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modules/nixos/oom.nix — running out of memory now kills the offending process (with a desktop notification via systembus-notify) instead of freezing the desktop for minutes until the kernel OOM killer fires. earlyoom over systemd-oomd, deliberately: oomd kills whole cgroups, and a Hyprland session runs as ONE scope (nothing here spawns per-app systemd scopes, unlike GNOME) — under pressure oomd would take out the entire desktop to save it. earlyoom kills the single largest process before the thrash point. nixpkgs default-enables oomd in an inert state (no slices monitored); it is disabled outright so there is one owner. Session plumbing is --avoid-listed (unanchored — NixOS wrappers rename comm to .foo-wrapped); no --prefer tuning, largest-RSS selection already finds the hog. All mkDefault; opt out with services.earlyoom.enable = false (README note added). Verified: V0 (flake check) + V2 — new checks.oom-protection runNixOSTest, executed: a chunked allocator (686 MB peak, 1 GB VM) is SIGTERM'd by earlyoom in 0.1 s, a bystander unit survives (the process-level granularity the module exists for), and systemd-oomd is asserted inactive. 25 s runtime. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
43 lines
1.8 KiB
Nix
43 lines
1.8 KiB
Nix
# Memory-pressure protection: keep the desktop alive when RAM runs out.
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#
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# A workstation that compiles from source WILL exhaust memory eventually —
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# a big `nix build`, a runaway eval, a browser tab. The kernel's own OOM
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# killer acts only after the system has thrashed itself unresponsive
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# (often minutes of frozen desktop) and then picks by badness score,
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# which can land on the compositor.
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#
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# earlyoom over systemd-oomd — a deliberate choice: oomd kills whole
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# cgroups, and a Hyprland session runs as ONE scope (nothing spawns
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# per-app systemd scopes here, unlike GNOME), so under pressure oomd
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# would take out the entire desktop to save it. earlyoom kills a single
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# process (highest oom_score ≈ the hog) BEFORE the thrash point — "kill
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# the build step, keep the session". nixpkgs default-enables oomd in an
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# inert state (no slices monitored); it's disabled outright below so
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# there is exactly one owner of the OOM story.
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{ lib, ... }:
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{
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services.earlyoom = {
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enable = lib.mkDefault true;
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# Desktop toast when something is killed (relayed via
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# systembus-notify), so a vanished build/tab is explained rather
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# than mysterious.
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enableNotifications = lib.mkDefault true;
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# Never pick the session plumbing: losing the compositor or the lock
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# screen IS the outage this module exists to prevent (and killing a
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# Wayland session-lock client trips its go-to-a-tty failsafe). No
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# --prefer tuning: highest-memory selection already targets the hog.
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# Matched unanchored — NixOS wrappers rename comm to ".foo-wrapped".
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extraArgs = lib.mkDefault [
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"--avoid"
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"(Hyprland|hyprlock|greetd|waybar|pipewire|wireplumber|Xwayland|nix-daemon|systemd)"
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];
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};
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# One owner (see header): oomd ships default-on but inert; make the
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# earlyoom choice explicit and total.
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systemd.oomd.enable = lib.mkDefault false;
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}
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