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Old 2008-01-01, 06:27   #1
fes016
 
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Oct 2007
USA

23 Posts
Default C2Q + Linux: which core is which?

I have been running 4 instances of prime95 on my Xeon X3210 (c2q) with the -An switches under Windows XP x64. I do TF on cores 0 & 2, and LL on cores 1 & 3. Now with the new year upon us, I figure I'd make a resolution to limit the use of M$ products ;) so I installed Fedora 8. I've got everything up and running, but my question is, does Linux count the cores the same way? I'm wondering because work seems to be done a little slower, at least for LL. The 2 LL instances went from 0.73/0.73 to 0.77/0.77. I don't know how TF is affected because now it outputs after roughly every 77 seconds as opposed to every 250 seconds. Another reason I'm wondering is because I noticed that the processor number and the core id's don't match in /proc/cpuinfo:
Code:
processor	0 1 2 3
physical id	0 0 0 0
siblings	4 4 4 4
core id		0 2 1 3
cpu cores	4 4 4 4
So when I set the affinity for each instance of prime95, what does it go by, the processor number or the core id? Does this mean I should switch the work for -A1 and -A2?


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Old 2008-01-02, 00:26   #2
fes016
 
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Oct 2007
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Well, I was finally able to access my Xeon X3210 system and swapped the work for -A1 and -A2, and the iteration times for the LL tests are now faster at 0.073/0.073 (oops, wrote the times wrong in the previous post, should have been 0.073/0.073 and 0.077/0.077 ). So now I have TF on cores 0 & 1, and LL on cores 2 & 3. Strange.

What's also strange is that for TF I still get outputs to the screen every ~77 seconds instead of ~250 seconds when I was running prime95 under Windows XP x64. Any idea why the change? I didn't edit any of the configuration files between installs. Is there a way to increase the time between outputs for TF? (The iteration output setting under Options->Preferences is for LL tests, isn't it?)


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Last fiddled with by fes016 on 2008-01-02 at 00:27
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Old 2008-01-02, 22:39   #3
patrik
 
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"Patrik Johansson"
Aug 2002
Uppsala, Sweden

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On my Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz "processor" and "core id" are the same. I'm running
Code:
---@nu:~> uname -a
Linux nu 2.6.18.2-34-default #1 SMP Mon Nov 27 11:46:27 UTC 2006 x86_64 x86_64 x86_64 GNU/Linux
---@nu:~> more /etc/SuSE-release
openSUSE 10.2 (X86-64)
VERSION = 10.2

Last fiddled with by patrik on 2008-01-02 at 22:41 Reason: Deleted login name for security reasons
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