Messages in this thread | | | Subject | Re: [PATCH] sched: Check nr_running before calling pick_next_task in schedule(). | From | Peter Zijlstra <> | Date | Sat, 02 Jul 2011 17:35:31 +0200 |
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On Sat, 2011-07-02 at 20:26 +0600, Rakib Mullick wrote: > Well, yes - branching seems definitely have some side effects.
It adds the cost of the test as well as a possible branch mis-predict.
> Thinking from UP's perspective, it will only hit slow path -- going > into idle.
Uhm, no, every time the machine is busy and does a schedule between tasks you still get to do that extra nr_running test and branch.
> In that case, that likely branch will just fail. And on an > UP system that slow path -- going into idle -- is the only way, taking > the fast path (trying picking a task) isn't the right thing, isn't > it?
I'm not at all sure I even understand what you're trying to say. I really don't understand what's the problem with going the long way with picking the idle task, the machine is idle, it doesn't have anything useful to do, who cares.
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