linux-kernel - Re: [PATCH 4/7] locking/pvqspinlock: Collect slowpath lock statistics

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Date:	Sun, 12 Jul 2015 10:22:33 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Waiman Long <Waiman.Long@...com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Scott J Norton <scott.norton@...com>,
	Douglas Hatch <doug.hatch@...com>
Subject: Re: [PATCH 4/7] locking/pvqspinlock: Collect slowpath lock statistics

On Sat, Jul 11, 2015 at 04:36:55PM -0400, Waiman Long wrote:
> This patch enables the accumulation of kicking and waiting related
> PV qspinlock statistics when the new QUEUED_LOCK_STAT configuration
> option is selected. It also enables the collection of kicking and
> wakeup latencies which have a heavy dependency on the CPUs being used.
> 
> The measured latencies for different CPUs are:
> 
> 	CPU		Wakeup		Kicking
> 	---		------		-------
> 	Haswell-EX	26.4us		 9.2us
> 	Westmere-EX	99.4US		25.5us
> 
> So Haswell is much faster than Westmere.
> 
> The accumulated lock statistics will be reported in debugfs under the
> pv-qspinlock directory.

You've again stuck this behind non-trivial patches :-(
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