37 lines
1.2 KiB
Nix
37 lines
1.2 KiB
Nix
{ config, lib, pkgs, modulesPath, ... }:
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{
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config = lib.mkIf config.boot.zfs.enabled {
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# Set ARC max to 5% of physical RAM at boot
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systemd.services."zfs-arc-limit" = {
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description = "Set ZFS ARC max to 5% of physical RAM";
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# Ensure the module is loaded before we write to /sys
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after = [ "systemd-modules-load.service" ];
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# Run early, but it’s fine if ZFS has already imported; the limit still applies
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wantedBy = [ "multi-user.target" ];
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path = [ pkgs.gawk ];
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script = ''
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set -euo pipefail
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# Total RAM in kB
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mem_kb=$(awk '/MemTotal:/ {print $2}' /proc/meminfo)
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echo "DEBUG: Total RAM: $mem_kb kB"
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# 5%, in bytes
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arc_max_bytes=$(( mem_kb * 1024 / 100 * 5 ))
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echo "DEBUG: Setting ZFS ARC max to: $arc_max_bytes bytes"
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param="/sys/module/zfs/parameters/zfs_arc_max"
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if [ -w "$param" ]; then
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echo "DEBUG: Writing to $param"
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echo "$arc_max_bytes" > "$param"
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echo "DEBUG: ZFS ARC max successfully set"
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else
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echo "WARN: $param not writable; is the zfs module loaded?" >&2
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exit 0
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fi
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'';
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serviceConfig = {
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Type = "oneshot";
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RemainAfterExit = true;
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};
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};
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};
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} |