Simulating an ARM multicore system with more than 8 cores

[mbabaie]

Hello @giactra,

I'm reaching out regarding an issue I recently faced with when trying to simulate a large multicore system (e.g., hundreds of cores if possible) with ARM ISA using gem5's standard library components. I realized that some of the available infrastructures only supports up-to 8 cores. For instance, the platforms available (i.e., VExpress_GEM5_V1 or V2, etc) they only support up-to 8 cores. Do you know any solutions on how to possibly scale up the system to more than 8 cores?

Best regards,
Maryam

[giactra]

Hi @mbabaie .

This has partly been addressed by https://github.com/orgs/gem5/discussions/821 (for sure there are other references in the gem5 mailing list).
TL;DR: it is definitely possible to have > 8 cores with VExpress_GEM5_V2 and VExpress_GEM5_Foundation. This you can do as of now with a vanilla Linux kernel and no changes needed.

If you want to use VExpress_GEM5_V1, you need to run a modified GIC Linux driver to allow more than 8 cores.

[mbabaie]

Thanks for your prompt reply.

I tried the VExpress_GEM5_Foundation with 8-core and 16-core systems with KVM CPU. Is it normal that for a long time nothing is printed on the board.terminal? I don't know how long l should let it run. My assumption was that perhaps it's not booting linux.

[giactra]

Just to be clear: is using KVM your ultimate goal or are you trying it just because it is referenced in the discussion I posted?

[mbabaie]

I aim to use KVM to accelerate booting linux and take a checkpoint.
I have tested the VExpress_GEM5_Foundation with 16-cores with atomic CPU and it successfully booted and took the checkpoint. However, it's very slow and took about 12 hours to finish the simulation. KVM will make it much faster.