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

GCC 4.7 Link-Time Optimization Performance

Michael Larabel

Published on 21 August 2012
Written by Michael Larabel
Page 1 of 3 - 17 Comments

With the recent interest regarding Link-Time Optimization support within the Linux kernel by GCC, here are some benchmarks of the latest stable release of GCC (v4.7.1) when benchmarking several common open-source projects with and without the performance-enhancing LTO compiler support.

This article, which spawned out of the many LTO comments from the Linux kernel link-time optimization article, has a few benchmarks conducted since then from an Intel Ivy Bridge system. More GCC LTO benchmarks will come in a future article. GCC's Link-Time Optimization support allows for creating faster generated binaries at the cost of increased compile times and greater system memory (RAM) usage. When building software with the performance-oriented feature, link-time optimizations are applied on recent versions of the GNU Compiler Collection that allow for in-lining of functions between different files, performing various compile-time optimizations across the binary as a whole, dropping dead code, and running entire checks across the whole binary rather than just individual files.

As explained on the GCC Wiki, "Link Time Optimization (LTO) gives GCC the capability of dumping its internal representation (GIMPLE) to disk, so that all the different compilation units that make up a single executable can be optimized as a single module. This expands the scope of inter-procedural optimizations to encompass the whole program (or, rather, everything that is visible at link time)...The fundamental mechanism used by the compiler to delay optimization until link time is to write the GIMPLE representation of the program on special sections in the output file. For the initial implementation on the branch, ELF was chosen as the container format for these sections, but in GCC-4.6 support has been added on the trunk for PE-COFF and Mach-O. In order to use LTO the target must support one of these binary formats."

Using GCC LTO requires passing "-flto" compiler flag to enable the main Link-Time Optimization features. There's also a "-fwhopr" that is similar to "-flto" but splits compilation to achieve scalability for very large code-bases that cannot fit all in memory at once.

For this quick GCC 4.7.1 LTO benchmarking, the Intel Core i7 3517UE "Ivy Bridge" system was running Ubuntu 12.10 x86_64 with GCC 4.7.1 from the Ubuntu Quantal repository and then running several common computational test profiles with and without the "-flto" compiler flag. All other CFLAGS/CXXFLAGS options were maintained the same throughout the testing process. This benchmarking was handled in a fully automated manner using the open-source multi-platform Phoronix Test Suite software.

<< Previous Page
1
Latest Linux Hardware Reviews
  1. Even With Re-Clocking, Nouveau Remains Behind NVIDIA's Proprietary Linux Driver
  2. The Power Consumption & Efficiency Of Open-Source GPU Drivers
  3. AMD R600g/RadeonSI Performance On Linux 3.16 With Mesa 10.3-devel
  4. Intel Pentium G3258 On Linux
Latest Linux Articles
  1. AMD Catalyst 14.6 Does Slightly Better With APITest OpenGL Tests
  2. Updated Source Engine Benchmarks On The Latest AMD/NVIDIA Linux Drivers
  3. Nouveau vs. Radeon vs. Intel Tests On Linux 3.16, Mesa 10.3-devel
  4. KVM Benchmarks On Ubuntu 14.10
Latest Linux News
  1. Builder: A New Development IDE Being Built For GNOME
  2. GDB 7.8 Betters Python Scripting, Adds Guile Support
  3. GNOME's GTK+ Is Still Striving For A Scene Graph, Canvas API
  4. Unreal Tournament Looks Great For Team Deathmatch
  5. LibreOffice 4.3 Released With Many Exciting Changes
  6. GNOME/GTK On Wayland Gains Focus At GUADEC
  7. GNOME Stakeholders Take Issue With Groupon Over their Gnome
  8. GStreamer VA-API Plug-In Update Adds New Features
  9. Qt 5.4 Going Into Feature Freeze Next Week With Exciting Changes
  10. OpenSUSE Factory Turns Into Rolling Release Distribution
Latest Forum Discussions
  1. Grand Theft Auto Running On Direct3D Natively On Linux Shows Gallium3D Potential
  2. Open-source drivers on ATI R7 260X
  3. AMD Athlon 5350 APU On Linux
  4. Debian + radeonsi
  5. Linus Torvalds On GCC 4.9: Pure & Utter Crap
  6. Updated and Optimized Ubuntu Free Graphics Drivers
  7. List of Linux friendly Kickstarter projects
  8. Porting Mesa to the Playstation 2