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

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Message-ID: <20140312061503.GH30956@twins.programming.kicks-ass.net>
Date:	Wed, 12 Mar 2014 07:15:03 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Dave Chinner <david@...morbit.com>
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 Wed, Mar 12, 2014 at 01:31:53PM +1100, Dave Chinner wrote:
> With the queuing spinlock, I expected to see somewhat better
> results, but I didn't at first. Turns out if you have any sort of
> lock debugging turned on, then the code doesn't ever go into the
> lock slow path and hence does not ever enter the "lock failed" slow
> path where all the contention fixes are supposed to be.

Yeah; its a 'feature' of the spinlock debugging to turn all spinlocks
into test-and-set thingies.

> Anyway, with all lock debugging turned off, the system hangs
> the instant I start the multithreaded bulkstat workload. Even the
> console is unrepsonsive. 

Oops, I only briefly tested this series in userspace and that seemed to
work. I'll go prod at it. Thanks for having a look though.

Is that bstat test any easier/faster to setup/run than the aim7 crap?
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