Re: regarding the x86_64 zero-based percpu patches

[Rusty Russell]

On Wednesday 14 January 2009 14:28:56 Tejun Heo wrote:
> The main problem is that the area needs to be congruent which
> basically mandates them to be contiguous.

I want to explore this assumption a little.  Logically, yes, if 50% of pages are free and we have 4096 cpus, the chance that a page is free on all CPUs is 1 in 2^4095.  But maybe such systems are fine with 2M pages for per-cpu areas at boot?  And can page mobility tricks help us make the odds reasonable here?
Only allowing movable pages in our expansion-of-percpu area?

Thanks,
Rusty.
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