Statics, reverse channel, Magma cross-role sites, EGL control plane,
registry rekey, build/gate mechanics, the 15 BARRIER_PULLED fields'
carrier rulings, and the dual-block mechanism's design recon.
The section explained what gPipeInputs IS and what breaks under spawn, but not the one fact
that decides the shape of the fix, and not how a call actually reaches the driver through it.
Both are now in the document rather than only in the conversation that found them.
- THE POINTER FACT, now stated first because everything else follows from it: several
BARRIER_PULLED fields do not hold values, they hold pointers into client-owned objects.
PipeFill.cpp:274 fills m_textureUnitBase with `&ctx.GetTextureUnitObject(0)` - a raw base
into the frontend's array - and :245 fills m_programForDraw with a SharedPtr<ProgramObject>.
PipeInputs.h:669 dereferences it as `m_textureUnitBase[unit]`. PipeFill.cpp:2591-2592 says
the same of the shader-buffer field: "four raw bases into the frontend's binding-point
table".
The consequence gets its own paragraph in 1.4, because it is the step most likely to be got
wrong: this CANNOT be fixed by moving the block into shared memory. Mapping the same pages
into both processes does not make a client heap address meaningful in the server, and a
SharedPtr's refcount does not cross at all. The 15 fields each need a different SOURCE, not
a shared location.
- NEW 1.2, one draw end to end: glBindTexture marks a tracker bit and sends nothing, because
push only happens at a verb boundary; glDrawArrays enters MGPipeValidateForVerb
(PipeFill.cpp:3347) whose four steps are barrier decision, dirty walk, emission (records,
carrying handles), and the residual fill - which is where BARRIER_PULLED happens; the record
goes on SEG_CMD; the apply thread dispatches to the backend; PrepareForDraw reads either a
record-carried handle against the server's own tables, or gPipeInputs; then the real driver
call. Plus the field lifetime: stamped with verb N's serial, read during verb N's apply,
Fatal{UnmigratedPipeInput} if read at verb N+1 without a refill - one verb, never longer.
- The same example carries the Espryt/Magma split concretely: the texture binding reaches
Espryt as a record with a handle (P5e retired GetTextureUnitObject for it) and reaches Magma
through gPipeInputs into the client's array. That is FieldOwnership.def's own
"P5e (Espryt unbarriered), P7 (Magma)" made legible, and it is why section 2.1's table has
eight rows in that state.
Sections renumbered 1.1-1.4. Doc citation lint: 129 citations, 0 problems.
P6's premise is that it is "only a transport swap". That premise was bought by P5c and has
expired. Measured on this head, the two roles still share state directly, so a spawned server
would have no source for it. P5f is the phase that makes the premise true, and P6 does not
start before it.
WHAT THE MEASUREMENT FOUND
- FieldOwnership.def still carries 21 BARRIER_PULLED rows over 15 distinct fields. That class
is defined as "the server answers by reading a value the client's residual fill left in THE
SINGLE SHARED gPipeInputs while the verb barrier holds both threads apart". Eight of those
fields were retired by P5e for Espryt's unbarriered path only - Magma has not moved at all.
The strict lane measures 10 live <field>@<verb> pairs today.
- gPipeInputs (MG_Backend/MGPipe/PipeInputs.h:835) is a plain process global,
`inline PipeInputs& gPipeInputs = *new PipeInputs();` - not a shm segment. The client fills
it (MG_Impl/Pipe/PipeFill.cpp), the backend reads it. Under spawn the two processes have
DIFFERENT objects, the 15 BARRIER_PULLED fields have no filler in the server's copy, and
every read is Fatal{UnmigratedPipeInput}. MG_Impl is not in the server, so "let the server
fill it" is not available either. The header says this itself at :279 and :902.
- The twelve Server* EGL forwarders do not use the wire at all: they post a function pointer
plus a stack-local void* through a one-slot mailbox (ServerLoop.cpp:533-568, :645). The
SurfaceOp / SurfaceReply / WindowKind schema is defined in protocol.fbs and unused.
- Process-level statics with per-context semantics (g_syncedRenderStateParameters,
ScopedDefaultUnpackState::s_synced) - and the full list is unknown, because this defect class
is structurally invisible to inproc.
- MGPipeFrontendKeyedRegistryScope is still live at ~12 sites in DirectGLES.cpp, carrying
P3b/P4b's debt: the registry is still keyed by frontend address / lifetime id.
THE SCOPE RULE
P5f takes the cross-process-blocking subset of P3b/P4b/P7/P8/P9 and nothing else. One test:
does it still hold in another address space? No -> P5f. Yes but slow or ugly -> it stays with
the phase that owns it. So Magma's nine fields and its direct writes into client storage come
here; content-addressed CSO, internal shader baking and the fixed-width rewrite stay P7's. The
reverse channel's asynchrony and ordering stay P9's; only the parts that touch client memory
move. Class C is NOT P5f's - a named refusal behaves identically in two processes.
THE CENTRAL MECHANISM: A TWO-BLOCK REHEARSAL
P5c set the same rule (rule E) and checked it by AUDIT - a human reading 59 lines. P5f checks
it by MACHINE: give each role its own PipeInputs under inproc, and its own copy of every
per-context static, behind a knob. Anything that depends on the two being the same object
becomes Fatal{UnmigratedPipeInput, "<Field>@<Verb>"} with the field and verb named.
That rehearses the process split's SEMANTICS without a second process. It matters because
today "the server read the value the client filled" and "the server read the value a record
carried" are indistinguishable at runtime - which is exactly what P6 would discover on day
one. The package order puts the mechanism (f1) BEFORE the migrations deliberately: let the red
appear first and let it be the worklist, rather than having each package declare itself done
and then looking for a criterion.
Exit gate: the two-block lane green; strict-expected-markers.txt EMPTY with its two-sided
ratchet still armed; zero BARRIER_PULLED rows; rsp reading zero per frame; Magma judged by the
same criteria as Espryt. The negative control is that turning the two-block knob OFF must move
at least one named case from green to red - otherwise the mechanism proves nothing, which is
ID-122's lesson.
ALSO IN THIS COMMIT
- ROADMAP gains the P5f row and the IPC track becomes P5e -> P5f -> P6; P6's status cell
becomes "blocked on P5f".
- README and CURRENT_STAGE_PROGRESS gain the same, plus the file-map entry.
- Both P6 documents gain a blocked banner naming what is not true yet.
Doc citation lint: 124 citations across docs/Disaggregated/*.md, 0 problems.
Two things land together: the plan and contract draft P6 needs before it starts, and the
working notes that until now existed on exactly one machine.
1. P6's plan and contract draft (neither started; not one line of code)
docs/Disaggregated/P6-SPAWN-PLAN.md the package plan
docs/Disaggregated/P6-CONTRACT-DRAFT.md the contract draft (moves to
MG_Remote/CONTRACT-P6.md when c6 lands)
The three findings that mattered, all written into the documents:
a. P6 is SMALLER than its roadmap cell suggests. The transport primitives are already in
the tree and already tested: SocketDoorbell including hangup detection and the two
lost-wakeup fences (Doorbell.cpp:211-360, four cases in FdPassingTest), SCM_RIGHTS fd
passing, ShmSegment::Adopt, and the SurfaceOp / WindowKind schema already defined in
protocol.fbs. inproc uses a real second shm mapping rather than an alias, and
SessionRings.h:22-28 says that was done so today is not the first time it runs. P6 is
assembly plus a control plane plus a process, not "write a socket transport".
b. The evidence for "P6 is only a transport swap" has EXPIRED. It was bought by P5c, whose
audit found 59 direct memory accesses in a tree that already looked clean. P5e changed
the tree again. So the first package, a6, is a read-only audit that writes no code, and
every contract row that depends on it is marked PENDING a6 rather than decided in
advance.
c. P6 does not get a game running on the phone. ANativeWindow* is meaningless in the child,
and protocol.fbs:186-196's own comment says Android transfers the window out of band -
that band is P12. P6 lands pbuffer / surfaceless / offscreen, which is what HeadlessGL,
the split-equivalent lane and trace replay need, and which is exactly what P6's own exit
gate measures. A real window reaching the server is a named refusal. This gets its own
section because "P6 is done" would otherwise read as "the game runs now".
The contract adds rule G: a role may not name a process-local handle. It extends P5c's
rule E (a role may not name the other role's memory) from memory to identity - EGLDisplay /
EGLSurface / EGLContext / ANativeWindow* / fd number / pid / mapped address either cross as
a token this contract defines or they do not cross, and a descriptor crosses only through
SCM_RIGHTS, where the kernel renumbers it.
What P5e left for P6 gets its own section. The latch semantics are already designed
(ARCHITECTURE.md:504) and are copied unchanged. What is new is that after run-ahead the
client no longer waits while the peer process can DIE: the client holds records that were
published and will never be applied, and Android's freezer suspends the child without
closing anything. So slow and dead must be distinguishable WITHOUT a timeout threshold.
That is P6's only new design; everything else is carriage. It shares a predicate with E1's
outstanding re-specification (ID-122), and the two should be designed together.
Two gates carried over from P5e's lessons: G2 requires integration-spawn's test-name set to
match integration-split's name for name, because a differing set means the lane is quietly
running less; and the arm-proof gate requires every entry to record the child pid and
transport=spawn in its OWN private log - ID-124 established that this kind of false green
really happens, and a spawn lane that actually ran monolith would pass every other gate.
S2's shape must be settled before it is written, and the document says why: E1 is the
cautionary case.
2. The working notes move into the repository (docs/Disaggregated/notes/, 415 .md files)
ROADMAP / CURRENT_STAGE_PROGRESS / MEASUREMENTS cite ruling numbers, audit line numbers and
the provenance of gate figures from ~/w7/notes/, a directory that exists on one machine and
is under no version control. A record cited hundreds of times that lives only locally is not
a record, so it moves in whole, with its directory structure intact.
Only .md moves. Scripts, run logs, census and gate result JSON, patches, APKs and nm dumps
stay where they are: they are evidence DATA rather than documents - large, regenerated per
run, and mostly carrying absolute paths and device serials that mean something only on the
machine that produced them. The mapping and this split are written in
docs/Disaggregated/notes/README.md.
Two exceptions are recorded there too: P6's BRIEF has been promoted to a first-class
document and keeps no copy under notes/, so the two cannot drift apart; and recovered/ holds
material salvaged from failed workflow runs, which may duplicate the like-named phase
directories and is kept because a few of those were the only complete version at the time.
CI's citation lint takes docs/Disaggregated/*.md only (non-recursive), and notes/ is
deliberately outside it: those notes' file:line citations were written against their own
code heads, and resolving them against today's HEAD would fail wholesale - which is not an
error, it is their correct state as a historical record. To check one, use the revision it
declares (--rev).
3. Inconsistencies fixed in passing
- README.md's status line still said P5e was in progress while the stage table already said
closed.
- CURRENT_STAGE_PROGRESS's next-step item 1 still listed the exit gate as pending, though
(a) and (b) were run in the previous commit; rewritten to closed plus the one item that
actually remains (E1).
- ROADMAP's P6 row still had the pre-phase plan in three of its cells; it now carries the
package order, the scope boundary and the two new gates.
Checked with check_doc_citations.py: 125 citations across docs/Disaggregated/*.md, 0 problems.
It said "in progress" because BRIEF-P5E section 3's exit gate had never been RUN, not because
the work was unfinished. It has now been run, item by item, recorded in ROADMAP's P5e
exit-gate cell:
- item 1: unit 2256/2256 under both strict arms.
- item 2/3: integration-split 179/179; the per-entry census has zero Fatal{ and exactly eight
Admitted{ rows.
- item 4(a): RUN_AHEAD=0 as the PAIRED control, 179/179 green - same server code, same
records, the only difference is whether the client waits.
- item 4(b): VERB_BARRIER=0 goes red (62/179 in the lane).
- item 4(c): Magma logs, verbatim, "run-ahead requested, server does not publish
kCapRunAheadApply - running lockstep", and the Espryt control logs "run-ahead ARMED". Both
taken from each entry's own private log.
- item 5: red-once rerun on the integrated tree, in the form ID-121 reordered it into -
reverting pa's arm yields GetProgramForDraw@DrawArrays, reverting mv's yields
GetBoundVertexArray@DrawArrays, EXACTLY ONE NAMED PAIR EACH, and each restores green.
- item 7: MOBILEGL_IPC_AUDIT=1, 179/179.
- item 6's G1 remains CI's to assert (ID-123).
The only item that does not pass is E1's control script itself (ID-122), and the diagnosis is
sharper than before: with its two masking defects fixed it is still red, and the
Fatal{BarrierViolation} it demands appears ZERO times in the whole run - at BATCH_WAITS's
default of 1 that overlap does not happen, and with run-ahead armed VERB_BARRIER=0 also
disarms run-ahead (ID-114), so the arm it produces is neither lockstep nor run-ahead. E1 needs
its falsification target redefined, not its threshold adjusted.
So the status is "closed, with one named outstanding item" rather than an unqualified close:
hiding a control that never passed behind the word "closed" is precisely the class of mistake
this phase kept recording.
BRIEF-P5E section 3 item 4 calls for three negative controls. Running them showed E1
(MOBILEGL_IPC_VERB_BARRIER=0) had THREE problems stacked, with the first two hiding the third.
This fixes the first two and narrows the third into something executable.
1. It selected a case that can never run in this lane.
E1's selection regex is (Triangle|ClearThenReadPixels), and the positive control gl added
under ID-115, TriangleScenario.TheServerStampedAVerbBoundaryOnThisDrawingFrame, matches it.
That case reads a PipeStats window out of the lane's OWN private log, so it runs only in the
strict-arming lane and skips everywhere else BY DESIGN, whatever this knob is set to. ID-62
makes a SKIPPED SELECTED entry a hard failure - correctly, because a control that silently
loses its subjects proves nothing. So E1 reported "the knob killed the pre-flight, not the
entry" while the knob was in fact working: four other selected entries went red with the
abort in the same run.
The fix excludes a case that can never run here, rather than teaching E1 to tolerate skips,
which would have thrown ID-62 away. ctest -R is POSIX ERE with no negative lookahead, so
run_control gains a fifth positional: a real ctest -E.
2. ctest and the log helper disagreed about who was selected.
run_control passed -E to ctest, but split_log_paths.py still filtered on -R alone, so it
counted the excluded entry as selected and then reported it as "did not run". The helper now
reads the same exclusion (SPLIT_LOG_EXCLUDE). An env var rather than another positional
because the helper's positional layout differs per mode - and a control whose two halves
disagree about its own subject set is exactly the class of bug this script exists to
prevent.
3. The real defect. ID-122 was right, and there is now a sharper statement of it.
With the first two fixed E1 is still red, and red on "10 selected entries did not fail": 4
of 14 went red, AND Fatal{BarrierViolation} appears ZERO times in the entire run - those 4
are red for other reasons. The evidence E1 demands has never appeared. The Fatal at
ClientSession.cpp:878 asserts an overlap OBSERVED BY THE APPLY THREAD, and at
MOBILEGL_IPC_BATCH_WAITS's default of 1 the barrier is taken at the next residual-reading
verb, so that overlap does not happen.
Further: with run-ahead armed, VERB_BARRIER=0 ALSO disarms run-ahead (it is the first
conjunct of RunAheadArmed(), ID-114), so the arm this knob produces is neither lockstep nor
run-ahead - it cannot serve as the negative control for either side.
E1 needs its falsification target REDEFINED, not its threshold adjusted. Left as a named
outstanding item, recorded in ID-122 and the open items.
E1's counting rule ("every selected entry must go red") is deliberately NOT relaxed here: it
was set to block the "any non-zero exit counts" false green, and loosening it before knowing
what E1 should falsify would only trade one false green for another.
The previous commit changed the status cell to "twelve packages landed, run-ahead armed" and
left the scope and exit-gate cells saying eight packages, 19 rulings, "the integration commit
flips kMGPipeP5eRunAheadReady", and an exit gate drafted BEFORE the phase started - several of
whose items later proved unexecutable as written. All three cells are rewritten:
- Scope cell: twelve packages in three waves (including fix1 / pa / mv / gl / ra2), rulings
ID-80..136, both constants flipped. It also names the largest migration (the per-draw
GetProgramForDraw) as having changed NO wire structure at all - the record already carried
the per-link ProgramArchive, and what was missing was a reader that still asked the frontend
object. Links to P5E-RUNAHEAD.md.
- Exit-gate cell: rewritten into what was actually measured (unit 2256, integration-split
179/179, integration-gpu 1357/1357, three flavours with each arm asserting its EFFECTIVE
compile define, strict hard green with zero Fatal, the device at VD32 level with monolith and
+69% p50 against lockstep), plus what has not been executed (the three negative controls, the
per-package red-once reruns, E1's control failing its own self-check, G1 still asserted by
CI), plus the criteria that are now VOID (rsp = 0 is empty by construction, rewritten by
ID-119; VERB_BARRIER=0 may not serve as the paired control, ID-114, because it also disarms
run-ahead).
- Debt table, rsp row: P5e rewrote what that number means. It now reads as the hard-green lane
plus eight Admitted rows, and says why the original criterion was empty - CountBarrierPull's
unbarriered arm sits before ++g_residualPulls and is [[noreturn]].
- Debt table, unmigrated row: client vertex arrays are a named refusal under run-ahead
(ID-82) and have their own expected-red lane, integration-clientarrays-split (ID-134);
staging stays P8's.
- Open question 18 added: the two sides of split are unbalanced (at VD32, apply 11-12 ms
against client 15.7 ms, with the client ~94% saturated). Moving work from client to apply
lowers the bottleneck directly - meaningless under lockstep, where the two add serially, and
a lever only because of run-ahead. It needs a fresh profile first: with the wait gone, every
tail item's denominator has changed.
- The header status line gains the P5E-RUNAHEAD.md link.
Doc citation check: seven files under docs/Disaggregated, 58 citations, 0 problems.
- New P5E-RUNAHEAD.md: P5e's phase report, a sibling of P5D-INPROC-PERFORMANCE.md. It carries
the twelve-package list, the three defect classes and the lesson each one cost (a runtime arm
no gate covered / build flavours no gate covered, where the FIRST gate added for them was
itself a false green / a guard that could never fire), the profile and both device tiers, the
unfinished items, and the next opportunity run-ahead unlocked.
- CURRENT_STAGE_PROGRESS.md: the stage table's P5e row becomes twelve packages + run-ahead
armed + ID-80..136; new section 2.7, the P5e landed-content table, in the same shape as
P5c's and P5b's; section 2.5 retitled as historical; two sections both numbered 4 fixed; five
P5e entries added to the open items; next-step item 1 rewritten from c0e to the evidence the
close still lacks; the ruling index extended from ID-79 to the load-bearing entries of
ID-136.
- ROADMAP.md: the P11 row gains P5e's correction - retiring the draw lockstep did NOT need
gPipeInputs versioning, because that race was in the metadata scalars. The row still holds
for the general case, and contract section 3.2's per-role stamp storage is still unlanded.
- README.md: the status line gains P5e and run-ahead, and "next is P6" becomes "P6 comes after
P5e".
Doc citation check: 3 problems, all pre-existing entries in CONTRACT-P5.md, none related to
this change.
Section 11's matrix ran at VD12, where BOTH monolith and run-ahead hit the 120 Hz panel
ceiling - so that section answers "can it reach the ceiling", not "which is faster". At render
distance 32 the load rises to ~3550 draws/frame (4.2x) and neither arm is near any cap (the
game's own enableVsync:false / maxFps:260, and the measured max is only 37-71). That is the
comparable round.
- Five runs per arm, interleaved, CPU clocks pinned (checked before AND after, both PINNED),
GPU held at pwrlevel 0, fan on; 75-150 s in-world settle before a 40 s window - VD32's chunk
streaming runs far longer than VD12's and reusing the 20 s settle would have counted loading
as steady state.
- monolith p50 median 58.5 (range 56.3-67.9), inproc run-ahead p50 median 59.9 (range
56.8-61.1), client CPU 16.19 vs 15.72 ms/frame. Level, run-ahead marginally ahead, and with
half monolith's spread.
- Against the lockstep it replaces: p50 +69%, client CPU -40%, apply CPU -43%. The heavier the
load the more it is worth, which is what the mechanism predicts: rendezvous count follows
draw count, ~900 per frame at VD12 and ~3600 at VD32.
- Both arms are client-thread saturated (~94%), so the client ms/frame column is each arm's
real bottleneck and the two are directly comparable.
New section 11.1 records an OPPORTUNITY rather than a defect: apply spends 11-12 ms against
the client's 15.7 ms, so the two sides are unbalanced and moving work from client to apply
lowers the bottleneck directly. Under lockstep that was meaningless (the two sides add
serially); run-ahead is what turns it into a lever. Left to a later phase.
options.txt restored from .p5e-backup to renderDistance:12; the device is unpinned, fan off,
GPU back to governed.
- CURRENT_STAGE_PROGRESS.md gains section 2.6: the four packages (pa / mv / gl / ra2), the
admission rule's three disjuncts and which real entry forced each one, coverage going from
116 to 179 entries plus 1357, the race the flip exposed and its root cause, and the finding
that a hard-green strict lane is necessary and NOT sufficient (ID-132). Code head is now
25fba0d5.
- MEASUREMENTS.md gains section 11: the device matrix. The section leads with clock pinning
because the first matrix was run without it and had to be thrown away - monolith's OWN arm
moved 4.43 -> 7.07 ms/frame between two runs, and the SLOWER run was the COOLER one: the
governor had dropped policy0 from 2745 to 748 MHz. It records pin_redmi.sh's write order and
read-back verification, and why pin_device.sh refusing to guess this machine's serial is
correct rather than a gap. Conclusion: at both pinned tiers monolith and run-ahead each hit
the 120 Hz panel ceiling and only lockstep cannot reach it.
- ROADMAP.md's P5e row and status line now say twelve packages landed, run-ahead armed.
The phase is NOT closed: which arm is faster ABOVE the panel ceiling is unanswered (this
device cannot hold a higher clock), and BRIEF-P5E section 3's three negative controls and
section 5's per-package red-once reruns have been reordered by ID-121 to after the lane goes
green, so they have not been executed yet.
- TOUCHING mv's FILE UNDER ID-136, deliberately and by ruling: MG_Backend/DirectGLES/
MultiDraw.cpp is mv's per ID-113, and the integrator overrode that boundary for this one
change because the two halves must not exist apart on any head. The boundary has not drifted.
- BoundDrawIndirectBufferId (MultiDraw.cpp) gets the handle arm its neighbour
ResolveBoundIndexBuffer already had, in mv's own idiom rather than a second one beside it:
the arm is `MG_Config::Transport != Monolith`, STATED (ID-81) and never inferred from a null
handle (ID-110); a null handle is "this verb bound no indirect buffer", the same 0 the
monolith arm returns for an empty slot; a missing backend resource is the named refusal
Fatal{RoleViolation, "multidraw-indirect-buffer-arm"}, a sibling of mv's
RefuseMissingIndexBufferRecord, never a quiet fall-back to the frontend. The monolith body
below it is unchanged token for token. The function moved down beside BoundIndexBufferId,
which is the same question about the other target.
- WHY A HANDLE ARM AND NOT A MIGRATION: the tier never reads a byte of the client's indirect
buffer. It binds its OWN scratch command buffer and wants to put back the name that was
there - a save/restore. With a transport the only other writer of this process's
GL_DRAW_INDIRECT_BUFFER is DirectGLES.cpp's DrawSyncBit::IndirectBuffer arm, which binds from
MGPipeApplier().VerbIndirectBuffer and nothing else, so "what was bound" IS "what the verb's
record named".
- Escalation (iii) withdrawn in the same commit - MGPipeBarriered's clause, the client's
verb-keyed half in ClientVerbIsBarriered, and the contract row. It was never wrong, it was
the wrong instrument: there is one draw opcode and the tier is chosen server-side per batch,
so the narrowest key both roles could compute charged EVERY plain glMultiDraw* on the
auto -> ext default - a per-batch rendezvous on the arm the phone ships, added to make a lane
green. THE CHECK ON AN ESCALATION IS "WHICH ARM PAYS FOR IT", NOT "WHICH LANE GOES GREEN";
the rule is recorded in PipeApply.h beside the three that remain and in CONTRACT-P5E §2.1.
- Red-once D: `if (false && ...)` on the new arm and the entry dies 3/3, deterministically, on
`Fatal{UnmigratedPipeInput, "GetBufferBindingSlot@DrawArrays"} [BARRIER-PULLED, UNBARRIERED,
the client did not fill it, retires in P8 (indirect), P9 (readback), P13 (transfer)]`.
Its counterpart is this head itself: the escalation is GONE and the lane is green, so nothing
needed it - and the strict census's admitted set drops from nine rows back to ID-128's eight,
because the pull no longer happens at all rather than being legalised.
- Gate on the flipped head: unit 2256/2256, isplit 179/179, gens rc=0, lane counts unchanged
(179 / 1357 / 2 / 2).
- ID-133: escalation (iii) in MGPipeBarriered - a draw_vbo with NumDraws > 1 that is NOT
kDrawIsIndirect is barriered. Espryt's indirect multi-draw tiers reach
MultiDrawImpl::RunIndirect, whose apply reads the client's GL_DRAW_INDIRECT_BUFFER binding
(BoundDrawIndirectBufferId, MultiDraw.cpp:87) - GetBufferBindingSlot, retiring in P8 - and
unbarriered that is Fatal{UnmigratedPipeInput, "GetBufferBindingSlot@DrawArrays"} on 18 lane
entries. Backtrace of the aborting thread, verbatim frames: CountBarrierPull <-
MultiDrawImpl::RunIndirect <- MultiDrawImpl::DrawElementsBatch <- ServerVerbSink::OnDrawVbo
<- PipeWireDecoder::DecodeAndApply <- PipeApplier::ApplyOne.
- TWO PREMISE CORRECTIONS, both measured, both in the report and in the contract. (a) There is
no indirect multi-draw OP: all twenty draw entry points collapse onto draw_vbo, and the tier
is resolved on the server per batch (ResolveTierForBatch), so the escalation cannot be keyed
on the tier and its cost is NOT confined to the opt-in tier lanes - a plain glMultiDraw* now
waits on the auto -> ext default too. NumDraws > 1 is the narrowest wire fact that contains
the reaching set; kDrawIsIndirect is excluded so Sodium's indirect draw, which resolves by
handle and pulls nothing, keeps running ahead. (b) The read is a SAVE/RESTORE of a GL binding
name around the tier's own scratch buffer, not a data dependency - so it can be retired
outright by giving BoundDrawIndirectBufferId the handle arm its neighbour
ResolveBoundIndexBuffer already has, and this escalation withdrawn. That is three lines in
MultiDraw.cpp, which ID-113 gives to mv, so it is reported rather than edited here.
- The client's half is verb-keyed because the fill decision is asked before the record exists:
{MultiDrawArrays, MultiDrawElements, MultiDrawElementsBaseVertex} is exactly the set whose
record can carry NumDraws > 1 without kDrawIsIndirect. The inclusion goes that way round on
purpose - a record the server calls barriered whose fields the client did not fill would be
an ADMITTED pull of a stale value, which is worse than the abort.
- ID-134: the two ClientVertexArrayScenario entries get the label integration-clientarrays-split
and an expected-red CI step that asserts the MARKER, shaped like gl's Magma lane. ID-131 heeded
by COUNTING, not by assuming: -L integration-split 181 -> 179, -L integration-gpu 1359 -> 1357,
the new label selects exactly 2. The step branches on whether run-ahead is actually ARMED,
because kMGPipeP5eRunAheadReady is a BUILD constant: on a head where it is false the refusal is
unreachable and the entries are legitimately green, so an unconditional demand for red would
fail for the one reason that is not a defect. The client says which world it is in in its own
log line; delete the green branch when the flip lands for good.
- CONTRACT-P5E §3.5 amended to the code: "outside a barriered fill" rested on the caller's claim
about the FUTURE, and a guard whose exemption cannot be false on the class it exists for is not
a guard - it never fired on any of the 70 red entries. The landed rule is "not while the applier
is inside, barriered fill or not", with the fill sites taking §2.5's forced wait first, twice
per filling verb because the block is written either side of the emitters.
- AND §3.2 IS MARKED UNLANDED, which nobody had noticed: "the server's stamp is server-private
… never into the shared block" describes storage the applier owns, and
MGPipeServerStampVerbBoundary still writes m_filled / m_currentVerb / m_serverStampedVerb into
gPipeInputs itself. That gap is what made the race possible. Splitting the stamp is the P11
item - but per-role stamps WITHOUT versioning the BARRIER_PULLED values would be worse than
today, because it turns a loud Fatal into a silent stale read.
- §2.1 carries escalation (iii) as a row, per its own rule that a new escalation is a ruling and
a row in the contract rather than a condition at a call site.
- Gate on the flipped head: unit 2256/2256, isplit 179/179 HARD GREEN, gens rc=0, doc citations
rc=0 (the three remaining are CONTRACT-P5.md's and pre-date this branch).
- ID-132's finding, diagnosed: with the flip thrown the 70 red lane entries are ONE race
and two debts. The race is the client's residual fill writing gPipeInputs while the apply
thread is inside an earlier UNBARRIERED record. Measured interleaving, verbatim:
`[MobileGLIntegra/ERROR] RA2-PROBE fill verb=DrawElements wireop=81 waitclass=-1
applierInside=1` then `[mgl-srv-apply/ERROR] RA2-PROBE unfresh field=IsCapabilityEnabled
verb=DrawElements serverStamped=0 ownership=RECORD-SUPPLIED` then
`[mgl-srv-apply/FATAL] MGPipe: Fatal{UnmigratedPipeInput, "IsCapabilityEnabled@DrawElements"}`.
The GL thread's MGPipeServerClearVerbBoundary withdrew the applier's own stamp mid-record.
- The marker's verb is the CLIENT's verb, which is what identifies the writer without a
probe at all: the applier can only ever put a verb of MGP_VERB_OP_LIST into the block, and
40 of the 54 unbracketed aborts named a verb that is not in it.
- A/B control on the same binary and the same records: MOBILEGL_IPC_RUN_AHEAD=0 is 8/8 green
where the default arm is 2/6 red, so the defect is in the wait rule and not in a record.
- RefusePipeInputsTouchWhileApplierOwnsIt could not fire on any of it: its run-ahead arm read
`if (isBarrieredFill) return;`, and that sentence is a claim about the FUTURE ("this thread
is about to park behind the record"). The order at the validate point is fill, then emit,
then park. So the arm now tests the fact - `isBarrieredFill && !ApplyThreadIsInsideApplier()`
- and the fill sites MAKE it true first with §2.5's forced wait (QuiesceApplierBeforeFill).
- TWICE PER VERB, because the block is written in two phases that straddle publication: the
serial bump / stamp withdrawal / verb rename run before the fourteen emitters and the
63-field walk of step 4 runs after them, and the records those emitters published are
records whose apply reads the block.
- ClientVerbIsBarriered: MGP_VERB_OP_LIST joins the whole draw family through one row
(DrawVbo -> DrawArrays), so inverting it verb-first answered kOpCount for DrawElements and
eighteen other draw verbs, and the "unknown verb answers barriered" default filled for each
while the record it published was a kWaitNone draw_vbo it never parked behind. The family's
row is applied to the family; every other unknown verb keeps the conservative answer, which
the wait above now makes honest. Measured alone it is worth 112 -> 133 isplit; with the wait
in place the lane is 161 either way, so this half is the PERFORMANCE half - without it every
indexed draw takes a forced drain and run-ahead is lockstep by another name on the draw path.
- Red-once A: put the guard's arm back to `if (isBarrieredFill) return;` and
RemoteGuards.ClientBarrieredFillWhileTheApplierIsInsideUnderRunAheadIsFatalByName exits 0
instead of aborting (`Value of: DiedOfAbort(child) Actual: false`), while its green control
keeps passing. Red-once B: delete the kDraw fallback and
RemoteRunAhead.AnIndexedDrawVerbIsUnbarrieredAndTouchesPipeInputsNotAtAll dies of signal 6
with `Fatal{RoleViolation, "gPipeInputs"} - the GL thread touched gPipeInputs
(MGPipeValidateForVerb) on a RUN-AHEAD session in a barriered fill that did not first wait
for the applier to catch up`.
- Both new cases run in the ordinary unit lane with run-ahead armed by the fixture, which is
what ID-132(1) asks for: the strict lane runs under lockstep and cannot see this class.
- Gate on the flipped head: unit 2256/2256, isplit 161/181 (was 112), gpu 1339/1359 (was 1290),
gens rc=0, flavours rc=0. The remaining 20 are two named debts, not this race: 18 are
`GetBufferBindingSlot@DrawArrays [UNBARRIERED]` on the two indirect multi-draw tiers, whose
retiring phase is P8, and 2 are ID-82's own refusal of client vertex arrays.
- The arm is stated and not inferred (ID-81): WaitForApplyToCatchUp's first test is
`m_runAheadArmed && m_started`, which reduces to Transport != Monolith. Under lockstep,
under monolith and under MOBILEGL_IPC_RUN_AHEAD=0 every line added here is a call that
returns, so those arms are unchanged.
kMGPipeP5eRunAheadReady (MG_Backend/Init.cpp) and kMGPipeP5eClientWaitRuleLanded
(MG_Pipe/PipeApply.h) both to true. They are ONE switch with two spellings and the integration
commit throws both.
THIS BRANCH IS NOT MERGEABLE AS IT STANDS and is parked so the defect it exposes can be worked on
against a reproducible head. Measured on this commit:
build rc=0 · unit 2254/2254 · gens rc=0 · flavours rc=0 (pull 915 TUs, push 929 TUs)
integration-split 112 / 181 (69 failed)
integration-gpu 1290 / 1359 (69 failed)
and the failures are FLAKY: 71 failed at -j 4, 68 at -j 1, and a single entry run alone passes and
then aborts on a repeat. A census over all 181 entries under each entry's own command and
ENVIRONMENT gives 70 red on 17 distinct <field>@<verb> pairs, over just FOUR fields:
27 GetRenderStateParametersVersion
25 GetTextureContextId
16 GetBufferBindingSlot
2 IsCapabilityEnabled
spread across eleven verbs - Clear, DrawArrays, DrawElements, DrawElementsBaseVertex,
DrawElementsIndirect, DrawElementsInstancedBaseVertex, EndTransformFeedback, GetIntegeri_v,
GetSyncStatus, MultiDrawElementsBaseVertex, ReadPixels. Several of those verbs are BARRIERED, which
is what makes this interesting: 16 of the 70 abort on the UNBARRIERED arm
(why=UNBARRIERED) and the other 54 are the plain unfresh-read abort with no [BARRIER-PULLED]
bracket at all, i.e. a RECORD-SUPPLIED field that the freshness stamp says was never filled.
One field at one verb, consistently, would be a missing migration. Four fields scattered over
eleven verbs, flaky run to run, including barriered ones, is a RACE - and the obvious candidate is
that gPipeInputs is shared mutable state whose mutual exclusion WAS the lockstep. The client still
fills it for barriered verbs while the apply thread is draining earlier unbarriered records, so the
client's fill and the server's verb-boundary stamp can now overlap in time. That is consistent with
P5d's own research conclusion, recorded in the roadmap, that retiring this barrier needs
gPipeInputs VERSIONING or double-buffering, deferred to P11 after P3b/P4b's handle-keyed twin
tables.
The strict lane being hard green (181/181, zero Fatal) is necessary and NOT sufficient, and this
commit is the proof: strict runs under lockstep, where ApplyOne stamps every record barriered, so it
cannot see anything that only happens when the client stops waiting. The lane measures remaining
DEBT; it does not measure whether run-ahead is correct.
The file carried gl's base measurement (7c6f6886, before pa and mv landed) and said so rather than
hiding it. The merge discharged that note exactly as written, and the two-sided ratchet named both
deltas by itself rather than being told:
- GetProgramForDraw@DrawArrays no longer appears - pa retired it, 62 entries to 0, and it was the
read that fired once per draw and kept every draw barriered. Removed here, in the wave that
retired it, which is the whole point of the other side of the ratchet: an expected set that keeps
rows nothing writes any more is how a lane rots green.
- GetBufferBindingSlot@DrawArrays is new, 18 entries, all of them the two indirect multi-draw
tiers. mv NAMED it as a latent row before it could fire - BoundDrawIndirectBufferId's
GetBufferBindingSlot(DrawIndirect), which "would surface as GetBufferBindingSlot@DrawArrays if an
indirect tier were ever forced under strict" - and then gated the five tiers, which forced it.
It retires in P8 (FieldOwnership.def:78), so it is a debt owed by a later phase and not by this
one. Added with that reason.
Measured on the integration tree, two independent instruments agreeing (Harness/split_log_paths.py
markers, and a separate per-entry census that drives each entry's own command and ENVIRONMENT from
ctest --show-only=json-v1):
integration-split 181 / 181 green
Fatal{UnmigratedPipeInput 0 distinct pairs
Admitted{ 10 distinct pairs - 8 by the generated table, 2 by escalation
So "the strict lane is hard green" is now a statement a script evaluates, not one a reader argues:
every entry completes, no Fatal marker over the log set ctest itself declares, every Admitted marker
checked against the same table the C++ answers from, and the ratchet fails in BOTH directions.
Gate on this head: build rc=0, unit 2254/2254, integration-split 181/181, integration-gpu 1359/1359,
gens all rc=0, flavours rc=0 (pull 915 TUs push-absent, push 929 TUs push=1).
swung0x48