1. Computers
  2. Display Drivers
  3. Graphics Cards
  4. Memory
  5. Motherboards
  6. Processors
  7. Software
  8. Storage
  9. Operating Systems


Facebook RSS Twitter Twitter Google Plus


Phoronix Test Suite

OpenBenchmarking.org

Avoiding Frame Jitter With GNOME's Mutter, Weston

GNOME

Published on 30 November 2012 12:29 PM EST
Written by Michael Larabel in GNOME
13 Comments

Owen Taylor has written a new blog post about avoiding jitter in composited frame display. Owen -- along with help from Kristian Høgsberg -- made improvements to the algorithm for compositor frame timing as used by GNOME's Mutter compositing window manager and also Wayland's Weston.

The basic algorithm up to this point was when receiving damage, a redraw should be scheduled immediately. If a redraw is scheduled and the system is still waiting for the previous swap to complete, a redraw should be done when the swap completes. This algorithm though doesn't work out ideally when showing content that runs at a fixed frame-rate that is less than the display's frame-rate, such as displaying video content at 24/30 FPS on a 60Hz display.

In the end the modified algorithm he came up with includes introducing a concept of "urgent" frames that can be marked by the application. Now when receiving damage, if it's part of an urgent frame, a redraw will be scheduled immediately. If it's not urgent, schedule a redraw for 2ms after the next VBlank. If a redraw is scheduled for time T and they're still waiting for the previous swap to complete at time T, redraw immediately when the swap completes. "I’m pretty happy with how this algorithm works out in testing, and it may be as good as we can get for X. The main downside I know of is that it only individually solves the two problems – handling clients that need all the rendering resources of the system and handling clients that want minimum jitter for displayed frames, it doesn’t solve the combination. The client that is rendering full-out at 24fps is also vulnerable to jitter from other clients drawing, just like the client that is choosing to run at 24fps. There are mitigation strategies – for example, not triggering a redraw when client that is obscured changes, but I don’t have a full answer. Unredirecting full-screen games definitely is a good idea."

Other possible approaches being evaluated for avoiding jitter in composited frame display include triple buffering with the compositor (though this could lead to wasted resources) or allowing applications to submit frames with their intended time frames. The later approach, however, wouldn't be good for X but could work nicely in a Wayland world.

Read the blog post at FishSoup.net.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
Latest Articles & Reviews
  1. NVIDIA's $1000+ GeForce GTX TITAN X Delivers Maximum Linux Performance
  2. OS X 10.10 vs. Ubuntu 15.04 vs. Fedora 21 Tests: Linux Sweeps The Board
  3. The New Place Where Linux Code Is Constantly Being Benchmarked
  4. 18-GPU NVIDIA/AMD Linux Comparison Of BioShock: Infinite
  5. Phoronix Test Suite 5.6 Adds New Phoromatic Enterprise Benchmarking Features
  6. OpenGL Threaded Optimizations Responsible For NVIDIA's Faster Performance?
Latest Linux News
  1. Improved OpenCL Support For Blender's Cycles Renderer
  2. Mesa 10.5.2 Packs In A Handful Of Fixes
  3. More Fedora/Ubuntu Linux vs. OS X OpenGL Benchmarks
  4. Intel Adds Mesa IR To NIR Translator & Makes Other NIR Improvements
  5. HAMMER2 Gets A Man Page
  6. Kodi 14.2 Released To End Out The "XBMC" 14.x Series
  7. Debian 8.0 Jessie RC2 Installer Released
  8. Shadow Warrior Is Being Released For Linux Next Week
  9. Intel Pushes A Bunch Of Broadwell Code Into Coreboot
  10. Open-Source Driver Fans Will Love NVIDIA's New OpenGL Demo
Most Viewed News This Week
  1. Introducing The Library Operating System For Linux
  2. AMD Is Hiring Two More Open-Source Linux GPU Driver Developers
  3. Allwinner Continues Jerking Around The Open-Source Community
  4. New SecureBoot Concerns Arise With Windows 10
  5. Systemd Change Allows For Stateless Systems With Tmpfs
  6. GNOME Shell & Mutter 3.16.0 Released
  7. GNU Nano 2.4.0 Brings Complete Undo System, Linter Support & More
  8. Red Hat Is Rolling Out A VirtIO DRM/KMS GPU Driver