Hey all, After quite a lot of waiting we've switched on OMTC on Windows by default today (bug 899785). This is a great move towards moving all our platforms onto OMTC (only linux is left now), and will allow us to remove a lot of code that we've currently been duplicating. Furthermore it puts us on track for enabling other features on desktop like APZ, off main thread animations and other improvements.
Having said that we realize that what we've currently landed and turned on is not completely bug free. There's several bugs still open (some more serious than others) which we will be addressing in the coming weeks, hopefully before the merge to Aurora. The main reason we've switched it on now is that we want to get as much data as possible from the nightly channel and our nightly user base before the aurora merge, as well as wanting to prevent any new regressions from creeping in while we fix the remaining problems. This was extensively discussed both internally in the graphics team and externally with other people and we believe we're at a point now where things are sufficiently stabilized for our nightly audience. OMTC is enabled and disabled with a single pref so if unforeseen, serious consequences occur we can disable it quickly at any stage. We will inevitably find new bugs in the coming weeks, please link any bugs you happen to come across to bug 899785, if anything se ems very serious, please let us know, we'll attempt to come up with a solution on the short-term rather than disabling OMTC and reducing the amount of feedback we get. There's also some important notes to make on performance, which we expect to be reported by our automated systems: - Bug 1000640 is about WebGL. Currently OMTC regresses WebGL performance considerably, patches to fix this are underway and this should be fixed on the very short term. - Several of the Talos test suite numbers will change considerably (especially with Direct2D enabled), this means Tscroll for example will improve by ~25%, but tart will regress by ~20%, and several other suites will regress as well. We've investigated this extensively and we believe the majority of these regressions are due to the nature of OMTC and the fact that we have to do more work. We see no value in holding off OMTC because of these regressions as we'll have to go there anyway. Once the last correctness and stability problems are all solved we will go back to trying to find ways to get back some of the performance regressions. We're also planning to move to a system more like tiling in desktop, which will change the performance characteristics significantly again, so we don't want to sink too much time into optimizing the current situation. - Memory numbers will increase somewhat, this is unavoidable, there's several steps which have to be taken when doing off main thread compositing (like double-buffering), which inherently use more memory. - On a brighter note: Async video is also enabled by these patches. This means that when the main thread is busy churning JavaScript, instead of stuttering your video should now happily continue playing! - Also there's some indications that there's a subjective increase in scrolling performance as well. If you have any questions please feel free to reach out to myself or other members of the graphics team! Bas _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
