On 27 September 2012 14:34, Viresh Kumar viresh.kumar@linaro.org wrote:
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 | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 143fd8c..5fa4ba4 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);
Hi Tejun,
Following change is also required with this patch:
--- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -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; }
Otherwise, we will end up running the re-reentrancy check, which we are trying to skip for delayed work.
-- viresh