Bugzilla

I don't think we have any blob fallback: all the worker threads are completely idle.

The reporter had an Adreno 506 which is on the less-powerful end of the spectrum. I can reproduce on Samsung A51 (Mali G72), but not a Pixel 5 (Adreno 620) or Pixel 7 (Mali G710). So this isn't specific to a model of GPU, but rather occurs on less powerful devices. On the more powerful devices I do see the frame time increase by a couple of milliseconds, but we're still comfortably in budget.

The provided profile is consistent with being GPU or perhaps memory bandwidth bound. Given the page is quite simple I would lean towards the latter. [Here](https://share.firefox.dev/3JRjd3R) is a profile on the A51 which is much more concentrated on `glClear()` clearing picture cache targets, which would validate that theory.

Enabling dark mode on both wikipedia and ponepaste.org results in picture caching no longer working. Instead of a single scrollable slice we appear to get 2 non-scrolling slices, meaning the entire page is invalidated when we scroll. On less powerful devices we cannot afford to do that. This is also the case on desktop. The question for those who understand picture caching slightly better is why we fail to create a scrollable slice, and can we fix that?

I don't think we have any blob fallback: all the worker threads are completely idle.

The reporter had an Adreno 506 which is on the less-powerful end of the spectrum. I can reproduce on Samsung A51 (Mali G72), but not a Pixel 5 (Adreno 620) or Pixel 7 (Mali G710). So this isn't specific to a model of GPU, but rather occurs on less powerful devices. On the more powerful devices I do see the frame time increase by a couple of milliseconds, but we're still comfortably in budget.

The provided profile is consistent with being GPU or perhaps more specifically memory bandwidth bound. Given the page is quite simple I would lean towards the latter. [Here](https://share.firefox.dev/3JRjd3R) is a profile on the A51 which is much more concentrated on `glClear()` clearing picture cache targets, which would validate that theory.

Enabling dark mode on both wikipedia and ponepaste.org results in picture caching no longer working. Instead of a single scrollable slice we appear to get 2 non-scrolling slices, meaning the entire page is invalidated when we scroll. On less powerful devices we cannot afford to do that. This is also the case on desktop. The question for those who understand picture caching slightly better is why we fail to create a scrollable slice, and can we fix that?