Re: [RFC PATCH v3 00/16] Core scheduling v3

[Tim Chen]

On 8/7/19 10:10 AM, Tim Chen wrote:

> 3) Load balancing between CPU cores
> -----------------------------------
> Say if one CPU core's sibling threads get forced idled
> a lot as it has mostly incompatible tasks between the siblings,
> moving the incompatible load to other cores and pulling
> compatible load to the core could help CPU utilization.
> 
> So just considering the load of a task is not enough during
> load balancing, task compatibility also needs to be considered.
> Peter has put in mechanisms to balance compatible tasks between
> CPU thread siblings, but not across cores.
> 
> Status:
> I have not seen patches on this issue.  This issue could lead to
> large variance in workload performance based on your luck
> in placing the workload among the cores.
> 

I've made an attempt in the following two patches to address
the load balancing of mismatched load between the siblings.

It is applied on top of Aaron's patches:
- sched: Fix incorrect rq tagged as forced idle
- wrapper for cfs_rq->min_vruntime
  https://lore.kernel.org/lkml/20190725143127.GB992@aaronlu/
- core vruntime comparison
  https://lore.kernel.org/lkml/20190725143248.GC992@aaronlu/

I will love Julien, Aaron and others to try it out.  Suggestions
to tune it is welcomed.

Tim

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