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

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Message-ID: <20140311104503.GA10916@gmail.com>
Date:	Tue, 11 Mar 2014 11:45:03 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Peter Zijlstra <peterz@...radead.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


* 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.

It would be nice to have per patch performance measurements though ... 
this split-up structure really enables that rather nicely.

Thanks,

	Ingo
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