linux-kernel - Re: Possible bug from kernel 2.6.22 and above, 2.6.24-rc4

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Message-ID: <47572353.4040606@jlab.org>
Date:	Wed, 05 Dec 2007 17:16:51 -0500
From:	Jie Chen <chen@...b.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Simon Holm Th??gersen <odie@...aau.dk>,
	Eric Dumazet <dada1@...mosbay.com>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: Possible bug from kernel 2.6.22 and above, 2.6.24-rc4

Ingo Molnar wrote:
> * Jie Chen <chen@...b.org> wrote:
> 
>>> sorry to be dense, but could you give me instructions how i could 
>>> remove the affinity mask and test the "barrier overhead" myself? I 
>>> have built "pthread_sync" and it outputs numbers for me - which one 
>>> would be the barrier overhead: Reference_time_1 ?
>> To disable affinity, do configure --enable-public-release 
>> --disable-thread_affinity. You should see barrier overhead like the 
>> following: Computing BARRIER time
>>
>> Sample_size  Average     Min    Max          S.D.        Outliers
>>  20      19.486162   19.482250   19.491400    0.002740      0
>>
>> BARRIER time =        19.486162 microseconds +/- 0.005371
>> BARRIER overhead =    8.996257 microseconds +/- 0.006575
> 
> ok, i did that and rebuilt. I also did "make check" and got 
> src/pthread_sync which i can run. The only thing i'm missing, if i run 
> src/pthread_sync, it outputs "PARALLEL time":
> 
>  PARALLEL time =                           22.486103 microseconds +/- 3.944821
>  PARALLEL overhead =                       10.638658 microseconds +/- 10.854154
> 
> not "BARRIER time". I've re-read the discussion and found no hint about 
> how to build and run a barrier test. Either i missed it or it's so 
> obvious to you that you didnt mention it :-)
> 
> 	Ingo

Hi, Ingo:

Did you do configure --enable-public-release? My qmt is for qcd 
calculation (one type of physics code). Without the above flag one can 
only test PARALLEL overhead. Actually the PARALLEL benchmark has the 
same behavior as the BARRIER. Thanks.


###############################################
Jie Chen
Scientific Computing Group
Thomas Jefferson National Accelerator Facility
12000, Jefferson Ave.
Newport News, VA 23606

(757)269-5046 (office) (757)269-6248 (fax)
chen@...b.org
###############################################
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