H Qais,

Sorry for the late reply.

On Fri, 5 Jun 2020 at 12:45, Qais Yousef [off-list ref] wrote:

On 06/04/20 14:14, Vincent Guittot wrote:

quoted

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.

I see call to  activate_task() for each wakeup of the sched-pipi thread

quoted

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