Sweep was the original producer/consumer split that motivated the
generic Pipeline primitive (round 1, commit 500894e). Now that
Pipeline + Sink exist, sweep stops shipping its own bespoke
threading.
- New SweepSink: Sink<WorkItem> impl in src/disc/sweep.rs. Owns
WritebackFile + Mapfile + ProgressSnapshot back-channel. apply()
carries the file-write + mapfile.record per WorkItem; close()
drains writeback, fsyncs, flushes mapfile.
- Disc::sweep: constructs SweepSink, calls Pipeline::spawn_named
(so the consumer thread keeps showing up as
freemkv-sweep-consumer), sends WorkItems, calls pipe.finish().
The producer-side ReadCtx state machine, decrypt, set_speed,
halt — all unchanged.
- Pipeline gains spawn_named(name, depth, sink) so callers can
preserve identifiable thread names without the primitive baking
one in. Also adds Pipeline::try_send for the throttled
StatsRequest path that must not block the producer.
- Deleted src/disc/sweep_pipeline.rs entirely. WorkItem,
ProgressSnapshot, ConsumerSummary moved into disc/sweep.rs as
module-private types. WorkItem::Finish dropped — dropping the
channel is the end-of-stream signal Pipeline already uses.
Behaviour-preserving: the sweep algorithm, mapfile invariants,
back-pressure via channel depth (DEFAULT_PIPELINE_DEPTH = 4) all
match the 0.17.13 implementation. New synthetic regression test
(sweep_pipeline_full_good_100_batches) exercises ~100 batches of
clean reads end-to-end through the new Pipeline path and verifies
bytes_good and ISO file size.
See freemkv-private/memory/0_18_redesign.md.
Patch was strictly serial (per-sector recovery: read → seek+write
→ mapfile.record → next). Lifting the write+record onto a consumer
thread lets the drive issue the next per-sector retry while the
previous block's recovered bytes are being committed — small but
real win on damaged discs with many bad sectors, and uniform with
sweep's threading model.
- New PatchSink: Sink<PatchItem> impl in src/disc/patch.rs. Owns
WritebackFile + Mapfile. apply() seeks+writes recovered bytes
and records mapfile state per item; close() runs sync_all and
mapfile.flush.
- Channel depth: WRITE_THROUGH_DEPTH (1). Patch wants minimum
buffering — back-pressure should kick in immediately so the
drive's per-sector retry budget isn't ahead of the writer.
- Disc::patch: keeps every existing recovery decision on the
producer (reverse walk, damage-window skip, NOT_READY pauses,
bridge-degradation handling, wedge exit, range watchdog).
WritebackFile ownership moves to the sink.
Behaviour-preserving: per-sector single-shot read budget unchanged
(BU40N+Initio bridge wedge concern still respected); recovery
algorithm bit-identical.
See freemkv-private/memory/0_18_redesign.md.
Single contributor: MattJackson.
Generic bounded producer/consumer pipeline. The same shape applies to
sweep, patch, and mux today via three near-duplicate implementations
(or, in patch's and mux's case, no implementation at all). 0.18
collapses them onto one primitive. See
freemkv-private/memory/0_18_redesign.md for full context.
Single contributor: MattJackson.
The type's job is the bounded-cache writeback pipeline (sync_file_range
+ posix_fadvise(DONTNEED)) — not generic writing. The 0.17 name was
ambiguous; reading `Writer::new(file)` gave no hint about what was
special. New name makes the role obvious at every call site.
Adds `WritebackFile::create(path)` and `WritebackFile::open(path)`
constructors so callers don't have to assemble a `File` first.
No alias kept; this is a clean 0.18 rename. See
freemkv-private/memory/0_18_redesign.md.
Single contributor: MattJackson.
Pre-0.17.11 sweep ran strictly serialised: SCSI read → decrypt → seek
+ write → mapfile.record → next read. Drive idled for the post-read
work; throughput capped at the sum of both costs. On a healthy disc
that's ~7-12 ms read + ~5-15 ms write/record per 64 KB batch, limiting
sustained throughput to ~10-12 MB/s on the test bed (BU40N + UHD inner
zone), well below the ~14-16 MB/s drive ceiling.
Decouples them: producer thread (caller's) owns SectorReader +
read_error state + decrypt + set_speed + halt; consumer thread (one
spawn) owns Writer + Mapfile, receives WorkItem messages, applies
file write + mapfile record. Bounded mpsc::sync_channel(4) gives
natural back-pressure. While the consumer writes batch N, the
producer is already reading batch N+1 — steady-state throughput is
now bound by the slower of the two pipelines (drive on healthy
discs), not their sum.
Side effects:
- Bisect path now decrypts. Pre-0.17.11 the bisect inner loop wrote
raw cyphertext for single-sector recoveries on encrypted discs —
quiet correctness bug exercised only by batch-fail-then-
bisect-succeed on encrypted media. New producer-side decrypt
covers main + bisect success paths uniformly.
- All read_ctx state stays single-threaded on producer (damage
window, jump multiplier, etc.). No locking added.
- Mapfile remains single-writer on consumer. No locking.
- Halt latency: producer breaks loop, sends Finish, consumer drains
≤4 in-flight items + sync_all. ~1 batch (~12 ms) typical.
- BU40N + Initio bridge wedge concern unchanged: still single SCSI
command in flight, error-path timing identical, no new retries.
New module: src/disc/sweep_pipeline.rs (WorkItem, ProgressSnapshot,
ConsumerInputs, spawn_consumer, consumer_loop, helpers). Public API
unchanged — Disc::copy / CopyOptions / CopyResult identical.
Patch (Pass N) is NOT changed; it's bound by drive recovery time, not
the read/write serialisation.
Pass 1 sweep speed on a healthy disc previously dipped from ~15 MB/s
to ~1 MB/s every ~30 s on a host with default Linux dirty-page
settings. Empirical cause: the kernel's vm.dirty_ratio (~20% of RAM)
lets hundreds of MB of dirty pages accumulate, then bursts a flush at
99% disk utilisation that blocks app writes for ~1 s. Confirmed on
the BU40N test bed — dirty pages grew 112 → 563 MB between bursts;
lowering vm.dirty_bytes to 64 MB at the host sysctl level eliminated
the dips. Shipping the equivalent inside libfreemkv so users do not
need to tune the host kernel.
- New crate::io::Writer: drop-in File wrapper (impl Write + Seek).
Wraps a per-platform WritebackPipeline that on Linux schedules
sync_file_range(WRITE) + lagging sync_file_range(WAIT_AFTER) +
posix_fadvise(DONTNEED) in 32 MB chunks, bounding dirty cache at
~64 MB. macOS and Windows ship a no-op stub.
- Disc::sweep wraps its output File in Writer. Loop body unchanged.
- Module is purpose-built so any large sequential output (patch,
mux) can adopt the same wrapper as a one-line change later.
matthew