Re: [PATCH 3/7] locking/pvqspinlock: Implement wait-early for overcommitted guest

[Davidlohr Bueso]

On Sat, 2015-07-11 at 16:36 -0400, Waiman Long wrote:
>  /*
> + * Queued Spinlock Spin Thresholds
> + * -------------------------------
> + * Because of the cacheline contention effect of the ticket spinlock, the
> + * same spin threshold for queued spinlock will run a bit faster. So we set
> + * a slight larger threshold for the queue head (1.25X) while the other queue
> + * nodes will keep the same threshold.

How did you come to 1.25x? These sort of magic numbers scare me.

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