[perf] shapedRuns_ eviction is all-or-nothing clear() at cap (UI-Shared.cpp) #123

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opened 2026-06-17 21:18:54 +02:00 by jorijnvdgraaf · 0 comments

jorijnvdgraaf commented

2026-06-17 21:18:54 +02:00

Owner

Found by an adversarially-verified performance audit (confirmed real after a skeptic pass).

Location: implementations/Crafter.Graphics-UI-Shared.cpp:112-113
Severity: medium · Effort: moderate · Category: algorithmic

Problem

At kMaxShapedRuns (8192) the cache does a full clear(). A stream of unique strings (FPS counters, timers) alongside many stable labels periodically nukes all stable entries, forcing a full-UI reshape on the next frame.

Fix

LRU / last-used-frame stamp + evict-oldest, keeping the hot set resident. Needs an auxiliary usage structure alongside the map. (Related to GPU-atlas eviction issue #55, but distinct — this is the CPU-side shaped-run cache.)

Verification

Confirm this actually improves net peformance.

Found by an adversarially-verified performance audit (confirmed real after a skeptic pass). **Location:** `implementations/Crafter.Graphics-UI-Shared.cpp:112-113` **Severity:** medium · **Effort:** moderate · **Category:** algorithmic ### Problem At `kMaxShapedRuns` (8192) the cache does a full `clear()`. A stream of unique strings (FPS counters, timers) alongside many stable labels periodically nukes all stable entries, forcing a full-UI reshape on the next frame. ### Fix LRU / last-used-frame stamp + evict-oldest, keeping the hot set resident. Needs an auxiliary usage structure alongside the map. (Related to GPU-atlas eviction issue #55, but distinct — this is the CPU-side shaped-run cache.) ### Verification Confirm this actually improves net peformance.

jorijnvdgraaf added the

claude:ready

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2026-06-17 21:35:34 +02:00