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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: AMD, ARM, IBM, Intel, NVIDIA

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 AMD Microrchitectures:

Family 19h, Models 0~Fh and 30h ~ 3Fh (EPYC Milan) 

Supported ARM Microrchitectures:

Juno r2

Supported IBM Microrchitectures:


Supported Intel Microarchitectures:

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

Supported Nvidia Microrchitectures:

Volta (requires [CUDA Toolkit[(


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.

System Environment Requirements

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

AMD: Running this software on AMD platforms depends on the AMD Energy Driver, AMD HSMP driver, and AMD E-SMI library being available with the correct permissions.

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

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

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.

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

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