Re: [PATCH] Correct nr_processes() when CPUs have been unplugged

[Rusty Russell]

On Wed, 4 Nov 2009 05:04:32 am Christoph Lameter wrote:
> On Tue, 3 Nov 2009, Ingo Molnar wrote:
> 
> > Sidenote: percpu areas currently are kept allocated on x86.
> 
> They must be kept allocated for all possible cpus. Arch code cannot decide
> to not allocate per cpu areas.
> 
> Search for "for_each_possible_cpu" in the source tree if you want more
> detail.

Yeah, handling onlining/offlining of cpus is a hassle for most code.

But I can see us wanting abstractions for counters which handle being per-cpu
or per-node and doing the folding etc. automagically.  It's best that this
be done by looking at all the existing users to see if there's a nice API
which would cover 90%.

Cheers,
Rusty.
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