Re: [RFC PATCH v4 00/19] Core scheduling v4

[Tim Chen]

On 10/30/19 11:33 AM, Vineeth Remanan Pillai wrote:
> Fourth iteration of the Core-Scheduling feature.
> 
> This version was aiming mostly at addressing the vruntime comparison
> issues with v3. The main issue seen in v3 was the starvation of
> interactive tasks when competing with cpu intensive tasks. This issue
> is mitigated to a large extent.
> 
> We have tested and verified that incompatible processes are not
> selected during schedule. In terms of performance, the impact
> depends on the workload:
> - on CPU intensive applications that use all the logical CPUs with
>   SMT enabled, enabling core scheduling performs better than nosmt.
> - on mixed workloads with considerable io compared to cpu usage,
>   nosmt seems to perform better than core scheduling.
> 
> v4 is rebased on top of 5.3.5(dc073f193b70):
> https://github.com/digitalocean/linux-coresched/tree/coresched/v4-v5.3.5
> 

The v4 core scheduler will crash when you toggle the core scheduling
tag of the cgroup while there are active tasks in the cgroup running.

The reason is because we don't properly move tasks in and out of the
core scheduler queue according to the new core scheduling tag status.
A task's core scheduler status will then get misaligned with its core
cookie status.

The patch below fixes that.

Thanks.

Tim

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