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

Ingo Molnar
2009-01-14T11:21:58Z

* Chris Mason <chris.mason@oracle.com> 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