On Feb 7, 2010, at 10:52 AM, Dan Gibson wrote:
The ways of Simics are strange indeed. I have no idea why 75MHz
would be blazing fast but 80MHz would be slow. You might try asking
on the Simics forum about it.
Thanks Dan. I have posted it on simics.net. I can update this group
with what they say once they respond.
There is a higher-level point to consider. Bear in mind with the
following comment that I have no idea what you're actually trying to
simulate.
I am trying to do fault injections when running simics+gems. I don't
need to model timing and such with a high degree of accuracy, but it
is important that I functionally simulate all operations of the
workload with a reasonable degree of accuracy.
I would advise against simulating a workload that is actually
performing I/O when you are taking measurements -- Simics' I/O
timing isn't sufficiently realistic, and GEMS does nothing to
improve I/O timing from what Simics provides. Instead, set up your
workload so that its "I/O operations" are consistently hitting in
memory -- either in the file cache or in a loopback device. In other
words, make sure you have fully warmed your input sets from disk,
and that you're not actually hitting any ethernet devices. Doing so
creates a decent proxy for a server busy period, without spending
CPU time just spinning in the idle loop (after all, its hard to
convince reviewers that optimizing the idle loop is interesting).
But if I am simulating a server workload in a distributed client-
server setting, wouldn't I want to make sure that I am having network
communication (that is simulated by simics) in my measurement window?
Pradeep.
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