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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>
This commit is contained in:
Tim Chen 2014-07-31 10:29:48 -07:00 committed by Herbert Xu
parent bbb9a7dd7f
commit 2ee507c472
2 changed files with 13 additions and 0 deletions
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1
include/linux/sched.h
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@ -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);

12
kernel/sched/core.c
View File

@ -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;