Re: getting processor numbers

Siddha, Suresh B
2007-04-03T20:14:15Z

On Tue, Apr 03, 2007 at 12:55:22PM -0700, Ulrich Drepper wrote:
> Siddha, Suresh B wrote:a
> > Not all of the cpu* directories in /sys/devices/system/cpu may be
> > online.
>
> Apparently this information isn't needed. It's very easy to verify:
>
> $ ls /sys/devices/system/cpu/*/online
> /sys/devices/system/cpu/cpu1/online /sys/devices/system/cpu/cpu2/online
> /sys/devices/system/cpu/cpu3/online
>
> This is a quad core machine and cpu0 doesn't have the 'online' file
> (2.6.19 kernel).

I think that is expected and intentional, as the current cpu hotplug code
doesn't support offlining cpu0.

> So, if nobody noticed this it's not needed and we can
> just remove CPUs from /sys/devices/system/cpu when they are brought
> offline, right?

No. Logical cpu hotplug uses these interfaces to make a cpu go offline
and online.

thanks,
suresh