GSoC Project | Basic Support for Trace Compass

[Sebastian Huber]

----- Am 3. Aug 2019 um 9:18 schrieb Ravindra Kumar Meena rmeena840 at gmail.com:

>>
>>
>> Yes, this is similar to what I see. I don't think this is what we want.
>> The 09.. are all idle threads. What I want is something similar to the
>> LTTNG output, see attached screen shot.
>>
> 
> Are you talking about CPU states the Trace Compass has?
> --CPU states
>      --IRQ 34
>      --SOFT_IRQ 1 Timer
>      --SOFT IRQ 7 Schedular
>      --SOFT IRQ 9 RCU data

No, we don't have support for interrupts yet. We can only support the states "usermode" and "idle".

> 
>>
>> It seems the prev_state is actually the state of the new thread. Doesn't
>> really make sense to me. Could you please clarify this with the LTTNG
>> mailing list?
>>
> In the lttng response, I shared with you previously.
> https://lists.lttng.org/pipermail/lttng-dev/2019-July/029121.html
> 
> They had mentioned that
> "My guess would be that prev_state is the previous state of the thread (TID)
> "
> 
> So I think prev_state is for prev_tid only.

Yes, prev_state is the state of the previous thread. See my other email which mentions the swapper. In the Trace Compass code you see that a tid == 0 is used to detect an idle CPU.

We have to set prev_tid to 0 if the previous thread is an idle thread, likewise for next_tid if the next thread is an idle thread.