linux-kernel - Re: [tip:core/rcu] Revert "rcu: Decrease memory-barrier usage based on semi-formal proof"

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Date:	Fri, 20 May 2011 16:09:22 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	paulmck@...ux.vnet.ibm.com
CC:	linux-kernel@...r.kernel.org, mingo@...hat.com, hpa@...or.com,
	tglx@...utronix.de, mingo@...e.hu,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:core/rcu] Revert "rcu: Decrease memory-barrier usage based
 on semi-formal proof"

On 05/20/2011 03:42 PM, Paul E. McKenney wrote:
> On Fri, May 20, 2011 at 02:04:06PM -0700, Yinghai Lu wrote:
>> On 05/19/2011 02:37 PM, tip-bot for Paul E. McKenney wrote:
>>> Commit-ID:  80d02085d99039b3b7f3a73c8896226b0cb1ba07
>>> Gitweb:     http://git.kernel.org/tip/80d02085d99039b3b7f3a73c8896226b0cb1ba07
>>> Author:     Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
>>> AuthorDate: Thu, 12 May 2011 01:08:07 -0700
>>> Committer:  Ingo Molnar <mingo@...e.hu>
>>> CommitDate: Thu, 19 May 2011 23:25:29 +0200
>>>
>>> Revert "rcu: Decrease memory-barrier usage based on semi-formal proof"
>>>
>>> This reverts commit e59fb3120becfb36b22ddb8bd27d065d3cdca499.
>>>
>>> This reversion was due to (extreme) boot-time slowdowns on SPARC seen by
>>> Yinghai Lu and on x86 by Ingo
>>> .
>>> This is a non-trivial reversion due to intervening commits.
>>>
>>> Conflicts:
>>>
>>> 	Documentation/RCU/trace.txt
>>> 	kernel/rcutree.c
>>>
>>> Signed-off-by: Ingo Molnar <mingo@...e.hu>
>>> ---
>>>  Documentation/RCU/trace.txt |   17 ++++--
>>>  kernel/rcutree.c            |  130 ++++++++++++++++++++++++------------------
>>>  kernel/rcutree.h            |    9 ++-
>>>  kernel/rcutree_plugin.h     |    7 +-
>>>  kernel/rcutree_trace.c      |   12 ++--
>>>  5 files changed, 102 insertions(+), 73 deletions(-)
>>>
>>
>> current tip/master that have this reverting and without setting DEBUG_LOCKING_API_SELFTESTS
>>
>> still get delay
>>
>> [   35.419453] cpu_dev_init done
>> [  128.981770] memory_dev_init done
>>
>> should take only 3 or 4 seconds.
> 
> Thank you for checking this out.
> 
> This is with the same configuration you sent earlier?  (Other than the
> DEBUG_LOCKING_API_SELFTESTS, of course.)
> 

8 socket westmere-ex. and compiled with gcc from opensuse 11.3.

if compile kernel from fedora 14, there will be not delay.

Thanks

Yinghai
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