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Date:	Sun, 15 Jun 2014 15:14:16 +0200
From:	Peter Zijlstra <>
To:	Waiman Long <>
Cc:	Thomas Gleixner <>,
	Ingo Molnar <>,
	"H. Peter Anvin" <>,,,,,,,
	Paolo Bonzini <>,
	Konrad Rzeszutek Wilk <>,
	Boris Ostrovsky <>,
	"Paul E. McKenney" <>,
	Rik van Riel <>,
	Linus Torvalds <>,
	Raghavendra K T <>,
	David Vrabel <>,
	Oleg Nesterov <>,
	Gleb Natapov <>,
	Scott J Norton <>,
	Chegu Vinod <>
Subject: Re: [PATCH v11 09/16] qspinlock, x86: Allow unfair spinlock in a
 virtual guest

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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