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

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Date:	Tue, 11 Mar 2014 12:02:02 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Waiman Long <waiman.long@...com>, 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
Subject: Re: [RFC][PATCH 0/7] locking: qspinlock

On Tue, Mar 11, 2014 at 11:45:03AM +0100, Ingo Molnar wrote:
> 
> * Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > 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?
> 
> Waiman, you indicated in the other thread that these look good to you, 
> right? If so then I can queue them up so that they form a base for 
> further work.

Ah, no that was on the qrwlock; I think we managed to cross wires
somewhere.

I've got this entire pile waiting for something:

  lkml.kernel.org/r/20140210195820.834693028@...radead.org

That's 5 mutex patches and the 2 qrwlock patches. Not sure what to do
with them. To merge or not, that is the question.
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