Workqueues queues work on current cpu, if the caller haven't passed a preferred cpu. This may wake up an idle CPU, which is actually not required.
This work can be processed by any CPU and so we must select a non-idle CPU here. This patch adds in support in workqueue framework to get preferred CPU details from the scheduler, instead of using current CPU.
Most of the time when a work is queued, the current cpu isn't idle and so we will choose it only. There are cases when a cpu is idle when it queues some work. For example, consider following scenario: - A cpu has programmed a timer and is IDLE now. - CPU gets into interrupt handler due to timer and queues a work. As the CPU is currently IDLE, we can queue this work to some other CPU.
Signed-off-by: Viresh Kumar viresh.kumar@linaro.org --- kernel/workqueue.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 042d221..d32efa2 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1238,7 +1238,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, struct global_cwq *last_gcwq;
if (cpu == WORK_CPU_UNBOUND) - cpu = raw_smp_processor_id(); + cpu = sched_select_cpu(0);
/* * It's multi cpu. If @work was previously on a different @@ -1383,7 +1383,7 @@ static void __queue_delayed_work(int cpu, struct workqueue_struct *wq, if (gcwq) lcpu = gcwq->cpu; if (lcpu == WORK_CPU_UNBOUND) - lcpu = raw_smp_processor_id(); + lcpu = sched_select_cpu(0); } else { lcpu = WORK_CPU_UNBOUND; }