On Tue, 14 May 2019 at 11:48, Boris Brezillon boris.brezillon@collabora.com wrote:
Add a way to dump perf counters through debugfs. The implementation is kept simple and has a number of limitations:
- it's not designed for multi-user usage as the counter values are reset after each dump and there's no per-user context
- only accessible to root users
- no counters naming/position abstraction. Things are dumped in a raw format that has to be parsed by the user who has to know where the relevant values are and what they mean
This implementation is intended to be used by mesa developers to help debug perf-related issues while we work on a more generic approach that would allow all GPU drivers to expose their counters in a consistent way. As a result, this debugfs interface is considered unstable and might be deprecated in the future.
An idea:
Add module_param_unsafe() module parameter and expose the debugfs files only when set. Seemingly the i915 team have been using it to a similar extend to highlight the feature is unstable.
Note: setting the _unsafe param taints the kernel, which AFAICT is the part which makes is extra useful.
I could be wrong of course :-)
HTH -Emil