From 8c34ab1910a79319731107ec8ecd2e80893ea30c Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Fri, 9 Sep 2016 23:59:33 +0200 Subject: [PATCH] cpufreq / sched: SCHED_CPUFREQ_IOWAIT flag to indicate iowait condition Testing indicates that it is possible to improve performace significantly without increasing energy consumption too much by teaching cpufreq governors to bump up the CPU performance level if the in_iowait flag is set for the task in enqueue_task_fair(). For this purpose, define a new cpufreq_update_util() flag SCHED_CPUFREQ_IOWAIT and modify enqueue_task_fair() to pass that flag to cpufreq_update_util() in the in_iowait case. That generally requires cpufreq_update_util() to be called directly from there, because update_load_avg() may not be invoked in that case. Signed-off-by: Rafael J. Wysocki Looks-good-to: Steve Muckle Acked-by: Peter Zijlstra (Intel) --- include/linux/sched.h | 1 + kernel/sched/fair.c | 8 ++++++++ 2 files changed, 9 insertions(+) diff --git a/include/linux/sched.h b/include/linux/sched.h index b0fa726b7f31..98fe95fea30c 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -3471,6 +3471,7 @@ static inline unsigned long rlimit_max(unsigned int limit) #define SCHED_CPUFREQ_RT (1U << 0) #define SCHED_CPUFREQ_DL (1U << 1) +#define SCHED_CPUFREQ_IOWAIT (1U << 2) #define SCHED_CPUFREQ_RT_DL (SCHED_CPUFREQ_RT | SCHED_CPUFREQ_DL) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 5d558cc91f08..a5cd07b25aa1 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4500,6 +4500,14 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) struct cfs_rq *cfs_rq; struct sched_entity *se = &p->se; + /* + * If in_iowait is set, the code below may not trigger any cpufreq + * utilization updates, so do it here explicitly with the IOWAIT flag + * passed. + */ + if (p->in_iowait) + cpufreq_update_this_cpu(rq, SCHED_CPUFREQ_IOWAIT); + for_each_sched_entity(se) { if (se->on_rq) break; -- 2.20.1