[PATCH 3/3] cpuidle: powernv: Avoid a branch in the core snooze_loop() loop

Anton Blanchard anton at ozlabs.org
Tue Apr 4 07:54:14 AEST 2017

From: Anton Blanchard <anton at samba.org>

When in the snooze_loop() we want to take up the least amount of
resources. On my version of gcc (6.3), we end up with an extra
branch because it predicts snooze_timeout_en to be false, whereas it
is almost always true.

Use likely() to avoid the branch and be a little nicer to the
other non idle threads on the core.

Signed-off-by: Anton Blanchard <anton at samba.org>
 drivers/cpuidle/cpuidle-powernv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index 8c991c254b95..251a60bfa8ee 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c
@@ -58,7 +58,7 @@ static int snooze_loop(struct cpuidle_device *dev,
 	while (!need_resched()) {
-		if (snooze_timeout_en && get_tb() > snooze_exit_time)
+		if (likely(snooze_timeout_en) && get_tb() > snooze_exit_time)

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