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From: Davidlohr Bueso <dave@stgolabs.net>
To: Waiman Long <Waiman.Long@hpe.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org, x86@kernel.org,
	linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org,
	linux-s390@vger.kernel.org, linux-arch@vger.kernel.org,
	xfs@oss.sgi.com, Jason Low <jason.low2@hp.com>,
	Dave Chinner <david@fromorbit.com>,
	Scott J Norton <scott.norton@hpe.com>,
	Douglas Hatch <doug.hatch@hpe.com>
Subject: Re: [RFC PATCH-tip 2/6] locking/rwsem: Enable optional count-based spinning on reader
Date: Tue, 14 Jun 2016 11:27:57 -0700	[thread overview]
Message-ID: <20160614182757.GA15903@linux-80c1.suse> (raw)
In-Reply-To: <1465927959-39719-3-git-send-email-Waiman.Long@hpe.com>

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

  reply	other threads:[~2016-06-14 18:28 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-14 18:12 [RFC PATCH-tip 0/6] locking/rwsem: Enable reader optimistic spinning Waiman Long
2016-06-14 18:12 ` [RFC PATCH-tip 1/6] locking/rwsem: Stop active read lock ASAP Waiman Long
2016-06-14 18:12 ` [RFC PATCH-tip 2/6] locking/rwsem: Enable optional count-based spinning on reader Waiman Long
2016-06-14 18:27   ` Davidlohr Bueso [this message]
2016-06-14 19:11     ` Waiman Long
2016-06-14 18:12 ` [RFC PATCH-tip 3/6] locking/rwsem: move down rwsem_down_read_failed function Waiman Long
2016-06-14 18:12 ` [RFC PATCH-tip 4/6] locking/rwsem: Change RWSEM_WAITING_BIAS for better disambiguation Waiman Long
2016-06-14 18:12 ` [RFC PATCH-tip 5/6] locking/rwsem: Enable spinning readers Waiman Long
2016-06-14 18:12 ` [RFC PATCH-tip 6/6] xfs: Enable reader optimistic spinning for DAX inodes Waiman Long
2016-06-14 18:24   ` Christoph Hellwig
2016-06-14 19:08     ` Waiman Long
2016-06-14 23:06   ` Dave Chinner
2016-06-15 18:55     ` Waiman Long

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