Re: Probing for physical number of cpus.

From: Roy Dragseth <>
Date: 2005-11-07 21:20:36
On Thursday 03 November 2005 22:06, Ashok Raj wrote:
> Actually even of you boot with maxcpus=1, we still create sysfs entries for
> each cpus physically present in the system.
> you should be able to look at /sys/devices/system/cpu/cpuX entries
> if you compiled with CONFIG_HOTPLUG_CPU enabled, then you could
> echo 1 > online file in the appropriate cpu directory to add more
> cpus.
> Let me know if you dont see this behaviour.

Hi, this is more in line of what I was hoping for ;-)

However I don't see this behaviour on my system.  I'm running RH EL 4 with 
this setup:

[root@testing ~]# ls /sys/devices/system/cpu/
[root@testing ~]# uname -a
Linux testing.cluster.none 2.6.9-22.EL #1 SMP Wed Oct 5 15:20:11 EEST 2005 
ia64 ia64 ia64 GNU/Linux
[root@testing ~]# cat /proc/cmdline
BOOT_IMAGE=scsi0:\EFI\redhat\vmlinuz-2.6.9-22.EL  console=ttyS0 maxcpus=1 rhgb 
quiet root=LABEL=/1 ro

Upgrading the kernel will not help because I need to be able to probe this 
under the install kernel.

Some background:

This is for the Rocks Cluster Distribution (, where the 
compute node installation is done using RH kickstart files that is 
automatically generated on, and fetched from, the frontend based on the 
information that is sent from the compute node when it  asks for the 
kickstart file.  For instance, the number of cpus on the node is used to 
configure the queueing system.

Any further hints is greatly appreciated.



  The Computer Center, University of Tromsų, N-9037 TROMSŲ Norway.
	      phone:+47 77 64 41 07, fax:+47 77 64 41 00
     Roy Dragseth, High Performance Computing System Administrator
	 Direct call: +47 77 64 62 56. email:
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Received on Mon Nov 07 21:21:14 2005

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