Add "number of rasterized blob image pixels" to the webrender profiler overlay

[mstange]

Sometimes Gecko produces very large blob items, and it looks like there are cases where webrender chooses to rasterize the entire item instead of just the portion on the screen. It would be nice to be able to detect these cases with the webrender profiler. Usually I only notice these cases due to jank from the texture upload.

[hgallagher1993]

Hi so I've taken a quick look at doing this and I guess the first question I have is, is there any preference for where it should be displayed on the overlay?

[gw3583]

I don't think there's a specific place - wherever seems to make the most sense to you should be fine :)

[hgallagher1993]

Hi so sorry for the massive delay, I thought I'd have more time to do this in September but didn't and then the end of September I moved from Ireland to Toronto and just completely forgot about it 😅

Anywho I've a couple of questions about this if it's still wanted. I'm guessing the actual incrementation of pixels to be displayed happens in add_rasterized_blob_images of the resource_cache? and if that's the case how do I actually get the pixels, is it something like multiplying the width and height in data.rasterized_rect.size? I ran a couple of reftests just to try and print out the height and width but the for loop in add_rasterized_blob_images never seemed to be hit (is there a reftest that will go into the loop?)

Completely new to this, thanks in advance 😄

[hgallagher1993]

Ping @mstange @gw3583 or anyone 👍

[mstange]

I can't answer your questions about the code because I don't really know it.

However, thinking about this again, I'm not sure if displaying the "number of rasterized blob image pixels" on a per-frame basis is actually useful. If this number is only displayed for one frame, you could easily miss it. Maybe what I want is more like "the total number of pixels that were ever rasterized for any blob images that are in use by the scene that is displayed in the current frame"...

Or more concretely: If you load the data URL that I mentioned in bug 1480155 comment 3 and scroll up and down, I want something to alert me to the fact that we're rasterizing and retaining way too many pixels (even if we don't upload all of them). I'm not actually sure what would be the best way to expose this.

[kvark]

If this number is only displayed for one frame, you could easily miss it.

unless it's displayed in a graph with history