[LITMUS^RT] The gap between the release time and the real beginning of execution

[Björn Brandenburg]

> On 19 Jul 2016, at 11:13, shijunjie92 <shijunjie92 at gmail.com> wrote:
> 
> When I use the feature trace tool to draw the Gantt chart of the cpus' execution. I notice that there is a gap between the release time and the beginning of the real execution. I have traced the code of 'rtspin.c' but found nothing. Can anyone explain the reason of the random gap or how to reduce the gap? (sometimes the gap is 2 ms)

That’s release latency. Either your platform’s timers are extremely imprecise (this is usually the case under virtualization), or you have extremely long non-preemptive sections, or there is some extreme overhead. In mainline LITMUS^RT (with a normal config), I would rule out the last two issues.

What hardware platform are you running your test on? This looks like a trace from a VM to me.

- Björn

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