Re: [PATCH] Hotplug CPUs for i386 2.5.44

Re: [PATCH] Hotplug CPUs for i386 2.5.44

[Pavel Machek]

Hi!

> Usage:
> 1) Apply patch, and boot resulting kernel.
> 2) echo 0 > /devices/root/sys/cpu0/online
> 3) echo 1 > /devices/root/sys/cpu0/online
> 
> The CPU actually spins with interrupts off, doing cpu_relax() and
> polling a variable.  It's basically useful for testing the unplug
> infrastructure and benchmarking.

Hehe, with this swsusp should be doable on
an smp machine (turn it into UP and suspend;
during resume, turn it into UP, resume, and go
back SMP). I guess I schould get some SMP
to play with...
			Pavel

[PATCH] Hotplug CPUs for i386 2.5.44

[Rusty Russell]

Doesn't apply to -mm5 because someone did wierd things with the CPU
placement in driverfs, which clashes with this patch which moves it to
kernel/cpu.c...

Usage:
1) Apply patch, and boot resulting kernel.
2) echo 0 > /devices/root/sys/cpu0/online
3) echo 1 > /devices/root/sys/cpu0/online

The CPU actually spins with interrupts off, doing cpu_relax() and
polling a variable.  It's basically useful for testing the unplug
infrastructure and benchmarking.

http://www.kernel.org/pub/linux/kernel/people/rusty/patches/hotcpu-x86-28-10-2002.2.5.44.diff.gz

Cheers!
Rusty.
--
  Anyone who quotes me in their sig is an idiot. -- Rusty Russell.

Re: [PATCH] Hotplug CPUs for i386 2.5.44

[Matthew Dobson]

Rusty Russell wrote:
> Doesn't apply to -mm5 because someone did wierd things with the CPU
> placement in driverfs, which clashes with this patch which moves it to
> kernel/cpu.c...
> 
> Usage:
> 1) Apply patch, and boot resulting kernel.
> 2) echo 0 > /devices/root/sys/cpu0/online
> 3) echo 1 > /devices/root/sys/cpu0/online
<grins sheepishly>

Errr..  you may want to use 
/devices/class/cpu/devices/[0..num_online_cpus()].  There are symlinks 
here for every registered CPU device, no matter how some NUMA wacko 
rearranges the root/sys directory topology.  ;)

Cheers!

-Matt


> The CPU actually spins with interrupts off, doing cpu_relax() and
> polling a variable.  It's basically useful for testing the unplug
> infrastructure and benchmarking.
> 
> http://www.kernel.org/pub/linux/kernel/people/rusty/patches/hotcpu-x86-28-10-2002.2.5.44.diff.gz
> 
> Cheers!
> Rusty.
> --
>   Anyone who quotes me in their sig is an idiot. -- Rusty Russell.
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