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With the R600g LLVM back-end the register pressure scheduler has now been replaced by the VLIW (Very Long Instruction Word) scheduler.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. The MSI X99S SLI PLUS Is Working & Running Well On Linux
  2. NVIDIA GeForce GTX 980: The Best GPU For Linux Gamers
  3. ROCCAT LUA: A Linux-Friendly Gaming Mouse
  4. Cheetah Mounts: The Affordable Way To Put Your TV On The Wall
Latest Linux Articles
  1. Preview: Radeon Gallium3D Performance For CS:GO On Linux
  2. XWayland Linux Gaming Performance With GNOME Wayland On Fedora 21
  3. EXT4/Btrfs/XFS/F2FS Benchmarks On Linux 3.17
  4. Fedora 21 Alpha First Impressions: It's Great
Latest Linux News
  1. Other Projects Participating In This Winter's Women Outreach Program
  2. Radeon 7.5 X.Org Driver Enables Hawaii, Adds New PCI IDs
  3. PHP As A Next-Generation Programming Language?
  4. Steam Linux Usage Rose 0.1% During September
  5. Understanding The Xen XSA-108 Security Issue
  6. Fedora 21 Workstation Is Making Great Progress
  7. Dash As The Default Shell For Fedora?
  8. CUPS Turn 15 Years Old, CUPS 2.0 Released
  9. VA-API Gallium3D State Tracker Added Back To Mesa
  10. Radeon DRM Gets New Information Ioctl Queries
Latest Forum Discussions
  1. Microsoft Announces... Windows 10 With A Start Menu
  2. Borderlands 2 Launches On Steam For Linux
  3. Take the Steam Survey results with a grain of salt. It is flawed.
  4. X.Org Is Looking For Some Female Help
  5. Hacking Express gate (Asus Splashtop)
  6. NVIDIA Alerts Nouveau: They're Starting To Sign/Validate GPU Firmware Images
  7. Updated and Optimized Ubuntu Free Graphics Drivers
  8. Nero CD/DVD Burning Software On Linux Is Dead