perf header: Move is_cpu_online to numa bench

The helper function is only used in the NUMA benchmark as typically
online CPUs are determined through perf_cpu_map__new_online_cpus().

Reduce the scope of the function for now.

Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Xu Yang <xu.yang_2@nxp.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Ben Zong-You Xie <ben717@andestech.com>
Cc: Benjamin Gray <bgray@linux.ibm.com>
Cc: Bibo Mao <maobibo@loongson.cn>
Cc: Clément Le Goffic <clement.legoffic@foss.st.com>
Cc: Dima Kogan <dima@secretsauce.net>
Cc: Dr. David Alan Gilbert <linux@treblig.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linux.dev>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yicong Yang <yangyicong@hisilicon.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-riscv@lists.infradead.org
Link: https://lore.kernel.org/r/20241107162035.52206-3-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Author: captain5050

tools/perf/bench/numa.c

@@ -27,6 +27,7 @@
 #include <sys/resource.h>
 #include <sys/wait.h>
 #include <sys/prctl.h>
+#include <sys/stat.h>
 #include <sys/types.h>
 #include <linux/kernel.h>
 #include <linux/time64.h>
@@ -35,6 +36,7 @@
 
 #include "../util/header.h"
 #include "../util/mutex.h"
+#include <api/fs/fs.h>
 #include <numa.h>
 #include <numaif.h>
 
@@ -533,6 +535,57 @@ static int parse_cpu_list(const char *arg)
 	return 0;
 }
 
+/*
+ * Check whether a CPU is online
+ *
+ * Returns:
+ *     1 -> if CPU is online
+ *     0 -> if CPU is offline
+ *    -1 -> error case
+ */
+static int is_cpu_online(unsigned int cpu)
+{
+	char *str;
+	size_t strlen;
+	char buf[256];
+	int status = -1;
+	struct stat statbuf;
+
+	snprintf(buf, sizeof(buf),
+		"/sys/devices/system/cpu/cpu%d", cpu);
+	if (stat(buf, &statbuf) != 0)
+		return 0;
+
+	/*
+	 * Check if /sys/devices/system/cpu/cpux/online file
+	 * exists. Some cases cpu0 won't have online file since
+	 * it is not expected to be turned off generally.
+	 * In kernels without CONFIG_HOTPLUG_CPU, this
+	 * file won't exist
+	 */
+	snprintf(buf, sizeof(buf),
+		"/sys/devices/system/cpu/cpu%d/online", cpu);
+	if (stat(buf, &statbuf) != 0)
+		return 1;
+
+	/*
+	 * Read online file using sysfs__read_str.
+	 * If read or open fails, return -1.
+	 * If read succeeds, return value from file
+	 * which gets stored in "str"
+	 */
+	snprintf(buf, sizeof(buf),
+		"devices/system/cpu/cpu%d/online", cpu);
+
+	if (sysfs__read_str(buf, &str, &strlen) < 0)
+		return status;
+
+	status = atoi(str);
+
+	free(str);
+	return status;
+}
+
 static int parse_setup_cpu_list(void)
 {
 	struct thread_data *td;

tools/perf/util/header.c

@@ -987,57 +987,6 @@ static int write_dir_format(struct feat_fd *ff,
 	return do_write(ff, &data->dir.version, sizeof(data->dir.version));
 }
 
-/*
- * Check whether a CPU is online
- *
- * Returns:
- *     1 -> if CPU is online
- *     0 -> if CPU is offline
- *    -1 -> error case
- */
-int is_cpu_online(unsigned int cpu)
-{
-	char *str;
-	size_t strlen;
-	char buf[256];
-	int status = -1;
-	struct stat statbuf;
-
-	snprintf(buf, sizeof(buf),
-		"/sys/devices/system/cpu/cpu%d", cpu);
-	if (stat(buf, &statbuf) != 0)
-		return 0;
-
-	/*
-	 * Check if /sys/devices/system/cpu/cpux/online file
-	 * exists. Some cases cpu0 won't have online file since
-	 * it is not expected to be turned off generally.
-	 * In kernels without CONFIG_HOTPLUG_CPU, this
-	 * file won't exist
-	 */
-	snprintf(buf, sizeof(buf),
-		"/sys/devices/system/cpu/cpu%d/online", cpu);
-	if (stat(buf, &statbuf) != 0)
-		return 1;
-
-	/*
-	 * Read online file using sysfs__read_str.
-	 * If read or open fails, return -1.
-	 * If read succeeds, return value from file
-	 * which gets stored in "str"
-	 */
-	snprintf(buf, sizeof(buf),
-		"devices/system/cpu/cpu%d/online", cpu);
-
-	if (sysfs__read_str(buf, &str, &strlen) < 0)
-		return status;
-
-	status = atoi(str);
-
-	free(str);
-	return status;
-}
-
 #ifdef HAVE_LIBBPF_SUPPORT
 static int write_bpf_prog_info(struct feat_fd *ff,
 			       struct evlist *evlist __maybe_unused)

tools/perf/util/header.h

@@ -196,7 +196,6 @@ int write_padded(struct feat_fd *fd, const void *bf,
 
 #define MAX_CACHE_LVL 4
 
-int is_cpu_online(unsigned int cpu);
 int build_caches_for_cpu(u32 cpu, struct cpu_cache_level caches[], u32 *cntp);
 
 /*