Le 27/09/2016 à 16:10, Rui Teng a écrit :
From: Anton Blanchard <anton@xxxxxxxxxx>
Pull in a version of Anton's null_syscall benchmark:
http://ozlabs.org/~anton/junkcode/null_syscall.c
Into tools/testing/selftests/powerpc/benchmarks.
Suggested-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Anton Blanchard <anton@xxxxxxxxxx>
Signed-off-by: Rui Teng <rui.teng@xxxxxxxxxxxxxxxxxx>
---
.../testing/selftests/powerpc/benchmarks/Makefile | 2 +-
.../selftests/powerpc/benchmarks/null_syscall.c | 157 +++++++++++++++++++++
2 files changed, 158 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/powerpc/benchmarks/null_syscall.c
[...]
+
+static void do_null_syscall(unsigned long nr)
+{
+ unsigned long i;
+
+ for (i = 0; i < nr; i++)
+ getppid();
+}
+
Looks like getppid() performs a rcu_read_lock(). Is that what we want ?
Shouldn't we use getpid() instead for a lighter syscall ?
Christophe
