linux-kernel - Re: [PATCH v3 0/7] locking/qspinlock: Enhance pvqspinlock performance

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Message-ID: <55B66C0E.5050504@hp.com>
Date:	Mon, 27 Jul 2015 13:36:14 -0400
From:	Waiman Long <waiman.long@...com>
To:	Davidlohr Bueso <dave@...olabs.net>
CC:	Peter Zijlstra <peterz@...radead.org>,
	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 v3 0/7] locking/qspinlock: Enhance pvqspinlock performance

On 07/26/2015 09:18 PM, Davidlohr Bueso wrote:
> On Wed, 2015-07-22 at 16:12 -0400, Waiman Long wrote:
>> Patch 3 allows the collection of various count data that are useful
>> to see what is happening in the system. They do add a bit of overhead
>> when enabled slowing performance a tiny bit.
> Ah ok you do mention the overhead. Hmmm but what's a tiny bit? A kernel
> build comparison would be pretty nice to have a "usability" view.
>
> Thanks,
> Davidlohr
>

You will probably see a few seconds of slowdown for a kernel build that 
took 3 mins. So it is about a few percents and it varies a bit from run 
to run.

Cheers,
Longman
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