Rusty Russel is a really good guy, and his writing is always fun. On this page he discusses what they had to do to get 4096-bit cpu masks into linux. 4096-bit masks are needed when you have a 4096-cpu shared memory machine from SGI. I saw an SGi talk on this work this morning and it was kind of interesting.
http://ozlabs.org/~rusty/index.cgi/tech/2009-01-07.html
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