syslink effort update
dillon at apollo.backplane.com
Fri Apr 27 12:02:36 PDT 2007
:Since most of it is a bit above me I'll ask about what I can understand.
:While I agree with you that 64 will probably suffice I also know of
:someone who thought that 640k would be enough memory and another who
:though that the world would never need more than one super-computer. But
:if I understand things correctly it will be fairly easy to upgrade to
:128 (or whatever) bits in the future should that be necessary since the
:sysid is centralized to sysreg, the SYSLINK protocol and whatever uses
:it. So basically all it would take is a change of type in a few places
:and a recompile right?
Well, only if GCC were to support 128 bit integers. The real issue
here is memory overhead. 64 bits is already 8 bytes, 128 bits
is 16 bytes. Plus cpu overhead for initializing and processing it all.
I don't think its a big deal, though, so yes: We could use 128 bits if
we needed to. I'm going to try to keep things in 64 bits for now but
it could very well be that 128 bits will be more workable in a cluster
environment, allowing the per-host sysids to be expanded into cluster-wide
unique sysids with very little effort.
<dillon at backplane.com>
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