Probing for physical number of cpus.

Probing for physical number of cpus.

[Roy Dragseth]

Hi.

Do anyone know how to figure out the physical number of cpus in an ia64 
system?  No, /proc/cpuinfo wont do because the kernel is booted with 
maxcpus=1.

When installing RH EL the install kernel is booted with maxcpus=1 and I need 
to figure out the physical number of cpus in the system for later use in the 
software setup.  I need to be able to get this from userspace.

Any hints is greatly appreciated.

Regards,
r.

-- 

  The Computer Center, University of Tromsø, N-9037 TROMSØ 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: royd@cc.uit.no

Re: Probing for physical number of cpus.

[Andreas Schwab]

Roy Dragseth <Roy.Dragseth@cc.uit.no> writes:

> Do anyone know how to figure out the physical number of cpus in an ia64 
> system?  No, /proc/cpuinfo wont do because the kernel is booted with 
> maxcpus=1.

Read and parse the ACPI tables off of /dev/mem, starting with the address
from /sys/firmware/efi/systab.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
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"And now for something completely different."

Re: Probing for physical number of cpus.

[Roy Dragseth]

On Friday 28 October 2005 14:43, Andreas Schwab wrote:
> Roy Dragseth <Roy.Dragseth@cc.uit.no> writes:
> > Do anyone know how to figure out the physical number of cpus in an ia64
> > system?  No, /proc/cpuinfo wont do because the kernel is booted with
> > maxcpus=1.
>
> Read and parse the ACPI tables off of /dev/mem, starting with the address
> from /sys/firmware/efi/systab.

Yikes!  Thanks for the answer.  I've been toying around with pmtools/acpidump 
which gives me a text dump, but I'm still a bit confused (to say the least).

r.

-- 

  The Computer Center, University of Tromsø, N-9037 TROMSØ 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: royd@cc.uit.no

Re: Probing for physical number of cpus.

[Ashok Raj]

On Thu, Nov 03, 2005 at 12:10:34AM -0800, Roy Dragseth wrote:
> 
>    On Friday 28 October 2005 14:43, Andreas Schwab wrote:
>    > Roy Dragseth <Roy.Dragseth@cc.uit.no> writes:
>    > > Do anyone know how to figure out the physical number of cpus in an
>    ia64
>    >  >  system?   No, /proc/cpuinfo wont do because the kernel is booted
>    with
>    > > maxcpus=1.
>    >
>    >  Read  and  parse the ACPI tables off of /dev/mem, starting with the
>    address
>    > from /sys/firmware/efi/systab.
> 
>    Yikes!    Thanks  for  the  answer.   I've  been  toying  around  with
>    pmtools/acpidump
>    which  gives  me a text dump, but I'm still a bit confused (to say the
>    least).
> 

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.

Cheers,
ashok

Re: Probing for physical number of cpus.

[Roy Dragseth]

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/
cpu0
[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 (www.rocksclusters.org), 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.

Regards,
r.

-- 

  The Computer Center, University of Tromsø, N-9037 TROMSØ 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: royd@cc.uit.no