Message-ID: <55A5B9B7.7090101@hp.com>
Date: Tue, 14 Jul 2015 21:39:03 -0400
From: Waiman Long <waiman.long@hp.com>
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To: Davidlohr Bueso <dave@stgolabs.net>
CC: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>,
        x86@kernel.org, linux-kernel@vger.kernel.org,
        Scott J Norton <scott.norton@hp.com>,
        Douglas Hatch <doug.hatch@hp.com>
Subject: Re: [PATCH 3/7] locking/pvqspinlock: Implement wait-early for overcommitted
 guest
References: <1436647018-49734-1-git-send-email-Waiman.Long@hp.com>  <1436647018-49734-4-git-send-email-Waiman.Long@hp.com> <1436817022.27924.74.camel@stgolabs.net>
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On 07/13/2015 03:50 PM, Davidlohr Bueso wrote:
> On Sat, 2015-07-11 at 16:36 -0400, Waiman Long wrote:
>>   /*
>> + * Queued Spinlock Spin Thresholds
>> + * -------------------------------
>> + * Because of the cacheline contention effect of the ticket spinlock, the
>> + * same spin threshold for queued spinlock will run a bit faster. So we set
>> + * a slight larger threshold for the queue head (1.25X) while the other queue
>> + * nodes will keep the same threshold.
> How did you come to 1.25x? These sort of magic numbers scare me.
>

Yes, this is kind of arbitrary. I am going to get rid of it in the v2 patch.

Cheers,
Longman
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