Re: [PATCH] mm: call cond_resched() per MAX_ORDER_NR_PAGES pages copy

[Naoya Horiguchi]

On Mon, Nov 18, 2013 at 02:29:24PM -0800, Dave Hansen wrote:
> 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.

I see.
Thanks for the explanation!

Naoya
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