24.13. gem5 fs_bigLITTLE
By default, we use configs/example/fs.py script.
The --gem5-script biglittle option enables the alternative configs/example/arm/fs_bigLITTLE.py script instead:
./run --arch aarch64 --emulator gem5 --gem5-script biglittle
Advantages over fs.py:
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more representative of mobile ARM SoCs, which almost always have big little cluster
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simpler than
fs.py, and therefore easier to understand and modify
Disadvantages over fs.py:
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only works for ARM, not other archs
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not as many configuration options as
fs.py, many things are hardcoded
We setup 2 big and 2 small CPUs, but cat /proc/cpuinfo shows 4 identical CPUs instead of 2 of two different types, likely because gem5 does not expose some informational register much like the caches: https://www.mail-archive.com/gem5-users@gem5.org/msg15426.html gem5 config.ini does show that the two big ones are DerivO3CPU and the small ones are MinorCPU.
TODO: why is the --dtb required despite fs_bigLITTLE.py having a DTB generation capability? Without it, nothing shows on terminal, and the simulation terminates with simulate() limit reached @ 18446744073709551615. The magic vmlinux.vexpress_gem5_v1.20170616 works however without a DTB.
Tested on: 18c1c823feda65f8b54cd38e261c282eee01ed9f