From mboxrd@z Thu Jan 1 00:00:00 1970 From: Prashanth Prakash Subject: [PATCH v3 1/2] cpuidle: Add new macro to enter a retention idle state Date: Wed, 15 Nov 2017 10:11:49 -0700 Message-ID: <1510765910-23739-2-git-send-email-pprakash@codeaurora.org> References: <1510765910-23739-1-git-send-email-pprakash@codeaurora.org> Return-path: Received: from smtp.codeaurora.org ([198.145.29.96]:47630 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933355AbdKORMC (ORCPT ); Wed, 15 Nov 2017 12:12:02 -0500 In-Reply-To: <1510765910-23739-1-git-send-email-pprakash@codeaurora.org> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: sudeep.holla@arm.com, rjw@rjwysocki.net, daniel.lezcano@linaro.org, will.deacon@arm.com, catalin.marinas@arm.com, Prashanth Prakash If a CPU is entering a low power idle state where it doesn't lose any context, then there is no need to call cpu_pm_enter()/cpu_pm_exit(). Add a new macro(CPU_PM_CPU_IDLE_ENTER_RETENTION) to be used by cpuidle drivers when they are entering retention state. By not calling cpu_pm_enter and cpu_pm_exit we reduce the latency involved in entering and exiting the retention idle states. CPU_PM_CPU_IDLE_ENTER_RETENTION assumes that no state is lost and hence CPU PM notifiers will not be called. We may need a broader change if we need to support partial retention states effeciently. On ARM64 based Qualcomm Server Platform we measured below overhead for for calling cpu_pm_enter and cpu_pm_exit for retention states. workload: stress --hdd #CPUs --hdd-bytes 32M -t 30 Average overhead of cpu_pm_enter - 1.2us Average overhead of cpu_pm_exit - 3.1us Signed-off-by: Prashanth Prakash Acked-by: Sudeep Holla --- include/linux/cpuidle.h | 40 ++++++++++++++++++++++++---------------- 1 file changed, 24 insertions(+), 16 deletions(-) diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h index 8f7788d..871f9e2 100644 --- a/include/linux/cpuidle.h +++ b/include/linux/cpuidle.h @@ -257,22 +257,30 @@ static inline int cpuidle_register_governor(struct cpuidle_governor *gov) {return 0;} #endif -#define CPU_PM_CPU_IDLE_ENTER(low_level_idle_enter, idx) \ -({ \ - int __ret; \ - \ - if (!idx) { \ - cpu_do_idle(); \ - return idx; \ - } \ - \ - __ret = cpu_pm_enter(); \ - if (!__ret) { \ - __ret = low_level_idle_enter(idx); \ - cpu_pm_exit(); \ - } \ - \ - __ret ? -1 : idx; \ +#define __CPU_PM_CPU_IDLE_ENTER(low_level_idle_enter, idx, is_retention) \ +({ \ + int __ret = 0; \ + \ + if (!idx) { \ + cpu_do_idle(); \ + return idx; \ + } \ + \ + if (!is_retention) \ + __ret = cpu_pm_enter(); \ + if (!__ret) { \ + __ret = low_level_idle_enter(idx); \ + if (!is_retention) \ + cpu_pm_exit(); \ + } \ + \ + __ret ? -1 : idx; \ }) +#define CPU_PM_CPU_IDLE_ENTER(low_level_idle_enter, idx) \ + __CPU_PM_CPU_IDLE_ENTER(low_level_idle_enter, idx, 0) + +#define CPU_PM_CPU_IDLE_ENTER_RETENTION(low_level_idle_enter, idx) \ + __CPU_PM_CPU_IDLE_ENTER(low_level_idle_enter, idx, 1) + #endif /* _LINUX_CPUIDLE_H */ -- Qualcomm Datacenter Technologies on behalf of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.