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With the R600g LLVM back-end the register pressure scheduler has now been replaced by the VLIW (Very Long Instruction Word) scheduler.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 Articles & Reviews
  1. OS X 10.10 vs. Ubuntu 15.04 vs. Fedora 21 Tests: Linux Sweeps The Board
  2. The New Place Where Linux Code Is Constantly Being Benchmarked
  3. 18-GPU NVIDIA/AMD Linux Comparison Of BioShock: Infinite
  4. Phoronix Test Suite 5.6 Adds New Phoromatic Enterprise Benchmarking Features
  5. OpenGL Threaded Optimizations Responsible For NVIDIA's Faster Performance?
  6. Big Graphics Card Comparison Of Metro Redux Games On Linux
Latest Linux News
  1. Git 2.4.0-rc0 Does A Ton Of Polishing
  2. The Most Common, Annoying Issue When Benchmarking Ubuntu On Many Systems
  3. Mesa Is At Nearly 1,500 Commits This Year
  4. Gestures & Other GTK3 Features For LibreOffice
  5. It's Now Easier To Try PHP 7 On Fedora & RHEL
  6. BQ Is Cleaning Up Their Aquaris E4.5 Ubuntu Kernel
  7. Allwinner Continues Jerking Around The Open-Source Community
  8. NVIDIA Linux 349.12 Beta Has Improved G-SYNC & VDPAU Features
  9. Canonical Just Made It Even Easier To Benchmark Ubuntu Linux In The Cloud
  10. NVIDIA GeForce GTX TITAN X Linux Testing Time
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. New SecureBoot Concerns Arise With Windows 10
  4. GNOME Shell & Mutter 3.16.0 Released
  5. GNU Nano 2.4.0 Brings Complete Undo System, Linter Support & More
  6. Systemd Change Allows For Stateless Systems With Tmpfs
  7. GCC 5 Compiler Is Getting Close To Being Released
  8. Chromebooks Powered By The MIPS Pistachio, Linux Support Evolving
%%CLICK_URL_UNESC%%