1ea910f662
Nothing stood between "memory is tight" and "processes die at random": the kernel OOM killer only fires after an allocation has already failed, so a machine under pressure thrashes in reclaim until something breaks somewhere fatal — seen in practice as Hyprland taking SIGBUS mid-memcpy from a client shm pool that memory pressure was tearing down. Enable systemd-oomd, which keys on PSI stall time rather than free pages, and mark app.slice — and only app.slice — as its kill candidate. Hyprland runs in session.slice, so the compositor is structurally ineligible as a victim: oomd takes the app that caused the pressure and the session survives. Thresholds (50% stall over 20s, Fedora's desktop defaults) live in an oomd.conf.d drop-in; candidacy ships as a vendor drop-in under /usr/lib/systemd/user so existing users get it on package upgrade with no per-user seeding. New installs enable the daemon from enable-services.sh; a migration covers existing ones, restarting an already-running oomd so it doesn't keep stale thresholds until reboot. Deliberately not earlyoom: it triggers only when free RAM and free swap are both under threshold, so Omarchy's large, mostly-idle swapfiles keep it asleep through exactly this failure. Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
22 lines
1.2 KiB
Plaintext
22 lines
1.2 KiB
Plaintext
# Without an OOM daemon there is nothing between "memory is tight" and
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# "processes start dying at random". The kernel OOM killer only fires once an
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# allocation has already failed outright, which is far too late for the
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# desktop: the machine thrashes in reclaim until something fails somewhere
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# fatal. Seen in practice as Hyprland taking SIGBUS mid-memcpy from a Wayland
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# client's shm pool, because the client was being torn down by the same memory
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# pressure. One app misbehaving should not cost the whole session.
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#
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# systemd-oomd keys on PSI stall time rather than on free pages, so it acts
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# while the machine is still thrashing instead of after an allocation failed.
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# Deliberately not earlyoom: that fires only when free RAM *and* free swap are
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# both under threshold, so a large, mostly-unused swapfile keeps it asleep
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# through exactly this failure.
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#
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# 50% means half of a ten-second window was spent stalled on memory reclaim.
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# Held for 20s straight, the desktop is already unusable and losing one app is
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# the cheaper outcome. Which cgroups are eligible is set separately, in
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# /usr/lib/systemd/user/app.slice.d/10-oomd.conf.
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[OOM]
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DefaultMemoryPressureDurationSec=20s
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DefaultMemoryPressureLimit=50%
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