Platform/GFX/WRperfmeetings

Meeting notes for our wr-perf sync sessions.

April 7 2020

Agenda:

• Intel Gen 7-7.5 progress blockers
  • https://bugzilla.mozilla.org/show_bug.cgi?id=1599502
• Review other bugs in wr-perf-p1
  • Guardian covid bug? https://bugzilla.mozilla.org/show_bug.cgi?id=1627458

• DirectComp - bugs to fix and bugs blocking shipping to more users?
  • https://bugzilla.mozilla.org/show_bug.cgi?id=1627117 (Profiling + Screenshot issue)
  • https://bugzilla.mozilla.org/show_bug.cgi?id=1624484 (HW stretching support issue)
  • https://bugzilla.mozilla.org/show_bug.cgi?id=1618370 (Grey line issue)

Notes & Next Steps:

• For Intel Gen 7-7.5 blockers
  • Dzmitry's scatter mode helps with GPU caching stalls on angle
    • Can we use this for all Windows? Would be nice to have the same path everywhere
    • We will do a test to see if this can be enabled for all Windows
  • Vertex data textures cause CPU
    • GW has workaround for this, seems like reasonable enough solution for now
  • There are some cases when scrolling down, when youtube creates and deletes DOM elements and that trips up picture caching
    • GW fixed the main cases, will get those landed.

After meeting, GW will kick-off a try build with these fixes included and then we can re-test to see how things are looking for this target.

• Partial Present?
  • In Beta
  • Do we have case where people having been testing DC off and partial present on in Nightly?
    • Presumably people who have the hardware stretching issue have that path
  • We will keep eye out for any other bugs

In general, lowering CPU times is valuable.

• Miko's idea for a bigger refactor
  • One approach - get rid of gecko transform display items, bring this WR style spatial tree into gecko, share it between gecko and wr (not an easy change to make but benefits might be nice)
  • Big project - would need to work out how to take steps towards that.
  • Gecko supplying spatial IDs and making them persistent would be a good starting point to investigate and get initial wins
  • Miko to write out a bug with some ideas and we can figure out next steps/how to prototype

• Nical - How hard to have dirty rects per tile?
  • Not sure. Ideally not bigger than 512x512
  • Nical make bug about investigating this - rasterizing in bigger chunks.

• Guardian Covid map big
  • Now clear straightforward wins there. Chrome also not great at that page also (still seems a bit better than FF)

March 19 2020

Improving Texture caching seems like the best bet for improving perf to unblock Intel Gen 7.5

• Nical has submitted: https://phabricator.services.mozilla.com/D67575
• Once that lands, Jrmuizel to re-measure perf and see how things stack up
• GW to see if he can repro the jerky scroll (frame skipping) on YouTube homepage on his older hardware (https://bugzilla.mozilla.org/show_bug.cgi?id=1576637)
• Nical also to spin off individual bugs for low-hanging texture caching fruit, so we can see what can be potentially done in parallel

Other tasks to prioritize this Quarter likely for GW:

• Segment building - @GW is there a bug on file for this? https://bugzilla.mozilla.org/show_bug.cgi?id=1611908

DirectComposition

• How to ship on older hardware?
• Markus, Jeff and Glenn to discuss - see if there is a way to make the artifacting a bit better
• Jrmuizel to see if we can't learn more about why Chrome doesn't ship on AMD

General

• Jrmuizel to take a look more at gen7 Intel hardware to see if there is anything we should do to unblock there
• jbonisteel to take a look at the WR future doc, potentially set up a triage meeting to discuss more