goto invalid;
 
 			if (nr_cpus == max_entries) {
-				max_entries += MAX_NR_CPUS;
+				max_entries += max(end_cpu - start_cpu + 1, 16UL);
 				tmp = realloc(tmp_cpus, max_entries * sizeof(struct perf_cpu));
 				if (tmp == NULL)
 					goto invalid;
@@ -226,14 +226,15 @@ struct perf_cpu_map *perf_cpu_map__new(const char *cpu_list)
 		cpu_list = p;
 	}
 
-	if (nr_cpus > 0)
+	if (nr_cpus > 0) {
 		cpus = cpu_map__trim_new(nr_cpus, tmp_cpus);
-	else if (*cpu_list != '\0') {
+	} else if (*cpu_list != '\0') {
 		pr_warning("Unexpected characters at end of cpu list ('%s'), using online CPUs.",
 			   cpu_list);
 		cpus = perf_cpu_map__new_online_cpus();
-	} else
+	} else {
 		cpus = perf_cpu_map__new_any_cpu();
+	}
 invalid:
 	free(tmp_cpus);
 out:
-- 
2.47.0.338.g60cca15819-goog