Kernel Support for Dual Core x86-64?

Kernel Support for Dual Core x86-64?

[Peter Fein]

Hi all-

My company is looking to build a cluster of Linux machines to run an
in-house compute-intensive application.  We're strongly considering
dual-processor, dual-core x86-64 systems for cost reasons (shared
hardware, less rack space).  I have a few questions, and despite
extensive googling, haven't been able to find satisfactory answers.

1. Can a dual core chip run two os-level *processes* simultaneously or
only two threads from the same process?  Our processes (written in
Python, with parts in C) are completely independent of each other.

2. What sort of speed up relative to a dual processor, single core
system could I expect to gain?  I realize this is highly application
dependent and I'm not looking for any hard figures.  I just want to get
a rough idea to see if the additional cost is worth it.

3. Any suggestions on compiler version?  We're currently using GCC-3.3.6
on our 32 bit boxes.

Thanks in advance!

-- 
Peter Fein                 pfein@pobox.com                 773-575-0694

Basically, if you're not a utopianist, you're a schmuck. -J. Feldman

Re: Kernel Support for Dual Core x86-64?

[Robert M. Hyatt]

Robert M. Hyatt, Ph.D.          Computer and Information Sciences
hyatt@uab.edu                   University of Alabama at Birmingham
(205) 934-2213                  136A Campbell Hall
(205) 934-5473 FAX              Birmingham, AL 35294-1170

On Sat, 17 Sep 2005, Peter Fein wrote:

> Hi all-
> 
> My company is looking to build a cluster of Linux machines to run an
> in-house compute-intensive application.  We're strongly considering
> dual-processor, dual-core x86-64 systems for cost reasons (shared
> hardware, less rack space).  I have a few questions, and despite
> extensive googling, haven't been able to find satisfactory answers.
> 
> 1. Can a dual core chip run two os-level *processes* simultaneously or
> only two threads from the same process?  Our processes (written in
> Python, with parts in C) are completely independent of each other.
> 


yes.   A dual-core is two separate processors, on a single NUMA "node".  
You can create two processes any way you want, from threads, to fork() 
to simply typings a&; b&, and the two processes will run on the two cpus 
just fine.  I've run on a quad 875 system at AMD, and the box appears to 
have 8 cpus since each processor is dual-core.  It runs like a bat out 
of Egypt also...


> 2. What sort of speed up relative to a dual processor, single core
> system could I expect to gain?  I realize this is highly application
> dependent and I'm not looking for any hard figures.  I just want to get
> a rough idea to see if the additional cost is worth it.
> 



technically it is 2x faster.  practically it depends on the application.  
My chess program runs at 2x the nodes per second, but the actual speedup 
is around 1.7-1.8X, due to internal search issues that have nothing to 
do with the dual-core.  In fact, If I run on a dual-core I get about 
1.7-1.8X, if I run on a dual-processor single-core opteron box (say 2 
850's or whatever) I get 1.7-1.8X speedup.  So I can barely tell the 
difference.



> 3. Any suggestions on compiler version?  We're currently using GCC-3.3.6
> on our 32 bit boxes.
> 

I use SuSe on opterons as does AMD on the ones they let me test on.  gcc 
3.3 is plenty good enough...





> Thanks in advance!
> 
> -- 
> Peter Fein                 pfein@pobox.com                 773-575-0694
> 
> Basically, if you're not a utopianist, you're a schmuck. -J. Feldman
> 
> -
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