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 <tim.c.chen@linux.intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 12 insertions, 0 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ec1a286..59965ec 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;