Greg Pomerantz
2f4768f354
Three root causes, all fixed and verified on the Pixel 9 Pro: 1. Present phase (backend + renderer): VSYNC_LOCKED_RENDER defers the render to the vsync wake; RENDER_AHEAD presents the previous frame at the start of render() (phase = wake + ~1.1 ms) and holds the new frame one slot. Crash fix: a held wgpu frame must be PRESENTED, never merely dropped, before the next acquire (AlreadyAcquired panic at launch otherwise); discard_pending_frame presents too. 2. Full-res prefetch churn (src/lib.rs): the 8-slot full cache cycled through a ~20-cell viewport forever (137 decodes/20 s) and each eviction free()'d a 50 MB Vec on the UI thread (20-52 ms CPU spikes, ~7/s = the residual SLOWEV NonMain jank). Fix: 60 s tombstone cooldown on evicted paths (idle prefetch skips, urgent tap bypasses) + off-thread reaper for the freed blobs (insert: 21 ms -> 4 us). 3. (earlier) Skia final flush + Mailbox present mode (vendor, M3). Instrumentation (all behind --features perf): OTHR/INVK/INVK_TAG/FLCK lines for cross-thread closure timing and push-site tagging. Warm measured swipe, 8580-file grid: cadence median 8.33 ms (exact 120 Hz), p99 15.5 ms, 5/552 gaps >16.7 ms (0.9%, max 28.3 ms, zero >33 ms); PRES phase median ~994 us, zero late frames. Docs updated (docs/BUGS/scroll-jank-120hz.md, full scorecard + line reference). Also: vendored i-slint-core + wgpu-hal (vkshim interposition patch), vkshim profiling tooling, backend made a non-optional dep, debuggable flag for simpleperf (REMOVE before shipping).
39 lines
1005 B
Rust
39 lines
1005 B
Rust
//! Handling of global timestamps.
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#[repr(C)]
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#[derive(Debug)]
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struct MachTimebaseInfo {
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numerator: u32,
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denominator: u32,
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}
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extern "C" {
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fn mach_timebase_info(out: *mut MachTimebaseInfo) -> u32;
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fn mach_absolute_time() -> u64;
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}
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/// A timer which uses mach_absolute_time to get its time. This is what the metal callbacks use.
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#[derive(Debug)]
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pub struct PresentationTimer {
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scale: MachTimebaseInfo,
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}
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impl PresentationTimer {
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/// Generates a new timer.
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pub fn new() -> Self {
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// Default to 1 / 1 in case the call to timebase_info fails.
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let mut scale = MachTimebaseInfo {
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numerator: 1,
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denominator: 1,
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};
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unsafe { mach_timebase_info(&mut scale) };
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Self { scale }
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}
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/// Gets the current time in nanoseconds.
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pub fn get_timestamp_ns(&self) -> u128 {
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let time = unsafe { mach_absolute_time() };
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(time as u128 * self.scale.numerator as u128) / self.scale.denominator as u128
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}
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}
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