The halt-aware send loop polled try_send on a 50 ms sleep slice when
the channel was full. That capped producer throughput at 1 / 50 ms =
20 frames/sec ≈ 1 MB/s at typical PES frame sizes — way below NFS,
let alone local SSD/NVMe. Multi-day diagnostic 2026-05-13/14 surfaced
it as the root cause of the 18 → 3 MB/s mux throughput regression on
0.21.x.
Replaced std::sync::mpsc::sync_channel with crossbeam_channel::bounded
and switched send_with_halt to send_timeout. Producer now BLOCKS on
consumer drain (kernel-wakeup) instead of polling — the timeout slice
(250 ms) only fires when the producer is waiting for stop signal
observation, never on the happy path.
Result: no throughput cap from this primitive at any medium speed.
Mux is bounded by actual storage / network bandwidth, not by our
channel implementation.
Same fix needs to land in autorip's mux.rs producer-side
sync_channel (separate sibling commit).
Documented in (internal)/memory/
feedback_send_with_halt_poll_throttle.md.
The 0.20.7 work lives downstream in autorip — process-level safety net
(hard watchdog 5-min mux escalation + std::process::exit, restart-loop
counter + auto-quarantine after 3 attempts, partial-state preservation,
failure_reason surfaced in /api/state).
Bumping libfreemkv to 0.20.7 keeps the 4 crates on the unified release
train per project docs.
Generalizes 0.20.5's hand-written wait_after_with_timeout into a
reusable primitive. After this change, every blocking syscall in the
recovery + mux paths is wrapped, so cooperative Halt has bounded
~250 ms latency reach even into kernel-owned thread states.
New module src/io/bounded.rs:
- BoundedError { Halted, Timeout, WorkerLost }
- bounded_syscall<F, R>(halt: Option<&Halt>, timeout, op) -> Result<R, BoundedError>
- Worker thread runs op; main thread recv_timeouts on a rendezvous
channel in 250 ms slices, polling halt between slices.
- Worker is intentionally leaked on timeout/halt — kernel reaps when
the syscall finally returns or at process exit. Calling thread is
NEVER trapped inside a kernel call.
- 6 unit tests cover the happy path + each error variant.
Refactored callsites:
- src/io/writeback/linux.rs::wait_after_with_timeout now delegates
to bounded_syscall. ~30 LOC of duplicated channel/thread plumbing
deleted. Same semantics, cleaner.
- src/io/writeback_file.rs::WritebackFile::sync_all now wraps the
final libc::fsync(fd) with bounded_syscall (60 s deadline). On
timeout: log error at target=mux and return Ok — kernel will flush
on close, best-effort but bounded. Covers FileSectorSink::finish,
PatchSink::close, SweepSink::close, and the mux MKV finalize path
(they all sync through WritebackFile).
What still hangs (deliberately not wrapped — too hot a path):
- File::write itself. Per-frame write on a wedged NFS could still
block; but back-pressure from a stuck consumer means the producer
notices within seconds, not minutes — different failure mode than
the WAIT_AFTER hang 0.20.5/0.20.6 fix.
Targets the recurring mux hang on NFS dest where the consumer thread
sits indefinitely inside libc::sync_file_range(SYNC_FILE_RANGE_WAIT_AFTER)
because the NFS server never returns a commit ack. The whole rip
wedges; halt is cooperative and can't reach inside a kernel syscall.
A. NFS detection at WritebackPipeline construction (fstatfs f_type ==
NFS_SUPER_MAGIC 0x6969). When NFS:
- Skip SYNC_FILE_RANGE_WAIT_AFTER entirely.
- Skip posix_fadvise(DONTNEED) — NFS client handles its own buffering.
- Still issue async SYNC_FILE_RANGE_WRITE (harmless hint).
Cannot hang on a syscall not made. fstatfs failure fails open (assume
local). Logged at info on construction so operators see which strategy
is active. The whole hang vector is removed for NFS deployments.
B. Hard timeout on WAIT_AFTER for non-NFS (defense in depth, since
even a degraded local disk could in principle hang the syscall).
Each WAIT_AFTER runs on a worker thread; main thread waits on a
sync_channel rendezvous with 30s deadline. On timeout: log error,
set per-pipeline 'degraded' Arc<AtomicBool>, downgrade to NFS-style
skip for the rest of the pipeline's life. Worker thread leaks
intentionally — it'll unwind when the syscall eventually returns or
the process exits. Converts indefinite freeze into 'log loud +
downgrade + keep ripping'.
C. Diagnostic logging for the 73%-of-this-movie reproduction:
- WritebackFile::seek logs every non-trivial seek (from, to, signed
delta) at target=mux so we can see if MkvMuxer seeks back before
a stall.
- WritebackPipeline::finalize logs the chunk being finalised before
any WAIT_AFTER call, so a hung chunk is identifiable by offset.
No new dependencies. macOS / Windows noop stubs unchanged. Net
+198 LOC libfreemkv (mostly writeback/linux.rs).
Four targeted changes to maximize mux throughput regardless of storage
backend (local SSD, local HDD, NFS, network share) and surface enough
log data to diagnose 'mux slow' reports without a re-rip:
1. POSIX_FADV_SEQUENTIAL on FileSectorSource::open (Linux only).
Widens the kernel readahead window for sequential ISO reads. One
syscall at open, free on every storage type.
2. POSIX_FADV_DONTNEED on the ISO read side after every 32 MiB chunk.
Mirrors the writeback DONTNEED that already runs on the write
side. Keeps the read-side page cache bounded during multi-GB ISO
reads — eliminates the OOM-pressure / eviction-storm risk on
long mux runs. Linux only; per-drop trace at target="mux".
3. WritebackFile::create_with_size_hint(path, size_bytes) calls
fallocate(FALLOC_FL_KEEP_SIZE) on Linux to pre-reserve extents
for the output. Reported file size stays 0 (writes grow it
naturally) but the on-disk extent allocation is contiguous —
reduces extent fragmentation for big sequential muxes. Wired
into mkv:// and m2ts:// output paths via DiscTitle::size_bytes.
No-op on macOS/Windows; old create() kept with #[allow(dead_code)]
for callers without a size hint.
4. Adaptive WRITEBACK_CHUNK_BYTES in the Linux writeback pipeline.
Tracks sync_file_range(WAIT_AFTER) elapsed_ms in a rolling
16-sample window. p95 > 200 ms → double chunk size (cap 256 MiB).
p95 < 20 ms → halve (floor 4 MiB). One algorithm, both
fast-storage (small chunks, responsive) and slow-storage (big
chunks, fewer commit round-trips) optimized. Per-chunk trace +
per-32-chunk debug snapshot + info-on-resize so an operator can
see where the autoscaler settled.
All four are universal — no storage-type detection, no env vars to
flip, no per-deploy tuning required. Total +201/-6 across four files.
WO-5 (partial): the patch backtrack inner loop ('while bt_pos <
backtrack_end' in disc/patch.rs) issues per-sector reads to fill the
gap created by a damage-window skip. A long backtrack span can run
minutes; without an inline halt poll, the outer halt only takes
effect when control returns to the per-range loop. Adds a halt poll
at the top of each iteration so cancellation propagates inside the
backtrack span.
Per-sector read failures inside the backtrack already drop through
to the main fail path; this only changes the cancellation latency
between an /api/stop call and the producer actually unwinding. Drops
worst-case unwind from 'whole backtrack span × per-sector recovery
timeout' (minutes) to 'one in-flight SCSI command' (seconds).
The broader Arc<AtomicBool> → Halt migration on CopyOptions /
SweepOptions / PatchOptions / Drive::halt and Pipeline::send halt-
awareness is deferred — separate cycle, larger API impact.
WO-3c: Delete dead non-NOT_READY retry block (~100 LOC). The block
declared retry_count = 0 inside the per-iteration Err arm, so the
'MAX_NON_NOT_READY_RETRIES=3' budget actually fired exactly once
(1s pause + 1 retry) before falling through to NonTrimmed. The
'exponential backoff: 2s, 4s, 8s' comment was wrong by construction.
Cross-pass NonTrimmed retry (each pass gives the same sectors another
shot) already covers the recovery case, and gives the drive minutes
between attempts instead of 1-8 seconds — empirically what stochastic
recovery on the BU40N actually needs.
WO-4 (targeted slice): Add wedge-family cooldown on HARDWARE_ERROR /
ILLEGAL_REQUEST senses. These are what the BU40N's firmware fast-fail
state returns; every subsequent read in that state comes back in
<100ms. Pre-fix patch hammered the drive: mark NonTrimmed, sleep 1s,
advance, hit next wedge, mark, sleep 1s — exactly the rapid-retry
cadence the firmware is sensitive to. Now a wedge-family sense triggers
WEDGE_FAMILY_COOLDOWN_SECS=30 cooldown (matches read_error.rs's
ZONE_ENTRY_COOLDOWN_SECS), and WEDGE_ABORT_THRESHOLD=16 consecutive
wedges aborts the pass for autorip eject+reload. Any non-wedge read
clears the counter.
Also drops the duplicate NonTrimmed dispatch (Mapfile::record is
idempotent so it wasn't a correctness bug, but it doubled per-failure
consumer work).
WO-2 (delete SectorReader trait):
- The 0.18 trait split into SectorSource (read-only) and SectorSink
(write-only) is final; the legacy SectorReader alias was a bridge.
- Renames every internal &mut dyn SectorReader (~25 sites) to
&mut dyn SectorSource. The trait method capacity() becomes
capacity_sectors() with a default of 0 (preserves SectorReader's
default-0 behavior).
- Deletes the SectorReader trait, its blanket-to-Source bridge, and
the FileSectorReader type alias. Adds explicit forwarding impls
for Box<dyn SectorSource> and &mut dyn SectorSource so generic
decorators like DecryptingSectorSource<S: SectorSource> compose.
WO-3a (extract Disc::patch):
- Moves Disc::patch (1230 lines) and bytes_bad_in_title from
disc/mod.rs into disc/patch.rs as a split inherent impl. Zero
behavior change — pure mechanical relocation. disc/mod.rs drops
from 3,945 to 2,714 LOC.
WO-6 (partial):
- Deletes src/labels/png_filenames.rs — was a 72-LOC stub with
detect() returning false, never wired into the PARSERS registry.
project docs doc drift fixes (audited 2026-05-13):
- JUMP_BASE_SECTORS: 256→1024 (64 MB base for UHD, not 8 MB)
- PASSN_DAMAGE_THRESHOLD_PCT: 12→6
- PASSN_SKIP_SECTORS_BASE: 64→32
- MAX_RANGE_SECS=180: replaced by proportional range_sectors × 25,
capped at RANGE_BUDGET_CAP_SECS=1800.
The 0.18 trait split into FrameSource (read-only) and FrameSink
(write-only) was an over-engineered API. Consumers don't think
"frame source backed by MKV" — they think "open MKV for reading".
The split paid a real API-complexity cost (two trait names, two
re-exports, dual impls per bidirectional type, deprecation bridge)
for one marginal property: compile-time direction-safety at the
trait-object boundary. The runtime error path on a wrong-direction
call (StreamReadOnly / StreamWriteOnly) is unambiguous and rare in
practice.
Deletions:
- pes::Stream is no longer #[deprecated]
- pes::FrameSource trait + its blanket-from-Stream bridge
- pes::FrameSink trait + the trampoline impls on every concrete type
- The compile-time-direction-safety test scaffolding
- Crate-root FrameSource / FrameSink re-exports
Additions:
- Stream is now Send-bounded (Stream: Send supertrait). Every
concrete impl was already Send-compliant — Box<dyn Read + Send>
and Box<dyn Write + Send> were already in place on the trait
objects MkvStream / M2tsStream / etc hold internally. Promoting
Send into the trait makes Box<dyn Stream> Send too, which lets
autorip drop its SendStream unsafe newtype.
The public API is now: one Stream trait, one concrete type per
format, two constructors (open/create or input/output). Bidirectional
types route through internal Mode { Read | Write } discriminants.
Net: -347 lines libfreemkv, -38 lines autorip, -5 lines freemkv.
v0.19.0 was tagged with a search-and-replace gone wrong:
rust-version, serde, and zip all had their version strings
replaced with "0.19.0". Edition 2024 rejected rust-version
0.19.0 (< 1.85), failing every CI build. No artifacts shipped
to crates.io.
Repair:
- rust-version: 0.19.0 → 1.86 (CI pin)
- serde: 0.19.0 → 1
- zip: 0.19.0 → 2
Also drops an unused start_lba binding in mux/disc.rs that
clippy 1.86 catches.
MattJackson