Re: [PATCH] i386 boottime for_each_cpu broken

[Zwane Mwaikambo <zwane@arm.linux.org.uk>]

Hello Bharata,

On Thu, 11 Aug 2005, Bharata B Rao wrote:

> I don't know the context of your work here, but a couple of 
> observations.
> 
> Since you populate cpu_possible_map with NR_CPUS, alloc_percpu()
> would end up allocating for all NR_CPUS.  Wouldn't you have achieved
> the same thing by compile time allocation ? Wouldn't this change
> lead to NR_CPUS allocations from alloc_percpu() for all users ?

The patch has been modified (courtesy Andi Kleen) to do something a bit 
smarter and only allocate for detected cpus in MADT or MP table. But my 
prime concern was that for_each_cpu didn't work at all during boot.

> Now since you have separated cpu_possible_map from cpu_callout_map,
> do we need to reflect cpu_possible_map with the value from
> cpu_callout_map after the cpu_callout_map is initialized fully from
> smp_prepare_cpus().

This should be taken care of using above.

> BTW, I am working on Kiran's dynamic percpu allocator patch and making
> it cpu hotplug aware. With that, alloc_percpu would initially allocate
> only for the possible cpus and would allocate for other cpus as and when
> they come up.

Great, that takes care of my concerns regarding processors which aren't 
enumerated during smp boot.

Thanks for the feedback,
	Zwane

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