From: Christoph Lameter <cl@linux-foundation.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andi Kleen <andi@firstfloor.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Minchan Kim <minchan.kim@gmail.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"hugh.dickins" <hugh.dickins@tiscali.co.uk>,
Nick Piggin <nickpiggin@yahoo.com.au>,
Ingo Molnar <mingo@elte.hu>
Subject: Re: [RFC][PATCH 6/8] mm: handle_speculative_fault()
Date: Tue, 5 Jan 2010 13:15:53 -0600 (CST) [thread overview]
Message-ID: <alpine.DEB.2.00.1001051301060.5119@router.home> (raw)
In-Reply-To: <alpine.LFD.2.00.1001051052150.3630@localhost.localdomain>
On Tue, 5 Jan 2010, Linus Torvalds wrote:
> Don't you see the problem? The spinlock (with ticket locks) essentially
> does the "xadd" atomic increment anyway, but then it _waits_ for it. All
> totally pointless, and all just making for problems, and wasting CPU time
> and causing more cross-node traffic.
For the xadd to work it first would have to acquire the cacheline
exclusively. That can only occur for a single processor and with the
fitting minimum holdtime for exclusive cachelines everything should be
fine. If the critical section is done (unlock complete) then the next
processor (which had to stopped waiting to access the cacheline) can
acquire the lock.
The wait state is the processor being stopped due to not being able to
access the cacheline. Not the processor spinning in the xadd loop. That
only occurs if the critical section is longer than the timeout.
--
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next prev parent reply other threads:[~2010-01-05 19:16 UTC|newest]
Thread overview: 121+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-04 18:24 [RFC][PATCH 0/8] Speculative pagefault -v3 Peter Zijlstra
2010-01-04 18:24 ` [RFC][PATCH 1/8] mm: Remove pte reference from fault path Peter Zijlstra
2010-01-04 18:24 ` [RFC][PATCH 2/8] mm: Speculative pagefault infrastructure Peter Zijlstra
2010-01-04 18:24 ` [RFC][PATCH 3/8] mm: Add vma sequence count Peter Zijlstra
2010-01-04 18:24 ` [RFC][PATCH 4/8] mm: RCU free vmas Peter Zijlstra
2010-01-05 2:43 ` Paul E. McKenney
2010-01-05 8:28 ` Peter Zijlstra
2010-01-05 16:05 ` Paul E. McKenney
2010-01-04 18:24 ` [RFC][PATCH 5/8] mm: Speculative pte_map_lock() Peter Zijlstra
2010-01-04 18:24 ` [RFC][PATCH 6/8] mm: handle_speculative_fault() Peter Zijlstra
2010-01-05 0:25 ` KAMEZAWA Hiroyuki
2010-01-05 3:13 ` Linus Torvalds
2010-01-05 8:17 ` Peter Zijlstra
2010-01-05 8:57 ` Peter Zijlstra
2010-01-05 15:34 ` Linus Torvalds
2010-01-05 15:40 ` Al Viro
2010-01-05 16:10 ` Linus Torvalds
2010-01-06 15:41 ` Peter Zijlstra
2010-01-05 9:37 ` Peter Zijlstra
2010-01-05 23:35 ` Linus Torvalds
2010-01-05 4:29 ` Minchan Kim
2010-01-05 4:43 ` KAMEZAWA Hiroyuki
2010-01-05 5:10 ` Linus Torvalds
2010-01-05 5:30 ` KAMEZAWA Hiroyuki
2010-01-05 7:39 ` KAMEZAWA Hiroyuki
2010-01-05 15:26 ` Linus Torvalds
2010-01-05 16:14 ` Linus Torvalds
2010-01-05 17:25 ` Andi Kleen
2010-01-05 17:47 ` Christoph Lameter
2010-01-05 18:00 ` Andi Kleen
2010-01-05 17:55 ` Linus Torvalds
2010-01-05 18:13 ` Christoph Lameter
2010-01-05 18:25 ` Linus Torvalds
2010-01-05 18:46 ` Christoph Lameter
2010-01-05 18:56 ` Linus Torvalds
2010-01-05 19:15 ` Christoph Lameter [this message]
2010-01-05 19:28 ` Linus Torvalds
2010-01-05 18:55 ` Paul E. McKenney
2010-01-05 19:08 ` Linus Torvalds
2010-01-05 19:23 ` Paul E. McKenney
2010-01-05 20:29 ` Peter Zijlstra
2010-01-05 20:46 ` Linus Torvalds
2010-01-05 21:00 ` Linus Torvalds
2010-01-05 23:29 ` Paul E. McKenney
2010-01-06 0:22 ` KAMEZAWA Hiroyuki
2010-01-06 1:37 ` Linus Torvalds
2010-01-06 2:52 ` KAMEZAWA Hiroyuki
2010-01-06 3:27 ` Linus Torvalds
2010-01-06 3:56 ` KAMEZAWA Hiroyuki
2010-01-06 4:20 ` Linus Torvalds
2010-01-06 7:06 ` KAMEZAWA Hiroyuki
2010-01-06 7:49 ` Minchan Kim
2010-01-06 9:39 ` Linus Torvalds
2010-01-07 1:00 ` KAMEZAWA Hiroyuki
2010-01-08 16:53 ` Peter Zijlstra
2010-01-08 17:22 ` Linus Torvalds
2010-01-08 17:43 ` Christoph Lameter
2010-01-08 17:52 ` Linus Torvalds
2010-01-08 18:33 ` Christoph Lameter
2010-01-08 18:46 ` Andi Kleen
2010-01-08 18:56 ` Christoph Lameter
2010-01-08 19:10 ` Andi Kleen
2010-01-08 19:11 ` Linus Torvalds
2010-01-08 19:28 ` Andi Kleen
2010-01-08 19:39 ` Linus Torvalds
2010-01-08 19:42 ` Linus Torvalds
2010-01-08 21:36 ` Linus Torvalds
2010-01-08 21:46 ` Christoph Lameter
2010-01-08 22:43 ` Linus Torvalds
2010-01-08 22:43 ` Linus Torvalds
2010-01-09 14:47 ` Ed Tomlinson
2010-01-10 5:27 ` Nitin Gupta
2010-01-05 15:14 ` Christoph Lameter
2010-01-05 8:18 ` Peter Zijlstra
2010-01-05 6:00 ` Minchan Kim
2010-01-05 4:48 ` Linus Torvalds
2010-01-05 6:09 ` Minchan Kim
2010-01-05 6:09 ` KAMEZAWA Hiroyuki
2010-01-05 6:24 ` Minchan Kim
2010-01-05 8:35 ` Peter Zijlstra
2010-01-05 13:45 ` Arjan van de Ven
2010-01-05 14:15 ` Andi Kleen
2010-01-05 15:17 ` Christoph Lameter
2010-01-06 3:22 ` Arjan van de Ven
2010-01-07 16:11 ` Christoph Lameter
2010-01-07 16:19 ` Linus Torvalds
2010-01-07 16:31 ` Linus Torvalds
2010-01-07 16:34 ` Paul E. McKenney
2010-01-07 16:36 ` Christoph Lameter
2010-01-08 4:49 ` Arjan van de Ven
2010-01-08 5:00 ` Linus Torvalds
2010-01-08 15:51 ` Christoph Lameter
2010-01-09 15:55 ` Arjan van de Ven
2010-01-07 17:22 ` Peter Zijlstra
2010-01-07 17:36 ` Linus Torvalds
2010-01-07 17:49 ` Linus Torvalds
2010-01-07 18:00 ` Peter Zijlstra
2010-01-07 18:15 ` Linus Torvalds
2010-01-07 21:49 ` Peter Zijlstra
2010-01-07 18:44 ` Linus Torvalds
2010-01-07 19:20 ` Paul E. McKenney
2010-01-07 20:06 ` Linus Torvalds
2010-01-07 20:25 ` Paul E. McKenney
2010-01-07 19:24 ` Christoph Lameter
2010-01-07 20:08 ` Linus Torvalds
2010-01-07 20:13 ` Linus Torvalds
2010-01-07 21:44 ` Peter Zijlstra
2010-01-07 22:33 ` Linus Torvalds
2010-01-08 0:23 ` KAMEZAWA Hiroyuki
2010-01-08 0:25 ` KAMEZAWA Hiroyuki
2010-01-08 0:39 ` Linus Torvalds
2010-01-08 0:41 ` Linus Torvalds
2010-01-07 23:51 ` Rik van Riel
2010-01-04 18:24 ` [RFC][PATCH 7/8] mm,x86: speculative pagefault support Peter Zijlstra
2010-01-04 18:24 ` [RFC][PATCH 8/8] mm: Optimize pte_map_lock() Peter Zijlstra
2010-01-04 21:41 ` [RFC][PATCH 0/8] Speculative pagefault -v3 Rik van Riel
2010-01-04 21:46 ` Peter Zijlstra
2010-01-04 23:20 ` Rik van Riel
2010-01-04 21:59 ` Christoph Lameter
2010-01-05 0:28 ` KAMEZAWA Hiroyuki
2010-01-05 2:26 ` Minchan Kim
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