First pass counted one buffer per download; it is one per segment. 20
active downloads at the default 8 segments = 160 buffers, so at 20 tasks
the binding constraint is the global cap, not the per-segment default —
256 MiB and the "<=60 MB RSS / 20 downloads" target (line 125) cannot both
hold whatever the default is.
Floor (64 KiB) and ceiling (16 MiB) unchanged — the 256/64 unreachability
argument is stronger under per-segment accounting. Changes:
- default 1 MiB (was 2): with the cap below, 32 live segments x 1 MiB =
32 MiB buffers -> ~45-50 MiB RSS, line 125 holds with margin.
- NEW maxActiveSegments (default 32): a global concurrent-segment cap is
the actual mechanism that bounds "20 active downloads"; docs/01 §2
implies it, docs/04 never states it. Without it no buffer policy hits
60 MB.
- maxTotalBufferBytes 128 MiB (was 256) and it must be ADDED to the
contract — currently absent, so the clamp CORE implements has no wire
representation and Options can't show/set it. Folded into B2a.
- line 125: keep 60 MB "given maxActiveSegments=32 and default buffers",
or explicitly raise to 120 MB — ADR records which. Flagged that
changing it is a defensible outcome CORE owns, not a number that
quietly loses.
- bufferBytes bounds are in FOUR schema files, not three:
Settings.schema.json connection.bufferBytes also has 4096-8388608.
Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01HPPSGhiArbvQgwC2DNiURS
buffer-sizing.md: the frozen 4 KiB–8 MiB and docs/04's 64 KiB–64 MiB both
miss. Recommend 64 KiB – 16 MiB, default 2 MiB, max_total_buffer_bytes
unchanged at 256 MiB:
- 4 KiB floor is smaller than one libcurl write callback -> a syscall per
chunk; 64 KiB is the smallest floor that coalesces.
- throughput vs write size is flat past ~8 MiB on NVMe; 8–16 MiB is
disk-stall absorption headroom for the fast-pipe/slow-disk case; 64 MiB
is cache pressure for zero gain.
- 32 segments x 64 MiB = 2 GiB vs the 256 MiB cap means the docs/04 max is
unreachable past 4 total active segments — a misleading Options value.
16 MiB is reachable for single-/light-multitask and clamps to 8 MiB
under heavy parallelism, which is correct.
- default 4 MiB x 20 downloads = 80 MiB, busting the "<=60 MB RSS / 20
downloads" DoD; 2 MiB fits. Filed as request B4.
proto-requests-m1.md: B3 endByte accepted as inclusive (HTTP Range
semantics, no curl-boundary off-by-one); [start,end) ask withdrawn; stage
6 designed against inclusive. New B3a: the Content-Length: 0 whole-file
case needs a representable zero-length segment — min_segment_bytes means
CORE never makes empty segments mid-download, so it's only the degenerate
case; mild preference for startByte+length over an endByte=startByte-1
sentinel.
Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01HPPSGhiArbvQgwC2DNiURS
samiandClaude Sonnet 5