FPS dropping as ulubis runs

[malcolmstill]

I noticed that as weston-simple-egl runs our frame rate slowly drops from just below 60 FPS towards 30 FPS.

I'm not sure whether this is happening because I'm running weston-simple-egl or would happen slowly regardless.

Theories as to why this might be:

• we're not deleting resources

[malcolmstill]

Okay, so I've looked into this a bit more. I'd wondered if:

• I was leaking resources on the Common Lisp side of things. Conclusion, I'm not. WL-RESOURCE objects seem not to be monotonically increasing (apart from WL-REGIONs on weston-terminal there is a bunch of clean up I need to do for object destruction but for this, i.e. weston-simple-egl the only objects being created as it runs are callbacks and I am properly disposing of these.

• I was leaking wl_resource on the libwayland side. I added wl-client-for-each-resource to cl-wayland. This allows me to iterate over all the resources for a given client on the libwayland side. I set up a wee counter and saw that my wl_resources are not increasing monotonically for any clients (when running weston-terminal and weston-simple-egl). Just to confirm how the wl_resources work I removed the wl-resource-destroy call where I clean up callbacks and lo and behold wl-client-for-each-resource shows that for the weston-simple-egl client that the resource list just increases and increases as it runs.

• I checked if this performance leak was existent on ulubis-sdl. It is not, ulubis-sdl will quite happily render at 60 FPS when running weston-simple-egl. This implies my Wayland code is sound, the performance leak is not to do with that.

What this suggests is the performance leak is in my DRM/KMS/GBM code. I wonder if I time different parts of the page flip code whether I'd see one call taking longer and longer. Or maybe the time between receiving page flip events might just increase.

[malcolmstill]

I'd also wondered whether my Mac Mini was just overheating and was just being clocked down. However, if I stop weston-simple-egl after a while and allow the machine to cool again, I do not recover the FPS. This makes me think it's not a temperature issue.

[malcolmstill]

I don't know if I actually did, but I thought I'd written a small program utilising DRM/KMS to check whether there was slow down in that and from what I recall there wasn't any but my memory is hazy.

Todo: redo this and check

[malcolmstill]

I want to fix this before adding anything else. If I can get a baseline of a compositor running at 60 FPS then I know I can add bells and whistles after that.