From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anton Blanchard Subject: [PATCH 3/3] cpuidle: powernv: Avoid a branch in the core snooze_loop() loop Date: Tue, 4 Apr 2017 07:54:14 +1000 Message-ID: <20170403215414.16951-3-anton@ozlabs.org> References: <20170403215414.16951-1-anton@ozlabs.org> Return-path: Received: from ozlabs.org ([103.22.144.67]:47869 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751210AbdDCVye (ORCPT ); Mon, 3 Apr 2017 17:54:34 -0400 In-Reply-To: <20170403215414.16951-1-anton@ozlabs.org> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, svaidy@linux.vnet.ibm.com, ego@linux.vnet.ibm.com, rjw@rjwysocki.net, daniel.lezcano@linaro.org, npiggin@gmail.com Cc: linuxppc-dev@lists.ozlabs.org, linux-pm@vger.kernel.org From: Anton Blanchard 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 --- 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, ppc64_runlatch_off(); HMT_very_low(); while (!need_resched()) { - if (snooze_timeout_en && get_tb() > snooze_exit_time) + if (likely(snooze_timeout_en) && get_tb() > snooze_exit_time) break; } -- 2.11.0