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 <[email protected]> Signed-off-by: Herbert Xu <[email protected]>
vbatts · Aug 25, 2014 · 2ee507c · 2ee507c
1 parent bbb9a7d
commit 2ee507c
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diff --git 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
@@ -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;