linux-kernel - Re: [PATCH-tip v2 0/2] locking/qrwlock: Improve qrwlock performance

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Date:	Thu, 09 Jul 2015 15:04:29 -0700
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Waiman Long <Waiman.Long@...com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Arnd Bergmann <arnd@...db.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	Will Deacon <will.deacon@....com>,
	Scott J Norton <scott.norton@...com>,
	Douglas Hatch <doug.hatch@...com>
Subject: Re: [PATCH-tip v2 0/2] locking/qrwlock: Improve qrwlock performance

On Thu, 2015-07-09 at 12:32 -0400, Waiman Long wrote:
> With this patch series in place, we can start converting some spinlocks
> back to rwlocks where it makes sense and the lock size increase isn't
> a concern.

Nice, have any users to convert? I can think of a few I've encountered,
but there must be quite a few, specially those nasty global spinlocks
where nobody cares about the size.

o hugetlb reservation map lock: Updating hugepage ranges does a two step
read/update for the reservation map. The first step could now be done
concurrently if converted.

o The infamous swap_lock; although I doubt any of the serious offenders
(ie zswap callbacks) would benefit much for anything
beyond /proc/meminfo and related.

o async cookie sync wait_event, battery/ata bootup(?).

etc. etc. Obviously the fairness factor is also something to consider.

Thanks,
Davidlohr 

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