linux-kernel - [RFC][PATCH 0/7] locking: qspinlock

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Message-Id: <20140310154236.038181843@infradead.org>
Date:	Mon, 10 Mar 2014 16:42:36 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Waiman Long <waiman.long@...com>
Cc:	arnd@...db.de, linux-arch@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, rostedt@...dmis.org,
	akpm@...ux-foundation.org, walken@...gle.com, andi@...stfloor.org,
	riel@...hat.com, paulmck@...ux.vnet.ibm.com,
	torvalds@...ux-foundation.org, oleg@...hat.com,
	Peter Zijlstra <peterz@...radead.org>
Subject: [RFC][PATCH 0/7] locking: qspinlock

Hi Waiman,

I promised you this series a number of days ago; sorry for the delay I've been
somewhat unwell :/

That said, these few patches start with a (hopefully) simple and correct form
of the queue spinlock, and then gradually build upon it, explaining each
optimization as we go.

Having these optimizations as separate patches helps twofold; firstly it makes
one aware of which exact optimizations were done, and secondly it allows one to
proove or disprove any one step; seeing how they should be mostly identity
transforms.

The resulting code is near to what you posted I think; however it has one
atomic op less in the pending wait-acquire case for NR_CPUS != huge. It also
doesn't do lock stealing; its still perfectly fair afaict.

Have I missed any tricks from your code?

The patches apply to tip/master + lkml.kernel.org/r/20140210195820.834693028@...radead.org

I've yet to look at the paravirt stuff.

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