repro (not for merge): idle Choreographer loop #58367 — empty playground pumps 60 doFrames/s - #58369
repro (not for merge): idle Choreographer loop #58367 — empty playground pumps 60 doFrames/s#58369capt-muji wants to merge 2 commits into
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…ync rate Four Android frame callbacks re-post themselves unconditionally on every doFrame, keeping the Choreographer armed at ~60fps while an app is foreground-idle with zero pending work (zero timers, zero animations, zero mount items, zero frames rendered): - JavaTimerManager.TimerFrameCallback (JavaTimerManager.kt) - FabricEventDispatcher.ScheduleDispatchFrameCallback - NativeAnimatedModule.animatedFrameCallback - FabricUIManager.DispatchUIFrameCallback Each now re-arms only when it has work, and re-arms lazily from its registration/posting path (createTimer / didDispatchMountItems / schedule). Measured on a stock RN 0.86.3 template app, idle foreground: ~600 doFrames/10s at 0.2-2ms each and 3.5-22.5% process CPU across API 28-36 devices; after this change: 0 doFrames, ~0% CPU, app fully functional.
… pumps 60 doFrames/s
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Summary
Reproducer for #58367 — not intended for merge (reproducer only, per the issue bot's request).
The playground renders nothing but an empty
View: on a physical Android device (verified API 28, 29 and 36), while this screen is foreground and idle, the framework keeps the main-thread Choreographer armed at ~60 doFrames/second with zero frames rendered and zero pending work — no timers, no animations, no mount items.Control: a plain native
Activityrendering an emptyViewreceives 0 doFrames at idle — the loop is entirely framework-driven. Full device matrix and root-cause analysis (four frame callbacks that re-arm unconditionally) are in #58367; the fix is in #58368.Test plan
adb shell atrace -t 10 -b 32768 view input -z -o /data/local/tmp/idle.atrace.gz && adb pull /data/local/tmp/idle.atrace.gz .grep -c "Choreographer#doFrame" idle.text→ ≈600 sections in 10 idle seconds, each containing only an empty "animation" stage — no layout, no drawadb shell dumpsys gfxinfo <rn_tester_pkg> reset && sleep 10 && adb shell dumpsys gfxinfo <rn_tester_pkg> | grep "Total frames rendered"→ 0Changelog:
[General] [Changed] - Add reproducer for #58367: RNTesterPlayground renders an empty View while the framework's idle Choreographer loop keeps firing ~60 doFrames/s (reproducer only, not intended for merge; fix in #58368)