perf metric: Add #num_cpus_online literal

Returns the number of CPUs online, unlike #num_cpus that returns the
number present.

Add a test of the property.

This will be used in future Intel metrics.

Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jing Zhang <renyu.zj@linux.alibaba.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Perry Taylor <perry.taylor@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20230830073026.1829912-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Author: captain5050

tools/perf/tests/expr.c

@@ -70,7 +70,7 @@ static int test__expr(struct test_suite *t __maybe_unused, int subtest __maybe_u
 {
 	struct expr_id_data *val_ptr;
 	const char *p;
-	double val, num_cpus, num_cores, num_dies, num_packages;
+	double val, num_cpus_online, num_cpus, num_cores, num_dies, num_packages;
 	int ret;
 	struct expr_parse_ctx *ctx;
 	bool is_intel = false;
@@ -227,7 +227,10 @@ static int test__expr(struct test_suite *t __maybe_unused, int subtest __maybe_u
 
 	/* Test toplogy constants appear well ordered. */
 	expr__ctx_clear(ctx);
+	TEST_ASSERT_VAL("#num_cpus_online",
+			expr__parse(&num_cpus_online, ctx, "#num_cpus_online") == 0);
 	TEST_ASSERT_VAL("#num_cpus", expr__parse(&num_cpus, ctx, "#num_cpus") == 0);
+	TEST_ASSERT_VAL("#num_cpus >= #num_cpus_online", num_cpus >= num_cpus_online);
 	TEST_ASSERT_VAL("#num_cores", expr__parse(&num_cores, ctx, "#num_cores") == 0);
 	TEST_ASSERT_VAL("#num_cpus >= #num_cores", num_cpus >= num_cores);
 	TEST_ASSERT_VAL("#num_dies", expr__parse(&num_dies, ctx, "#num_dies") == 0);

tools/perf/util/expr.c

@@ -427,6 +427,13 @@ double expr__get_literal(const char *literal, const struct expr_scanner_ctx *ctx
 		result = cpu__max_present_cpu().cpu;
 		goto out;
 	}
+	if (!strcmp("#num_cpus_online", literal)) {
+		struct perf_cpu_map *online = cpu_map__online();
+
+		if (online)
+			result = perf_cpu_map__nr(online);
+		goto out;
+	}
 
 	if (!strcasecmp("#system_tsc_freq", literal)) {
 		result = arch_get_tsc_freq();