POWER-FINAL-30 — storage and decode performance pass

Status: SUPERSEDED, NEVER FLASHED ALONE (2026-10-14; contained in 31–34, installed as part of 33). Package out/y2linux-platform-v1-power-final-candidate-30/ (fallback = 29), receipts out/deep-sleep-final/build30-receipts/. BOOTIMG 7d95f85517e8744fc4c19c904e422decaade4cf9d7cd19004b186e4cb4c302b9, Y2ROOT 65467e6ab707cca8078a315ed31ed8f845cf11566151b37ac4910836fe2b82c2. Identity: build Y2LINUX-PLATFORM-V1-POWER-FINAL-30, kernel 6.18.56-y2linux-platform-v1-power-final-30, root 2026.08-platform-v1.60, release 1.0.0-platform-v1-power-final-candidate.30; Linux 6aa52e3, Reborn f08cf93. Contains 27–29.

Measured on 29 (boot cac3e209)

• Library database (317 tracks, 393 KB): query 2.7 ms, open+checks ≈56 ms, initial catalog ≈70 ms; warm rescan ≈200 ms.
• session.json durable save 7.9 ms (1.0 ms without fsync), on user actions only.
• Start-up scan 6975 ms, all of it cold SD directory reads: find /media/sd -type d 7955 ms cold / 38 ms warm for 118

  directories; one cold listing = ~200 unmerged 512-byte reads (~50 ms). The card itself: 85 MB/s sequential.

• Pre-mount fsck.exfat -n: 315 ms cold.
• FFmpeg pipeline (stage benchmark, % of one core at 1.2–1.3 GHz): MP3 320k decode 1.3 / pipeline 2.5; CD FLAC 0.9 /

  2.1; 24/96 FLAC 2.1 / 4.6; AAC 0.9 / 2.0; alimiter ≈ half of each pipeline.

What 30 changes

• Kernel: plugged directory readahead for exFAT (0068), FAT (0069) and the ext4 batch reader (0070): a cold

  directory cluster is one request instead of one per 512-byte sector. Read path only.

• noatime for SD cards of every format and the internal Y2Media partition (no access-time writes during playback).
• Reborn f08cf93: the limiter runs only when the DSP graph can raise a peak (active EQ or positive net gain); the

  default pipeline costs about half as much CPU and loud masters are no longer limited above −0.18 dBFS.

Tests

test_exfat_readahead (three plugged loops, noatime), test_platform_storage_tools/test_internal_media (mount options), Reborn limiter_only_when_the_graph_can_raise_a_peak (+ workspace tests, clippy, fmt). Kernel warnings unchanged (47). validate PASS, ELF 354, installed ARM, privacy, inventory, container suite 711 OK.

Owner checks after the flash

1. Normal boot; the start-up scan in Reborn's log (scan_completed elapsed_ms) should drop from ≈7000 ms to well

   under 1000 ms; cold find /media/sd -type d likewise.

2. Playback sounds unchanged (default settings: no limiter stage; EQ on: limiter present).
3. mount | grep -E "media/(sd|internal)" shows noatime.