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Put the ring on the 68000, and find the disc stops whenever the player is not asking

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ROADMAP P5. The loader moved in session 21 and the frame clock in 22; the ring
producer was the last policy living outside the machine. src/player/ring.i does
`aligned` placement, the descriptor ring, a prefill, 51.2's slack rule and a
seek, and the host keeps only the transport.

It needed a container change. `aligned` asks whether the next record fits
before the end of the ring -- a length asked BEFORE the record is fetched -- and
every reader in this tree answered that by walking the frame stream, which is
exactly what a player streaming off a disc cannot do. DLX4 carries nframes u16
record lengths in the scene header. Frame payloads are byte-identical to the
DLX3 encode, so no fitted constant moves; the scene header goes 5,920 to 6,164 B.

The producer reproduces the host's tiling exactly: 18 wraps, 14.7 KB mean hole,
pixel-exact, a third independent implementation of the same policy.

What it exposed is bigger than the item. A channel only moves bytes while it has
a request and only the CPU can issue one, so the disc stands still between
records by an amount the PLAYER sets, not the medium -- and no host-filled run
could see it. At 488 KB/s in a 256 KB ring a one-deep request queue gives away
6.8% of the pipe and underruns 59 of 120 frames; two-deep gives away 3.4% and
underruns none. The container's whole surplus over the wire is 8.7%, so the
player's own loop was spending most of the slack a branch point saves up.
Prefill is the weaker lever: six records of it still leaves 24 underruns.

Three silent bugs are recorded in FINDINGS 55.7 -- all produced wrong pixels or
a desync rather than a fault -- plus a rig one: MAME renders a screen line by
line, so snapshotting the frame the decoder finished in captures a tear that
reads exactly like a decoder bug.

check.sh gains the machine-owned ring and a seek with the decode after it.
decode.bin is unchanged at 1,296 B and a host-filled run executes none of the
new code, so every FINDINGS 49/51 figure stands. ALL GREEN before and after.

Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6
This commit is contained in:
prosolis
2026-08-24 21:45:05 -07:00
parent c419251266
commit 2676f3b835
16 changed files with 1880 additions and 38 deletions
Download Patch File Download Diff File Expand all files Collapse all files
tools/bench/check.sh
+68
View File
@@ -338,4 +338,72 @@ grep -q "^OK" tmp/selfpace_check.log || {
echo " frames start; if it changed WHAT they draw, the interrupt is"
echo " corrupting decoder state."; tail -4 tmp/selfpace_check.log; exit 1; }
echo "--- session 23: the 68000 fills its own ring (FINDINGS 55) ---"
# ROADMAP P5. Until now the RING was filled by tools/bench/stream.lua: the host
# held the record index, chose where each record went, wrote the descriptor and
# advertised it. A player has no host. src/player/ring.i does all of that on the
# 68000, out of the DLX4 record index in the scene header, and this script keeps
# only the part that is not the CPU's -- a transport that answers one request at
# a time at a modelled rate.
#
# WHAT IS GATED:
# * pixel-exact, which is the only test that can see a wrong placement: the
# block loop reads with a monotonically increasing a0 and no bounds check,
# so a record placed over one the decoder has not finished corrupts pixels
# rather than faulting (49.2);
# * the host AUDITS every placement against its own index and its own list of
# live records, and refuses the run on the first disagreement;
# * the wrap policy still produces the SAME 18 wraps and 14.7 KB mean hole the
# host producer produced in FINDINGS 49.4 -- a third independent
# implementation of `aligned` landing on the same tiling;
# * zero underruns at a two-deep request queue, which is the finding: a
# one-deep queue leaves the channel idle between records and underran 59 of
# 120 frames on this same container and rate.
DLX_PACE=2 DLX_RINGOWN=1 DLX_QDEPTH=2 bash tools/bench/pace_run.sh 256 488 \
> tmp/ringown_check.log 2>&1 || {
echo "FAIL: the machine-owned ring pass did not complete."
tail -10 tmp/ringown_check.log; exit 1; }
grep -aE "MACHINE-OWNED|PREFILL:|CHANNEL IDLE|UNDERRUNS|SEEK SLACK" tmp/ringown_check.log \
| sed "s/\[STR\] / /"
grep -q "MISPLACED" tmp/ringown_check.log && {
echo "FAIL: the 68000 placed a record over one the decoder still owned."
exit 1; }
grep -q "UNDERRUNS: 0/120" tmp/ringown_check.log || {
echo "FAIL: the machine-owned ring underran at a two-deep queue. That is the"
echo " configuration FINDINGS 55 says keeps the channel busy; if it no"
echo " longer does, the poll site in src/player/stream.s moved."
exit 1; }
grep -q "ring: 18 wraps" tmp/ringown_check.log || {
echo "FAIL: the machine's own \`aligned\` no longer tiles this container the"
echo " way FINDINGS 49.4's host producer did (18 wraps). The policy is"
echo " meant to be the SAME policy in a different place."
exit 1; }
grep -q "^OK" tmp/ringown_check.log || {
echo "FAIL: the machine-owned ring pass was not pixel-exact -- a record was"
echo " placed or described wrongly."; tail -4 tmp/ringown_check.log
exit 1; }
echo "--- session 23: a seek, and the decode after it (FINDINGS 55) ---"
# The branch point rehearsed. A second pass over the scene begins with a real
# seek in src/player/ring.i: the channel is waited quiet, the ring is declared
# empty, the disc address of record 0 comes out of the index rather than from a
# walk, and the whole lookahead 51.3 says takes seconds of play to accumulate is
# thrown away and rebuilt from the prefill. What is gated afterwards is the one
# thing that can see a wrong seek: the last frame of the SECOND pass has to be
# pixel-exact, and a SKIP block is a claim about the previous frame, so it is
# only right if every frame after the seek was.
DLX_PACE=2 DLX_RINGOWN=1 DLX_QDEPTH=2 DLX_ITER=2 \
bash tools/bench/pace_run.sh 256 488 > tmp/ringseek_check.log 2>&1 || {
echo "FAIL: the seek pass did not complete."; tail -10 tmp/ringseek_check.log
exit 1; }
grep -aE "SEEK PASS|CHANNEL IDLE|UNDERRUNS" tmp/ringseek_check.log | sed "s/\[STR\] / /"
grep -q "SEEK PASS 2" tmp/ringseek_check.log || {
echo "FAIL: no second pass -- the seek never happened, so this gated nothing."
exit 1; }
grep -q "UNDERRUNS: 0/120" tmp/ringseek_check.log || {
echo "FAIL: the pass after the seek underran."; exit 1; }
grep -q "^OK" tmp/ringseek_check.log || {
echo "FAIL: the decode after the seek was not pixel-exact."
tail -4 tmp/ringseek_check.log; exit 1; }
echo "ALL GREEN"
tools/bench/pace_run.sh
+25 -1
View File
@@ -16,6 +16,18 @@
# kbps 0 = unlimited pipe. There is no default rate anywhere in this tree
# (FINDINGS 50) and there is none here either.
#
# DLX_RINGOWN=1 hands the RING to the 68000 as well (ROADMAP P5,
# src/player/ring.i): this script's Lua stops placing records and becomes a
# transport that answers one request at a time. DLX_PREFILL_FR is then the
# prefill policy, in whole records. It needs a DLX4 container, because the
# machine cannot learn a record's length by walking a stream it has not fetched.
#
# DLX_ITER=2 runs the scene TWICE, which under DLX_RINGOWN means a real seek
# between the passes: the channel goes quiet, the ring is declared empty and the
# whole accumulated lookahead is thrown away and rebuilt from the prefill. It
# needs DLX_PACE=2, because rebasing the frame clock across a pass is the
# machine's to do and a host-written tick would carry on counting.
#
# DLX_PACE selects WHO KEEPS THE TIME: 1 (default) is the host writing the tick,
# 2 is the 68000 writing it off the CRTC's V-DISP (ROADMAP P3, FINDINGS 54).
# Everything else about the run is identical, which is the whole point -- the
@@ -27,11 +39,21 @@ RING=${1:?ring KB}; KBPS=${2:?pipe KB/s, or 0 for unlimited}
CUT_AT=$3; CUT_FR=${4:-1}
DLX=${DLX:-tmp/rc_fr_singe_scsi_span.dlx}
PACE=${DLX_PACE:-1}
OWN=${DLX_RINGOWN:-0}
ITERS=${DLX_ITER:-1}
if [ "$OWN" = 1 ] && [ "$ITERS" != 1 ] && [ "$PACE" != 2 ]; then
echo "DLX_ITER>1 needs DLX_PACE=2: the frame clock is rebased per pass by"
echo "src/player/stream.s, and a host-written tick would go on counting"
echo "through the seek and open every slot of the second pass at once."
exit 2
fi
TAG="r${RING}_k${KBPS}${CUT_AT:+_cut${CUT_AT}x${CUT_FR}}"
# The default tag is left ALONE when the host keeps the time: tools/bench/
# pace_sweep.sh reads tmp/pace_r<ring>_k<kbps>.log by name, and renaming the
# host-paced logs would break a sweep that has nothing to do with this option.
if [ "$PACE" != 1 ]; then TAG="${TAG}_p$PACE"; fi
if [ "$OWN" = 1 ]; then TAG="${TAG}_own"; fi
if [ "$ITERS" != 1 ]; then TAG="${TAG}_x$ITERS"; fi
tools/vasm/vasmm68k_mot -Fbin -o tmp/stream.bin src/player/stream.s > /dev/null
[ -f tmp/stream_disk.bin ] || python3 tools/bench/prep_stream.py "$DLX" > tmp/prep_stream.log
@@ -41,6 +63,8 @@ mkdir -p "tmp/snap_pace_$TAG"; rm -f "tmp/snap_pace_$TAG/x68000"/*.png
# command and the run dies with "SDL_VIDEODRIVER=dummy: command not found".
CUTENV=(); [ -n "$CUT_AT" ] && CUTENV=(DLX_CUT_AT="$CUT_AT" DLX_CUT_FR="$CUT_FR")
( cd tmp && env DLX_PACE=$PACE DLX_RING_KB=$RING DLX_STREAM_KBPS=$KBPS \
DLX_RINGOWN=$OWN DLX_ITER=$ITERS \
${DLX_PREFILL_FR:+DLX_PREFILL_FR=$DLX_PREFILL_FR} \
"${CUTENV[@]}" DLX_SLACK_CSV="slack_$TAG.csv" \
SDL_VIDEODRIVER=dummy stdbuf -oL timeout -k 5 900 \
mame x68000 -bios ipl10 -ramsize 2M -video soft -window -sound none \
@@ -53,6 +77,6 @@ grep -q "snapshot taken" "tmp/pace_$TAG.log" || {
echo "FAIL($TAG): no snapshot marker -- the pass did not complete."
tail -6 "tmp/pace_$TAG.log"; exit 1; }
echo "=== $TAG"
grep -aE "decoder (SELF-PACED|PACED|FREE)|FRAME CLOCK|ring: |UNDERRUNS|NO IDLE|SEEK SLACK|RING-BOUND|RATE-BOUND|BUILD TIME|PIPE CUT|DEADLINE|REQUIRED" \
grep -aE "decoder (SELF-PACED|PACED|FREE)|FRAME CLOCK|ring: |UNDERRUNS|NO IDLE|SEEK SLACK|RING-BOUND|RATE-BOUND|BUILD TIME|PIPE CUT|DEADLINE|REQUIRED|MACHINE-OWNED|PREFILL:|CHANNEL IDLE|MISPLACED|SEEK PASS" \
"tmp/pace_$TAG.log" | sed "s/\[STR\] / /"
python3 tools/bench/verify_decode.py "$DLX" --snap "tmp/snap_pace_$TAG" | tail -2
tools/bench/prep_load.py
+1 -1
View File
@@ -34,7 +34,7 @@ a = ap.parse_args()
d = DLX(a.container)
if d.version < 3:
sys.exit(f"{a.container} is DLX{d.version}: load.i checks for the 'DLX3' magic")
sys.exit(f"{a.container} is DLX{d.version}: load.i wants DLX3 or DLX4")
if d.idx_bytes != 1:
sys.exit("2-byte codebook indices: load.i expands one source byte per pixel")
tools/bench/prep_stream.py
+29
View File
@@ -18,6 +18,10 @@ This writes three files instead:
filesystem and feeds it into a bounded ring, so the emulated
machine's RAM stops bounding how much of a window can be
tested. A stock 2 MB machine can now run all 120 frames.
<out>_idx.bin the DLX4 RECORD INDEX, nframes u16 big-endian, straight out
of the container's scene header. This is what the 68000
producer reads (src/player/ring.i); it is not derived here,
because deriving it is precisely what a player cannot do.
<out>_meta.lua geometry, and the record index.
THE RECORD INDEX IS NOT A CONVENIENCE. src/player/stream.s takes each frame's
@@ -71,12 +75,34 @@ for (o, n) in d.frames:
index.append((start, len(disk) - start))
open(a.out + "_disk.bin", "wb").write(bytes(disk))
# THE CONTAINER'S OWN INDEX, and it is checked against this layout rather than
# regenerated from it. src/player/ring.i walks the disk with a running sum of
# these lengths and never reads a record's length word before fetching it, so a
# container index that disagreed with the disk image by one byte would place
# every later record at the wrong address -- and the block loop reads without a
# bounds check (49.2), so the symptom would be wrong pixels, not a fault.
if d.has_index:
want = [ln // 4 for _, ln in index]
if d.index != want:
bad = next(i for i in range(len(want)) if d.index[i] != want[i])
sys.exit(f"{a.container}: the DLX4 index disagrees with this disk "
f"layout at record {bad}: {d.index[bad]} vs {want[bad]} "
f"longwords")
open(a.out + "_idx.bin", "wb").write(
b"".join(q.to_bytes(2, "big") for q in d.index))
else:
if os.path.exists(a.out + "_idx.bin"):
os.remove(a.out + "_idx.bin") # a stale index is worse than none
rec = np.array([n for _, n in index])
with open(a.out + "_meta.lua", "w") as fh:
fh.write("-- generated by tools/bench/prep_stream.py -- do not edit\nreturn {\n")
fh.write(f" W={d.W}, H={d.H}, fps={d.fps}, nframes={d.nframes}, dark={dark},\n")
fh.write(f" cb1_len={cb1.nbytes}, cb4_len={cb4.nbytes}, pal_len={palb.nbytes},\n")
fh.write(f" disk_len={len(disk)}, maxrec={int(rec.max())},\n")
fh.write(f" dlx_version={d.version}, "
f"has_index={'true' if d.has_index else 'false'},\n")
fh.write(f" padrec={{{','.join(str(ln) for _, ln in index)}}},\n")
fh.write(" index={\n")
for off, ln in index:
fh.write(f" {{off={off}, len={ln}}},\n")
@@ -89,5 +115,8 @@ print(f" disk image {len(disk):,} B -> {a.out}_disk.bin "
f"(records: min {rec.min():,} median {int(np.median(rec)):,} "
f"max {rec.max():,})")
print(f" wire rate {rec.mean()*d.fps/1024:.1f} KB/s video at {d.fps} fps")
if d.has_index:
print(f" DLX4 record index: {2*d.nframes:,} B of scene header, and it "
f"agrees with the disk image on all {d.nframes} records")
print(f" A ring must hold one whole record contiguously: >= {rec.max():,} B "
f"({rec.max()/1024:.1f} KB) before any policy or prefill.")
tools/bench/stream.lua
+421 -17
View File
@@ -52,7 +52,18 @@
-- no provenance that was never a bus measurement at all
-- (FINDINGS 42.1). A default is how a folklore number ends up
-- silently underneath a table nobody restates it in.
-- DLX_PREFILL_KB bytes to deliver before releasing the CPU (default 0)
-- DLX_PREFILL_KB bytes to deliver before releasing the CPU (default 0).
-- Host-owned ring only: with DLX_RINGOWN the machine does
-- its own prefill and DLX_PREFILL_FR is the knob.
-- DLX_RINGOWN 1 = THE 68000 OWNS THE RING (ROADMAP P5,
-- src/player/ring.i). This script stops placing records and
-- becomes a TRANSPORT: it answers one request at a time,
-- delivering XF_LEN bytes from XF_OFF to XF_DST in
-- len/rate seconds, and the machine decides which record,
-- where in the ring, and when. It also AUDITS every
-- placement the machine makes against its own index.
-- DLX_PREFILL_FR whole records the machine's prefill waits for before it
-- releases the decoder (default 2; see ring_prefill)
-- DLX_PACE 1 = hold the decoder to META.fps, with the HOST writing
-- the tick (default 0 = free-run)
-- 2 = hold it to META.fps with the 68000 writing its own
@@ -101,6 +112,26 @@ local STALLS, SPINS, DESC = 0x1802C, 0x18030, 0x18100
local PACE, PACEON, CLKON = 0x18034, 0x18038, 0x1803C
local CLK_VDISP, CLK_FPS, CLK_ERR = 0x18064, 0x18068, 0x1806C
local LATEFR, LATEMAX, LATE1ST = 0x18080, 0x18084, 0x18088
-- src/player/ring.i. The transport mailbox, then the producer's state and its
-- instruments. Nothing below 0x18300 changed: the decoder's handshake with the
-- ring (FR_HEAD/FR_TAIL/DESC) is the same one FINDINGS 49 and 51 measured, which
-- is what makes a self-filled run a test of ring.i and not of a new rig.
local XF_SLOT, XF_SLSZ = 0x18300, 16
local XF_GO, XF_ACK, XF_QD = 0x18320, 0x18324, 0x18328
local A_RINGOWN, A_RNG_B, A_RNG_SZ, A_IDX_B = 0x1832C, 0x18330, 0x18334, 0x18338
local A_RQ_NEXT, A_WCUR, A_RCUR = 0x1833C, 0x18340, 0x18344
local A_NHOLE, A_NHOLEB, A_NFULL = 0x18354, 0x18358, 0x1835C
local A_NPOLL, A_NISSUE = 0x18360, 0x18364
local A_SLKMIN, A_SLKAT = 0x18368, 0x1836C
local A_PFREC, A_PFDONE = 0x18370, 0x18374
local A_NSEEK, A_SKWAIT = 0x18378, 0x1837C
-- The scene header's record index, pushed into RAM before the CPU is launched.
-- It sits ABOVE the codebooks rather than in the low RAM around ring.i's own
-- tables: setup() runs one raster frame before launch() and the IPL is still
-- executing in that gap, so anything written below ~$20000 can be overwritten
-- before the 68000 ever sees it. That cost an hour: the machine read a table of
-- zeroes and asked the transport for a 0-byte record.
local IDXRAM = 0x30000 -- the DLX4 index, in RAM
local DESCN = 64
local CB1, CB4 = 0x20000, 0x22000
local RING = 0x40000
@@ -125,6 +156,21 @@ local PACED = (os.getenv("DLX_PACE") == "1") or SELFCLK
local CUT_AT = tonumber(os.getenv("DLX_CUT_AT") or "")
local CUT_FR = tonumber(os.getenv("DLX_CUT_FR") or "") or 1
local SLACK_CSV = os.getenv("DLX_SLACK_CSV")
local RINGOWN = (os.getenv("DLX_RINGOWN") == "1")
local PREFILL_FR = tonumber(os.getenv("DLX_PREFILL_FR") or "") or 2
-- Passes over the scene. With DLX_RINGOWN each pass after the first begins
-- with a REAL seek in src/player/stream.s: the channel is waited quiet, the
-- ring is declared empty and the lookahead 51.3 says takes seconds of play to
-- accumulate is thrown away and rebuilt from the prefill. The check that
-- matters afterwards is the one this rig always makes -- the last frame of the
-- last pass has to be pixel-exact, and a SKIP block is a claim about the
-- previous frame, so it is only right if every frame after the seek was.
local ITERS = tonumber(os.getenv("DLX_ITER") or "") or 1
-- How many requests the player may have outstanding at once. 1 is the obvious
-- loop and leaves the channel idle from every completion until the next poll;
-- 2 keeps the next request queued so it never stops. Both are real designs and
-- the difference between them is what this rig measures.
local QDEPTH = tonumber(os.getenv("DLX_QDEPTH") or "") or 2
-- One snapshot per frame tick instead of one at the end of the run. This is a
-- DOCUMENTATION artefact -- 120 PNGs of a paced player, for a recording -- and
-- it is deliberately not on any path tools/bench/check.sh takes. Needs
@@ -140,6 +186,16 @@ local BPS = (KBPS > 0) and (KBPS - AUDIO_KBPS) * 1024 or math.huge
local code do local f=io.open("stream.bin","rb"); code=f:read("a"); f:close() end
local cb do local f=io.open("stream_cb.bin","rb"); cb=f:read("a"); f:close() end
local DISK = assert(io.open("stream_disk.bin","rb"))
local idxblob do
local f = io.open("stream_idx.bin","rb")
if f then idxblob = f:read("a"); f:close() end
end
if RINGOWN and not idxblob then
print("[STR] DLX_RINGOWN needs the DLX4 record index (stream_idx.bin). "
.."Re-run tools/bench/prep_stream.py on a DLX4 container: the machine "
.."cannot derive record lengths by walking a stream it has not fetched.")
manager.machine:exit(); return
end
local YOFF = (MODE.height - META.H) // 2
local function T() local t=M.time; return t.seconds + t.attoseconds/1e18 end
@@ -264,6 +320,202 @@ local function produce(now)
end
end
-- -------------------------------------------------------------- transport
-- THE OTHER HALF OF ROADMAP P5. With DLX_RINGOWN the producer above is not
-- used at all: src/player/ring.i decides which record to fetch, where to put it
-- and when it is safe, and this becomes the part that is genuinely not the
-- CPU's -- an SPC and one DMAC channel moving bytes at a rate.
--
-- IT IS BUILT OUT OF MEMORY TAPS, not out of the machine-frame notifier, and
-- that is a measurement decision rather than a stylistic one. A notifier sees
-- the machine once per raster frame, 17.64 ms (54.5), and the thing being
-- measured here is the gap between a transfer COMPLETING and the CPU issuing
-- the next one -- which is a fraction of a frame slot. Sampling it at 17.64 ms
-- would have quantised the very quantity in question, and in the flattering
-- direction if the ack were early or the pessimistic one if late.
--
-- write tap on XF_GO fires inside the 68000's write, so the issue time is
-- exact. The bytes are copied in there and then: the
-- CPU cannot observe them before its ack anyway, because
-- it does not advertise the record until it retires.
-- read tap on XF_ACK synthesises the completion word from emulated time --
-- `done` iff now >= t_done -- so the CPU learns of the
-- completion on the exact cycle it happens, the way it
-- would from a status register.
-- A 68000 bus access is 16 bits, so a longword is two tap calls: the write is
-- acted on at the LOW half (written second, so the whole value is there) and
-- the read latches its answer at the HIGH half so the two halves cannot
-- straddle a completion.
local xf = {go = 0, ack = 0, busy = 0.0, gap = 0.0, gapmax = 0.0, ngap = 0,
latch = 0, tfree = 0, copylate = 0.0, ncopylate = 0}
-- q[n] = the n-th request (n counts from 1): when the CPU issued it, when the
-- transport will have finished it, and whether its bytes have been moved yet.
local q = {}
local npass = 1
local function xf_deliver(off, dst, len, now)
DISK:seek("set", off)
push(dst, DISK:read(len), 1, len)
end
-- The host as AUDITOR rather than as producer. Every placement the machine
-- makes is checked against this script's own record index and its own list of
-- records the decoder has not finished with -- the same overlap test the host
-- producer used to make its decisions with, now used only to grade them. A
-- wrong placement corrupts pixels rather than faulting (49.2), so it has to be
-- caught where it is made.
local function audit(idx, off, dst, len)
local rec = META.index[idx + 1]
if not rec then return string.format("record %d does not exist", idx) end
if off ~= rec.off then
return string.format("record %d: machine asked for disc offset %d, the "
.."index says %d", idx, off, rec.off) end
if len ~= rec.len then
return string.format("record %d: machine asked for %d B, the index says %d",
idx, len, rec.len) end
local w = dst - RING
if w < 0 or w + len > RINGSZ then
return string.format("record %d: placed at ring offset %d..%d, outside a "
.."%d B ring", idx, w, w + len, RINGSZ) end
local tail = SP:read_u32(FR_TAIL)
local i = 1
while i <= #live do
if live[i].idx < tail then table.remove(live, i) else i = i + 1 end
end
for _, r in ipairs(live) do
if w < r.off + r.len and r.off < w + len then
return string.format("record %d at %d..%d overlaps record %d at %d..%d, "
.."which the decoder has not consumed",
idx, w, w + len, r.idx, r.off, r.off + r.len) end
end
live[#live+1] = {idx = idx, off = w, len = len}
return nil
end
-- THE TAP OBJECTS ARE KEPT ALIVE HERE ON PURPOSE. install_*_tap returns a
-- handle and the tap dies with it: dropping it on the floor leaves the taps
-- working until Lua's collector next runs, and then the mailbox silently stops
-- answering. That looks exactly like a wedged producer -- the machine polled
-- 2.4 million times for an ack that had already been computed.
-- THE TAP OBJECTS ARE KEPT ALIVE HERE ON PURPOSE. install_*_tap returns a
-- handle and the tap dies with it: dropping it on the floor leaves the taps
-- working until Lua's collector next runs, and then the mailbox silently stops
-- answering. That looks exactly like a wedged producer -- the machine polled
-- 2.4 million times for an ack that had already been computed.
local TAPS = {}
local function install_transport()
-- NOTHING IN A TAP CALLBACK TOUCHES THE MEMORY SPACE. MAME 0.277 segfaults
-- if a tap reads or writes the space it was triggered from -- a nested access
-- part way through the CPU's own -- and it does it intermittently, which is
-- the worst way to find out. So the taps do pure Lua: the write tap stamps
-- the EXACT emulated time the 68000 issued a request, the read tap answers
-- the completion count from those stamps, and every actual memory access is
-- done from the machine-frame notifier.
--
-- What that buys is the thing worth having: issue and completion times are
-- both exact, so the gap between a transfer finishing and the next one
-- starting -- the disc standing still because nobody has asked it for
-- anything -- is measured at cycle resolution rather than at 17.64 ms.
TAPS[#TAPS+1] = SP:install_write_tap(XF_GO, XF_GO + 3, "dlx_xf_go",
function(offset, data, mask)
if offset ~= XF_GO + 2 then return data end -- low half, written second
-- ...and it must be the INCREMENT, not any other write to the word.
-- ring_init clears the mailbox at boot, which lands on this address with
-- the request fields still empty; without this test the transport answered
-- that clear as if it were a request and audited a 0-byte record 0.
if data ~= ((xf.go + 1) & 0xFFFF) then return data end
xf.go = xf.go + 1
q[xf.go] = {tissue = T(), served = false}
return data
end)
TAPS[#TAPS+1] = SP:install_read_tap(XF_ACK, XF_ACK + 3, "dlx_xf_ack",
function(offset, data, mask)
if offset == XF_ACK then
-- Latched on the high half so the two halves of one longword read cannot
-- straddle a completion. Requests complete IN ORDER: one channel, one
-- transfer at a time, however many are queued.
local now = T()
while true do
local r = q[xf.ack + 1]
if not (r and r.served and now >= r.tdone) then break end
xf.ack = xf.ack + 1
end
xf.latch = xf.ack
return (xf.latch >> 16) & 0xFFFF
end
return xf.latch & 0xFFFF
end)
end
-- Service every request the machine has issued but this script has not yet
-- looked at: read what was asked for, grade the placement, move the bytes, and
-- work out when the channel will have finished it. Called from the
-- machine-frame notifier, which is where this script may touch memory.
local function transport_service(t)
local n = xf.ack + 1
while q[n] do
local r = q[n]
if r.served then n = n + 1; goto continue end
local slot = XF_SLOT + ((n - 1) % 2) * XF_SLSZ
local off, dst = SP:read_u32(slot), SP:read_u32(slot + 4)
local len, idx = SP:read_u32(slot + 8), SP:read_u32(slot + 12)
if idx == 0 and n > 1 then
-- A new pass: everything the auditor knows about the ring is about the
-- scene we just left. The decoder has not consumed the new records and
-- the old ones are no longer anybody's.
live, nsent, arrival = {}, 0, {}
npass = npass + 1
P(string.format("SEEK PASS %d: the machine seeked back to record 0 at "
.."%.3f s and is refilling from empty", npass, r.tissue))
end
local err = audit(idx, off, dst, len)
if err then
P("MISPLACED: "..err)
P(" The machine owns the ring in this run, so this is a policy bug in "
.."src/player/ring.i, not a rig one -- and it would have shown up as "
.."wrong pixels, because the block loop reads without a bounds check.")
M:exit(); return
end
-- ONE CHANNEL: a transfer starts when the channel is free AND the request
-- exists, so a queued request starts the instant its predecessor lands and
-- a late one starts when it is issued. The difference is the gap, and the
-- gap is the player's, not the medium's -- no host-filled run could see it,
-- because the host producer placed records whenever it liked.
local startt = math.max(r.tissue, xf.tfree)
if xf.tfree > 0 then
local g = startt - xf.tfree
if g > 0 and nsent < META.nframes then
xf.gap, xf.ngap = xf.gap + g, xf.ngap + 1
if g > xf.gapmax then xf.gapmax = g end
end
end
local dur = (BPS == math.huge) and 0 or (len / BPS)
local done = startt + dur
-- A cut is a seek: the transfer freezes for its duration rather than
-- carrying on invisibly. Freezing is the conservative reading and the one
-- 51.6 settled on for the host producer -- a drive that is repositioning is
-- not banking bytes it will burst on arrival.
if cut_t0 and done > cut_t0 and startt < cut_t1 then
done = done + (cut_t1 - math.max(startt, cut_t0))
end
xf_deliver(off, dst, len, t)
r.tdone, r.served = done, true
xf.tfree = done
xf.busy = xf.busy + dur
nsent = math.max(nsent, idx + 1)
arrival[idx + 1] = done -- resident when the last byte lands
delivered = delivered + len
-- The one place this rig is coarser than the machine: a record whose
-- modelled transfer was shorter than the wait for this notifier was already
-- "done" by the time the bytes could be moved. Counted, not absorbed.
if t > done then
xf.copylate, xf.ncopylate = xf.copylate + (t - done), xf.ncopylate + 1
end
n = n + 1
::continue::
end
end
-- ------------------------------------------------------------------ setup
local function setup()
MODE.apply(SP)
@@ -280,10 +532,24 @@ local function setup()
end
for i = 1, #code do SP:write_u8(0x10000+i-1, string.byte(code,i)) end
SP:write_u32(FLAG, 0); SP:write_u32(FR_HEAD, 0); SP:write_u32(FR_TAIL, 0)
SP:write_u32(ITER, 1); SP:write_u32(NFR, META.nframes)
SP:write_u32(ITER, ITERS); SP:write_u32(NFR, META.nframes)
SP:write_u32(PACE, 0); SP:write_u32(PACEON, PACED and 1 or 0)
SP:write_u32(CLKON, SELFCLK and 1 or 0)
SP:write_u32(CLK_FPS, META.fps)
SP:write_u32(A_RINGOWN, RINGOWN and 1 or 0)
if RINGOWN then
-- The scene header the machine reads: the DLX4 record index, exactly the
-- bytes the container carries, pushed into RAM the way a loaded scene
-- header would be. ring_init turns it into the disc-offset table a seek
-- needs; nothing here derives a record boundary for the machine.
push(IDXRAM, idxblob, 1, #idxblob)
SP:write_u32(A_IDX_B, IDXRAM)
SP:write_u32(A_RNG_B, RING)
SP:write_u32(A_RNG_SZ, RINGSZ)
SP:write_u32(A_PFREC, PREFILL_FR)
SP:write_u32(XF_QD, QDEPTH)
install_transport()
end
P(string.format("stream.bin=%d B, codebooks %d+%d B, disk %d B, %d frames",
#code, META.cb1_len, META.cb4_len, META.disk_len, META.nframes))
P(string.format("decoder %s%s", SELFCLK
@@ -292,9 +558,15 @@ local function setup()
or "FREE-RUNNING (tests wrap, not buffering -- 49.7.2)",
CUT_AT and string.format(", pipe cut at tick %d for %.2f fr",
CUT_AT, CUT_FR) or ""))
P(string.format("ring %d KB at %06X, pipe %s, prefill %d KB, maxrec %d B",
P(string.format("ring %d KB at %06X, pipe %s, prefill %s, maxrec %d B",
RING_KB, RING, (KBPS > 0) and (KBPS.." KB/s") or "unlimited",
PREFILL // 1024, META.maxrec))
RINGOWN and (PREFILL_FR.." records (the machine's own)")
or ((PREFILL // 1024).." KB"), META.maxrec))
if RINGOWN then
P(string.format("ring OWNED BY THE 68000 (src/player/ring.i): this script "
.."is a transport with a %d-deep request queue, %d B of "
.."DLX4 index at %06X", QDEPTH, #idxblob, IDXRAM))
end
if META.maxrec > RINGSZ then
P("RING TOO SMALL: one record does not fit. stream.s needs a whole record "
.."contiguous."); M:exit()
@@ -322,13 +594,18 @@ local slack_series = {}
SUB = emu.add_machine_frame_notifier(function()
local ok, err = pcall(function()
local t = T()
if RINGOWN then transport_service(t) end
if st == "boot" then
if t < 3.0 then return end
setup(); last_t, pf_t0 = t, t; st = "prefill"; return
end
if st == "prefill" then
produce(t)
if delivered >= PREFILL then
if not RINGOWN then produce(t) end
-- RINGOWN: there is nothing for the host to prefill. The machine issues
-- its own requests, so it has to be running first; ring_prefill then
-- holds the decoder until PF_REC records are resident, which is the same
-- policy in the place a player would keep it.
if RINGOWN or delivered >= PREFILL then
P(string.format("prefill done: %.1f KB in %.3f s, releasing the CPU",
delivered/1024, t - pf_t0))
launch(); t_rel = t; st = "running"
@@ -344,6 +621,14 @@ SUB = emu.add_machine_frame_notifier(function()
-- which is the point: the same bytes are gated either way.
local tick = SELFCLK and SP:read_u32(PACE)
or math.floor((t - t_rel) * META.fps)
if tick < pace then
-- src/player/stream.s rebased the clock for a new pass: tick 0 is the
-- instant the decoder was released after the seek's prefill, not the
-- start of the run. Everything sampled per tick starts again with it.
pace, tick_t = -1, {}
min_ahead, min_at = math.huge, -1
sum_ahead, n_ahead, slack_series = 0, 0, {}
end
if tick > pace then
pace = tick
if not SELFCLK then SP:write_u32(PACE, pace) end
@@ -372,7 +657,12 @@ SUB = emu.add_machine_frame_notifier(function()
if nsent < META.nframes then
if ahead < min_ahead then min_ahead, min_at = ahead, tick end
sum_ahead, n_ahead = sum_ahead + ahead, n_ahead + 1
slack_series[#slack_series+1] = {tick, ahead, n_ring, n_rate}
-- Column 3 is "has the producer been refused for space yet",
-- which is what makes a later minimum meaningful: before the first
-- refusal the ring is still filling. With the ring owned by the
-- machine that counter is ring.i's, not this script's.
slack_series[#slack_series+1] =
{tick, ahead, RINGOWN and SP:read_u32(A_NFULL) or n_ring, n_rate}
end
if CUT_AT and tick >= CUT_AT and not cut_t0 then
cut_t0, cut_t1 = t, t + CUT_FR / META.fps
@@ -382,12 +672,38 @@ SUB = emu.add_machine_frame_notifier(function()
end
end
end
produce(t)
if not RINGOWN then produce(t) end
if RINGOWN and os.getenv("DLX_RINGDBG") == "1" then
dbg_n = (dbg_n or 0) + 1
if dbg_n % 30 == 0 then
P(string.format("DBG t=%.2f flag=%X go=%d ack=%d tfree=%.3f queued=%s "
.."head=%d tail=%d rq=%d poll=%d full=%d wcur=%d rcur=%d",
t, SP:read_u32(FLAG), xf.go, xf.ack, xf.tfree,
tostring(q[xf.ack+1] ~= nil), SP:read_u32(FR_HEAD),
SP:read_u32(FR_TAIL), SP:read_u32(A_RQ_NEXT),
SP:read_u32(A_NPOLL), SP:read_u32(A_NFULL),
SP:read_u32(A_WCUR), SP:read_u32(A_RCUR)))
end
end
if cut_t0 and not cut_done and t >= cut_t1 then cut_done = true end
local fl = SP:read_u32(FLAG)
if fl == 1 and not t0 then t0 = t; return end
if fl == 0xEE then
P("BITSTREAM DESYNC -- the decoder consumed the wrong number of bytes.")
if RINGOWN then
local tail, head = SP:read_u32(FR_TAIL), SP:read_u32(FR_HEAD)
P(string.format(" tail=%d head=%d rq=%d wcur=%d rcur=%d go=%d ack=%d",
tail, head, SP:read_u32(A_RQ_NEXT), SP:read_u32(A_WCUR),
SP:read_u32(A_RCUR), xf.go, xf.ack))
P(string.format(" DESC[%d]=%08X, the index says record %d is at ring "
.."offset ? len %d", tail,
SP:read_u32(DESC + (tail % 64)*4), tail,
META.index[tail+1] and META.index[tail+1].len or -1))
local ls = {}
for _, r in ipairs(live) do
ls[#ls+1] = string.format("%d@%d+%d", r.idx, r.off, r.len) end
P(" host thinks live: "..table.concat(ls, " "))
end
P(" Under a ring that is the whole point: it means a record was placed "
.."or described wrongly, not that the codec changed.")
M:exit(); return
@@ -400,6 +716,11 @@ SUB = emu.add_machine_frame_notifier(function()
" (fps*VTOTAL does not fit the 16-bit accumulator)" or ""))
M:exit(); return
end
if fl == 0xE3 then
P("RING INIT REFUSED: the record index has more entries than "
.."src/player/ring.i's disc-offset table (ROFFMAX) can hold.")
M:exit(); return
end
if fl == 0xE1 then
P("PRODUCER STALLED OUT -- stream.s spun SPINMAX times with no new "
.."record. Delivered "..nsent.."/"..META.nframes..".")
@@ -443,10 +764,62 @@ SUB = emu.add_machine_frame_notifier(function()
vd, pace + 1, vd/(pace + 1), META.fps, vt,
31500/(META.fps*vt), 181.35*vd/(pace+1)))
end
local rholes, rhole_b = holes, hole_bytes
if RINGOWN then
rholes, rhole_b = SP:read_u32(A_NHOLE), SP:read_u32(A_NHOLEB)
end
P(string.format("ring: %d wraps, %d B of hole (mean %.1f KB, %.1f%% of "
.."the ring)", holes, hole_bytes,
holes > 0 and hole_bytes/holes/1024 or 0,
100*(holes > 0 and hole_bytes/holes or 0)/RINGSZ))
.."the ring)", rholes, rhole_b,
rholes > 0 and rhole_b/rholes/1024 or 0,
100*(rholes > 0 and rhole_b/rholes or 0)/RINGSZ))
if RINGOWN then
-- The producer's own account of itself. These are read out of the
-- machine's RAM, not kept here: the point of the run is that this
-- script did not make any of these decisions.
local pf = SP:read_u32(A_PFDONE)
local npoll, nissue = SP:read_u32(A_NPOLL), SP:read_u32(A_NISSUE)
local nfull = SP:read_u32(A_NFULL)
local slk, slkat = SP:read_u32(A_SLKMIN), SP:read_u32(A_SLKAT)
local nseek, skw = SP:read_u32(A_NSEEK), SP:read_u32(A_SKWAIT)
P(string.format("MACHINE-OWNED RING: %d records placed by the 68000, "
.."%d polls, %d refused for space (ring-bound), "
.."%d seeks", nissue, npoll, nfull, nseek))
P(string.format("PREFILL: released the decoder at %d records "
.."(policy: %d); LEAST SLACK %d records at frame %d",
pf, PREFILL_FR, slk, slkat))
-- THE NUMBER THIS RIG EXISTS TO PRODUCE. The channel only moves
-- bytes while a request is outstanding and only the CPU can issue the
-- next one, so the disc stands still between the completion of one
-- record and the issue of the next. That gap is a property of the
-- PLAYER's loop, not of the medium, and no host-filled run could see
-- it -- the host producer placed records whenever it liked.
local span = (arrival[nissue] or t) - (t0 or t)
P(string.format("CHANNEL IDLE: %.1f ms over %d gaps (worst %.1f ms) = "
.."%.1f%% of the %.2f s the transport was needed for; "
.."busy %.1f ms",
xf.gap*1000, xf.ngap, xf.gapmax*1000,
span > 0 and 100*xf.gap/span or 0, span,
xf.busy*1000))
-- THE RIG'S OWN RESOLUTION, PRINTED RATHER THAN LEFT IMPLICIT.
-- The transport's timing is exact (memory taps), but the BYTES are
-- moved from the machine-frame notifier, so a record whose modelled
-- transfer is shorter than the wait for that notifier is acked later
-- than the model says it landed. Every millisecond here is a
-- millisecond the decoder may have waited that the medium would not
-- have made it wait.
if xf.ncopylate > 0 then
P(string.format("RIG RESOLUTION: %d of %d transfers were acked late "
.."because the bytes are moved on the notifier, by "
.."%.1f ms in total (mean %.1f ms) -- an artefact of "
.."this rig, not of the player",
xf.ncopylate, nissue, xf.copylate*1000,
xf.copylate*1000/xf.ncopylate))
end
if skw > 0 then
P(string.format(" the last seek waited %d polls for the channel "
.."to go quiet before it could start", skw))
end
end
-- The decoder's own spin counter, kept for what it is: evidence that
-- stream.s outran the pipe, NOT evidence of an underrun. See the note
-- on `arrival` above.
@@ -490,15 +863,22 @@ SUB = emu.add_machine_frame_notifier(function()
for _,e in ipairs(slack_series) do
if e[3] > 0 and e[2] < ss_min then ss_min, ss_at = e[2], e[1] end
end
if ss_min == math.huge then ss_min, ss_at = -1, -1 end
P(string.format("SEEK SLACK: ceiling %d frames (%.0f ms), first "
.."reached at tick %d; mean %.1f over the window",
ceiling, 1000*ceiling/META.fps, ceil_at,
sum_ahead/math.max(1,n_ahead)))
if n_ring > 0 then
-- WHOSE REFUSAL COUNT. With the ring owned by the machine the host
-- producer's counters are not merely stale, they are zero -- it never
-- placed anything -- so the classification has to come from
-- src/player/ring.i's own N_FULL. Reading n_ring here in a RINGOWN
-- run would have reported RATE-BOUND on every run by construction.
local ring_ref = RINGOWN and SP:read_u32(A_NFULL) or n_ring
if ring_ref > 0 then
P(string.format(" RING-BOUND: the ring filled (%d refusals). Once "
.."full it survives delivery stopped dead for %d "
.."frames = %.0f ms; min after first fill %d "
.."(tick %d)", n_ring, ceiling,
.."(tick %d)", ring_ref, ceiling,
1000*ceiling/META.fps, ss_min, ss_at))
else
P(string.format(" RATE-BOUND: the ring NEVER filled in %d frames. "
@@ -530,6 +910,16 @@ SUB = emu.add_machine_frame_notifier(function()
for i = 0, META.nframes-1 do
local a = arrival[i+1]
if a then
-- INSTRUMENT NOTE, and it only bites under the self-clock.
-- tick_t[] is when this script OBSERVED the machine's tick, which
-- is the next machine-frame boundary after it -- up to 17.64 ms
-- late (54.5). So these deadlines are generous by that much and
-- this count UNDERSTATES lateness. The sharp instrument for the
-- same question is the decoder's own stall counter, which is exact
-- because the machine takes it: at 488 KB/s with a one-deep request
-- queue this reported 6 records late where the 68000 counted 59
-- frames that had to wait. Host-paced (DLX_PACE=1) the deadline is
-- a host model and is exact, so FINDINGS 49.6's table is unaffected.
local due = SELFCLK and tick_t[i+1] or (t_rel + i / META.fps)
if not due then due = t_rel + i / META.fps end
local late = a - due
@@ -550,14 +940,28 @@ SUB = emu.add_machine_frame_notifier(function()
.."at %s", prefill_s*1000, prefill_s*META.fps,
(KBPS > 0) and (prefill_s * BPS / 1024) or 0.0,
(KBPS > 0) and (KBPS.." KB/s") or "an unlimited pipe"))
M.video:snapshot()
P("snapshot taken after the sequential pass -- last frame, decoded "
.."entirely out of a "..RING_KB.." KB ring")
st = "snapped"; return
-- ONE FRAME OF SETTLE BEFORE THE CAPTURE, and it is not cosmetic.
-- MAME renders a screen scanline by scanline and the machine-frame
-- notifier fires at the END of that frame, so a bitmap for a frame in
-- which GVRAM changed holds some lines drawn before the change and some
-- after. Snapshotting it captures a TEAR -- and the symptom is a
-- pixel-exactness failure in the bottom blocks plus a broken double-scan
-- pairing, which reads exactly like a decoder bug and is not one. It
-- only bites when the decoder finishes its last frame LATE in a screen
-- frame, which is why it never showed up until a run with underruns in
-- it. Waiting one whole frame renders the finished picture with nothing
-- writing to GVRAM.
st = "settle"; return
end
if t > 900 then P("TIMEOUT flag="..string.format("%08X",fl)); M:exit() end
return
end
if st == "settle" then
M.video:snapshot()
P("snapshot taken after the sequential pass -- last frame, decoded "
.."entirely out of a "..RING_KB.." KB ring")
st = "snapped"; return
end
if st == "snapped" then M:exit(); return end
end)
if not ok then print("[STR] LUA ERROR: "..tostring(err)); M:exit() end