Re: Motley Fool: More Problems at eBay
Gregory Alan Bolcer (gbolcer@endTECH.com)
Sat, 03 Jul 1999 07:41:08 -0700
I had a parallel hardware class at USC taught by Kai Hwang who
leads the spark (not to be confused with Sun/sparc) research group
that does benchmarking for parallel and multithreaded computer architectures.
The Sun/sparc is a very elegant architecture, it's greatest strength
is its ability to context switch between processes at a very low
level. I think we compared the pentium pro architecture with the
sparc/v8 (or v7, whichever it was at the time). The results were
of course scalability. The sparc could context switch within one
or two clock cycles while the pentium pro took approximately 20-50.
I can see how that'd be an advantage, however, it would slowly go
away as you scaled to more and more processes. The sparc we looked
at had 8 context frames. As you spawn more and more, these advantages
depend more on the ability to access RAM--a technology that's improving
with leaps and bounds in the PC arena. Two of the other advantages
that the sparc had were large split instruction/data cache and superpipelining
of instructions and data. Both of these techniques are included in the PII & PIII's,
so I think a lot of these disadvantages are going away and becoming more
operating system dependent rather than 'big iron'.
Gavin Thomas Nicol wrote:
> > Wow, this seems really counter-intuitive. What advantage
> > does big iron bring that overcomes the disadvantage of
> > spinning up a new OS process to handle a CGI?
> As I said before, RAM, and CPU which reduces the cost
> of fork and exec to a point where the cost of the
> alternative (multi-threaded plugin managing locks etc.)
> is higher. Again, this is also dead reliable... and is
> not suitable for databases, where the cost of establishing
> connections is high.