Re: HOTPLUG CPU Support for SMT

[Srivatsa Vaddagiri]

On Mon, May 30, 2005 at 04:50:27PM +0000, Zwane Mwaikambo wrote:
> Yes, older 2.6-mm kernel (2.6.10-mm) trees have the "toy" i386 hotplug 
> cpu implementation which does what you want.

AFAIK in the i386 "toy" implementation, when a CPU is offlined, it stops
taking interrupts and stops running tasks, but it _still_ executes a while
loop in the context of its idle task (with IRQs disabled). The loop
is exited when we have to bring online the CPU again. What this means is 
I don't think by offlining the CPU, we are removing any activity associated
with the corresponding h/w thread. 

Maybe the toy implementation could be modified to take care of it? Something
like lowering the priority of the h/w thread so that it consumes minimal 
CPU resources to execute its while loop.

-- 


Thanks and Regards,
Srivatsa Vaddagiri,
Linux Technology Center,
IBM Software Labs,
Bangalore, INDIA - 560017
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