perf bench: Fix perf bench syscall loop count

Command 'perf bench syscall fork -l 100000' offers option -l to run for
a specified number of iterations. However this option is not always
observed. The number is silently limited to 10000 iterations as can be
seen:

Output before:
# perf bench syscall fork -l 100000
# Running 'syscall/fork' benchmark:
# Executed 10,000 fork() calls
Total time: 23.388 [sec]

2338.809800 usecs/op
427 ops/sec
#

When explicitly specified with option -l or --loops, also observe
higher number of iterations:

Output after:
# perf bench syscall fork -l 100000
# Running 'syscall/fork' benchmark:
# Executed 100,000 fork() calls
Total time: 716.982 [sec]

7169.829510 usecs/op
139 ops/sec
#

This patch fixes the issue for basic execve fork and getpgid.

Fixes: ece7f7c0507c ("perf bench syscall: Add fork syscall benchmark")
Signed-off-by: Thomas Richter <[e-mail]>
Acked-by: Sumanth Korikkar <[e-mail]>
Tested-by: Athira Rajeev <[e-mail]>
Cc: Tiezhu Yang <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Namhyung Kim <[e-mail]>

tools/perf/bench/syscall.c

···
 #define __NR_fork -1
 #endif
 
-#define LOOPS_DEFAULT 10000000
-static	int loops = LOOPS_DEFAULT;
+static	int loops;
 
 static const struct option options[] = {
 	OPT_INTEGER('l', "loop",	&loops,		"Specify number of loops"),
···
 	const char *name = NULL;
 	int i;
 
+	switch (syscall) {
+	case __NR_fork:
+	case __NR_execve:
+		/* Limit default loop to 10000 times to save time */
+		loops = 10000;
+		break;
+	default:
+		loops = 10000000;
+		break;
+	}
+
+	/* Options -l and --loops override default above */
 	argc = parse_options(argc, argv, options, bench_syscall_usage, 0);
 
 	gettimeofday(&start, NULL);
···
 			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 */
-			if (i == 10000)
-				loops = 10000;
-			break;
 		default:
 			break;
 		}