Hello Everyone,
We're currently using MARSSx86 and have countered some problem that we
hope you can help solve.
We have installed Ubuntu 10.04 (Lucid) 64-bit Server as the guest
operation system, and run several SEPComp benchmarks on the guest
operation system.
For now, we use the "start-sim, run benchmark, kill-sim" shell command
sequence (as outlined in the MARSSx86 wiki: ) to run the benchmarks.
However, we found that the resulting statistics (such as those
reported by DRAMSim2) vary a lot across different runs with the same
configuration.
Because our benchmarks load and parse data from disk when its run
(with the "disk" being a QEMU disk image on the host harddisk), and
such loading/parsing can take several seconds (in native mode), our
educated guess is that, since we have set the configuration file such
that PTLsim will only simulate for 1 billion cycles (which translates
to only 0.25 seconds of guest environment given the 4GHz core
frequency), we have probably only simulated the load-data-from-disk
stage instead of the actual computation stage. Since the actual time
spent on the load-data-from-disk stage depends on how the host
environment schedule disk requests, the time may not consistent across
different runs, and thus the inconsistent statistics reported.
We wonder if there is any mechanism in MARSSx86/PTLSim/QEMU such that
we can bypass the load-data-from-disk stage, or bypass/ignore any
influences it brings, and directly simulate the actual computation
stages of the benchmarks? Currently we work-around this problem in a
quite manual way: for each benchmark, we insert the "start-sim" call
in its source code just before the computation stage starts; however,
this approach may not only be likely to be imprecise but also become a
hassle to apply to the vast number of benchmarks.
As a side note: we use a machine configuration based on the ooo core,
with four cores on the CPU. The host is also an Ubuntu 10.04 64-bit
Server.
Your answer is greatly appreciated.
My regards,
Min-Zhong Lu ([email protected])
Dept. of Computer Science and Information Engineering,
National Taiwan University
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