topic Re: smp kernel in Operating System - Linux

smp kernel

Chakravarthi — Tue, 20 Apr 2004 06:53:28 GMT

Hi,

I have a Machine with Dual CPU, and the kernel which is built on the machine is smp kernel, using the same kernel i want to boot the machine with single cpu support, how this can be accomplished..

thanks
chakri

Re: smp kernel

Steven E. Protter — Tue, 20 Apr 2004 07:19:44 GMT

The smp kernel works just fine on single cpu machines. I've tested this myself.

The grub interface has a kernel selection feature at boot time. Just pick it on the list after install.

The config file is called grub.conf and you can set the default numericly.

I have always done my kernel installs from up2date, thats how i get them.

SEP

Re: smp kernel

Mark Grant — Tue, 20 Apr 2004 07:34:52 GMT

As usual, SEP is correct.

I just thought I'd clarify that you don't actually have to do anything at all. Not even change your boot loader config. Just remove the CPU and it will still work. Like SEP, I have done this myself.

Re: smp kernel

Stuart Browne — Tue, 20 Apr 2004 17:55:22 GMT

If you want to physically remove a CPU, that's all fine.

However, I am unaware of a 'logical' way to remove a processor (i.e. to tell an SMP kernel to use only one of the two physical processors).

Re: smp kernel

Chakravarthi — Wed, 21 Apr 2004 02:35:32 GMT

hi,

append="console=tty0 console=ttyS1,19200n8 maxcpus=1"

by adding above line in lilo.conf, i could boot with one cpu

Re: smp kernel

Chakravarthi — Wed, 21 Apr 2004 02:36:56 GMT

Is there any way to debug the cpu errors,

i'm runnig REDHAT AD, on a PIII server with two processors, machine boots fine,, but when we give load to the machine , machine hangs,,, but with single cpu machine works fine..

Re: smp kernel

Martin P.J. Zinser — Wed, 21 Apr 2004 13:15:35 GMT

Hello Chakri,

ok, now you tell us what the problem is ;-)

Can you give us the Redhat version and kernel
(uname -a) you are using. SMP is by no means trivial and things can go wrong. It might be that a kernel upgrade will proof helpful.

Greetings, Martin

Re: smp kernel

Mark Grant — Wed, 21 Apr 2004 13:43:08 GMT

I used to get that on an old smp PIII. I never really pinned it down to anything in particular except it only ever seemed to happen when I had X running. As I had X running most of the time anyway, it wasn't a brilliantly useful deduction.

However, after a few kernel releases, download, compile, install, rinse & repeat the problem just went away. So I'd see if you can upgrade your kernel. Maybe upgrade X too

Re: smp kernel

Stuart Browne — Wed, 21 Apr 2004 18:40:30 GMT

mm.. maxcpus=.. kewl.. will remember that one..

But yes, as Martin says, more details please!

Re: smp kernel

Chakravarthi — Thu, 22 Apr 2004 01:00:32 GMT

Hi,

I'm using a PIII machine with Dual CPU, running Redhat Advanced Server

Red Hat Linux Advanced Server release 2.1AS (Pensacola)

kernel : kernel-2.4.9-e.3

the kernel was compiled for single CPU, so we enabled dual CPU option and recompiled the kernel,

the machine works fine as long as we dont run any processes, once the cpu loads goes up the machine hangs without giving any error, i have to had boot the machine, this can happen anytime, even i'm not able to get the messages on the monitor,

dont know where to start the debug process....
thanks
chakri

Re: smp kernel

Stuart Browne — Thu, 22 Apr 2004 01:15:53 GMT

Start by updating the kernel.

RHAS2.1 has a 2.4.9-e27 (at least) available, and I think there's an e31.

After updating the kernel, poke it again, and see if it still occurs.

Re: smp kernel

Steven E. Protter — Thu, 22 Apr 2004 01:35:19 GMT

Even if its available don't go with kernel 2.6

Give them time to get it stable.

In the old versions of red hat even numbered kernels were more stable. It would appear that has been changed in the Enterprise versions.

SEP

Re: smp kernel

Stuart Browne — Thu, 22 Apr 2004 02:15:01 GMT

The 2.4 series of RH Enterprise kernels is already incorporating various 2.6 series features.

If you are running RH Enterprise (you are) you should always stick with their released kernels.

It's what your maintenance payments are going towards creating and maintaing!

Re: smp kernel

Nobody's Hero — Thu, 22 Apr 2004 07:01:16 GMT

I had the same problem. Had an smp kernel running on RH9. Added another 800mhz cpu and the machine would die if I pushed it. I tried all kinds of patching. I resolved the problem by adding the second CPU and then did a re-install of RH9. Now the box is in production and running great.