Re: [libevl][PATCH 2/2] tests: sched-quota-accuracy: Add preempting FIFO thread

On 20.06.26 13:17, Philippe Gerum wrote:
> Philippe Gerum <[email protected]> writes:
> 
>> Jan Kiszka <[email protected]> writes:
>>
>>> From: Jan Kiszka <[email protected]>
>>>
>>> Test that higher-prio SCHED_FIFO threads do not run on the bill of
>>> SCHED_QUOTA threads and that their accounting is not otherwise
>>> disturbed.
>>>
>>
>> This patch introduced a regression when determining the accuracy of the
>> policy with respect to allotting threads the expected runtime budget:
>>
>> root@phytec-mira-evl:~# evl test sched-quota-accuracy
>> sched-quota-accuracy: 494.0%
>>
>> The proper result would rather be close to the following:
>>
>> root@phytec-mira-evl:~# evl test sched-quota-accuracy
>> sched-quota-accuracy: 99.1%
> 
> Ok, I guess the fact that the calibration process does not factor in the
> disruptor explains the full breakage we have with the accounting now:
> 
> root@phytec-mira-evl:~# evl test sched-quota-accuracy -- -v
> picked CPU1 for execution
> CPU1: calibrating: 893547 loops/sec
> CPU1: new thread group #0, quota sum is 10%
> CPU1: done quota_thread[0], count=150399
> CPU1: done quota_thread[1], count=145636
> CPU1: done quota_thread[2], count=141552
> CPU1: 3 threads: cap=10%, effective=49.0%, disruption=49.6%
> sched-quota-accuracy: 489.7%
> 
> Which does not make any sense since the effective value should be capped
> at 10% in the above case, compared to the nominal (full) report which
> should be:
> 
> root@phytec-mira-evl:~# evl test sched-quota-accuracy -- -v
> picked CPU1 for execution
> CPU1: calibrating: 899203 loops/sec
> CPU1: new thread group #0, quota sum is 10%
> CPU1: done quota_thread[0], count=26818
> CPU1: done quota_thread[1], count=26709
> CPU1: done quota_thread[2], count=35612
> CPU1: 3 threads: cap=10%, effective=9.9%
> sched-quota-accuracy: 99.1%
> 
> Dropping this patch from the -next branch for now.
> 

I would rather recommend taking a trace and debugging the scheduler -
this could very likely be remaining issue in the quota fix.

Jan

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