Re: [PATCH 1/2] sched/uclamp: Add a new sysctl to control RT default boost value

[Qais Yousef]

On 06/04/20 14:14, Vincent Guittot wrote:
> I have tried your patch and I don't see any difference compared to
> previous tests. Let me give you more details of my setup:
> I create 3 levels of cgroups and usually run the tests in the 4 levels
> (which includes root). The result above are for the root level
> 
> But I see a difference at other levels:
> 
>                            root           level 1       level 2       level 3
> 
> /w patch uclamp disable     50097         46615         43806         41078
> tip uclamp enable           48706(-2.78%) 45583(-2.21%) 42851(-2.18%)
> 40313(-1.86%)
> /w patch uclamp enable      48882(-2.43%) 45774(-1.80%) 43108(-1.59%)
> 40667(-1.00%)
> 
> Whereas tip with uclamp stays around 2% behind tip without uclamp, the
> diff of uclamp with your patch tends to decrease when we increase the
> number of level

Thanks for the extra info. Let me try this.

If you can run perf and verify that you see activate/deactivate_task showing up
as overhead I'd appreciate it. Just to confirm that indeed what we're seeing
here are symptoms of the same problem Mel is seeing.

> Beside this, that's also interesting to notice the ~6% of perf impact
> between each level for the same image

Interesting indeed.

Thanks

--
Qais Yousef