Re: [Xen-devel] [PATCH v11 09/16] qspinlock, x86: Allow unfair spinlock in a virtual guest

[Peter Zijlstra <peterz@xxxxxxxxxxxxx>]

On Thu, Jun 12, 2014 at 05:08:28PM -0400, Waiman Long wrote:
> >Native performance is king, try your very utmost bestest to preserve
> >that, paravirt is a distant second and nobody sane should care about the
> >virt case at all.
> 
> The patch won't affect native performance unless the kernel is built with
> VIRT_UNFAIR_LOCKS selected. The same is also true when PARAVIRT_SPINLOCKS is
> selected. There is no way around that.

VIRT_UNFAIR_LOCKS is an impossible switch to have; a distro cannot make
the right choice.

> I do agree that I may over-engineer on this patch,

Simple things first, then add complexity.

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