"Luke Lonergan" <llonergan@greenplum.com> writes:
> That said, I find typical memory bandwidth for the P4 in applications is
> limited at about 2GB/s. See here for more detail:
> http://www.cs.virginia.edu/stream/standard/Bandwidth.html
> In fact, looking at the results there, the IBM 650m2 only gets 6GB/s
> on all 8 CPUs. I wouldn't be surprised if the strange L3 cache
> architecture of the IBM 650 is holding it back from streaming memory
> access efficiently.
Given Gavin's latest report, I'm wondering how much the IBM slows down
when a spinlock operation is involved. If the memory architecture isn't
good about supporting serialized access to memory, that gaudy sounding
bandwidth number might have little to do with PG's real-world behavior.
On the other hand, we already know that Xeons suck about as badly as
can be on that same measure; could the pSeries really be worse?
regards, tom lane