CrunchBang Linux

dracayr

New Member

Registered: 2012-12-08

Posts: 3

multicore

Hi,
I've been using Crunchbang for about 6 months now, but this is my first time posting here, so greetings everyone

I installed a realtime kernel from the debian repositories (testing, I believe) a while ago for pianoteq (which is a mindblowingly amazing program) and to play around with some MIDI appliciations.
My normal kernel is the standard crunchbang kernel, 3.2.0-0.bpo.4-486 at this time. The nearest RT-enabled kernel I could find in the repositories was 3.2.0-0.bpo.3-rt-686-pae. So I installed that, which went smoothly: Realtime works and everything's fine.
Too fine, even. You see, while configuring the cpu governors for use with pianoteq, I noticed that I could configure 4 cpu cores, which I had never noticed on the standard kernel. So I booted back into the other kernel and to be sure, cpufreq-info only lists one core. (I really should have picked up on the missing cores sooner, but I don't really do much cpu-intensive stuff so I never noticed).
I ran some benchmarks and it appears that apparently the standard kernel really does only recognize and use one core, while the rt-686-pae kernel is capable of using all 4 equally (that is, 2 physical and 2 virtual cores).
Now this isn't really high-priority for me, as I can just boot into the RT-kernel if I need to. But it would nevertheless be nice to have all cores recognized on my main system.

My CPU is a Intel i3-2330M.

Also, I don't know if this is relevant, but when I installed the RT-686-pae kernel, I could not install the recommended libc6-i686 since that would break some dependencies.

Thanks,
dracayr

Last edited by dracayr (2012-12-08 22:25:26)

el_koraco

#!/loony/bun

From: inside Ed

Registered: 2011-07-25

Posts: 4,749

Re: multicore

Your CPU is 64 bit, you should reinstall to 64 bit, especially if you wanna use relatime stuff, you'll get much better performance. Alternatively, isntall the backports kernel that ends in 686-pae or something. The 486 kernel is optimized for very old computer and doesn't support multiple cores. Information wise, your computer doesn't actually have four cores, it has two, and they're hyperthreading. Not to get too technical, it's a CPU design that makes computer believe it has more cores. In this case, each core has two threads, so 2+2=4.

64 bit is the way to go, trust me, but you need to reinstall, there's no upgrading to it.

dracayr

New Member

Registered: 2012-12-08

Posts: 3

Re: multicore

Thanks, I didn't know that the 486 kernel doesn't support multicore. (This is the kernel that was installed when I installed #!.. I don't quite get why #! uses a default kernel which does not support multiple cpu cores)
I'll hold off from changing to 64-bit for now because I don't want to reinstall, and the 32-bit system is fast enough for pianoteq, which is the only realtime application I use (meaning when I press a key on my keyboard, I hear the sound without any perceivable delay, which is good enough for me )
I'll be sure to change to the 686 kernel, though.

EDIT: actually, I believe I will reinstall, since I read this: http://crunchbang.org/forums/viewtopic.php?id=23445 

Last edited by dracayr (2012-12-08 23:15:14)