Messages in this thread | | | Date | Mon, 18 Nov 2013 14:29:24 -0800 | From | Dave Hansen <> | Subject | Re: [PATCH] mm: call cond_resched() per MAX_ORDER_NR_PAGES pages copy |
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On 11/18/2013 01:56 PM, Naoya Horiguchi wrote: >> > Why bother trying to "optimize" it? > I thought that if we call cond_resched() too often, the copying thread can > take too long in a heavy load system, because the copying thread always > yields the CPU in every loop.
I think you're confusing cond_resched() and yield(). The way I look at it:
yield() means: "Hey scheduler, go right now and run something else I'm done running"
cond_resched() means: "Schedule me off if the scheduler has already decided something else _should_ be running"
I'm sure I'm missing some of the subtleties, but as I see it, yield() actively goes off and finds something else to run. cond_resched() only schedules you off if you've *already* run too long.
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