Re: [RFC PATCH-tip 2/6] locking/rwsem: Enable optional count-based spinning on reader
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- To: Waiman Long <Waiman.Long@xxxxxxx>
- Subject: Re: [RFC PATCH-tip 2/6] locking/rwsem: Enable optional count-based spinning on reader
- From: Davidlohr Bueso <dave@xxxxxxxxxxxx>
- Date: Tue, 14 Jun 2016 11:27:57 -0700
- Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, x86@xxxxxxxxxx, linux-alpha@xxxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxxxx, linux-s390@xxxxxxxxxxxxxxx, linux-arch@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, Jason Low <jason.low2@xxxxxx>, Dave Chinner <david@xxxxxxxxxxxxx>, Scott J Norton <scott.norton@xxxxxxx>, Douglas Hatch <doug.hatch@xxxxxxx>
- In-reply-to: <1465927959-39719-3-git-send-email-Waiman.Long@hpe.com>
- List-id: <linux-ia64.vger.kernel.org>
- References: <1465927959-39719-1-git-send-email-Waiman.Long@hpe.com> <1465927959-39719-3-git-send-email-Waiman.Long@hpe.com>
- User-agent: Mutt/1.5.24 (2015-08-30)
On Tue, 14 Jun 2016, Waiman Long wrote:
This patch provides a way for the kernel code to designate specific
rwsems to be more aggressive in term of optimistic spinning that the
writers will continue to spin for some additional count-based time to
see if it can get the lock before sleeping. This aggressive spinning
mode should only be used on rwsems where the readers are unlikely to
go to sleep.
Yikes, exposing this sort of thing makes me _very_ uneasy, not to mention
the ad-hoc nature and its easiness to mess up. I'm not really for this, even
if it shows extraordinary performance boosts on benchmarks.
Thanks,
Davidlohr
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