shared memory -- benchmarks, measurements

[Michael Haberler]

In article <EMV.91Mar4113610 at poe.aa.ox.com>, emv at ox.com (Ed Vielmetti) writes:
|> 
|> I'm looking for some guidance on measuring the performance of a system
|> which seems to have a lot of contention for a piece of (system V
|> style) shared memory.

I'd watch for behaviour of programs with several shared memory segmments
attached. On some architectures, there's an upper limit on how many 
segments are actually attached, and if more than that number of segments
are used, they are detached and reattached by the kernel on the fly -
with page faults and a kernel trap. That can mean a big difference in
performance.

I could imagine that that limit might be decreased by the use of
shared libraries.

- michael