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

[Jeremy Fitzhardinge]

H. Peter Anvin wrote:
> Either way, I really suspect that the right thing to do is to use 
> negative offsets, with the possible exception of a handful of things 
> (40 bytes or less, perhaps like current) which can get small positive 
> offsets and end up in the "super hot" cacheline.
>
> The sucky part is that I don't believe GNU ld has native support for a 
> "hanging down" section (one which has a fixed endpoint rather than a 
> starting point), so it requires extra magic around the link (or 
> finding some way to do it with linker script functions.) 

If you're going to do another linker pass, you could have a script to 
extract all the percpu symbols and generate a set of derived zero-based 
ones and then link against that.

Or generate a vmlinux with relocations and "relocate" all the percpu 
symbols down to 0.

   J
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