Two problems, both found by looking at the panel rather than the metric.
The frame-stats line reported ONE instantaneous frame every 5 seconds --
about 1 frame in 500 -- printed beside a 100-frame average. Both hide exactly
the fault they are used to chase: a 2ms duplicate and a 21ms double-wait
average to precisely 10ms, so a ticker stalling on half its frames still
reports a healthy "Avg FPS: 100.0". That reading cost several rounds of
chasing the wrong layer. The line now aggregates every frame since the last
log and reports median, p95, max, min, and explicit stall and skip rates
(past 1.5x the median missed a refresh; under half never reached the panel,
because dirty tracking skipped the swap so the frame never waited on vsync).
On the hardware this now reads:
leaderboard 100.0 fps over 501 frames | median 10.00ms p95 10.05ms
max 10.34ms | stalls 0 (0.0%) skips 0 (0.0%)
The binding rebuild's blit patch becomes opt-in (RGB_PATCH_BLIT=1, default
off). Reordering that loop to row-major changes what a torn frame looks like:
column-major tearing shows as a vertical seam, row-major as a horizontal split
between the panel's upper and lower halves. On a 1/32 scan panel that reads as
a one-pixel fold across the middle of every panel, which is what was reported
on hardware and what went away when the blit was reverted. All of the measured
gain comes from the SwapOnVSync change, so the risky half is simply not worth
taking; the header says so.
Also fixes --install resolving its paths against $HOME, which is /root under
sudo, so it looked in /root/rgbmatrix-nogil-build and died with "no built
module found" on a machine where the build had just succeeded. It now resolves
SUDO_USER's home. Both build paths are verified on the Pi: default yields one
GIL-release site, RGB_PATCH_BLIT=1 yields two.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Scrolling ran at 44-46 fps on a 2x128x64 chain and 14-17% of frames took
41-53ms, which reads as judder. Four independent causes, each measured on
the hardware; details and the diagnostic recipe are in
docs/SCROLL_PERFORMANCE.md.
The high-FPS loop slept a flat 8ms after every render. display() has
already blocked on the panel's vsync by then, so that sleep was added to a
wait that had happened: ~4ms of render plus 8ms put each iteration at ~12ms
against a 10ms refresh grid, so every swap missed a refresh and the loop
settled at 50fps while asking for 125 -- with no headroom, so a further
14% of frames slipped again. It now sleeps only the remainder, with a 1ms
floor so plugin threads still get the GIL.
ScrollHelper stepped position on a wall clock at 1/scroll_delay steps per
second. Plugins set scroll_delay to the frame period, so that comparison
sat exactly on its own threshold: a frame arriving a hair early moved zero
pixels and rendered an identical frame, dirty-tracking skipped the swap, it
returned in ~2ms, and the beat repeated. No scroll_delay value tunes that
out -- a shorter delay trades stalled frames for periodic double-steps.
Both modes now accumulate elapsed time at the same configured speed, so
position stays proportional to real time.
Sub-pixel blending goes back to off by default. It renders a half-step by
mixing two adjacent columns, which on a coarse panel showing pixel-font
text alternates crisp and smeared frames and reads as shimmer -- visibly
worse than integer stepping on the hardware. Vegas mode still opts in.
disk_cache uses orjson when importable, falling back to the stdlib. Encoding
a ~1MB record drops from 14.8ms to 5.4ms end-to-end, and that work holds the
GIL while a marquee is on screen. display_manager also checksummed the whole
framebuffer twice per frame (dirty tracking, then the preview snapshot); the
snapshot now takes the checksum the caller already computed.
New src/common/scroll_config.py resolves scroll settings in one place. Five
ticker plugins each hand-rolled this and disagreed: odds-ticker ranked the
deprecated scroll_pixels_per_second above the documented scroll_speed/delay
pair, and because that key carries a schema default the documented settings
were dead for every user (ChuckBuilds/ledmatrix-plugins#408), while
ledmatrix-leaderboard read the same key only as a fallback. The resolver also
warns when a speed will not advance a whole number of pixels per refresh,
which is the property that actually determines whether a scroll looks smooth.
scripts/build_rgbmatrix_nogil.sh rebuilds the rgbmatrix binding so it
releases the GIL. Upstream declares SwapOnVSync without nogil, unlike
SetPixel/Clear/Fill beside it, so the render thread held the GIL for the
whole vsync wait and starved background threads into long uninterruptible
bursts. The script patches, builds and self-verifies into a scratch tree;
--install backs up the original and rolls back if the service does not come
back healthy.
Measured after: 100 fps locked, no stalls observed, render thread down from
51% to 19% of one core.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
