MobileGL/docs/Disaggregated/notes/perf-p14/HANDOFF.md

P14 perf pass: handoff (checkpoint 2026-10-07)

Worktree .claude/worktrees/perf (branch perf, pushed to origin/feat/disaggregated). Estimate: ESTIMATE.md. BENCH.md / README.md are not written yet (see "Next").

Head and running totals

Head: 94705adc (plus this handoff commit). rd12, Lenovo Y700 (Adreno 750), clocks pinned, no per-frame glFinish (FINISH=false, the primary mode; finish=true serialises the split arms on one FenceWait round trip per frame), best of 3:

arm	Espryt start -> now	Magma start -> now	dev (pull) Espryt / Magma
monolith	69.8 -> 88.6	45.4 -> 69.5	115.1 / 86.1
inproc	71.1 -> ~107	63.2 -> ~99
shm	62.8 -> ~82	58.6 -> ~85
tcp	50.0 -> ~64	45.6 -> ~61

(split-arm "now" values are from the p14p A/B, before the last two monolith commits; re-measure.) GPU busy 22-33 % everywhere: every arm is CPU-bound on one thread.

Latest layer split (rd12 monolith, render thread ms/frame, simpleperf, head 94705adc = p14r)

layer	Espryt feat	Espryt dev	Magma feat	Magma dev
driver	1.56	1.40	2.15	1.98
backend	1.21	0.59	1.95	2.12
applier	0.07	0	0.13	0
client half	1.96	0.36	2.01	0.69
harness	6.46	6.27	6.50	6.25
total CPU	11.27	8.62	12.77	11.05

Client half top: validate self 0.22-0.26, verb port (MG_Record) 0.15-0.18, Tracker::Update 0.14-0.17, CopyField 0.07-0.09, VAO memo probe 0.07-0.09. Espryt backend top: PrepareForDraw 0.10, AdoptUnchangedBufferSets 0.10, PerNativeContext<...>::Current 0.084, SyncTextureToBackendByHandle 0.066, IsBufferDrawCleanByHandle 0.058. Magma backend top: SetupWireDraw self 0.35, BindDescriptorSetDeduped 0.23 (dynamic UBO offset moves every chunk draw), AcquireWireSlice 0.19.

Per-draw counts (instrumented build, p14count2.patch in the scratchpad, not committed): rd12 1471 draws/frame, 3.3 GL calls/draw; after the protocol change 66.8 B/validate (bind 16 B + uniform span ~47 B), VertexBuffers/IndexBuffer 100 % no-op.

Commits this pass (newest first)

94705adc inline applier / fill plan / word-wise spans / memo-answered draw bindings (+6 % Espryt, +3.7 % Magma); 81bdfb1f Espryt twin lookups w/o SharedPtr copy + one TLS block (+3.8 %); 032dcd24 Magma vertex-input layout kept on its record + slot-indexed buffer front; c1497bb8 VAO-kept bindings, uniform spans, context-values gate (split arms +5-10 %; stream span merge fixes a tcp regression); 0158a115 Magma pass-continuation memo; 8883e496 fill pins + VAO hash memo; 80dc9d45 VAO memo; 5788a602 Magma descriptor rebind; afcf8d96 Espryt AdoptUnchangedBufferSets; e6281b26, 4ef9705e Magma lookups/sampler memo; b556ec31, a9108e1a Espryt; 549a34bb server fault latch; 8346d809 slot allocator front; 267211e8 Magma hash memo + scratch.

In flight / next

1. Espryt backend lookups: PerNativeContext<T>::Current (TLS cache per T + non-inline serial/epoch calls), IsBufferDrawCleanByHandle, AdoptUnchangedBufferSets (compares the window every draw because the bind re-apply bumps VertexBuffersSerial), SyncTextureToBackendByHandle.
2. Tracker::Update: 18 shutters evaluated per draw, 4 fire. Needs a cheap "nothing but the VAO and the uniform moved" signal; no central frontend mutation epoch exists yet.
3. Residual fill: now a precomputed walk, but still ~11 CopyField per draw.
4. Magma: SetupWireDraw self, per-draw dynamic-offset descriptor bind.
5. Final full matrix (dev + 4 arms x 2 backends x openra/rd12, REPS=3), then BENCH.md, README.md, DEBTS.md rows (Magma 16 %, W9: closed with readings - render-state CSO cache mints 0/frame, Magma pipeline memo 99.0 % hit on rd12, 92.7 % on openra), FCL re-run on the final lib.

Harness

Scratchpad scripts (session-local): build_trace.sh W:/perf .p14X (trace APK, suffix = package top.mobilegl.plugin.p14X.trace), sign_install.sh <apk> <name>. W: is subst of .claude/worktrees (MAX_PATH). Then:

cd tools/device_bench/disagg
FIXTURES=<main checkout>/tools/trace_replay/fixtures PREP_PKGS=top.mobilegl.plugin.p14X.trace bash matrix_p14.sh prep
ARMS="monolith@p14a monolith@p14b" BACKENDS="DirectGLES DirectVulkan" WLS=rd12 REPS=3 TAG=ab bash matrix_p14.sh run
python p14_report.py ../../../.trace-work/perf-p14/ab
ARMS="monolith@p14X inproc@p14X shm@p14X tcp@p14X" REPS=1 TAG=ssim bash matrix_p14.sh ssim   # SSIM gate
ARM=monolith BACKEND=DirectGLES WL=rd12 TAG=prof PKG_FEAT=... SYMDIR=<unstripped libs> bash profile_p14.sh
python layers.py <perf.data> <binary_cache> MobileGLTraceRe <cpu ms/frame> --tail-ms=N [--detail=backend]

FIXTURES must point at a checkout with real LFS goldens (worktrees have pointer files). Host tests: WSL archlinux ~/mgl-perf-bld (clang, split+inproc, tests on); ServerSpawnTest / FuzzArm2 / PeerLatchTest fail there with Refuse{BuildFingerprint} (no build stamp in that tree), environmental.

Device state

HA27Q3LQ: CPU/GPU clocks PINNED (bash pin_clocks.sh restore to undo). FCL lib/config/props restored (md5 checked; debug.mobilegl.* props unset). Trace APKs top.mobilegl.plugin.p14*.trace installed.

CI

No run has completed since f8a9466b (each push cancelled the previous). workflow_dispatch runs on the checkpoint head: see the milestone message / below.