Hi,


I have bought a new server with Intel Core Duo processor T2300 with Asus N4L-VM motherboard, and in anticipation of the server arriving, I am trying to figure out suitable kernel options for building an optimized kernel. Now I am just doubting a bit about the kernel configuration options for the processor type.

Right now, I am using:
* Processor family: Pentium M
* Symmetric multi-processing support
- maximum no. of CPUs: 2
- Multi-core scheduler support

Should these options work? In particular, is Pentium M an appropriate choice for a Dual Core or should I choose a more generic type?

Am I missing some other options to optimize it a bit more?

Cheers
Erik

PS. I will be running SuSE linux 10.1, kernel version 2.6.16.13-4-default

I have a new Core Duo Laptop, and Suse Linux 10.1 installed the SMP kernel by default. It runs very well, and I also have XGL running nicely. Unless you are really doing some cpu intensive stuff, and need to squeze every optimization out, I'd just run stock SMP. It should do fine.

I have a Intel D 920 (EM64T) and Suse Linux 10.1 did not install the SMP kernel by default, in fact in /proc/cpuinfo I only see one proccesor.. why?

I just remembered I had a Dell Inspiron 9400 Laptop which also has a T2400 processor so I tried fiddling around with the kernel but nothing conclusive yet. I now have a kernel which appears to be 3% faster in starting up jboss 4.0.4 (measured while starting up multiple times).

In any case, the Pentium M setting in the kernel config appears to work. The only thing is that I changed multiple parameters at the same time so this result is not really scientific.

I will do some other tests varying only one parameter at a time and will post the results here as well. Only this will take some time, so perhaps I will have some results next weekend.

It is not that there is a need to squeeze everything out but I just want to have the most optimal system I can have. I already spent a lot of effort getting the correct hardware and now I am just curious how much I can achieve by tweaking the software side. In the final system I also want to see what the effects of the IO scheduler is on disk performance. This is interesting because the disks itself (Maxtor 6H400F0) will have NCQ so the functionality of the anticipatory or CFQ IO scheduler is probably too much and the dead line scheduler would perhaps be a better choice. In that case, the IO scheduler would optimize the performance of applications while the disks themselves optimize the actual reading and writing of data to disk.

I guess that if you are actually running the default kernel instead of the SMP kernel then you will see only one processor. Just install the SMP kernel and remove the default kernel using yast and then try again. Also, ksysguard is very nice, you can use it to show processor utilization of the individual CPUs as well as their processor frequencies.

Cheers
Erik

Hi all,

As promised some results of my performance experiments. In short, it is totally utterly pointless to try to optimize the linux kernel in SuSE 10.1 for the processor type. None of the settings I did had any effect at all on the performance. Also, changing the processor type to Pentium M did not help. At least now I know it is useless to try to optimize it. Also, it appears the SUSE linux 10.1 kernel already has support for the intel core duo built-in.

Anyway, it also makes it really easy. Just use the SMP kernel.

Cheers
Erik

Like I said, the stock kernel is more than adequate. I'm not sure, but I believe the i686 kernel is already built to support the MMX/SSE/SSE2/SSE3 instruction sets that it needs to support, mainly the extra registers for task switching, which can be determined at boot time (if I remember from my x86 assembly classes).

The kernel doesn't need to know how to support each instruction, it just needs to create it's memory maps according to how many registers are needed, something that can be done at boot time. Any optimizations done to the kernel beyond i686 are only going to improve areas in the kernel that are highly computational, which there aren't many of. Drivers, on the otherhand, may need more optimization (like the frame buffer drivers), but there again, the kernel driver portion of the graphics drivers only act as a direct i/o channel for the user space driver in X.

Now, I have the smp kernel in suse 10.1 with an intel dual core (intel D 920) and still I can't see both processors in the /proc/cpuinfo. And BTW it's seem that the stack size of the smp kernel it's fix (unlike the regular kernel) because I have been trying to install my wireless card using the ndiswrapper and I had kernel panic (I already installed my laptop's wireless and it work great).
GrueMaster, Can you see both of your CPU's without doing anything extra to the smp suse kernel??
and Erik, How did you change all the different options to re-compile the kernel?
Thanks,

I can see both cores in /proc/cpuinfo. They show up as processor 0 & proccessor 1. There is also a new entry that I hadn't noticed before on older kernels: Core 1 or Core 2. Kind of interesting.

You might want to check your bios. Some bioses (namely Intel's), have a setting that will enable single processor mode, effectively shutting off the second core. Also, make sure that acpi is enabled at boot time (no acpi=off in the kernel boot options). Beyond that, I'm at a loss as to why you aren't seeing both cores.

Hi obiwan76,


Be sure to also post the output of 'cat /proc/cpuinfo' with in particular the 'model name' of the processor. And just as a sanity check, what does 'uname -a' say.

And recompiling the kernel is really easy. What you need to know is the 'kernel howto' (ask google) for basic instructions. Install the kernel-source package. After doing that, copy the /boot/config-<version>-<name> (this is where SuSE puts it) to /usr/src/linux/.config. Now you have the same configuration as that of the kernel that SuSE built for you. Now you can modify options using one of the methods (e.g. 'make xconfig').

Also, I changed the CONFIG_LOCALVERSION in the .config file to give me kernel a unique name. The rest is in the HOWTOs, but I suspect the problem is not in the kernel.

Cheers
Erik

Hi Erik and GrueMaster,
Thanks for your help!!!, It was a problem in the bios, I changed the Max CPUID. Now, I can see both cpu's and I was able to do some OpenMp prgraming using the non-comercial (free) intel fortran compiler...
M

Cool! Welcome to the dual core club. If you have any other questions, be sure to post a new thread.