Best configuration for linux + dual P4 Xeon + hyperthreading

luma · 2003-03-27, 12:43

Hi all,

I have a dual P4 Xeon 2 GHz running Linux Debian... And it support hyperthreading.
Linux (like Windows) seems to have 4 cpu.

I run mprime like this :
mprime -B
mprime -B -A1

I have setup "A1" whith a different computer ID but stats on primenet website is not showing me the pseudo second computer...

Any idea?

Is there a better way to launch the soft? Can we (like windows) configure affinity?

Thanks

QuintLeo · 2003-03-27, 15:01

I just run 2 seperate mprime clients - in seperate directories, completely different files - on my dual Athlons and my BP6s.

Each CPU shows up seperately in Primenet stats (makes it easy to see when I've had a CPU hang on one of the BP6 boxes).

mda2376 · 2003-03-27, 21:53

Processor affinity becomes very important with hyperthreading cpus.. With hyperthreading dual cpu, CPU0 and CPU1 (as with CPU2 and CPU3) share the same processor, multiple threads executing on the same physical processor (although to the operating system a different virtual processor) that work with the same parts of the processor (floating point operations for instrance) are effectively each getting half the speed of a single chip.

What happends in my system is after a little while, the kernel migrates both processes to CPU2 and CPU3 respectively and they process along at half speed while physcial cpu 0 sits idle. I've found that the -B and -A flags dont really seem to do anything (as far as I've seen).

I have installed the 2.5.66 kernel hopeing a more hyperthreading aware kernel would migrate the processes more intelegently, but no luck.

There looks to be 2 ways it can be done.
PSET ( http://www.hockin.org/~thockin/pset/ ) which looks only to have a patch for kernel 2.2, and
cpuctl ( http://linux-diag.sourceforge.net/affinity.html ) which requires a kernel module and an update to mprime to make use of it. Support for something similar may already exist in the 2.5 kernel without a patch/module.

Maybe if I get some free time this weekend I will look into patching the code to include (possible) processor affinity support in 2.5 kernels.

Matt

luma · 2003-03-28, 10:26

Thanks for your answer Matt!
I work on a 2.4.20 kernel and I cannot move to 2.5.x... So I will continue using mprime with no optimization... As you said, mprime is running on cpu 2 and 3 most of the time... I can see sometime some migration... But it works quite good.

Regards

2003-03-27, 12:43	#1
luma Mar 2003 2 Posts	Best configuration for linux + dual P4 Xeon + hyperthreading Hi all, I have a dual P4 Xeon 2 GHz running Linux Debian... And it support hyperthreading. Linux (like Windows) seems to have 4 cpu. I run mprime like this : mprime -B mprime -B -A1 I have setup "A1" whith a different computer ID but stats on primenet website is not showing me the pseudo second computer... Any idea? Is there a better way to launch the soft? Can we (like windows) configure affinity? Thanks

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2003-03-27, 15:01	#2
QuintLeo Oct 2002 Lost in the hills of Iowa 2⁶·7 Posts	I just run 2 seperate mprime clients - in seperate directories, completely different files - on my dual Athlons and my BP6s. Each CPU shows up seperately in Primenet stats (makes it easy to see when I've had a CPU hang on one of the BP6 boxes).

2003-03-27, 21:53	#3
mda2376 Mar 2003 8₁₀ Posts	Processor affinity becomes very important with hyperthreading cpus.. With hyperthreading dual cpu, CPU0 and CPU1 (as with CPU2 and CPU3) share the same processor, multiple threads executing on the same physical processor (although to the operating system a different virtual processor) that work with the same parts of the processor (floating point operations for instrance) are effectively each getting half the speed of a single chip. What happends in my system is after a little while, the kernel migrates both processes to CPU2 and CPU3 respectively and they process along at half speed while physcial cpu 0 sits idle. I've found that the -B and -A flags dont really seem to do anything (as far as I've seen). I have installed the 2.5.66 kernel hopeing a more hyperthreading aware kernel would migrate the processes more intelegently, but no luck. There looks to be 2 ways it can be done. PSET ( http://www.hockin.org/~thockin/pset/ ) which looks only to have a patch for kernel 2.2, and cpuctl ( http://linux-diag.sourceforge.net/affinity.html ) which requires a kernel module and an update to mprime to make use of it. Support for something similar may already exist in the 2.5 kernel without a patch/module. Maybe if I get some free time this weekend I will look into patching the code to include (possible) processor affinity support in 2.5 kernels. Matt

2003-03-28, 10:26	#4
luma Mar 2003 2₁₆ Posts	Thanks for your answer Matt! I work on a 2.4.20 kernel and I cannot move to 2.5.x... So I will continue using mprime with no optimization... As you said, mprime is running on cpu 2 and 3 most of the time... I can see sometime some migration... But it works quite good. Regards