linux-kernel - Re: [PATCH 5/7] locking/pvqspinlock: Add pending bit support

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Date:	Tue, 14 Jul 2015 14:47:56 -0400
From:	Waiman Long <waiman.long@...com>
To:	Peter Zijlstra <peterz@...radead.org>
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>
Subject: Re: [PATCH 5/7] locking/pvqspinlock: Add pending bit support

On 07/12/2015 04:21 AM, Peter Zijlstra wrote:
> On Sat, Jul 11, 2015 at 04:36:56PM -0400, Waiman Long wrote:
>> Like the native qspinlock, using the pending bit when it is lightly
>> loaded to acquire the lock is faster than going through the PV queuing
>> process which is even slower than the native queuing process. It also
>> avoids loading two additional cachelines (the MCS and PV nodes).
>>
>> This patch adds the pending bit support for PV qspinlock. The
>> pending bit code has a smaller spin threshold. It will default back
>> to the queuing method if it cannot acquired the lock within a certain
>> time limit.
> -ENONUMBERS

Will send out an updated patchset with patch-to-patch performance numbers.

Cheers,
Longman
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