Re: [RFC 00/15] x86_64: Optimize percpu accesses

[Jeremy Fitzhardinge]

Christoph Lameter wrote:
> Jeremy Fitzhardinge wrote:
>
>   
> > You want to virtually map the percpu area?  How and when would it get
> > extended?
> >     
>
> It would get extended when cpu_alloc() is called and the allocator finds that there is no per cpu memory available.
>   

Which, I take it, allocates percpu memory.  It would have the same 
caveats as vmalloc memory, with respect to accessing it during fault 
handlers and nmi handlers, I take it.

How would cpu_alloc() actually get used?  It doesn't make much sense for 
general code, since we don't have the notion of a percpu pointer to 
memory (vs a pointer to percpu memory).  Is the intended use for 
allocating percpu memory in modules?  What other uses?

   J
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