From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Shi Subject: Re: [PATCH 3/3] cpuidle/menu: add per cpu pm_qos_resume_latency consideration Date: Thu, 19 Jan 2017 17:25:37 +0800 Message-ID: <01f9b016-0b7c-44ac-70e5-8cd9b8bd1500@linaro.org> References: <1484227624-6740-1-git-send-email-alex.shi@linaro.org> <1484227624-6740-4-git-send-email-alex.shi@linaro.org> <20170117093837.GA2085@mai> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20170117093837.GA2085@mai> Sender: linux-kernel-owner@vger.kernel.org To: Daniel Lezcano Cc: Greg Kroah-Hartman , "Rafael J . Wysocki" , vincent.guittot@linaro.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Ulf Hansson , Rasmus Villemoes , Arjan van de Ven , Rik van Riel List-Id: linux-pm@vger.kernel.org > That said, I have the feeling that is taking the wrong direction. Each time we > are entering idle, we check the latencies. Entering idle can be done thousand > of times per second. Wouldn't make sense to disable the states not fulfilling > the constraints at the moment the latencies are changed ? As the idle states > have increasing exit latencies, setting an idle state limit to disable all > states after that limit may be more efficient than checking again and again in > the idle path, no ? You'r right. save some checking is good thing to do. >>From 9e1cc3e02b8d954e606dd5a0f6466a8d5b3efab7 Mon Sep 17 00:00:00 2001 From: Alex Shi Date: Wed, 26 Oct 2016 15:26:22 +0800 Subject: [PATCH 2/2] cpuidle/menu: add per cpu pm_qos_resume_latency consideration Kernel or user may have special requirement on cpu response time, like if a interrupt is pinned to a cpu, we don't want the cpu goes too deep sleep. This patch can prevent this thing happen by consider per cpu resume_latency setting in cpu sleep state selection in menu governor. The pm_qos_resume_latency ask device to give reponse in this time. That's similar with cpu cstates' entry_latency + exit_latency. But since most of cpu cstate either has no entry_latency or add it into exit_latency So, we just can restrict this time requirement as states exit_latency. We can set a wanted latency value according to the value of /sys/devices/system/cpu/cpuX/cpuidle/stateX/latency. to just a bit less than related state's latency value. Then cpu can get to this state or higher. Signed-off-by: Alex Shi Acked-by: Rik van Riel To: linux-kernel@vger.kernel.org Cc: linux-pm@vger.kernel.org Cc: Ulf Hansson Cc: Daniel Lezcano Cc: Rasmus Villemoes Cc: Arjan van de Ven Cc: Rik van Riel Cc: "Rafael J. Wysocki" --- drivers/base/cpu.c | 2 ++ drivers/cpuidle/governors/menu.c | 10 ++++++++++ 2 files changed, 12 insertions(+) diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c index 4c28e1a..2c3b359 100644 --- a/drivers/base/cpu.c +++ b/drivers/base/cpu.c @@ -17,6 +17,7 @@ #include #include #include +#include #include "base.h" @@ -376,6 +377,7 @@ int register_cpu(struct cpu *cpu, int num) per_cpu(cpu_sys_devices, num) = &cpu->dev; register_cpu_under_node(num, cpu_to_node(num)); + dev_pm_qos_expose_latency_limit(&cpu->dev, 0); return 0; } diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index 07e36bb..cc7d873 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -19,6 +19,7 @@ #include #include #include +#include /* * Please note when changing the tuning values: @@ -280,11 +281,13 @@ static unsigned int get_typical_interval(struct menu_device *data) static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) { struct menu_device *data = this_cpu_ptr(&menu_devices); + struct device *device; int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY); int i; unsigned int interactivity_req; unsigned int expected_interval; unsigned long nr_iowaiters, cpu_load; + int resume_latency; if (data->needs_update) { menu_update(drv, dev); @@ -295,6 +298,13 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) if (unlikely(latency_req == 0)) return 0; + device = get_cpu_device(dev->cpu); + + /* resume_latency is 0 means no restriction */ + resume_latency = dev_pm_qos_read_value(device); + if (resume_latency) + latency_req = min(latency_req, resume_latency); + /* determine the expected residency time, round up */ data->next_timer_us = ktime_to_us(tick_nohz_get_sleep_length()); -- 2.8.1.101.g72d917a > > For example, a zero PM_QOS_CPU_DMA_LATENCY latency should prevent to enter the > select's idle routine. That's a good idea. I will give a draft change to review! :)