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perf #418: publish landblocks under the meter, not one per streaming tick

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Phase-1 measurement (new [publish-timing]/[stream-tick] probe surfaces,
ACDREAM_PROBE_REVEAL_TIMING=1) refuted the ~31 ms-per-admission
hypothesis: the hold runs at ~64 fps with the streaming tick at ~32 Hz,
the whole 625-block window costs only ~500 ms of publication CPU (far
blocks ~0.17 ms, near 2-43 ms), and steady state showed ZERO meter
yields with ~0.22 ms of the 2 ms budget used - yet exactly one block
published per tick against a ~400-deep completion queue.

The real limiter: Runtime's collision-generation activation is a
deliberate two-poll transaction (the first
TryAcquireCollisionPrefixMutationPermission poll parks residents and
refuses by design), and LandblockPresentationPipeline.Advance's metered
arm returned Completed=false on ANY nonterminal commit, which
DrainAndApply treats as end-of-frame. One landblock per 32 Hz tick =
the flat 32/s, with the authored budget ~90% idle.

Fix: the metered arm now uses the same Runtime-owned gate the unmetered
arm and the synchronous CompletePublication API always used
(CanContinueMutationSynchronously). The second poll runs in the same
frame under the same meter, so the unchanged 2 ms elapsed-time ceiling
is now genuinely the authoritative per-frame bound; with any real debt
(live residents parked mid-game, pending withdrawals, dispatch backlog)
publication defers to the next frame exactly as before. No budget
values change, no reveal-gate/readiness change, and the streamed result
is byte-identical - only the frame scheduling of identical operations.

Measured A/B (this binary, two runs): totalMs 12689 / 12734 vs baseline
26728/27395/27503; loaded slope 32/s -> bursts of 100-360/s, 625/625 in
~6-7 s vs ~23 s. The remaining ~12.7 s floor is fully attributed in
docs/ISSUES.md: ~8 s of real budgeted readiness work plus retail's
authored tunnel exit (TunnelContinue 2-5 s + two 1 s fades, golden
constants), so the <12 s acceptance needs a lead decision on the
hold-time budget, not another hidden limiter.

New regression pin:
MeteredLoaded_NonterminalCommitWithoutDebt_CompletesInOneMeteredAdvance.
Gates: Release build 0 errors; App tests 5576/3 skips/0 failed;
Runtime tests 1756/0.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
Erik 2026-08-17 20:11:35 +02:00
parent 45f379560a
commit 11106c70e7
6 changed files with 408 additions and 5 deletions
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70
src/AcDream.App/Streaming/LandblockPresentationPipeline.cs
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@ -64,6 +64,13 @@ public sealed class LandblockPresentationPipeline
public bool SpatialPresentationCommitted;
public bool EnvCellReplayCommitted;
public bool LiveRecoveryCommitted;
/// <summary>
/// #418 measurement only (<c>ACDREAM_PROBE_REVEAL_TIMING=1</c>): the
/// per-stage wall-clock attribution of this one publication. Null
/// whenever the probe env is unset.
/// </summary>
public PublicationStageTimings? Timing;
}
private readonly Action<LandblockBuild, LandblockMeshData>?
@ -460,6 +467,7 @@ public sealed class LandblockPresentationPipeline
Origin: completedBuild.Origin),
meshData),
Tier = LandblockStreamTier.Far,
Timing = PublicationTimingProbe.CreateTimings(),
};
_publications.Add(acceptedResult, transaction);
}
@ -509,6 +517,7 @@ public sealed class LandblockPresentationPipeline
LandblockId = farLandblock.LandblockId,
Cost = LandblockStreamResultCost.Estimate(farBuild, meshData),
Tier = LandblockStreamTier.Far,
Timing = PublicationTimingProbe.CreateTimings(),
};
_publications.Add(acceptedResult, transaction);
}
@ -553,6 +562,7 @@ public sealed class LandblockPresentationPipeline
Cost = estimate
?? LandblockStreamResultCost.Estimate(build, meshData),
Tier = tier,
Timing = PublicationTimingProbe.CreateTimings(),
};
_publications.Add(result, created);
return created;
@ -565,6 +575,26 @@ public sealed class LandblockPresentationPipeline
bool ensureProgress)
{
bool progressed = false;
void RunTimed(string stage, Action operation)
{
if (transaction.Timing is not { } timing)
{
operation();
return;
}
long start = System.Diagnostics.Stopwatch.GetTimestamp();
try
{
operation();
}
finally
{
timing.Add(
stage,
System.Diagnostics.Stopwatch.GetTimestamp() - start);
}
}
bool TryRun(
StreamingWorkCost cost,
string stage,
@ -572,7 +602,7 @@ public sealed class LandblockPresentationPipeline
{
if (meter is null)
{
operation();
RunTimed(stage, operation);
progressed = true;
return true;
}
@ -585,7 +615,7 @@ public sealed class LandblockPresentationPipeline
return false;
try
{
operation();
RunTimed(stage, operation);
meter.Complete();
progressed = true;
return true;
@ -810,8 +840,33 @@ public sealed class LandblockPresentationPipeline
}
if (transaction.PhysicsPublication.RuntimeMutationPending)
{
if (meter is not null
|| !_physicsPublisher
// #418: Runtime's collision-generation activation is a
// deliberate two-poll transaction — the first
// CommitCollisionGeneration poll closes the prefix
// quiescence boundary (parking any affected residents)
// and returns nonterminal; only a later poll may
// consume mutation permission. The metered path used
// to defer that later poll to the NEXT frame
// unconditionally, which serialized the whole
// completion drain to ONE landblock per streaming tick
// (DrainAndApply breaks on an incomplete publication):
// the measured login hold published exactly 32
// blocks/s at a 32 Hz tick rate with ZERO meter
// yields and ~0.2 ms of its 2 ms budget used. Runtime
// explicitly supports consuming that finite suffix
// synchronously when it reports no cross-cutting debt
// (CanContinueMutationSynchronously — the same gate
// the unmetered path and the synchronous
// CompletePublication API already use), so the
// metered path now polls again within the same frame
// under the SAME meter: every extra poll still passes
// TryRun/TryReserve, so the elapsed-time budget
// remains the authoritative per-frame bound. With any
// real debt (live residents parked mid-game, pending
// withdrawals, dispatch backlog) Runtime keeps
// reporting nonterminal-with-debt and this defers to
// the next frame exactly as before.
if (!_physicsPublisher
.CanContinueMutationSynchronously())
{
return new LandblockPublicationAdvance(
@ -976,6 +1031,13 @@ public sealed class LandblockPresentationPipeline
}
_publications.Remove(result);
if (transaction.Timing is { } completedTiming)
{
PublicationTimingProbe.EmitPublication(
transaction.LandblockId,
transaction.Kind.ToString(),
completedTiming);
}
return new LandblockPublicationAdvance(true, progressed);
}
}