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hardware: tighten mq-deadline read_expire for jellyfin coexistence

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Simon Gardling
2026-04-17 19:47:20 -04:00
parent cebdd3ea96
commit 9ea45d4558
1 changed files with 10 additions and 4 deletions
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14
modules/hardware.nix
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@@ -12,7 +12,7 @@ let
parent=''${1%%[0-9]*} parent=''${1%%[0-9]*}
dev="/sys/block/$parent" dev="/sys/block/$parent"
[ -d "$dev/queue/iosched" ] || exit 0 [ -d "$dev/queue/iosched" ] || exit 0
echo 15000 > "$dev/queue/iosched/read_expire" echo 500 > "$dev/queue/iosched/read_expire"
echo 15000 > "$dev/queue/iosched/write_expire" echo 15000 > "$dev/queue/iosched/write_expire"
echo 128 > "$dev/queue/iosched/fifo_batch" echo 128 > "$dev/queue/iosched/fifo_batch"
echo 16 > "$dev/queue/iosched/writes_starved" echo 16 > "$dev/queue/iosched/writes_starved"
@@ -36,11 +36,17 @@ in
hardware.cpu.amd.updateMicrocode = true; hardware.cpu.amd.updateMicrocode = true;
hardware.enableRedistributableFirmware = true; hardware.enableRedistributableFirmware = true;
# HDD I/O tuning for torrent seeding workload (high-concurrency random reads). # HDD I/O tuning for torrent seeding workload (high-concurrency random reads)
# sharing the pool with latency-sensitive sequential reads (Jellyfin playback).
# #
# mq-deadline sorts requests into elevator sweeps, reducing seek distance. # mq-deadline sorts requests into elevator sweeps, reducing seek distance.
# Aggressive deadlines (15s) let the scheduler accumulate more ops before dispatching, # read_expire=500ms keeps reads bounded so a Jellyfin segment can't queue for
# maximizing coalescence — latency is irrelevant since torrent peers tolerate 30-60s. # seconds behind a torrent burst; write_expire=15s lets the scheduler batch
# writes for coalescence (torrent writes are async and tolerate delay).
# The bulk of read coalescence already happens above the scheduler via ZFS
# aggregation (zfs_vdev_aggregation_limit=4M, read_gap_limit=128K,
# async_read_max=32), so the scheduler deadline only needs to be large enough
# to keep the elevator sweep coherent -- 500ms is plenty on rotational disks.
# fifo_batch=128 keeps sweeps long; writes_starved=16 heavily favors reads. # fifo_batch=128 keeps sweeps long; writes_starved=16 heavily favors reads.
# 4 MiB readahead matches libtorrent piece extent affinity for sequential prefetch. # 4 MiB readahead matches libtorrent piece extent affinity for sequential prefetch.
# #