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Message-ID: <1454626163.2072.55.camel@j-VirtualBox>
Subject: Re: [PATCH] locking/mutex: Avoid spinner vs waiter starvation
From: Jason Low <jason.low2@hp.com>
To: huang ying <huang.ying.caritas@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
        Ding Tianhong <dingtianhong@huawei.com>,
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        Tim Chen <tim.c.chen@linux.intel.com>,
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Date: Thu, 04 Feb 2016 14:49:23 -0800
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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@hp.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