31.01.2013, 20:08, "Steven Rostedt" <rostedt@xxxxxxxxxxx>:
> On Mon, 2013-01-28 at 03:46 +0400, Kirill Tkhai wrote:
>
>> The patch aims to decrease the number of calls of push_rt_task()
>> in push_rt_tasks().
>>
>> It's not necessary to push more than 'num_online_cpus() - 1' tasks.
>> If just pushed task doesn't leave its new CPU during our local call
>> of push_rt_tasks() than we won't push another task to the CPU.
>> If it leave or change priority than it will pull new task by itself.
>
> I'm curious. Have you hit situations where this was an issue? Or was
> this just discovered by code review?
No, I did't hit this situation. It's impossible to hook every situation.
Thanks for your explanation.
Kirill
>
> -- Steve
>
>> Signed-off-by: Kirill V Tkhai <tkhai@xxxxxxxxx>
>> CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
>> CC: Ingo Molnar <mingo@xxxxxxxxxx>
>> CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
>> CC: linux-rt-users <linux-rt-users@xxxxxxxxxxxxxxx>
>> ---
>> kernel/sched/rt.c | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
>> index 4e8f0f4..edf046d 100644
>> --- a/kernel/sched/rt.c
>> +++ b/kernel/sched/rt.c
>> @@ -1703,8 +1703,10 @@ out:
>>
>> static void push_rt_tasks(struct rq *rq)
>> {
>> + int num_cpus = num_online_cpus() - 1;
>> +
>> /* push_rt_task will return true if it moved an RT */
>> - while (push_rt_task(rq))
>> + while (push_rt_task(rq) && --num_cpus > 0)
>> ;
>> }
--
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