From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Davidlohr Bueso <davidlohr@hp.com>,
Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
Jason Low <jason.low2@hp.com>,
Darren Hart <dvhart@linux.intel.com>,
Mike Galbraith <efault@gmx.de>, Jeff Mahoney <jeffm@suse.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Scott Norton <scott.norton@hp.com>, Tom Vaden <tom.vaden@hp.com>,
Aswin Chandramouleeswaran <aswin@hp.com>,
Waiman Long <Waiman.Long@hp.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [RFC patch 0/5] futex: Allow lockless empty check of hashbucket plist in futex_wake()
Date: Tue, 26 Nov 2013 12:56:28 +0100 [thread overview]
Message-ID: <20131126115628.GK10022@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20131126112140.GC2410@gmail.com>
On Tue, Nov 26, 2013 at 12:21:40PM +0100, Ingo Molnar wrote:
> I'm somewhat reluctant to chalk it up to a single mfence - maybe
> timings/behavior changed in some substantial way?
Ah indeed! We also changed the case where an enqueueing futex sees the
uval change and bails. It is now far more expensive due to having to
both queue and unqueue, whereas before it wouldn't queue at all.
I suppose the idea was to offset that by not requiring locking on the
wake side.
next prev parent reply other threads:[~2013-11-26 11:56 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-25 20:58 Thomas Gleixner
2013-11-25 20:58 ` [RFC patch 1/5] futex: Misc cleanups Thomas Gleixner
2013-11-25 20:58 ` [RFC patch 2/5] futex: Document ordering guarantees Thomas Gleixner
2013-11-25 20:58 ` [RFC patch 3/5] futex: Split out unlock from queue_me() Thomas Gleixner
2013-11-25 20:58 ` [RFC patch 4/5] futex: Enqueue waiter before user space check Thomas Gleixner
2013-11-26 0:20 ` Darren Hart
2013-11-25 20:58 ` [RFC patch 5/5] futex: Allow lockless empty check of hash bucket plist Thomas Gleixner
2013-11-26 8:12 ` [RFC patch 0/5] futex: Allow lockless empty check of hashbucket plist in futex_wake() Davidlohr Bueso
2013-11-26 8:52 ` Peter Zijlstra
2013-11-26 11:21 ` Ingo Molnar
2013-11-26 11:56 ` Peter Zijlstra [this message]
2013-11-26 12:34 ` Thomas Gleixner
2013-11-26 15:38 ` Davidlohr Bueso
2013-11-26 14:49 ` Davidlohr Bueso
2013-11-26 19:25 ` Davidlohr Bueso
2013-11-26 20:51 ` Davidlohr Bueso
2013-11-26 23:56 ` Thomas Gleixner
2013-11-28 7:44 ` Davidlohr Bueso
2013-11-28 11:58 ` Thomas Gleixner
2013-11-28 11:59 ` Peter Zijlstra
2013-11-28 14:23 ` Thomas Gleixner
2013-12-01 4:37 ` Davidlohr Bueso
2013-12-02 11:01 ` Thomas Gleixner
2013-12-01 12:10 ` Ingo Molnar
2013-12-01 12:56 ` Peter Zijlstra
2013-12-01 16:55 ` Ingo Molnar
2013-12-01 18:58 ` Linus Torvalds
2013-12-01 20:39 ` Eric Dumazet
2013-12-01 21:46 ` Linus Torvalds
2013-12-03 17:59 ` Darren Hart
2013-12-02 12:35 ` Ingo Molnar
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