oomd is userspace Out-Of-Memory (OOM) killer for linux systems.
Out of memory killing has historically happened inside kernel space. On a memory overcommitted 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 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 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 livedlocked in kernelspace is minimized. In practice at Facebook, we've regularly seen 30 minute host lockups go away entirely.
Building and installing
Note that oomd requires PSI to function. This kernel feature has been landed upstream and is staged for the 4.20 release.
$ git clone https://github.com/facebookincubator/oomd $ cd oomd $ meson build && ninja -C build $ cd build && sudo ninja install
See docs/configuration.md for a high level overview and some examples.
See docs/core_plugins.md for a quick reference on core plugin capabilities.
oomd depends on gtest/gmock 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 for a tutorial.
Help / Discussion / Support
Join our #oomd channel on irc.freenode.net!
oomd is GPL 2 licensed, as found in the LICENSE file.