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 <tmricht@linux.ibm.com>
Acked-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Tested-by: Athira Rajeev <atrajeev@linux.ibm.com>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Link: https://lore.kernel.org/r/20250304092349.2618082-1-tmricht@linux.ibm.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

diff --git a/tools/perf/bench/syscall.c b/tools/perf/bench/syscall.c
index ea4dfc07cbd6b847a4f64784dea93983f8038f6e..e7dc216f717f5a27756950dfa58d0205d12cba93 100644 (file)
--- a/tools/perf/bench/syscall.c
+++ b/tools/perf/bench/syscall.c
@@ -22,8 +22,7 @@
 #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"),
@@ -80,6 +79,18 @@ static int bench_syscall_common(int argc, const char **argv, int syscall)
        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);
@@ -94,16 +105,9 @@ static int bench_syscall_common(int argc, const char **argv, int syscall)
                        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;
                }