perf(cg): skip prefill loop on cache-warm frames via generation tracking by softmarshmallow · Pull Request #618 · gridaco/grida

softmarshmallow · 2026-03-31T16:41:30Z

Add a monotonically increasing generation counter to PictureCache that increments on any mutation (insert, invalidate). The prefill loop now compares the current generation, variant key, and layer count against the last successful prefill — when all match, the entire O(N) iteration is skipped in O(1).

On 135K-node scenes, this eliminates ~800µs of HashMap lookups per cache-warm frame. Measured improvements on 01-135k.perf.grida:

rt_pan_fast_fit p50: 111µs → 76µs (-32%)
rt_pan_fast_fit p95: 263µs → 153µs (-42%)
pan_settle_slow_fit settle: 1034µs → 709µs (-31%)
Criterion large_baseline/pan: -14.0% (p < 0.01)

Summary by CodeRabbit

Refactor
- Improved rendering performance with optimized scene caching that reduces unnecessary processing when scenes remain unchanged.
Documentation
- Added documentation describing cache validation optimization techniques and performance benefits for scene rendering.

…y fixtures Removed all 12 original fixtures that relied on unsupported CSS features (grid, margin, tables, viewport units). Added 21 new fixtures organized by category (layout, box, paint, text, mixed), each testing a specific CSS property group using only features the HTML→IR pipeline supports. Co-Authored-By: Claude Opus 4.6 <[email protected]>

- Add csscascade adapter, cascade driver, and arena DOM modules - Add HTML import module (html/mod.rs) with Stylo-based CSS resolution - Wire grida-dev to load .html files via from_html_str - Support ~35 CSS properties: layout (flex, block, display:none), box model (width/height/min/max/padding/overflow), paint (backgrounds, gradients, borders, shadows, opacity), text (font, color, align, line-height, letter-spacing, word-spacing, text-transform, decoration), and inline style attributes - Map block containers to flex-column for correct flex-child sizing - Emit text-only elements as Container+TextSpan to preserve box model Co-Authored-By: Claude Opus 4.6 <[email protected]>

Keep HTML import pipeline additions alongside main's raster image refactoring (load_raster/RasterScene). Remove duplicate pub mod query. Co-Authored-By: Claude Opus 4.6 <[email protected]>

The CSS cascade adapter uses a process-global DEMO_DOM static, so concurrent from_html_str calls race on that shared slot causing Stylo debug_assert panics. Added a mutex to serialize HTML tests. Also ran cargo fmt to fix formatting. Co-Authored-By: Claude Opus 4.6 <[email protected]>

Co-Authored-By: Claude Opus 4.6 <[email protected]>

- Replace css_box_shadow_to_cg with comprehensive css_effects_to_cg handling box-shadow, filter: blur(), filter: drop-shadow(), and backdrop-filter: blur() in a single pass - Add css_text_shadow_to_effects for text-shadow on TextSpan nodes - Add css_blend_mode_to_cg mapping all 16 CSS mix-blend-mode values - Wire effects + blend_mode into all three emitters (container, rect, text) - Fix test mutex poisoning cascade with lock_html() helper - Add 8 deterministic tests for effects properties Co-Authored-By: Claude Opus 4.6 <[email protected]>

Wire text-decoration-color and text-decoration-style from Stylo into TextDecorationRec. Mark thickness and skip-ink as TODO (gecko-only in Stylo servo mode). Add L0 fixtures for text-decoration variants and 2D CSS transforms (implementation pending). Co-Authored-By: Claude Opus 4.6 <[email protected]>

Add docs/wg/format/ with canonical tracking docs for the Grida IR schema and its mapping from CSS, HTML, and SVG. Tables are oxfmt- formatted to minimize diffs on future edits. Co-Authored-By: Claude Opus 4.6 <[email protected]>

Add docs/wg/format/index.md as docusaurus entry point. Add format:md frontmatter to grida.md, css.md, svg.md for MDX compatibility. Link format mapping docs from format/README.md, format/AGENTS.md, and docs/AGENTS.md. Co-Authored-By: Claude Opus 4.6 <[email protected]>

Remove CSS_PROPERTY_MAPPING.md (aspirational, marked unimplemented features as done) and html/TODO.md (superseded by docs/wg/format/). Update csscascade README roadmap to reflect current state. Add doc pointer in html/mod.rs to the canonical tracking docs. Co-Authored-By: Claude Opus 4.6 <[email protected]>

- Remove dead no-op code (is_none → assign None) in emit_container - Remove unconditional eprintln in from_html_str (library code) - Add thread safety warning to from_html_str doc comment - Document text-decoration single-line limitation with TODO - Fix index.md missing format:md frontmatter - Fix svg.md stroke table missing Notes header column - Fix fixture title claiming "Thickness" coverage - Remove text-shadow/text-transform from README excluded list Co-Authored-By: Claude Opus 4.6 <[email protected]>

feat: HTML/CSS → Grida IR import pipeline

Add a monotonically increasing generation counter to PictureCache that increments on any mutation (insert, invalidate). The prefill loop now compares the current generation, variant key, and layer count against the last successful prefill — when all match, the entire O(N) iteration is skipped in O(1). On 135K-node scenes, this eliminates ~800µs of HashMap lookups per cache-warm frame. Measured improvements on 01-135k.perf.grida: - rt_pan_fast_fit p50: 111µs → 76µs (-32%) - rt_pan_fast_fit p95: 263µs → 153µs (-42%) - pan_settle_slow_fit settle: 1034µs → 709µs (-31%) - Criterion large_baseline/pan: -14.0% (p < 0.01) Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

vercel · 2026-03-31T16:41:44Z

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coderabbitai · 2026-03-31T16:42:06Z

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Walkthrough

The PR adds a generation-based cache invalidation optimization to skip redundant picture cache prefill operations. A monotonic counter in PictureCache increments on mutations; Renderer records the generation plus metadata (variant key and layer count) after prefill, then skips the O(N) iteration on subsequent frames if all three values remain unchanged.

Changes

Cohort / File(s)	Summary
Picture Cache Mutation Tracking `crates/grida-canvas/src/cache/picture.rs`	Added `generation: u64` field and public `generation()` accessor. Cache mutations (`set_node_picture`, `set_node_picture_variant`, `invalidate`, `invalidate_node`) now increment generation using `wrapping_add(1)`. Added `variant_store_is_empty()` helper. Restructured `set_node_picture_variant` control flow to ensure consistent generation increments across all insert paths.
Prefill Skip Optimization `crates/grida-canvas/src/runtime/scene.rs`	Added three tracking fields to `Renderer`: `last_prefill_generation`, `last_prefill_variant_key`, and `last_prefill_layer_count`. In `prefill_picture_cache_for_plan`, a new fast-path computes effective variant key and visible layer count; if all three tracking values match current cache state, prefill iteration is skipped. Tracking fields updated after successful prefill and initialized to sentinel values (`u64::MAX/u64::MAX/0`).
Optimization Documentation `docs/wg/feat-2d/optimization.md`	Added new section describing the "Picture Cache Prefill Skip" mechanism, explaining generation counter semantics, variant key unification for effect-free scenes, skip-path correctness across stable/unstable transitions, and performance deltas.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

perf(cg): unify picture cache variants for effects-free nodes #614: Introduces variant key unification (storing effect-free nodes under variant_key=0), which this PR builds upon with the generation counter and skip-path logic.
perf(canvas): use FxHash for NodeId-keyed caches #600: Modifies the same PictureCache struct, replacing internal HashMap types while this PR adds generation tracking and accessors.

Suggested labels

cg, performance

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main optimization: skipping the prefill loop on cache-warm frames using generation tracking.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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chatgpt-codex-connector · 2026-03-31T16:44:30Z

crates/grida-canvas/src/runtime/scene.rs

+        if current_gen == self.last_prefill_generation
+            && effective_key_for_tracking == self.last_prefill_variant_key
+            && layer_count == self.last_prefill_layer_count
+        {


Include visible-set identity in prefill skip key

The new fast-path returns early when generation, variant_key, and only the count of planned layers match, but panning can change which nodes are visible while keeping the same count. In that case this check skips prefill_picture_cache_for_plan() even though newly visible nodes are not cached yet; since prefill is the only path that inserts node pictures, those nodes can remain uncached across frames (same generation/count), causing sustained cache misses and a performance regression during viewport movement.

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Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

softmarshmallow and others added 13 commits March 29, 2026 19:32

merge: resolve conflicts with origin/main

7822147

Keep HTML import pipeline additions alongside main's raster image refactoring (load_raster/RasterScene). Remove duplicate pub mod query. Co-Authored-By: Claude Opus 4.6 <[email protected]>

feat: add L0 fixtures for effects CSS properties

7f02f7b

Co-Authored-By: Claude Opus 4.6 <[email protected]>

docs: add format mapping reference and TODO trackers

53324e4

Add docs/wg/format/ with canonical tracking docs for the Grida IR schema and its mapping from CSS, HTML, and SVG. Tables are oxfmt- formatted to minimize diffs on future edits. Co-Authored-By: Claude Opus 4.6 <[email protected]>

Merge pull request #608 from gridaco/feature/elastic-tesla

3501b8f

feat: HTML/CSS → Grida IR import pipeline

softmarshmallow changed the base branch from main to canary March 31, 2026 16:41

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style(cg): cargo fmt – fix formatting in scene.rs

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Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

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softmarshmallow merged commit 855e48c into canary Mar 31, 2026
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softmarshmallow added the performance label Mar 31, 2026

coderabbitai bot mentioned this pull request Apr 1, 2026

perf(cg): render cost prediction module, prefill skip optimization, and Skia benchmarks #619

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This was referenced Apr 6, 2026

feat(canvas): headless Editor for non-browser testing #630

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perf(canvas): sub-pixel node culling at low zoom #636

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perf(cg): skip prefill loop on cache-warm frames via generation tracking#618

perf(cg): skip prefill loop on cache-warm frames via generation tracking#618
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