Re: FOR REVIEW: New x86-64 vsyscall vgetcpu()

From: Chase Venters
Date: Fri Jun 16 2006 - 17:14:16 EST


On Fri, 16 Jun 2006, Andi Kleen wrote:


To this last point, it might be more reasonable to map in a page that
contained a new structure with a stable ABI, which mirrored some of
the task_struct information, and likely other useful information as
needs are identified in the future. In any case, it would be hard
to beat a single memory read for performance.

That would mean making the context switch and possibly other
things slower.

In general you would need to make a very good case first that all this
complexity is worth it.

Cache-coloring and kernel bookkeeping effects could be minimized if this
was provided as an mmaped page from a device driver, used only by
applications which care.

I don't see what difference that would make. You would still
have the fixed offset problem and doing things on demand often tends
to be even more complex.


-Andi (who thinks these proposals all sound very messy)
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