Re: [PATCH 2/4, v2] x86: enlightenment for ticket spin locks - Xen implementation

From: Jan Beulich
Date: Wed Jun 30 2010 - 10:03:14 EST

>>> On 30.06.10 at 15:23, Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:
> For spinlocks, the pvop calls should only be in the slow case: when a
> spinlock has been spinning for long enough, and on unlock when there's
> someone waiting for the lock. The fastpath (no contention lock and
> unlock) should have no extra calls.

Then what was all that performance regression noise concerning
pvops spinlocks about, leading to CONFIG_PARAVIRT_SPINLOCKS
being separated from the base CONFIG_PARAVIRT?

Afaics the unlock still involves a function call *in all cases* with
pvops spinlocks, whereas it's a single inline instruction without.


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