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rtapp execution gives unreliable actual duty cycle #89

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@douglas-raillard-arm

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@douglas-raillard-arm

The following JSON configuration was used on a Juno R0, big core running with "performance" cpufreq governor and idle states disabled:

{
    "tasks": {
        "pelt1": {
            "loop": 1,
            "policy": "SCHED_OTHER",
            "phases": {
                "p000001": {
                    "loop": 125,
                    "run": 8000,
                    "timer": {
                        "ref": "pelt1",
                        "period": 16000
                    },
                    "cpus": [
                        1
                    ]
                }
            },
            "delay": 0
        }
    },
    "global": {
        "duration": -1,
        "calibration": 247,
        "default_policy": "SCHED_OTHER",
        "logstats": false,
        "ftrace": "loop",
        "lock_pages": false
    }

This leads to active time in a period of ~8.5ms in one trace and ~9ms in another, instead of 8 in both.
traces.tar.gz

This may be related to the "loop" ftrace configuration, will update the ticket with further information as they come.

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