From: wiz@telesismfg.com (Karl Schendel)
Newsgroups: comp.databases.ingres

On Aug 22,  9:03, Matthew Skalicky wrote:
> Subject: iidbms configurations

> If I have multiple iidbms engines accessing a single database,
> what is the performance hit? Does Ingres assume a monolithic
> processor image in an SMP machine? If it does, is Ingres
> fighting over shared memory when engines are spread over multiple
> cpu's. Is it better to lock iidbms engines to a specific processor
> or let them balance across a number of processors?

Generally you want the OS to schedule processors, not you or Ingres.
I think the only concession Ingres (up to 1.2) makes for SMP is that
it will spin-wait for a little bit if a semaphore is not available
and II_NUM_OF_CPUS is greater than 1 -- the idea being that another
dbms server on another CPU might finish up shortly, and a few spins
is cheaper than a context switch.

Of course, what you really want to do in an SMP environment is go
to OpenIngres 2.0 with OS threads.  That way the OS is more directly
involved and it can do all the right things, including cache preference
algorithms, etc etc.

-- 
Karl Schendel            Phone: (412) 963-8844
Telesis Computer Corp      Fax: (412) 963-1373
wiz@telesismfg.com

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