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T

andros fb45f6a582 README: replace mermaid xychart with grouped-bar images

Mermaid's xychart-beta cannot draw grouped bars or a legend: two bar
series overlap on the same axis position, so the paired GPU-vs-cairo
comparison was unreadable. Render the charts as images with real
grouped bars, value labels and a legend (bench/make-charts.py), and
embed them from .github/assets/.

2026-07-24 11:38:01 +02:00

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Benchmark harness

Redisplay-throughput benchmarks: the GPU backend vs stock Emacs, on the same binary (GPU on vs off). These produce the tables in the top-level README.md.

Requirements

An Emacs built --with-gpu (point EMACS at it).
python3 with Pillow and numpy.
xvfb-run (only for run-bench-hires.sh).

Run (GNU/Linux, X11)

# On-screen, ~1616x912 frame on the current display:
EMACS=/path/to/gpu/emacs ./run-bench.sh [RUNS]

# Headless 4K render throughput (GPU renders to an FBO, no present):
EMACS=/path/to/gpu/emacs ./run-bench-hires.sh [RUNS]

Each prints a stock-vs-GPU fps table with the speedup ratio. RUNS defaults to 3; the median is reported.

What it measures

Five workloads, each forcing (redisplay t) per frame (median of N runs, 80-frame warm-up first). GPU side runs vsync off (GL_NO_VSYNC=1) to measure frame cost, not the 60 Hz cap.

Workload	Stresses
`line-scroll`	one line/frame: few new glyphs (cairo is strong here)
`page-scroll`	one window/frame: many new glyphs
`full-redraw`	`redraw-frame`: everything repainted
`typing`	one `self-insert`/frame: minimal dirty rect, floor is one buffer swap
`image-scroll`	scrolling images: cached texture re-composite vs cairo re-blit from CPU

Buffer: 8000-line font-locked Emacs Lisp; image test uses a synthesized PNG.

Absolute numbers depend on GPU, driver and display server. The meaningful quantity is the ratio between the two modes on the same machine.

Files

gl-bench.el — the workloads. Reads GL_MODE (gpu/vanilla), GL_BENCH_COLS/GL_BENCH_ROWS, GL_BENCH_OUT. The scripts set these.
run-bench.sh — on-screen comparison.
run-bench-hires.sh — headless 4K render-throughput comparison.
make-charts.py — regenerates the README chart images from the numbers (matplotlib).

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