As David Kreuter said and you also, "it depends". That said, tho, VM
will quite happily run at 100% cpu utilization. You don't have a
problem with thrashing just because the processor(s) is going flat out.
Now, where it most depends, is really what you have running. If your
total load is x number of Linux instances running the same thing, I
don't know what to tell you other than if you have cpu demand such that
you need 50% more cycles than you have, yes you'll see things running
more slowly. If you have an application mix where you have long running
tasks as well as short, interactive things, what you will see is that CP
will get the short, Q1, tasks thru the system first with no or little
delay by taking cycles away from the longer running, Q3 tasks. I don't
know where Linux running Websphere apps fits in that scheme. Don't be
afraid, tho, of running with the processor at a high level of utilization.
Jim
Richard Heritage wrote:
I know this is an "it depends" question, but I hope some of you can give
me a very general answer. As an MVS guy, I'm used to being able to run
the processor very close to or even at 100% without significant
performance degradation. Assuming that everything is configured and
tuned properly (a big assumption, I know), can VM drive the processor
the same way? Our application people are used to other platforms that
don't tolerate high CPU utilization so well and think things are going
to start falling apart when we hit 80%. I'd like to reassure them--but
only if it's accurate to do so! This is a WebSphere application running
on multiple SUSE instances, with the data on DB2 under z/OS. Is it
reasonable for me to expect--again, assuming everything else is
right--to be able to run at 90+ percent without problems?
Richard Heritage
Lead Systems Software Engineer
IT @ Johns Hopkins
--
Jim Bohnsack
Cornell University
(607) 255-1760
[EMAIL PROTECTED]
