From 2ee507c472939db4b146d545352b8a7c79ef47f8 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Thu, 31 Jul 2014 10:29:48 -0700 Subject: [PATCH] sched: Add function single_task_running to let a task check if it is the only task running on a cpu This function will help an async task processing batched jobs from workqueue decide if it wants to keep processing on more chunks of batched work that can be delayed, or to accumulate more work for more efficient batched processing later. If no other tasks are running on the cpu, the batching process can take advantgae of the available cpu cycles to a make decision to continue processing the existing accumulated work to minimize delay, otherwise it will yield. Signed-off-by: Tim Chen Signed-off-by: Herbert Xu --- include/linux/sched.h | 1 + kernel/sched/core.c | 12 ++++++++++++ 2 files changed, 13 insertions(+) diff --git a/include/linux/sched.h b/include/linux/sched.h index 5c2c885ee52b..e6d2c056d8e0 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -167,6 +167,7 @@ extern int nr_threads; DECLARE_PER_CPU(unsigned long, process_counts); extern int nr_processes(void); extern unsigned long nr_running(void); +extern bool single_task_running(void); extern unsigned long nr_iowait(void); extern unsigned long nr_iowait_cpu(int cpu); extern void get_iowait_load(unsigned long *nr_waiters, unsigned long *load); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index ec1a286684a5..59965ec0b7de 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2366,6 +2366,18 @@ unsigned long nr_running(void) return sum; } +/* + * Check if only the current task is running on the cpu. + */ +bool single_task_running(void) +{ + if (cpu_rq(smp_processor_id())->nr_running == 1) + return true; + else + return false; +} +EXPORT_SYMBOL(single_task_running); + unsigned long long nr_context_switches(void) { int i; -- 2.20.1