Changing c-states breaks magic-trace / IPT

I was experiencing issues where my traces were completely empty around the snapshot. After investigating the perf file it hinted at "instruction trace errors" which led me to

https://perf.wiki.kernel.org/index.php/Perf_tools_support_for_Intel%C2%AE_Processor_Trace

which mentions

> It is not uncommon to get overflows when transitioning to a C-state, so these errors are not significant.

I was testing this on a TGL laptop and after disabling turbo boost I got pretty stable traces again.

I am wondering whether other people share the same experience with switching c-states or whether there is maybe something else behind it?

If not it might be worth mentioning disabling c-states in the readme / tutorial? Turbo boost was enough for me but probably something lik e the max_cstate kernel flags work as well.

This is on 5.15.17.

Start by reproducing the empty snapshots on the reported TGL laptop with c-states and turbo boost varied, then inspect the perf file for instruction trace errors. Compare the results with the linked Intel Processor Trace guidance and the max_cstate kernel flags. Done means establishing whether c-state transitions cause the failures and, if confirmed, identifying the README or tutorial location for the guidance.

Written by the indexing model from the issue text.