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https://github.com/facebookincubator/oomd

A userspace out-of-memory killer
https://github.com/facebookincubator/oomd

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A userspace out-of-memory killer

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README 

        
# oomd



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oomd is *userspace* Out-Of-Memory (OOM) killer for linux systems.



## Background



Out of memory killing has historically happened inside kernel space. On a

[memory overcommitted][0] linux system, malloc(2) and friends usually never

fail. However, if an application dereferences the returned pointer and the

system has run out of physical memory, the linux kernel is forced to take extreme

measures, up to and including killing processes. This is sometimes a slow and

painful process because the kernel can spend an unbounded amount of time

swapping in and out pages and evicting the page cache. Furthermore,

[configuring policy][1] is not very flexible while being somewhat complicated.



oomd aims to solve this problem in userspace. oomd leverages PSI and cgroupv2

to monitor a system holistically. oomd then takes corrective action in

userspace before an OOM occurs in kernel space. Corrective action is configured

via a flexible plugin system, in which custom code can be written. By default,

this involves killing offending processes. This enables an unparalleled level

of flexibility where each workload can have custom protection rules.

Furthermore, time spent livelocked in kernelspace is minimized. In practice at

Facebook, we've regularly seen 30 minute host lockups go away entirely.



## Installing on Debian 11+ or Ubuntu 20.04+



`# apt install oomd`



## Installing from RPMs on Fedora



oomd is packaged in Fedora as of Fedora 32 and can be installed with:



    $ sudo dnf install oomd



Finally, enable and start it with:



    $ sudo systemctl enable --now oomd.service



## Building from source



Note that oomd requires PSI to function. This kernel feature has been merged

into the 4.20 release.



oomd currently depends on [meson][2] and [jsoncpp][4]. [libsystemd][6] is an

optional dependency.



oomd also requires GCC 8+ or clang 6+. Other compilers have not been tested.



    $ git clone https://github.com/facebookincubator/oomd

    $ cd oomd/oomd

    $ meson build && ninja -C build

    $ cd build && sudo ninja install



## Configuration



See [docs/configuration.md](docs/configuration.md) for a high level overview

and some examples.



See [docs/core_plugins.md](docs/core_plugins.md) for a quick reference on

core plugin capabilities.



See [docs/production_setup.md](docs/production_setup.md) for guidelines on

how oomd should be set up in a production environment.



## Running tests



oomd depends on [gtest/gmock][5] to run tests. Installing gtest/gmock from master

is preferred.



If meson detects gtest/gmock is installed, meson will generate build rules for tests.



    $ cd oomd

    $ rm -rf build

    $ meson build && ninja test -C build



## Writing custom plugins



It is both possible and encouraged to write custom plugins. The codebase is designed

to make writing plugins as easy as possible.



See [docs/writing_a_plugin.md](docs/writing_a_plugin.md) for a tutorial.



## Help / Discussion / Support



Join our **#oomd** channel on irc.freenode.net!



## License



oomd is GPL 2 licensed, as found in the [LICENSE](LICENSE) file.



[0]: https://www.kernel.org/doc/Documentation/vm/overcommit-accounting

[1]: https://lwn.net/Articles/317814/

[2]: http://mesonbuild.com/

[4]: https://github.com/open-source-parsers/jsoncpp

[5]: https://github.com/google/googletest

[6]: https://github.com/systemd/systemd/tree/master/src/libsystemd/