Cache topology aware scheduling

[Alan Bateman]

On 06/09/2024 08:10, Danny Thomas wrote:
> Thanks Franz, Alan,
>
> I spun up a quick experiment with a custom scheduler here:
>
> https://github.com/DanielThomas/virtual-threads-cluster-aware 
> <https://urldefense.com/v3/__https://github.com/DanielThomas/virtual-threads-cluster-aware__;!!ACWV5N9M2RV99hQ!LpIm0wPe4UjF5tJvF0CQKTE98rTBgsqe-WIHDLDCt3HheQHfb-ldWdCf7vfWNxI8nEmUjf3AyP91_aq0XA$>

Would I be correct to say that this experiment is a FJP (in async/fifo 
mode) for each "cluster" with the worker threads bound to the processors 
in that cluster. A "front-end" scheduler forwards tasks to one of the 
FJP instances. If a platform thread starts or unparks a virtual thread 
then the target's task will be submitted to a random FJP instance. If a 
virtual thread starts or unparks another virtual thread then it will be 
submitted to the "current" FJP. Assuming I have this right thing I would 
expect it works well for workloads where there are platform threads in 
the picture as that will have the effect of balancing the load across 
the FJP instances. In other cases then I assume it could be a bit 
unbalanced, at least not without something that nudges virtual threads 
to other clusters.

-Alan
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