There are likely two causes here. First, until we have APZ enabled its very unlikely that we can ever maintain a high frame-rate scrolling on low-end hardware. OMTC is a prerequisite for APZ (async pan/zoom). Low end hardware is simply not fast enough to repaint and buffer-rotate with 60FPS.
Now for Intel hardware being slow there could be a couple reasons, and APZ might fix them actually. If I remember correctly Atom GPUs are PowerVR based, which is a tile based rendering architecture. It splits the frame buffer in small tiles and renders those. To do this efficiently it defers rendering for as long as possible. Other GPUs start rendering as soon as possible, whereas PowerVR waits until the entire frame is ready and then renders it then. We do a couple operations while rendering that might force a pipeline flush, which likely forces PowerVR to render right away, which is very bad for PowerVR’s particular render model. If you can point us to some specific hardware we really suck on we can definitely look into this. Andreas On May 30, 2014, at 6:25 AM, avi...@gmail.com wrote: > On Friday, May 30, 2014 8:22:25 AM UTC+3, Matt Woodrow wrote: >> Thanks Avi! >> >> >> >> I can reproduce a regression like this (~100% slower on >> >> iconFade-close-DPIcurrent.all) with my machine forced to use the intel >> >> GPU, but not with the Nvidia one. > > Indeed, and it's not the first time we notice that Firefox performs much > worse with Intel iGPUs compared to nvidia. > > This comment: https://bugzilla.mozilla.org/show_bug.cgi?id=894128#c30 > compares scrolling performance on a Wikipedia page, on a different system > than the one I used to produce these OMTC numbers with. > > It suggests that we were already doing badly enough with intel iGPUs even > before OMTC (about 300% worse and much more noisy intervals than nvidia on a > Wikipedia page if we're to believe those numbers), and it looks as if with > OMTC the regression compared to nvidia increased even more (in relative > terms). > > In comment 1 of the same bug 894128, I also compared the performance of > Chrome and IE on the same pages. > > FWIW, IE is able to maintain 100% smooth scrolling on some really complex > pages even on a _very_ low end Atom system (Intel iGPU), while Firefox > doesn't come anywhere near it. > > While scroll and tab animations are possibly different things, I do think > there's a line which connects these dots, and it's that for whatever reason, > Firefox does really badly on Intel iGPUs. > > Which is unfortunate, because on many many systems these are the only > available GPUs, and they're already considered good enough for the majority > of users to not need a dedicated GPU. > > - avih > _______________________________________________ > dev-platform mailing list > dev-platform@lists.mozilla.org > https://lists.mozilla.org/listinfo/dev-platform _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
