Start out by installing and building gem5: https://www.gem5.org/documentation/general_docs/building
If you need to do a full system simulation to run some benchmarks with pthreads, openmp, etc. you will probably need to use KVM to accelerate the kernel boot portion
See: https://www.gem5.org/documentation/gem5-stdlib/x86-full-system-tutorial
This may require the following:
sudo chmod 666 /dev/kvm
You will probably also have to set the value in /proc/sys/kernel/perf_event_paranoid to 1
Run Parsec like this: https://github.com/gem5/gem5/blob/stable/configs/example/gem5_library/x86-parsec-benchmarks.py
If you ever encounter an issue like FileLockException: Timeout occured. it can be resolved by removing the lockfiles that are present in ~/.cache/gem5, as the simulator typically locks the kernel and benchmark files when doing a run, meaning if you kill it while it is holding the lock, subsequent runs of the simulator will fail with that error.