Re: [PATCH -v9][RFC] mutex: implement adaptive spinning

[Ingo Molnar]

* Chris Mason <chris.mason@xxxxxxxxxx> wrote:

> v10 is better that not spinning, but its in the 5-10% range.  So, I've 
> been trying to find ways to close the gap, just to understand exactly 
> where it is different.
> 
> If I take out:
> 	/*
> 	 * If there are pending waiters, join them.
> 	 */
> 	if (!list_empty(&lock->wait_list))
> 		break;
> 
> 
> v10 pops dbench 50 up to 1800MB/s.  The other tests soundly beat my 
> spinning and aren't less fair.  But clearly this isn't a good solution.

i think since we already decided that it's ok to be somewhat unfair (_all_ 
batching constructs introduce unfairness, so the question is never 'should 
we?' but 'by how much?'), we should just take this out and enjoy the speed 
...

	Ingo
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