Open Bug 1007449 Opened 8 years ago Updated 8 years ago
non-integer zooms cause severe scrolling slowdown
User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:29.0) Gecko/20100101 Firefox/29.0 (Beta/Release) Build ID: 20140428193813 Steps to reproduce: In about:config, I had set layout.css.devPixelsPerPx to 1.75. Info: Running Ubuntu GNOME 14.04 with Cinnamon and kernel 3.14. Hardware acceleration is enabled, smooth scrolling is also enabled. I can replicate this issue just by changing the zoom level with CTRL+mouse wheel. Actual results: Scrolling in some websites, such as feedly.com, is very slow. The same websites, with the same profile, etc, work perfectly smoothly if an integer scaling is used (i.e. layout.css.devPixelsPerPx is set to -1.0 or 2). Expected results: Performance should be similar with scaling 1.75 or 2.
Does it happen if hardware acceleration is disabled?
QA Whiteboard: [bugday-20140519]
Yes, it also happens with hardware acceleration disabled, to certain extent. Funny enough, I'd say it runs smoother with hardware acceleration disabled. It's all difficult to quantify, as it's just myself scrolling and appreciating the effects. Maybe there is any benchmark I can run using different configurations and get some numbers? I've only found benchmarks about canvas. Incidentally, I've tried http://www.kevs3d.co.uk/dev/canvasmark/ and got the following approximate numbers: layout.css.devPixelsPerPx 1.75 HW Accel disabled 8500 layout.css.devPixelsPerPx 2 HW Accel disabled 9000 layout.css.devPixelsPerPx 1.75 HW Accel enabled 8200 layout.css.devPixelsPerPx 2 HW Accel enabled 9000 Could something like rendering a complex page, and executing a script that scrolls the page 1 pixel every time and calls itself recursively, give meaningful numbers?
See also bug 645900.
Component: Untriaged → Layout
Product: Firefox → Core
Tried Grafx Bot (https://quality.mozilla.org/2010/07/test-day-help-us-test-hardware-acceleration-using-grafx-bot/), in order to see if I could get some objective numbers with zooms 1.75 and 2, but it is apparently not working, at least not in my system.
You need to log in before you can comment on or make changes to this bug.