Iris's phone came back "now THAT is smooth", and reading that run against
the bench's own timings found three things the report was getting wrong
-- two of them shipped yesterday in the fix for the last three.
`missed vsyncs` counted idleness. Every gap between frames was treated as
cadence, so the bench's own pauses read as stutter: 276 for sixteen 300ms
rests between flings, 2410 for twelve hundred 50ms keystroke gaps, 821
for four hundred 50ms stream gaps -- each within a few percent of the
arithmetic. A gap now measures anything only if the frame before it had
asked for another one.
`late` counted the swapchain wait as cost. A well-paced loop spends each
frame blocked in the acquire, so its total sits at exactly one refresh
period and every frame lands on the budget boundary -- 0.4ms of work and
5.7ms of waiting is not a late frame. It is judged on `FrameParts::work`.
And the refresh rate is the larger of what the platform claims and what
the run sustained, because each can only be wrong one way.
`Display.getRefreshRate()` answered 60 for a run that drew 3405 frames in
33.1s, since a phone that varies its rate answers with whatever mode it
is in when asked. The first attempt at measuring it instead took the
fastest tenth of the gaps and reported 88Hz for this repo's 60Hz
emulator, whose app manages 54 -- a budget no frame there could meet,
invented out of the app's best moments, and caught only by running the
corrected report on the emulator before shipping it. A sustained rate is
a floor and cannot do that. Both are printed when they disagree.
Also corrected in the docs: "103fps on a 120Hz screen" divided the fling
phase by its whole duration, rests included. Both runs sustained ~120.3fps
through the motion, so the callback ordering was never costing frames --
what changed is the clock, which moves no frame count at all, which is
exactly why nothing in a report could show it.
`fling_profile.rs` is `frame_profile.rs` and gained a stream run, which
says where the frame time now is: folding an arriving event is 0.35ms and
applying the diff 0.41ms, while the frame is 3.86ms here and 9.5ms on the
phone. 401 events move the item count 652 -> 654, so nearly every one is
a delta into the same row -- the cost is re-shaping one growing message,
not `fold_event`'s per-event clone, which was the hypothesis and is what
measuring it ruled out.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Iris, from her phone: "some stuttering when flinging in particular.
Harder to notice with my finger directly moving the scroll." Her fling
phase was 103fps on a 120Hz screen at p50 6.3ms.
Two of the four things found are corrections to the instrument, not the
renderer. The swapchain acquire -- `get_current_texture`, which *blocks*
until the compositor frees an image -- was inside the span the report
called iris's CPU work, so a fling comfortably ahead of the display read
as milliseconds of being slow. A frame is now three measured parts
(`FrameParts`: build, acquire, submit), per phase as well as per run. And
nothing could say a frame was never *produced*: `late` counts frames that
cost too much, which a reader does not see, while a frame that never
happens leaves the last one up for two refreshes, which is the stutter.
`PhaseStats::missed` counts vsyncs nothing was drawn for. It closes on
the emulator: 1548 frames + 452 missed over 33.0s at 60Hz is 1980
vsyncs.
The other two are the frame loop. `Choreographer.postFrameCallback`
schedules for the next vsync after the call, and iris asked at the *end*
of the callback -- so any frame whose work ran past the boundary
registered too late and got the vsync after, one frame over budget
silently costing a second. It is asked for immediately after
`tick_animations` now, on both backends. And the fling was advanced on
`Instant::now()` rather than the vsync `do_frame` carries: frames are
presented on an even cadence whatever clock computes them, so sampling
the spline at "whenever the callback ran" moves the content unevenly with
no frame late enough to appear in any report -- and a drag never had it,
which is the asymmetry Iris described. `PointerClock` is `DeviceClock`
and the view keeps one, anchored by whichever of a touch or a frame comes
first, so a fling is advanced on the clock its velocity was measured on.
`opt-level` for the Android release build goes from "s" to 3. The table
in RUST.md picked "s" on bytes alone; over the same warm fling eight
times iris's own per-frame work is p90 0.15ms/p99 0.42ms at "s" against
p90 0.09ms/p99 0.26ms at 3, for 1.8 MB of arm64 APK.
`app-rust/tests/fling_profile.rs` is the rig that established what a
fling frame actually costs and is kept for next time (Iris: "please keep
the profiling rig around for future use"): only one frame in six lays
anything out, and the multi-millisecond spikes are all first-pass.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Iris: "the organization of the rust rewrite is a mess right now... there
shouldn't be anything related to the app inside of iris. Iris is supposed
to be the UI framework alone." And, on the crate count: "I'm confused why
the app only code needs more than one crate though."
Nine cargo workspaces become three, and the port's project code -- which
sat in five places, four of them inside the framework -- becomes one crate,
`ai-app`, in `app-rust/`:
client-core -> app-rust/src/client
iris/transcript-ui -> app-rust/src/ui
iris/transcript-fixture -> app-rust/src/ui/fixture.rs + tests/ + touch/
iris/desktop-app -> app-rust/src/desktop + src/bin_desktop.rs
iris/android-app -> app-rust/src/android + android-project/
android-shell -> app-rust/src/shell
iris/ keeps core, macro, the iris crate, tabs-ui and rig-input, and now
mentions no session, transcript, setup or server anywhere.
Only two of the old splits had a reason that survived reading. event-model
stays a crate at the repo root because server/ depends on it too, so a
crate is what makes the backend and the app agree by construction. The two
Android .so names looked like a hard constraint -- a package produces one
library artifact -- until P2 turned out to already plan merging those two
Android apps into one; both faces now come out of libai_app.so, picked
apart by features so `--no-default-features --features shell` keeps wgpu,
parley and iris out of the Compose app's APK. docs/RUST.md's "One app
crate" has the rest, including what each remaining feature is for.
DECISIONS.md and SUBAGENTS.md move into docs/ with everything else.
Verified: ./run-tests.sh and `cd iris && cargo test` green, clippy and fmt
clean in all five workspaces, `cargo ndk -t x86_64` links libai_app.so,
build-apk.sh produces an APK that installs and launches on this checkout's
emulator (Gl ... virgl, as expected), and the phone-sized headless
screenshot renders the transcript unchanged.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
iris
