linux-kernel - Re: [PATCH] locking/mutex: Avoid spinner vs waiter starvation

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Message-ID: <1454626163.2072.55.camel@j-VirtualBox>
Date:	Thu, 04 Feb 2016 14:49:23 -0800
From:	Jason Low <jason.low2@...com>
To:	huang ying <huang.ying.caritas@...il.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ding Tianhong <dingtianhong@...wei.com>,
	Waiman Long <waiman.long@....com>,
	Ingo Molnar <mingo@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Davidlohr Bueso <dave@...olabs.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Paul E. McKenney" <paulmck@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Will Deacon <Will.Deacon@....com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Waiman Long <Waiman.Long@...com>, jason.low2@....com,
	scott.norton@....com
Subject: Re: [PATCH] locking/mutex: Avoid spinner vs waiter starvation

On Thu, 2016-02-04 at 16:55 +0800, huang ying wrote:
> Hi, Low,
> 
> On Thu, Feb 4, 2016 at 9:35 AM, Jason Low <jason.low2@...com> wrote:
> > I've done some testing with this patch with some of the AIM7 workloads
> > and found that this reduced throughput by about 10%. The reduction in
> > throughput is expected since spinning as a waiter is less efficient.
> >
> > Another observation I made is that the top waiter spinners would often
> > times require needing to reschedule before being able to acquire the
> > lock from spinning when there was high contention. A waiter can go into
> > the cycle of spin -> reschedule -> spin -> reschedule. So although the
> > chance of starvation is reduced, this patch doesn't fully address the
> > issue of waiter starvation.
> 
> Could you share your workload?  I want to reproduce it in 0day/LKP+ environment.

CC'ing Scott, who wrote the automation scripts.

Jason