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

Radeon Gallium3D LLVM Now Uses VLIW Scheduler

Mesa

Published on 21 June 2012 08:14 PM EDT
Written by Michael Larabel in Mesa
6 Comments

With a commit this afternoon to Mesa, the R600 Gallium3D driver with the LLVM back-end is now using the performance-boosting VLIW scheduler.

With the R600g LLVM back-end the register pressure scheduler has now been replaced by the VLIW (Very Long Instruction Word) scheduler. The VLIW scheduler for supporting the Radeon HD 2000 through HD 6000 series graphics cards is far from being ideal in terms of being optimally efficient as it ignores some complicated instructions right now, but it should be an improvement over the status quo.

According to Tom Stellard, the AMD employee that has been working on open-source OpenCL as of late for Gallium3D, reports that switching to the new scheduler resulted in a 50% performance boost for a SHA1 compute shader test. However, he has yet to see the performance impact of the VLIW scheduler on complicated graphics shaders.

From the commit:
It's not optimal, but it's better than the register pressure scheduler that was previously being used. The VLIW scheduler currently ignores all the complicated instruction groups restrictions and just tries to fill the instruction groups with as many instructions as possible. Though, it does know enough not to put two trans only instructions in the same group.

We are able to ignore the instruction group restrictions in the LLVM backend, because the finalizer in r600_asm.c will fix any illegal instruction groups the backend generates.

Enabling the VLIW scheduler improved the run time for a sha1 compute shader by about 50%. I'm not sure what the impact will be for graphics shaders. I tested Lightsmark with the VLIW scheduler enabled and the framerate was about the same, but it might help apps that use really big shaders.
It looks like it's time for me to start some new R600g benchmarks!

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 Linux Hardware Reviews
  1. Rosewill RS-MI-01: An Ultra Low-Cost Mini-ITX Chassis
  2. D-Link DCS-2330L HD Wireless Network Camera
  3. Gigabyte AM1M-S2H
  4. AMD's New Athlon/Semprons Give Old Phenom CPUs A Big Run For The Money
Latest Linux Articles
  1. AMD Catalyst 14.4 On Linux With Radeon R3 APU Graphics
  2. Red Hat Enterprise Linux 7.0 RC Benchmarks
  3. AMD Catalyst 14.4 Brings Few Linux Performance Improvements
  4. The Performance Of Fedora 20 Updated
Latest Linux News
  1. NGINX 1.6 Brings SPDY 3.1 & Other New Features
  2. Linux Foundation Announces A Core Infrastructure Initiative
  3. More Steam Linux Tests/Benchmarks Might Be Coming
  4. NVIDIA's Amazing Single-Board ARM Computer Might Be Delayed
  5. Fedora 21 To Get A Playground, New Features
  6. PC-BSD Is Developing Its Own Desktop Environment
  7. Valve Is Bringing VOGL To Windows & Working On Regression Tests
  8. Canonical Is Taking Over Linux 3.13 Kernel Maintenance
  9. Google Web Designer Is Now Natively Available On Linux
  10. Ubuntu 14.10 Is Codenamed The Utopic Unicorn
  11. Audacious 3.5 Lightweight Audio Player Released
  12. Steam Updated For Ubuntu 14.04 LTS, SteamOS
Latest Forum Discussions
  1. What Else Would You Like To See On Phoronix This Spring?
  2. HTPC-upgrade advice: AMD Richland A8-7600 or Kaveri A10-6700T ???
  3. Linux Kernel Developers Fed Up With Ridiculous Bugs In Systemd
  4. The GNOME Foundation Is Running Short On Money
  5. The Most Amazing OpenGL Tech Demo In 64kb
  6. Announcing radeontop, a tool for viewing the GPU usage
  7. New card. Open source drivers only.
  8. Script for Fan Speed Control