Re: [RFC patch v3 00/20] Cache aware scheduling

[Chen, Yu C]

On 6/19/2025 2:39 PM, Yangyu Chen wrote:
> Nice work!
>
> I've tested your patch based on commit fb4d33ab452e and found it
> incredibly helpful for Verilator with large RTL simulations like
> XiangShan [1] on AMD EPYC Geona.
>
> I've created a simple benchmark [2] using a static build of an
> 8-thread Verilator of XiangShan. Simply clone the repository and
> run `make run`.
>
> In a static allocated 8-CCX KVM (with a total of 128 vCPUs) on EPYC
> 9T24, before the patch, we have a simulation time of 49.348ms. This
> was because each thread was distributed across every CCX, resulting
> in extremely high core-to-core latency. However, after applying the
> patch, the entire 8-thread Verilator is allocated to a single CCX.
> Consequently, the simulation time was reduced to 24.196ms, which
> is a remarkable 2.03x faster than before. We don't need numactl
> anymore!
>
> [1] https://github.com/OpenXiangShan/XiangShan
> [2] https://github.com/cyyself/chacha20-xiangshan
>
> Tested-by: Yangyu Chen <cyy@xxxxxxxxxxxx>

Thanks Yangyu for your test. May I know if these 8-threads have any
data sharing with each other, or each thread has their dedicated
data? Or, there is 1 main thread, the other 7 threads do the
chacha20 rotate and put the result to the main thread?
Anyway I tested it on a Xeon EMR with turbo-disabled and saw ~20%
reduction in the total time.

Thanks,
Chenyu