irisandClaude Fable 5.1
e49d0e606f
Takes the -gpu host pair the earlier software-mode comparison flagged as
missing. Under real GPU rendering (--features force-gles: the default
Vulkan backend has no adapter at all under plain host-GPU boot, confirmed
by the exact wgpu error), iris's median frame (15.0ms) is faster than
Compose's (20.0ms) on the same session content -- the opposite shape from
the software-mode table. The new redraw-to-submit/submit-to-present split
shows iris's own CPU work is a median 0.2ms per frame; almost the whole
frame is time handing off to the driver, consistent with (but not proof
of) the software-mode gap being mostly SwiftShader's CPU rasterisation
cost rather than iris-specific slowness.
A same-mode software force-gles run, meant to isolate the backend, hit a
third distinct crash instead (SwiftShader's GL path reports itself as
OpenGL ES 3.0, which has no compute shaders, and iris's device request
assumes them unconditionally) -- real scope to fix, not done here, so the
software-mode question stays open. A real intermittent touch-scroll
dropout was also reproduced (six consecutive swipes produced zero
redraws while taps kept working; an identical retry then succeeded) and
is not explained. The idle-redraw and virtualised-culling findings from
the software-mode pass were confirmed to hold under real GPU rendering
too.
DECISIONS.md's DEFERRED item carries the updated table; the iris-vs-
Masonry choice itself is still Iris's to make. IRIS.md records the
FrameReport::record_split/FrameStats::cpu_p50/gpu_wait_p50 API from the
prior commit (e2a1fad), which this pass's measurement used.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>