Re: [PATCH] Avoid moving tasks when a schedule can be made.

[Ingo Molnar <mingo@elte.hu>]

* Nick Piggin <nickpiggin@yahoo.com.au> wrote:

> >Once we've gone to the trouble of deciding which tasks to move and how
> >many (and the estimate should be very conservative), and locked the source
> >and destination runqueues, it is a very good idea to follow up with our
> >threat of actually moving the tasks rather than bail out early.
> 
> Oh, I forgot: Ingo once introduced some code to bail early (though for 
> different reasons and under different conditions), and this actually 
> was found to cause significant regressions in some database workloads.

well, we both did changes with that effect - pretty much any change in 
this area can cause a regression on _some_ workload ;) So there wont be 
any silver bullet.

> So it is not a nice thing to tinker with unless there is good reason.

unbound latencies with hardirqs off are obviously a good reason - but i 
agree that the solution is not good enough, yet.

	Ingo