nix.daemonIOSchedClass

Nix daemon process I/O scheduling class. This class propagates to build processes. best-effort is the default class for regular tasks. The idle class is for extremely low-priority tasks that should only perform I/O when no other task does.

Please note that while using the idle scheduling class can improve responsiveness of a system performing expensive builds, it might also slow down or starve crucial configuration updates during load.

idle may therefore be a sensible class for systems that experience only intermittent phases of high I/O load, such as desktop or portable computers used interactively. Other systems should use the best-effort class.