perf smt: Compute SMT from topology

The topology records sibling threads. Rather than computing SMT using
siblings in sysfs, reuse the values in topology. This only applies
when the file smt/active isn't available.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Ahmad Yasin <ahmad.yasin@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Caleb Biggers <caleb.biggers@intel.com>
Cc: Florian Fischer <florian.fischer@muhq.space>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.garry@huawei.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Kshipra Bopardikar <kshipra.bopardikar@intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Miaoqian Lin <linmq006@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Perry Taylor <perry.taylor@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Link: https://lore.kernel.org/r/20220831174926.579643-4-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 9 insertions, 86 deletions

diff --git a/tools/perf/util/smt.c b/tools/perf/util/smt.c
index 8fed03283c85..ce90c4ee4138 100644
--- a/tools/perf/util/smt.c
+++ b/tools/perf/util/smt.c
@@ -1,100 +1,23 @@
 // SPDX-License-Identifier: GPL-2.0-only
-#include <stdio.h>
-#include <stdlib.h>
-#include <unistd.h>
-#include <linux/bitops.h>
+#include <string.h>
 #include "api/fs/fs.h"
+#include "cputopo.h"
 #include "smt.h"
 
-/**
- * hweight_str - Returns the number of bits set in str. Stops at first non-hex
- *	       or ',' character.
- */
-static int hweight_str(char *str)
-{
-	int result = 0;
-
-	while (*str) {
-		switch (*str++) {
-		case '0':
-		case ',':
-			break;
-		case '1':
-		case '2':
-		case '4':
-		case '8':
-			result++;
-			break;
-		case '3':
-		case '5':
-		case '6':
-		case '9':
-		case 'a':
-		case 'A':
-		case 'c':
-		case 'C':
-			result += 2;
-			break;
-		case '7':
-		case 'b':
-		case 'B':
-		case 'd':
-		case 'D':
-		case 'e':
-		case 'E':
-			result += 3;
-			break;
-		case 'f':
-		case 'F':
-			result += 4;
-			break;
-		default:
-			goto done;
-		}
-	}
-done:
-	return result;
-}
-
-int smt_on(void)
+bool smt_on(const struct cpu_topology *topology)
 {
 	static bool cached;
-	static int cached_result;
-	int cpu;
-	int ncpu;
+	static bool cached_result;
+	int fs_value;
 
 	if (cached)
 		return cached_result;
 
-	if (sysfs__read_int("devices/system/cpu/smt/active", &cached_result) >= 0) {
-		cached = true;
-		return cached_result;
-	}
-
-	cached_result = 0;
-	ncpu = sysconf(_SC_NPROCESSORS_CONF);
-	for (cpu = 0; cpu < ncpu; cpu++) {
-		unsigned long long siblings;
-		char *str;
-		size_t strlen;
-		char fn[256];
+	if (sysfs__read_int("devices/system/cpu/smt/active", &fs_value) >= 0)
+		cached_result = (fs_value == 1);
+	else
+		cached_result = cpu_topology__smt_on(topology);
 
-		snprintf(fn, sizeof fn,
-			"devices/system/cpu/cpu%d/topology/thread_siblings", cpu);
-		if (sysfs__read_str(fn, &str, &strlen) < 0) {
-			snprintf(fn, sizeof fn,
-				"devices/system/cpu/cpu%d/topology/core_cpus", cpu);
-			if (sysfs__read_str(fn, &str, &strlen) < 0)
-				continue;
-		}
-		/* Entry is hex, but does not have 0x, so need custom parser */
-		siblings = hweight_str(str);
-		free(str);
-		if (siblings > 1) {
-			cached_result = 1;
-			break;
-		}
-	}
 	cached = true;
 	return cached_result;
 }