[Beowulf] Moores Law is dying
Jon Forrest
jlforrest at berkeley.edu
Tue Apr 14 14:41:46 PDT 2009
Joe Landman wrote:
> ... so I see you have never used an interprocedural analysis (-ipa)
> switch :)
>
> Allows you do do things like, I dunno, inline one whole routine inside
> another ...
I've never used this but from your description I don't
see how it leads to larger text sizes at runtime. After all, if you have
routine A which is 10 bytes, and routine B which is 20 bytes,
it would seem that they collectively take 30 bytes no matter
if they stand alone or one inside the other. I might not
be understanding this right, though.
> Usually leads to much larger program text sizes.
>
> This said, I have seen very large programs from RISC days hitting well
> more than 1 GB of text. I haven't played with any recently though.
Let's say this is about right. Do you see such programs getting
even larger in the future?
>> Why is sharing expensive in performance? It might take a little
>> overhead to setup and manage, but why is having multiple virtual
>> addresses map to the same physical memory expensive?
>
> Contention. Memory hot spots. Been there, done that. We are about to
> do this all over again (collectively).
Naively I would think that text memory hot spots would be a good
thing, because then all the benefits of caching would kick in.
There would be no cache coherence overhead since text is read-only.
Why is this a bad thing?
--
Jon Forrest
Research Computing Support
College of Chemistry
173 Tan Hall
University of California Berkeley
Berkeley, CA
94720-1460
510-643-1032
jlforrest at berkeley.edu
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