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ithreads & linux SMP

 
 
none
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      02-18-2006
If I use fedora core 2 linux with SMP enabled, perl ithreads, and an
intel hyper-threaded server with ram in both banks, will a perl program
that uses ithreads to launch threads launch a thread on each
"processor"?

My motherboard used to show 2 cpus with my old linux distro (redhat
8?), but now it is not showing that with top.

I am trying to test a threaded application before going out and buying
a dual core server. I happen to have this hyper threaded machine and am
testing it out, but have been unable to confirm that the ithreads will
take advantage of hyper-threading or a dual core cpu.

Top does not show 2 cpu's, although I am sure the previous install of
redhat 8 or 9 that I had did reflect that. dmesg reports 2 cpu's.
Again, this is not a dual core or dual processor machine, it is an
intel hyper-threaded machine.

I am hoping that I can buy a dual core machine and use some form of
perl threads to improve performance of a custom application.

Linux localhost.localdomain 2.6.11-1.1369_FC4smp #1 SMP Thu Jun 2
23:08:39 EDT 2005 i686 i686 i386 GNU/Linux

This is perl, v5.8.6 built for i386-linux-thread-multi

from dmesg:
Processor #0 15:2 APIC version 20
Processor #1 15:2 APIC version 20
Initializing CPU#0
Initializing CPU#1

 
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xhoster@gmail.com
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      02-18-2006
"none" <(E-Mail Removed)> wrote:
> If I use fedora core 2 linux with SMP enabled, perl ithreads, and an
> intel hyper-threaded server with ram in both banks, will a perl program
> that uses ithreads to launch threads launch a thread on each
> "processor"?


Last time I tested hyperthreading, my conclusion was that yes, it would use
both "processors", but doing so didn't provide much, if any, advantage
under my typical workload. (As opposed to real multiple processors or
dual-core processors, which did provide an advantage--to the extent the job
was parallelizable, anyway.)


> My motherboard used to show 2 cpus with my old linux distro (redhat
> 8?), but now it is not showing that with top.
>
> I am trying to test a threaded application before going out and buying
> a dual core server.


If you want to know how your application will perform on a dual core
machine, you need to test it on a dual core machine. Testing it on a
hyperthreaded machine will be useless or worse.

> I happen to have this hyper threaded machine and am
> testing it out, but have been unable to confirm that the ithreads will
> take advantage of hyper-threading or a dual core cpu.


That would be like test-driving a Fiat in order to decide if you want
to buy a Ford. Hey, they both start with F, right?


Xho

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macapone@yahoo.com
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      02-28-2006
By the way (not related to perl), to view the two processors in fedora
versions of top, hyperthreading or dual-CPU (top won't know the
difference), hit the 1 (that's "one") key. The screen display will
toggle CPU usage as a total or for each CPU.

 
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none
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      03-09-2006
thankyou for the wonderful insightful advice on how top works and how
it is useless for me to test on a hyperthreaded machine.

back to my original question, does perl ithreads use both processors on
a dual core machine or not?

keeping in mind that some thread packages do NOT take advanatge of more
than one processor, does this one do it (ithreads)?

 
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