From: Ingo Molnar <mingo@kernel.org>
To: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Jason Low <jason.low2@hp.com>, Davidlohr Bueso <davidlohr@hp.com>,
Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Alex Shi <alex.shi@linaro.org>, Andi Kleen <andi@firstfloor.org>,
Michel Lespinasse <walken@google.com>,
Davidlohr Bueso <davidlohr.bueso@hp.com>,
Matthew R Wilcox <matthew.r.wilcox@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Rik van Riel <riel@redhat.com>,
Peter Hurley <peter@hurleysoftware.com>,
linux-kernel@vger.kernel.org, linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH v6 5/6] MCS Lock: Restructure the MCS lock defines and locking code into its own file
Date: Fri, 27 Sep 2013 08:02:13 +0200 [thread overview]
Message-ID: <20130927060213.GA6673@gmail.com> (raw)
In-Reply-To: <1380236265.3467.103.camel@schen9-DESK>
* Tim Chen <tim.c.chen@linux.intel.com> wrote:
> > If we prefer to optimize this a bit though, perhaps we can first move
> > the node->lock = 0 so that it gets executed after the "if (likely(prev
> > == NULL)) {}" code block and then delete "node->lock = 1" inside the
> > code block.
>
> I suppose we can save one single assignment. The gain is probably not
> noticeable as once we set node->next to NULL, node->locked is likely in
> local cache line and the assignment operation is cheap.
Would be nice to have this as a separate, add-on patch. Every single
instruction removal that has no downside is an upside!
You can add a comment that explains it.
Thanks,
Ingo
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WARNING: multiple messages have this Message-ID (diff)
From: Ingo Molnar <mingo@kernel.org>
To: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Jason Low <jason.low2@hp.com>, Davidlohr Bueso <davidlohr@hp.com>,
Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Alex Shi <alex.shi@linaro.org>, Andi Kleen <andi@firstfloor.org>,
Michel Lespinasse <walken@google.com>,
Davidlohr Bueso <davidlohr.bueso@hp.com>,
Matthew R Wilcox <matthew.r.wilcox@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Rik van Riel <riel@redhat.com>,
Peter Hurley <peter@hurleysoftware.com>,
linux-kernel@vger.kernel.org, linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH v6 5/6] MCS Lock: Restructure the MCS lock defines and locking code into its own file
Date: Fri, 27 Sep 2013 08:02:13 +0200 [thread overview]
Message-ID: <20130927060213.GA6673@gmail.com> (raw)
In-Reply-To: <1380236265.3467.103.camel@schen9-DESK>
* Tim Chen <tim.c.chen@linux.intel.com> wrote:
> > If we prefer to optimize this a bit though, perhaps we can first move
> > the node->lock = 0 so that it gets executed after the "if (likely(prev
> > == NULL)) {}" code block and then delete "node->lock = 1" inside the
> > code block.
>
> I suppose we can save one single assignment. The gain is probably not
> noticeable as once we set node->next to NULL, node->locked is likely in
> local cache line and the assignment operation is cheap.
Would be nice to have this as a separate, add-on patch. Every single
instruction removal that has no downside is an upside!
You can add a comment that explains it.
Thanks,
Ingo
next prev parent reply other threads:[~2013-09-27 6:02 UTC|newest]
Thread overview: 129+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1380144003.git.tim.c.chen@linux.intel.com>
2013-09-25 22:10 ` [PATCH v6 0/6] rwsem: performance optimizations Tim Chen
2013-09-25 22:10 ` Tim Chen
2013-09-25 22:10 ` [PATCH v6 1/6] rwsem: check the lock before cpmxchg in down_write_trylock Tim Chen
2013-09-25 22:10 ` Tim Chen
2013-09-25 22:10 ` [PATCH v6 2/6] rwsem: remove 'out' label in do_wake Tim Chen
2013-09-25 22:10 ` Tim Chen
2013-09-25 22:10 ` [PATCH v6 3/6] rwsem: remove try_reader_grant label do_wake Tim Chen
2013-09-25 22:10 ` Tim Chen
2013-09-25 22:10 ` [PATCH v6 4/6] rwsem/wake: check lock before do atomic update Tim Chen
2013-09-25 22:10 ` Tim Chen
2013-09-25 22:10 ` [PATCH v6 5/6] MCS Lock: Restructure the MCS lock defines and locking code into its own file Tim Chen
2013-09-25 22:10 ` Tim Chen
2013-09-26 6:46 ` Ingo Molnar
2013-09-26 6:46 ` Ingo Molnar
2013-09-26 8:40 ` Peter Zijlstra
2013-09-26 8:40 ` Peter Zijlstra
2013-09-26 9:37 ` Ingo Molnar
2013-09-26 9:37 ` Ingo Molnar
2013-09-26 18:18 ` Tim Chen
2013-09-26 18:18 ` Tim Chen
2013-09-26 19:27 ` Jason Low
2013-09-26 19:27 ` Jason Low
2013-09-26 20:06 ` Davidlohr Bueso
2013-09-26 20:06 ` Davidlohr Bueso
2013-09-26 20:23 ` Jason Low
2013-09-26 20:23 ` Jason Low
2013-09-26 20:40 ` Davidlohr Bueso
2013-09-26 20:40 ` Davidlohr Bueso
2013-09-26 21:09 ` Jason Low
2013-09-26 21:09 ` Jason Low
2013-09-26 21:41 ` Tim Chen
2013-09-26 21:41 ` Tim Chen
2013-09-26 22:42 ` Jason Low
2013-09-26 22:42 ` Jason Low
2013-09-26 22:57 ` Tim Chen
2013-09-26 22:57 ` Tim Chen
2013-09-27 6:02 ` Ingo Molnar [this message]
2013-09-27 6:02 ` Ingo Molnar
2013-09-27 6:26 ` Jason Low
2013-09-27 6:26 ` Jason Low
2013-09-27 11:23 ` Peter Zijlstra
2013-09-27 11:23 ` Peter Zijlstra
2013-09-27 13:44 ` Joe Perches
2013-09-27 13:44 ` Joe Perches
2013-09-27 13:48 ` Peter Zijlstra
2013-09-27 13:48 ` Peter Zijlstra
2013-09-27 14:05 ` Joe Perches
2013-09-27 14:05 ` Joe Perches
2013-09-27 14:18 ` Peter Zijlstra
2013-09-27 14:18 ` Peter Zijlstra
2013-09-27 14:14 ` [PATCH] checkpatch: Make the memory barrier test noisier Joe Perches
2013-09-27 14:14 ` Joe Perches
2013-09-27 14:26 ` Peter Zijlstra
2013-09-27 14:26 ` Peter Zijlstra
2013-09-27 14:34 ` Joe Perches
2013-09-27 14:34 ` Joe Perches
2013-09-27 14:50 ` Peter Zijlstra
2013-09-27 14:50 ` Peter Zijlstra
2013-09-27 15:17 ` Paul E. McKenney
2013-09-27 15:17 ` Paul E. McKenney
2013-09-27 15:34 ` Peter Zijlstra
2013-09-27 15:34 ` Peter Zijlstra
2013-09-27 16:04 ` Paul E. McKenney
2013-09-27 16:04 ` Paul E. McKenney
2013-09-27 16:04 ` Paul E. McKenney
2013-09-27 23:40 ` Oliver Neukum
2013-09-27 23:40 ` Oliver Neukum
2013-09-28 7:54 ` Peter Zijlstra
2013-09-28 7:54 ` Peter Zijlstra
2013-09-27 16:12 ` [PATCH v6 5/6] MCS Lock: Restructure the MCS lock defines and locking code into its own file Jason Low
2013-09-27 16:12 ` Jason Low
2013-09-27 16:19 ` Tim Chen
2013-09-27 16:19 ` Tim Chen
2013-10-02 19:19 ` Waiman Long
2013-10-02 19:19 ` Waiman Long
2013-10-02 19:30 ` Jason Low
2013-10-02 19:30 ` Jason Low
2013-10-02 19:37 ` Waiman Long
2013-10-02 19:37 ` Waiman Long
2013-09-26 22:22 ` Davidlohr Bueso
2013-09-26 22:22 ` Davidlohr Bueso
2013-09-27 15:29 ` Paul E. McKenney
2013-09-27 15:29 ` Paul E. McKenney
2013-09-27 18:09 ` Tim Chen
2013-09-27 18:09 ` Tim Chen
2013-09-28 2:58 ` Waiman Long
2013-09-28 2:58 ` Waiman Long
2013-09-27 19:38 ` Tim Chen
2013-09-27 19:38 ` Tim Chen
2013-09-27 20:16 ` Jason Low
2013-09-27 20:16 ` Jason Low
2013-09-27 20:38 ` Paul E. McKenney
2013-09-27 20:38 ` Paul E. McKenney
2013-09-27 22:46 ` Tim Chen
2013-09-27 22:46 ` Tim Chen
2013-09-27 23:01 ` Paul E. McKenney
2013-09-27 23:01 ` Paul E. McKenney
2013-09-27 23:54 ` Jason Low
2013-09-27 23:54 ` Jason Low
2013-09-28 0:02 ` Davidlohr Bueso
2013-09-28 0:02 ` Davidlohr Bueso
2013-09-28 2:19 ` Paul E. McKenney
2013-09-28 2:19 ` Paul E. McKenney
2013-09-28 4:34 ` Jason Low
2013-09-28 4:34 ` Jason Low
2013-09-30 15:51 ` Waiman Long
2013-09-30 15:51 ` Waiman Long
2013-09-30 16:10 ` Jason Low
2013-09-30 16:10 ` Jason Low
2013-09-30 16:36 ` Waiman Long
2013-09-30 16:36 ` Waiman Long
2013-10-01 16:48 ` Tim Chen
2013-10-01 16:48 ` Tim Chen
2013-10-01 20:01 ` Waiman Long
2013-10-01 20:01 ` Waiman Long
2013-10-01 21:16 ` Tim Chen
2013-10-01 21:16 ` Tim Chen
2013-10-02 1:25 ` Waiman Long
2013-10-02 1:25 ` Waiman Long
2013-10-02 18:43 ` Tim Chen
2013-10-02 18:43 ` Tim Chen
2013-10-02 19:32 ` Waiman Long
2013-10-02 19:32 ` Waiman Long
2013-09-30 16:28 ` Tim Chen
2013-09-30 16:28 ` Tim Chen
2013-09-25 22:10 ` [PATCH v6 6/6] rwsem: do optimistic spinning for writer lock acquisition Tim Chen
2013-09-25 22:10 ` Tim Chen
2013-09-26 6:53 ` Ingo Molnar
2013-09-26 6:53 ` Ingo Molnar
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