linux-kernel - Re: [PATCH tip/locking/core v9 4/6] locking/pvqspinlock: Collect slowpath lock statistics

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Message-ID: <20151105170911.GK3604@twins.programming.kicks-ass.net>
Date:	Thu, 5 Nov 2015 18:09:11 +0100
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>,
	Davidlohr Bueso <dave@...olabs.net>
Subject: Re: [PATCH tip/locking/core v9 4/6] locking/pvqspinlock: Collect
 slowpath lock statistics

On Thu, Nov 05, 2015 at 11:59:21AM -0500, Waiman Long wrote:
> >Mostly I just wanted to point out that it was possible; you need not
> >change to sysfs because debugfs lacks the capability.
> >
> >But now that you ask, I think debugfs might be the better place, such
> >statistics (and the proposed CONFIG symbol) are purely for debug
> >purposes, right?
> 
> Davidlohr had asked me to use per-cpu counters to reduce performance
> overhead so that they can be usable in production system. That is another
> reason why I move to sysfs.

Yes, the per-cpu thing certainly makes sense. But as said, that does not
require you to move to sysfs.

> BTW, do you have comments on the other patches in the series? I would like
> to collect all the comments before I renew the series.

I still have to look at the last two patches, I've sadly not had time
for that yet.
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