Skip to content


Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?
This branch is 141 commits behind LLNL:dev.

Latest commit


Git stats


Failed to load latest commit information.
Latest commit message
Commit time


Build Status Read the Docs

Welcome to Variorum, a platform-agnostic library exposing monitor and control interfaces for several features in hardware architectures.

version 0.4.1

Last Update

2 April 2021



Variorum is an extensible vendor-neutral library for exposing power and performance monitoring and control of low-level hardware knobs.


To get started building and using Variorum, check out the full documentation here:

Getting Started

Installation is simple. You will need CMAKE version 2.8 or higher and GCC. Variorum does not support in-source builds. In most cases, the installation is as follows:

    $ cd variorum/
    $ mkdir build && mkdir install
    $ cd build/
    $ cmake -DCMAKE_INSTALL_PREFIX=../install ../src
    $ make
    $ make install

Note that Variorum depends on hwloc and JANSSON. The build system will first check for a specified local install of these dependencies, then it will check if it has been pre-installed. If it can find neither, it will clone and build the dependency from source (will fail on machines without internet access).

By default BUILD_DOCS=ON, so the build system looks for Doxygen and Sphinx. If you do not want to include these dependencies, simply toggle BUILD_DOCS=OFF in CMakeCache.txt or run the CMake command as follows:

$ cmake -DCMAKE_INSTALL_PREFIX=../install -DBUILD_DOCS=OFF ../src

CMake Host Config Files

We provide configuration files for specific systems to pre-populate the cache. This configuration file will define various compilers, and paths to hwloc installs. These can be used as follows:

    $ cd variorum/
    $ mkdir build && mkdir install
    $ cd build/
    $ cmake -C ../host-configs/your-local-configuration-file.cmake ../src
    $ make

Platform and Microarchitecture Support

Variorum has support for an increasing number of platforms and microarchitectures:

Platforms supported: Intel, IBM, NVIDIA, ARM

Supported Intel Microarchitectures:

0x2A (Sandy Bridge)
0x2D (Sandy Bridge)
0x3E (Ivy Bridge)
0x3E (Haswell)
0x4F (Broadwell)
0x9E (Kaby Lake)
0x55 (Skylake)

If you are unsure of your architecture number, check the "model" field in lscpu or /proc/cpuinfo (note that it will not be in hexadecimal).

Supported IBM Microrchitectures:


Supported Nvidia Microrchitectures:

Volta (requires [CUDA Toolkit[(

Supported ARM Microrchitectures:

Juno r2


From within the build directory, unit tests can be executed as follows:

    $ make test

Please report any failed tests to the project team at


For sample code, see the examples/ directory.

Support Additional Intel Platforms

  1. Under Intel/ directory, create a .h and .c header and source file for the respective platform. This will contain features specific to that platform, which may or may not exist in previous generations.
  2. Modify Intel/config_intel.c to set the function pointers for the respective platform.
  3. Include the new header file in Intel/config_architecture.h.

System Environment Requirements

This software has certain system requirements depending on what hardware you are running on.

Intel: Running this software on Intel platforms depends on the files /dev/cpu/*/msr being present with R/W permissions. Recent kernels require additional capabilities. We have found it easier to use our own msr-safe kernel module, but running as root (or going through the bother of adding the capabilities to the binaries) is another option.

IBM: Running this software on IBM platforms depends on the OPAL files being present with R/W permissions.

Nvidia: Running this software on Nvidia platforms depends on CUDA being loaded.

ARM: Running this software on ARM platforms depends on the Linux Hardware Monitoring (hwmon) subsystem for access to the monitoring and control interfaces.

Bug Tracker

Bugs and feature requests are being tracked on GitHub Issues.

Mailing List

If you have questions about Variorum, identify a bug, or have ideas about expanding the functionality of Variorum and are interested in contributing to its development, please send an email to our open mailing list at We are very interested in improving Variorum and exploring new use cases.

If you are interested in keeping up with Variorum or communicating with its developers and users, please join our open mailing list by sending an email as follows:

Subject: (leave this field empty)

Subscribe variorum-users


We welcome all kinds of contributions: new features, bug fixes, documentation, edits, etc.!

To contribute, make a pull request, with dev as the destination branch. We use GitHub Actions to run CI tests, and your branch must pass these tests before being merged.

See the CONTRIBUTING for more information.


Stephanie Brink,
Aniruddha Marathe,
Tapasya Patki,
Barry Rountree,

Please feel free to contact the developers with any questions or feedback.

We collect names of those who have contributed to Variorum over the years. See the current list in AUTHORS.


Variorum is released under the MIT license. For more details, see the LICENSE and NOTICE files.

SPDX-License-Identifier: MIT



Tool for hardware-level feature control



Code of conduct





No packages published


  • C++ 66.7%
  • C 19.0%
  • Python 8.8%
  • CMake 2.2%
  • Fortran 0.8%
  • HTML 0.7%
  • Other 1.8%