From: Alex Shi <alex.shi@intel.com>
To: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>,
Ingo Molnar <mingo@elte.hu>, Rik van Riel <riel@redhat.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Andrea Arcangeli <aarcange@redhat.com>,
Mel Gorman <mgorman@suse.de>, Andi Kleen <andi@firstfloor.org>,
Andrew Morton <akpm@linux-foundation.org>,
Michel Lespinasse <walken@google.com>,
"Wilcox, Matthew R" <matthew.r.wilcox@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: Performance regression from switching lock to rw-sem for anon-vma tree
Date: Tue, 18 Jun 2013 07:18:56 +0800 [thread overview]
Message-ID: <51BF9960.904@intel.com> (raw)
In-Reply-To: <1371494746.27102.633.camel@schen9-DESK>
On 06/18/2013 02:45 AM, Tim Chen wrote:
>>> + if (unlikely(sem->count < RWSEM_WAITING_BIAS)) {
>>> > > + cpu_relax();
>>> > > + continue;
>>> > > + }
> The above two if statements could be cleaned up as a single check:
>
> if (unlikely(sem->count < RWSEM_WAITING_BIAS))
> return sem;
>
> This one statement is sufficient to check that we don't have a writer
> stolen the lock before we attempt to acquire the read lock by modifying
> sem->count.
>
>
Thanks. I will send out the patchset base your suggestion.
--
Thanks
Alex
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WARNING: multiple messages have this Message-ID (diff)
From: Alex Shi <alex.shi@intel.com>
To: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>,
Ingo Molnar <mingo@elte.hu>, Rik van Riel <riel@redhat.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Andrea Arcangeli <aarcange@redhat.com>,
Mel Gorman <mgorman@suse.de>, Andi Kleen <andi@firstfloor.org>,
Andrew Morton <akpm@linux-foundation.org>,
Michel Lespinasse <walken@google.com>,
"Wilcox, Matthew R" <matthew.r.wilcox@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: Performance regression from switching lock to rw-sem for anon-vma tree
Date: Tue, 18 Jun 2013 07:18:56 +0800 [thread overview]
Message-ID: <51BF9960.904@intel.com> (raw)
In-Reply-To: <1371494746.27102.633.camel@schen9-DESK>
On 06/18/2013 02:45 AM, Tim Chen wrote:
>>> + if (unlikely(sem->count < RWSEM_WAITING_BIAS)) {
>>> > > + cpu_relax();
>>> > > + continue;
>>> > > + }
> The above two if statements could be cleaned up as a single check:
>
> if (unlikely(sem->count < RWSEM_WAITING_BIAS))
> return sem;
>
> This one statement is sufficient to check that we don't have a writer
> stolen the lock before we attempt to acquire the read lock by modifying
> sem->count.
>
>
Thanks. I will send out the patchset base your suggestion.
--
Thanks
Alex
next prev parent reply other threads:[~2013-06-17 23:19 UTC|newest]
Thread overview: 92+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1371165333.27102.568.camel@schen9-DESK>
[not found] ` <1371167015.1754.14.camel@buesod1.americas.hpqcorp.net>
2013-06-14 16:09 ` Performance regression from switching lock to rw-sem for anon-vma tree Tim Chen
2013-06-14 16:09 ` Tim Chen
2013-06-14 22:31 ` Davidlohr Bueso
2013-06-14 22:31 ` Davidlohr Bueso
2013-06-14 22:44 ` Tim Chen
2013-06-14 22:44 ` Tim Chen
2013-06-14 22:47 ` Michel Lespinasse
2013-06-14 22:47 ` Michel Lespinasse
2013-06-17 22:27 ` Tim Chen
2013-06-17 22:27 ` Tim Chen
2013-06-16 9:50 ` Alex Shi
2013-06-16 9:50 ` Alex Shi
2013-06-17 16:22 ` Davidlohr Bueso
2013-06-17 16:22 ` Davidlohr Bueso
2013-06-17 18:45 ` Tim Chen
2013-06-17 18:45 ` Tim Chen
2013-06-17 19:05 ` Davidlohr Bueso
2013-06-17 19:05 ` Davidlohr Bueso
2013-06-17 22:28 ` Tim Chen
2013-06-17 22:28 ` Tim Chen
2013-06-17 23:18 ` Alex Shi [this message]
2013-06-17 23:18 ` Alex Shi
2013-06-17 23:20 ` Alex Shi
2013-06-17 23:20 ` Alex Shi
2013-06-17 23:35 ` Davidlohr Bueso
2013-06-17 23:35 ` Davidlohr Bueso
2013-06-18 0:08 ` Tim Chen
2013-06-18 0:08 ` Tim Chen
2013-06-19 23:11 ` Davidlohr Bueso
2013-06-19 23:11 ` Davidlohr Bueso
2013-06-19 23:24 ` Tim Chen
2013-06-19 23:24 ` Tim Chen
2013-06-13 23:26 Tim Chen
2013-06-13 23:26 ` Tim Chen
2013-06-19 13:16 ` Ingo Molnar
2013-06-19 13:16 ` Ingo Molnar
2013-06-19 16:53 ` Tim Chen
2013-06-19 16:53 ` Tim Chen
2013-06-26 0:19 ` Tim Chen
2013-06-26 0:19 ` Tim Chen
2013-06-26 9:51 ` Ingo Molnar
2013-06-26 9:51 ` Ingo Molnar
2013-06-26 21:36 ` Tim Chen
2013-06-26 21:36 ` Tim Chen
2013-06-27 0:25 ` Tim Chen
2013-06-27 0:25 ` Tim Chen
2013-06-27 8:36 ` Ingo Molnar
2013-06-27 8:36 ` Ingo Molnar
2013-06-27 20:53 ` Tim Chen
2013-06-27 20:53 ` Tim Chen
2013-06-27 23:31 ` Tim Chen
2013-06-27 23:31 ` Tim Chen
2013-06-28 9:38 ` Ingo Molnar
2013-06-28 9:38 ` Ingo Molnar
2013-06-28 21:04 ` Tim Chen
2013-06-28 21:04 ` Tim Chen
2013-06-29 7:12 ` Ingo Molnar
2013-06-29 7:12 ` Ingo Molnar
2013-07-01 20:28 ` Tim Chen
2013-07-01 20:28 ` Tim Chen
2013-07-02 6:45 ` Ingo Molnar
2013-07-02 6:45 ` Ingo Molnar
2013-07-16 17:53 ` Tim Chen
2013-07-16 17:53 ` Tim Chen
2013-07-23 9:45 ` Ingo Molnar
2013-07-23 9:45 ` Ingo Molnar
2013-07-23 9:51 ` Peter Zijlstra
2013-07-23 9:51 ` Peter Zijlstra
2013-07-23 9:53 ` Ingo Molnar
2013-07-23 9:53 ` Ingo Molnar
2013-07-30 0:13 ` Tim Chen
2013-07-30 0:13 ` Tim Chen
2013-07-30 19:24 ` Ingo Molnar
2013-07-30 19:24 ` Ingo Molnar
2013-08-05 22:08 ` Tim Chen
2013-08-05 22:08 ` Tim Chen
2013-07-30 19:59 ` Davidlohr Bueso
2013-07-30 19:59 ` Davidlohr Bueso
2013-07-30 20:34 ` Tim Chen
2013-07-30 20:34 ` Tim Chen
2013-07-30 21:45 ` Davidlohr Bueso
2013-07-30 21:45 ` Davidlohr Bueso
2013-08-06 23:55 ` Davidlohr Bueso
2013-08-06 23:55 ` Davidlohr Bueso
2013-08-07 0:56 ` Tim Chen
2013-08-07 0:56 ` Tim Chen
2013-08-12 18:52 ` Ingo Molnar
2013-08-12 18:52 ` Ingo Molnar
2013-08-12 20:10 ` Tim Chen
2013-08-12 20:10 ` Tim Chen
2013-06-28 9:20 ` Ingo Molnar
2013-06-28 9:20 ` Ingo Molnar
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