[Beowulf] Moores Law is dying

Joe Landman landman at scalableinformatics.com
Tue Apr 14 17:11:53 EDT 2009

Jon Forrest wrote:
>> that compilers will never try to unroll code at that level, even when
>> enormous memory systems are commonplace?
> Again, the enormous memory systems you mention consist mostly
> of enormous amounts of data, not text.

... 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 ...

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.


>> and "the program" being run on a multitasking
>> operating system is the union of all "sub" programs being run on the
>> system, with or without shared libraries (sharing is expensive in
>> performance, remember -- we do it to save memory because it is a scarce
>> resource).
> 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).

Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics LLC,
email: landman at scalableinformatics.com
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