Open sourcing oomd, a new approach to handling OOMs

Over on the Facebook code site, Daniel Xu announces the release of oomd under the GPLv2. Oomd is a user-space "out of memory" killer that was mentioned in our recent article on the block I/O latency controller and it uses the pressure stall information covered in an even more recent article."Oomd constantly monitors PSI [Pressure Stall Information] metrics to assess whether a system is under unrecoverable load. PSI alone is insufficient, so oomd also monitors the system holistically. This is in contrast to Linux's OOM killer, which focuses primarily on the kernel's concerns. Since OOM detection criteria can vary depending on workload, the plugin system supports customization to both the detection and process kill strategies.Thanks to this new ability to monitor key system resource indicators, oomd is able to take corrective action in userspace before a system-wide OOM occurs. Corrective action is configured via a flexible plugin system that is capable of executing custom code. Thus, in addition to oomd's default process SIGKILL behavior, application developers can customize their plugin with alternate strategies, such as sending a 'back off' RPC to the main workload or dumping system logs to a remote service."