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[209.132.180.67]) by mx.google.com with ESMTP id p84-v6si26978890pfl.17.2018.07.16.01.30.17; Mon, 16 Jul 2018 01:30:31 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730744AbeGPIzo (ORCPT + 99 others); Mon, 16 Jul 2018 04:55:44 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:54306 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726190AbeGPIzo (ORCPT ); Mon, 16 Jul 2018 04:55:44 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 71104ED1; Mon, 16 Jul 2018 01:29:28 -0700 (PDT) Received: from e110439-lin.cambridge.arm.com (e110439-lin.cambridge.arm.com [10.1.210.68]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id A4A2E3F5A0; Mon, 16 Jul 2018 01:29:25 -0700 (PDT) From: Patrick Bellasi To: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Cc: Ingo Molnar , Peter Zijlstra , Tejun Heo , "Rafael J . Wysocki" , Viresh Kumar , Vincent Guittot , Paul Turner , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes , Steve Muckle , Suren Baghdasaryan Subject: [PATCH v2 01/12] sched/core: uclamp: extend sched_setattr to support utilization clamping Date: Mon, 16 Jul 2018 09:28:55 +0100 Message-Id: <20180716082906.6061-2-patrick.bellasi@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180716082906.6061-1-patrick.bellasi@arm.com> References: <20180716082906.6061-1-patrick.bellasi@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The SCHED_DEADLINE scheduling class provides an advanced and formal model to define tasks requirements which can be translated into proper decisions for both task placements and frequencies selections. Other classes have a more simplified model which is essentially based on the relatively simple concept of POSIX priorities. Such a simple priority based model however does not allow to exploit some of the most advanced features of the Linux scheduler like, for example, driving frequencies selection via the schedutil cpufreq governor. However, also for non SCHED_DEADLINE tasks, it's still interesting to define tasks properties which can be used to better support certain scheduler decisions. Utilization clamping aims at exposing to user-space a new set of per-task attributes which can be used to provide the scheduler with some hints about the expected/required utilization for a task. This will allow to implement a more advanced per-task frequency control mechanism which is not based just on a "passive" measured task utilization but on a more "active" approach. For example, it could be possible to boost interactive tasks, thus getting better performance, or cap background tasks, thus being more energy efficient. Ultimately, such a mechanism can be considered similar to the cpufreq's powersave, performance and userspace governor but with a much fine grained and per-task control. Let's introduce a new API to set utilization clamping values for a specified task by extending sched_setattr, a syscall which already allows to define task specific properties for different scheduling classes. Specifically, a new pair of attributes allows to specify a minimum and maximum utilization which the scheduler should consider for a task. Signed-off-by: Patrick Bellasi Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Tejun Heo Cc: Rafael J. Wysocki Cc: Vincent Guittot Cc: Viresh Kumar Cc: Paul Turner Cc: Todd Kjos Cc: Joel Fernandes Cc: Steve Muckle Cc: Juri Lelli Cc: Dietmar Eggemann Cc: Morten Rasmussen Cc: linux-kernel@vger.kernel.org Cc: linux-pm@vger.kernel.org --- include/linux/sched.h | 16 ++++++++ include/uapi/linux/sched.h | 4 +- include/uapi/linux/sched/types.h | 64 +++++++++++++++++++++++++++----- init/Kconfig | 19 ++++++++++ kernel/sched/core.c | 39 +++++++++++++++++++ 5 files changed, 132 insertions(+), 10 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 43731fe51c97..fd8495723088 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -279,6 +279,17 @@ struct vtime { u64 gtime; }; +enum uclamp_id { + /* No utilization clamp group assigned */ + UCLAMP_NONE = -1, + + UCLAMP_MIN = 0, /* Minimum utilization */ + UCLAMP_MAX, /* Maximum utilization */ + + /* Utilization clamping constraints count */ + UCLAMP_CNT +}; + struct sched_info { #ifdef CONFIG_SCHED_INFO /* Cumulative counters: */ @@ -649,6 +660,11 @@ struct task_struct { #endif struct sched_dl_entity dl; +#ifdef CONFIG_UCLAMP_TASK + /* Utlization clamp values for this task */ + int uclamp[UCLAMP_CNT]; +#endif + #ifdef CONFIG_PREEMPT_NOTIFIERS /* List of struct preempt_notifier: */ struct hlist_head preempt_notifiers; diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h index 22627f80063e..c27d6e81517b 100644 --- a/include/uapi/linux/sched.h +++ b/include/uapi/linux/sched.h @@ -50,9 +50,11 @@ #define SCHED_FLAG_RESET_ON_FORK 0x01 #define SCHED_FLAG_RECLAIM 0x02 #define SCHED_FLAG_DL_OVERRUN 0x04 +#define SCHED_FLAG_UTIL_CLAMP 0x08 #define SCHED_FLAG_ALL (SCHED_FLAG_RESET_ON_FORK | \ SCHED_FLAG_RECLAIM | \ - SCHED_FLAG_DL_OVERRUN) + SCHED_FLAG_DL_OVERRUN | \ + SCHED_FLAG_UTIL_CLAMP) #endif /* _UAPI_LINUX_SCHED_H */ diff --git a/include/uapi/linux/sched/types.h b/include/uapi/linux/sched/types.h index 10fbb8031930..7421cd25354d 100644 --- a/include/uapi/linux/sched/types.h +++ b/include/uapi/linux/sched/types.h @@ -21,8 +21,33 @@ struct sched_param { * the tasks may be useful for a wide variety of application fields, e.g., * multimedia, streaming, automation and control, and many others. * - * This variant (sched_attr) is meant at describing a so-called - * sporadic time-constrained task. In such model a task is specified by: + * This variant (sched_attr) allows to define additional attributes to + * improve the scheduler knowledge about task requirements. + * + * Scheduling Class Attributes + * =========================== + * + * A subset of sched_attr attributes specifies the + * scheduling policy and relative POSIX attributes: + * + * @size size of the structure, for fwd/bwd compat. + * + * @sched_policy task's scheduling policy + * @sched_nice task's nice value (SCHED_NORMAL/BATCH) + * @sched_priority task's static priority (SCHED_FIFO/RR) + * + * Certain more advanced scheduling features can be controlled by a + * predefined set of flags via the attribute: + * + * @sched_flags for customizing the scheduler behaviour + * + * Sporadic Time-Constrained Tasks Attributes + * ========================================== + * + * A subset of sched_attr attributes allows to describe a so-called + * sporadic time-constrained task. + * + * In such model a task is specified by: * - the activation period or minimum instance inter-arrival time; * - the maximum (or average, depending on the actual scheduling * discipline) computation time of all instances, a.k.a. runtime; @@ -34,14 +59,8 @@ struct sched_param { * than the runtime and must be completed by time instant t equal to * the instance activation time + the deadline. * - * This is reflected by the actual fields of the sched_attr structure: + * This is reflected by the following fields of the sched_attr structure: * - * @size size of the structure, for fwd/bwd compat. - * - * @sched_policy task's scheduling policy - * @sched_flags for customizing the scheduler behaviour - * @sched_nice task's nice value (SCHED_NORMAL/BATCH) - * @sched_priority task's static priority (SCHED_FIFO/RR) * @sched_deadline representative of the task's deadline * @sched_runtime representative of the task's runtime * @sched_period representative of the task's period @@ -53,6 +72,28 @@ struct sched_param { * As of now, the SCHED_DEADLINE policy (sched_dl scheduling class) is the * only user of this new interface. More information about the algorithm * available in the scheduling class file or in Documentation/. + * + * Task Utilization Attributes + * =========================== + * + * A subset of sched_attr attributes allows to specify the utilization which + * should be expected by a task. These attributes allows to inform the + * scheduler about the utilization boundaries within which is safe to schedule + * the task. These utilization boundaries are valuable information to support + * scheduler decisions on both task placement and frequencies selection. + * + * @sched_util_min represents the minimum utilization + * @sched_util_max represents the maximum utilization + * + * Utilization is a value in the range [0..SCHED_CAPACITY_SCALE] which + * represents the percentage of CPU time used by a task when running at the + * maximum frequency on the highest capacity CPU of the system. Thus, for + * example, a 20% utilization task is a task running for 2ms every 10ms. + * + * A task with a min utilization value bigger then 0 is more likely to be + * scheduled on a CPU which can provide that bandwidth. + * A task with a max utilization value smaller then 1024 is more likely to be + * scheduled on a CPU which do not provide more then the required bandwidth. */ struct sched_attr { __u32 size; @@ -70,6 +111,11 @@ struct sched_attr { __u64 sched_runtime; __u64 sched_deadline; __u64 sched_period; + + /* Utilization hints */ + __u32 sched_util_min; + __u32 sched_util_max; + }; #endif /* _UAPI_LINUX_SCHED_TYPES_H */ diff --git a/init/Kconfig b/init/Kconfig index 041f3a022122..1d45a6877d6f 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -583,6 +583,25 @@ config HAVE_UNSTABLE_SCHED_CLOCK config GENERIC_SCHED_CLOCK bool +menu "Scheduler features" + +config UCLAMP_TASK + bool "Enable utilization clamping for RT/FAIR tasks" + depends on CPU_FREQ_GOV_SCHEDUTIL + default false + help + This feature enables the scheduler to track the clamped utilization + of each CPU based on RUNNABLE tasks currently scheduled on that CPU. + + When this option is enabled, the user can specify a min and max CPU + bandwidth which is allowed for a task. + The max bandwidth allows to clamp the maximum frequency a task can + use, while the min bandwidth allows to define a minimum frequency a + task will always use. + + If in doubt, say N. + +endmenu # # For architectures that want to enable the support for NUMA-affine scheduler # balancing logic: diff --git a/kernel/sched/core.c b/kernel/sched/core.c index fe365c9a08e9..6a42cd86b6f3 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -739,6 +739,28 @@ static void set_load_weight(struct task_struct *p, bool update_load) } } +#ifdef CONFIG_UCLAMP_TASK +static inline int __setscheduler_uclamp(struct task_struct *p, + const struct sched_attr *attr) +{ + if (attr->sched_util_min > attr->sched_util_max) + return -EINVAL; + if (attr->sched_util_max > SCHED_CAPACITY_SCALE) + return -EINVAL; + + p->uclamp[UCLAMP_MIN] = attr->sched_util_min; + p->uclamp[UCLAMP_MAX] = attr->sched_util_max; + + return 0; +} +#else /* CONFIG_UCLAMP_TASK */ +static inline int __setscheduler_uclamp(struct task_struct *p, + const struct sched_attr *attr) +{ + return -EINVAL; +} +#endif /* CONFIG_UCLAMP_TASK */ + static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags) { if (!(flags & ENQUEUE_NOCLOCK)) @@ -2176,6 +2198,11 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p) p->se.cfs_rq = NULL; #endif +#ifdef CONFIG_UCLAMP_TASK + p->uclamp[UCLAMP_MIN] = 0; + p->uclamp[UCLAMP_MAX] = SCHED_CAPACITY_SCALE; +#endif + #ifdef CONFIG_SCHEDSTATS /* Even if schedstat is disabled, there should not be garbage */ memset(&p->se.statistics, 0, sizeof(p->se.statistics)); @@ -4243,6 +4270,13 @@ static int __sched_setscheduler(struct task_struct *p, return retval; } + /* Configure utilization clamps for the task */ + if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) { + retval = __setscheduler_uclamp(p, attr); + if (retval) + return retval; + } + /* * Make sure no PI-waiters arrive (or leave) while we are * changing the priority of the task: @@ -4749,6 +4783,11 @@ SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr, else attr.sched_nice = task_nice(p); +#ifdef CONFIG_UCLAMP_TASK + attr.sched_util_min = p->uclamp[UCLAMP_MIN]; + attr.sched_util_max = p->uclamp[UCLAMP_MAX]; +#endif + rcu_read_unlock(); retval = sched_read_attr(uattr, &attr, size); -- 2.17.1