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locking: qspinlock

From:  Peter Zijlstra <peterz@infradead.org>
To:  Waiman Long <waiman.long@hp.com>
Subject:  [RFC][PATCH 0/7] locking: qspinlock
Date:  Mon, 10 Mar 2014 16:42:36 +0100
Message-ID:  <20140310154236.038181843@infradead.org>
Cc:  arnd@arndb.de, linux-arch@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, rostedt@goodmis.org, akpm@linux-foundation.org, walken@google.com, andi@firstfloor.org, riel@redhat.com, paulmck@linux.vnet.ibm.com, torvalds@linux-foundation.org, oleg@redhat.com, Peter Zijlstra <peterz@infradead.org>
Archive‑link:  Article

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@infradead.org

I've yet to look at the paravirt stuff.



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