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Date: Fri, 1 Apr 2016 12:31:43 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <waiman.long@hpe.com>
Cc: Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        Scott J Norton <scott.norton@hpe.com>,
        Douglas Hatch <doug.hatch@hpe.com>, Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH] locking/qrwlock: Allow multiple spinning readers
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On Thu, Mar 31, 2016 at 06:12:38PM -0400, Waiman Long wrote:
> >>However, if we allow a limited number of readers to spin on the
> >>lock simultaneously, we can eliminates some of the reader-to-reader
> >>latencies at the expense of a bit more cacheline contention and
> >>probably more power consumption.
> >So the embedded people might not like that much.
> 
> It could be. It is always a compromise.

So ARM is the only one that currently waits without spinning and could
care; so Will might have an opinion. One 'solution' would be to make
this an optional feature.