From: Ulrich Drepper <drepper@gmail.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
Darren Hart <dvhltc@us.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
Avi Kivity <avi@redhat.com>,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Eric Dumazet <eric.dumazet@gmail.com>,
"Peter W. Morreale" <pmorreale@novell.com>,
Rik van Riel <riel@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
Gregory Haskins <ghaskins@novell.com>,
Sven-Thorsten Dietrich <sdietrich@novell.com>,
Chris Mason <chris.mason@oracle.com>,
John Cooper <john.cooper@third-harmonic.com>,
Chris Wright <chrisw@sous-sol.org>
Subject: Re: [PATCH V2 0/6][RFC] futex: FUTEX_LOCK with optional adaptive spinning
Date: Tue, 6 Apr 2010 13:02:28 -0700 [thread overview]
Message-ID: <y2qa36005b51004061302t53bccf60v2cc152e7c64b20ca@mail.gmail.com> (raw)
In-Reply-To: <alpine.LFD.2.00.1004062024560.32352@localhost.localdomain>
On Tue, Apr 6, 2010 at 12:31, Thomas Gleixner <tglx@linutronix.de> wrote:
> We need to figure out a more efficient way to
> do the spinning in the kernel where we have all the necessary
> information already.
Really? The owner information isn't in general available in the
kernel. Futex operation doesn't require the value used to be the PID
(or negative of the PID). That is a dramatic limitation of the
usefulness of futexes.
At userlevel there is access to other fields of the data structure
which can contain the owner information.
I would like to see the method using a per-thread pinned page and an
update of a memory location on scheduling. For benchmarking at least.
I agree that a sys_yield_to() syscall would be at the very least
useful as well. But it's useful for other things already.
next prev parent reply other threads:[~2010-04-06 20:02 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-05 20:23 [PATCH V2 0/6][RFC] futex: FUTEX_LOCK with optional adaptive spinning Darren Hart
2010-04-05 20:23 ` [PATCH 1/6] futex: replace fshared and clockrt with combined flags Darren Hart
2010-04-05 20:23 ` [PATCH 2/6] futex: add futex_q static initializer Darren Hart
2010-04-05 20:23 ` [PATCH 3/6] futex: refactor futex_lock_pi_atomic Darren Hart
2010-04-05 20:23 ` [PATCH 4/6] futex: Add FUTEX_LOCK with optional adaptive spinning Darren Hart
2010-04-06 16:55 ` Thomas Gleixner
2010-04-07 17:26 ` Darren Hart
2010-04-07 19:59 ` Thomas Gleixner
2010-04-08 3:25 ` Darren Hart
2010-04-08 23:10 ` Peter W. Morreale
2010-04-09 5:41 ` Darren Hart
2010-04-09 13:13 ` Peter W. Morreale
2010-04-05 20:23 ` [PATCH 5/6] futex: handle timeout inside adaptive lock spin Darren Hart
2010-04-06 8:27 ` Thomas Gleixner
2010-04-07 17:31 ` Darren Hart
2010-04-07 18:44 ` Gregory Haskins
2010-04-07 23:15 ` Darren Hart
2010-04-05 20:23 ` [PATCH 6/6] futex: Add aggressive adaptive spinning argument to FUTEX_LOCK Darren Hart
2010-04-08 5:58 ` Darren Hart
2010-04-05 20:48 ` [PATCH V2^W V4 0/6][RFC] futex: FUTEX_LOCK with optional adaptive spinning Darren Hart
2010-04-05 21:15 ` [PATCH V2 " Avi Kivity
2010-04-05 21:54 ` Darren Hart
2010-04-05 22:21 ` Avi Kivity
2010-04-05 22:59 ` Darren Hart
2010-04-06 13:28 ` Avi Kivity
2010-04-06 13:35 ` Peter Zijlstra
2010-04-06 13:41 ` Avi Kivity
2010-04-06 14:09 ` Peter Zijlstra
2010-04-06 16:10 ` Avi Kivity
2010-04-06 16:53 ` Alan Cox
2010-04-06 13:51 ` Alan Cox
2010-04-06 15:28 ` Darren Hart
2010-04-06 16:06 ` Avi Kivity
2010-04-06 16:14 ` Thomas Gleixner
2010-04-06 16:20 ` Avi Kivity
2010-04-07 6:18 ` john cooper
2010-04-08 3:33 ` Darren Hart
2010-04-09 5:52 ` john cooper
2010-04-06 16:54 ` Alan Cox
2010-04-06 18:15 ` Thomas Gleixner
2010-04-06 16:44 ` Alan Cox
2010-04-06 17:34 ` Ulrich Drepper
2010-04-10 23:35 ` Alan Cox
2010-04-10 23:53 ` Ulrich Drepper
2010-04-06 19:31 ` Thomas Gleixner
2010-04-06 20:02 ` Ulrich Drepper [this message]
2010-04-06 23:16 ` Thomas Gleixner
2010-04-06 23:36 ` Darren Hart
2010-04-07 6:08 ` drepper
2010-04-08 3:41 ` Darren Hart
2010-04-08 4:29 ` drepper
2010-04-07 5:33 ` Avi Kivity
2010-04-06 21:22 ` Darren Hart
2010-04-05 23:15 ` Darren Hart
2010-04-05 23:29 ` Chris Wright
2010-04-06 13:30 ` Avi Kivity
2010-04-06 8:48 ` Peter Zijlstra
2010-04-06 14:47 ` Ulrich Drepper
2010-04-06 14:51 ` Peter Zijlstra
2010-04-06 15:33 ` Darren Hart
2010-04-06 15:37 ` Peter Zijlstra
2010-04-06 15:29 ` Peter Zijlstra
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