perf bench syscall: Add fork syscall benchmark

This is a follow up patch for the execve bench which is actually
fork + execve, it makes sense to add the fork syscall benchmark
to compare the execve part precisely.

Some archs have no __NR_fork definition which is used only as a
check condition to call test_fork(), let us just define it as -1
to avoid build error.

Suggested-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: loongson-kernel@lists.loongnix.cn
Link: https://lore.kernel.org/r/1679381821-22736-1-git-send-email-yangtiezhu@loongson.cn
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/arch/x86/include/uapi/asm/unistd_32.h

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 */
-#ifndef __NR_execve
-#define __NR_execve 11
+#ifndef __NR_fork
+#define __NR_fork 2
 #endif
 #ifndef __NR_getppid
 #define __NR_getppid 64

tools/arch/x86/include/uapi/asm/unistd_64.h

@@ -1,4 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __NR_fork
+#define __NR_fork 57
+#endif
 #ifndef __NR_execve
 #define __NR_execve 59
 #endif

tools/perf/bench/bench.h

@@ -23,6 +23,7 @@ int bench_sched_messaging(int argc, const char **argv);
 int bench_sched_pipe(int argc, const char **argv);
 int bench_syscall_basic(int argc, const char **argv);
 int bench_syscall_getpgid(int argc, const char **argv);
+int bench_syscall_fork(int argc, const char **argv);
 int bench_syscall_execve(int argc, const char **argv);
 int bench_mem_memcpy(int argc, const char **argv);
 int bench_mem_memset(int argc, const char **argv);

tools/perf/bench/syscall.c

@@ -18,6 +18,10 @@
 #include <unistd.h>
 #include <stdlib.h>
 
+#ifndef __NR_fork
+#define __NR_fork -1
+#endif
+
 #define LOOPS_DEFAULT 10000000
 static	int loops = LOOPS_DEFAULT;
 
@@ -31,6 +35,23 @@ static const char * const bench_syscall_usage[] = {
 	NULL
 };
 
+static void test_fork(void)
+{
+	pid_t pid = fork();
+
+	if (pid < 0) {
+		fprintf(stderr, "fork failed\n");
+		exit(1);
+	} else if (pid == 0) {
+		exit(0);
+	} else {
+		if (waitpid(pid, NULL, 0) < 0) {
+			fprintf(stderr, "waitpid failed\n");
+			exit(1);
+		}
+	}
+}
+
 static void test_execve(void)
 {
 	const char *pathname = "/bin/true";
@@ -71,6 +92,12 @@ static int bench_syscall_common(int argc, const char **argv, int syscall)
 		case __NR_getpgid:
 			getpgid(0);
 			break;
+		case __NR_fork:
+			test_fork();
+			/* Only loop 10000 times to save time */
+			if (i == 10000)
+				loops = 10000;
+			break;
 		case __NR_execve:
 			test_execve();
 			/* Only loop 10000 times to save time */
@@ -92,6 +119,9 @@ static int bench_syscall_common(int argc, const char **argv, int syscall)
 	case __NR_getpgid:
 		name = "getpgid()";
 		break;
+	case __NR_fork:
+		name = "fork()";
+		break;
 	case __NR_execve:
 		name = "execve()";
 		break;
@@ -143,6 +173,11 @@ int bench_syscall_getpgid(int argc, const char **argv)
 	return bench_syscall_common(argc, argv, __NR_getpgid);
 }
 
+int bench_syscall_fork(int argc, const char **argv)
+{
+	return bench_syscall_common(argc, argv, __NR_fork);
+}
+
 int bench_syscall_execve(int argc, const char **argv)
 {
 	return bench_syscall_common(argc, argv, __NR_execve);

tools/perf/builtin-bench.c

@@ -53,6 +53,7 @@ static struct bench sched_benchmarks[] = {
 static struct bench syscall_benchmarks[] = {
 	{ "basic",	"Benchmark for basic getppid(2) calls",		bench_syscall_basic	},
 	{ "getpgid",	"Benchmark for getpgid(2) calls",		bench_syscall_getpgid	},
+	{ "fork",	"Benchmark for fork(2) calls",			bench_syscall_fork	},
 	{ "execve",	"Benchmark for execve(2) calls",		bench_syscall_execve	},
 	{ "all",	"Run all syscall benchmarks",			NULL			},
 	{ NULL,		NULL,						NULL			},