linux-kernel - Re: [PATCH v2 0/4] locking/mutex: Enable optimistic spinning of lock waiter

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Message-ID: <20160322095912.GD6356@twins.programming.kicks-ass.net>
Date:	Tue, 22 Mar 2016 10:59:12 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Waiman Long <waiman.long@....com>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ding Tianhong <dingtianhong@...wei.com>,
	Jason Low <jason.low2@....com>,
	Davidlohr Bueso <dave@...olabs.net>,
	"Paul E. McKenney" <paulmck@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Will Deacon <Will.Deacon@....com>,
	Tim Chen <tim.c.chen@...ux.intel.com>
Subject: Re: [PATCH v2 0/4] locking/mutex: Enable optimistic spinning of lock
 waiter

On Mon, Mar 21, 2016 at 11:19:02PM -0400, Waiman Long wrote:
> Instead, the subject was
> 
> [lkp] [locking/mutex] 5267438002: +38.9%
> fileio.time.involuntary_context_switches
> 
>       4409 ±  1%     +38.9%       6126 ±  2%
> fileio.time.involuntary_context_switches
>       6.00 ±  0%     +33.3%       8.00 ±  0%
> fileio.time.percent_of_cpu_this_job_got
>      36.06 ±  0%     +43.0%      51.55 ±  0%  fileio.time.system_time
>    1828660 ±  0%     -92.5%     137258 ±  0%
> fileio.time.voluntary_context_switches
> 
> Given that the number of voluntary context switches dropped by 92.5%, an
> increase in involuntary context switches that is order of magnitude less
> than the voluntary context switches should be OK, I think.
> 
> Do you know how to report back that this increase is expected and is nothing
> to worry about? Do I just reply it back?

Nah, just ignore.