PoC: log Tier-B visibility cache hit rate#15
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Elton Carreiro (EltonCarreiro) wants to merge 1 commit into
Closed
PoC: log Tier-B visibility cache hit rate#15Elton Carreiro (EltonCarreiro) wants to merge 1 commit into
Elton Carreiro (EltonCarreiro) wants to merge 1 commit into
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Add observability to the fb_hasVisibleDescendants short-circuit by instrumenting cache hit/miss counters. Track calls and hits using atomic operations, logging statistics every 50 calls to measure cache effectiveness without impacting performance. Include last walk depth and result in logs to aid debugging on dense screens. No behavioral changes. Co-Authored-By: Claude <noreply@anthropic.com>
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Summary
Pure-observability PR — adds logging to
fb_hasVisibleDescendantsso we can measure how often the Tier B short-circuit actually fires on production / staging traffic. No behaviour change, just a log line.Context
fb_isVisible(XCUIElement+FBIsVisible.m:47) is a three-tier cascade:additionalAttributes[FB_XCAXAIsVisibleAttribute](cached).fb_hasVisibleDescendantswalks_allDescendantsand short-circuits to YES if any of them has a cached-visible entry.The hypothesis is that Tier B almost never fires in the standard
/sourcepath because nothing pre-populates the cache before XML generation runs. This PR confirms or refutes that hypothesis with hard data.Changes
WebDriverAgentLib/Categories/XCUIElement+FBIsVisible.m:Adds
<stdatomic.h>andFBLogger.himports.Wraps
fb_hasVisibleDescendantswith process-wide_Atomic NSUIntegercounters forcallsandhits.Every 50 calls, emits one log line:
Counters are process-wide, not per-request — they accumulate over the lifetime of the runner. Comparing hit rate before/after a workload is a simple subtract.
What we expect to see
Baseline (no warming): hit rate near 0% — confirming Tier B is dead code in the standard
/sourcepath because the cache is never pre-populated.If the rate turns out to be meaningfully > 0%, that's a surprise and worth investigating before we invest in pre-warming variants.
How to test
GET /sourcecalls against a representative app/screen.[VisCache] Tier-B stats:and read the hit rate.Why this as its own PR
Separated from #14 (visibility-cache pre-warming PoC) so it can land independently and give us data on master before we commit to the larger change. Safe to merge — no behaviour change, just logging.
🤖 Generated with Claude Code