From: Arnaldo Carvalho de Melo

Sent: 09 December 2021 18:51

...

quoted

diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
index 8cb5a1c3489e..d92ae4efd2e6 100644
--- a/tools/perf/tests/builtin-test.c
+++ b/tools/perf/tests/builtin-test.c

@@ -606,6 +606,9 @@ int cmd_test(int argc, const char **argv)
         if (ret < 0)
                 return ret;

+	/* Unbuffered output */
+	setvbuf(stdout, NULL, _IONBF, 0);
+

You only want _IOLBF (line buffered).

Otherwise you are likely to get a lot of write() system calls.
Even multiple ones from the same printf().

Although it can be better just to ensure there is a fflush(stdout)
inside the loop.

	David

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