From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756414AbbJ1XFJ (ORCPT ); Wed, 28 Oct 2015 19:05:09 -0400 Received: from shelob.surriel.com ([74.92.59.67]:58276 "EHLO shelob.surriel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755970AbbJ1XFG (ORCPT ); Wed, 28 Oct 2015 19:05:06 -0400 From: riel@redhat.com To: linux-kernel@vger.kernel.org Cc: arjan@linux.intel.com, khilman@ti.com, len.brown@intel.com, rafael.j.wysocki@intel.com, daniel.lezcano@linaro.org, javi.merino@arm.com, tuukka.tikkanen@linaro.org Subject: [PATCH 1/3] cpuidle,x86: increase forced cut-off for polling to 20us Date: Wed, 28 Oct 2015 18:46:54 -0400 Message-Id: <1446072416-13622-2-git-send-email-riel@redhat.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1446072416-13622-1-git-send-email-riel@redhat.com> References: <1446072416-13622-1-git-send-email-riel@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Rik van Riel The cpuidle menu governor has a forced cut-off for polling at 5us, in order to deal with firmware that gives the OS bad information on cpuidle states, leading to the system spending way too much time in polling. However, at least one x86 CPU family (Atom) has chips that have a 20us break-even point for C1. Forcing the polling cut-off to less than that wastes performance and power. Increase the polling cut-off to 20us. Systems with a lower C1 latency will be found in the states table by the menu governor, which will pick those states as appropriate. Signed-off-by: Rik van Riel --- drivers/cpuidle/governors/menu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index 22e4463d1787..ecc242a586c9 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -330,7 +330,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) * We want to default to C1 (hlt), not to busy polling * unless the timer is happening really really soon. */ - if (data->next_timer_us > 5 && + if (data->next_timer_us > 20 && !drv->states[CPUIDLE_DRIVER_STATE_START].disabled && dev->states_usage[CPUIDLE_DRIVER_STATE_START].disable == 0) data->last_state_idx = CPUIDLE_DRIVER_STATE_START; -- 2.1.0