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ChuckandClaude Opus 5.5 5aa7a63127 feat(timing): time garbage-collection pauses in the frame stats (#722)
A GcMonitor in src/common/frame_timing.py, installed once per process from gc.callbacks by the display manager (and render_bench), counts collections and seconds per generation, the longest, and those of 20 ms or more. A long one tags the next presented frame 'gc' in record(), so frame_soak shows its late rate under 'after work'; the stats file gains an additive 'gc' block printed as a 'Garbage collection' line; and a Render stall dump says when a long collection ran inside the stall. Diagnostic only: nothing tunes, freezes or disables the collector.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-01 21:29:08 -04:00

480 lines
21 KiB
Python

#!/usr/bin/env python3
"""Soak a running display and report how often moving frames reached the panel late.
Runs NEXT TO the display service, as any user: it only reads the stats file the
service writes (src/common/frame_timing.py) at the start and end of the run and
reports the difference. Nothing is stopped, restarted or drawn.
# 10 minutes, as the display is now
python3 scripts/frame_soak.py
# the same with the web preview open (the preview's PNG encodes are one of
# the things that used to make the render loop miss refreshes). An open
# preview is encoded at most once a second; through 3.8.0 it was up to
# five times, so a --preview run from before that change is not comparable
# with one from after it
python3 scripts/frame_soak.py --preview
# quick look at the totals since the service started
python3 scripts/frame_soak.py --show
# keep the report for a before/after comparison
python3 scripts/frame_soak.py --duration 600 --json soak-before.json
Exit status: 0 when the late-frame rate is within ``--max-late-pct``, 1 when it
is not, 2 when there was nothing to measure (no stats file, the service
restarted mid-run, or nothing scrolled).
What the numbers mean
---------------------
late frames frames that reached the panel one or more refreshes after they
were due -- the panel showed the previous frame again, which on
a moving strip is a visible hitch. This is the pass/fail number.
freezes gaps of 250ms+ inside a scroll: recomposes, plugin handovers
the display controller does not tag (see handover gaps),
blocking calls on the render thread. Reported, not failed on,
since some are handovers between plugins rather than faults.
handover gaps the same length of gap where the display controller had just
started a screen's turn (also the same mode's again): its
first display() drawing. Counted here instead of under
freezes. Stats from a service older than this count have no
such line, and their freezes include these, so do not
compare freeze counts across that change.
blit copying the frame into the matrix canvas (rgbmatrix SetImage).
Grows with width x height x pwm_bits.
wait blocked in SwapOnVSync, i.e. slack before the refresh.
work everything else between two frames: drawing, scrolling, and
waiting for the GIL.
after work frames presented straight after tagged render-thread work
(Vegas strip extensions, live-element patches), with their own
late rate. Shown only when something tagged its work.
"""
from __future__ import annotations
import argparse
import json
import os
import sys
import time
from pathlib import Path
from typing import Any, Dict, Optional
sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
from src.common.frame_timing import ( # noqa: E402
BUCKET_COUNT,
SCHEMA_VERSION,
default_stats_path,
)
#: Touched by the web UI while someone has the preview open; a fresh marker
#: puts the display service's snapshot writer at the viewer rate
#: (snapshot_policy.VIEWER_INTERVAL). Same path as
#: DisplayManager._viewer_marker_path.
VIEWER_MARKER = "/tmp/led_matrix_preview_viewer" # nosec B108 - fixed path shared with the service
#: A stats file not rewritten for this long means nothing is being presented.
STALE_SECONDS = 30.0
def load(path: str) -> Optional[Dict[str, Any]]:
try:
with open(path, encoding="utf-8") as handle:
stats = json.load(handle)
except (OSError, ValueError):
return None
if not isinstance(stats, dict) or stats.get("version") != SCHEMA_VERSION:
return None
return stats
def _histogram(stats: Dict[str, Any], name: str) -> Dict[int, int]:
raw = (stats.get("histograms") or {}).get(name) or {}
return {int(k): int(v) for k, v in raw.items()}
def diff(before: Dict[str, Any], after: Dict[str, Any]) -> Dict[str, Any]:
"""What happened between two snapshots of the same process."""
tb, ta = before["totals"], after["totals"]
totals = {}
for key, value in ta.items():
if isinstance(value, dict):
totals[key] = {k: v - tb.get(key, {}).get(k, 0)
for k, v in value.items()}
elif key == "worst_interval_ms":
# A running maximum can't be differenced; it is reported as the
# worst since the service started.
totals[key] = value
else:
totals[key] = value - tb.get(key, 0)
histograms = {}
for name in (after.get("histograms") or {}):
hb, ha = _histogram(before, name), _histogram(after, name)
histograms[name] = {k: v - hb.get(k, 0) for k, v in ha.items()
if v - hb.get(k, 0) > 0}
return {"totals": totals, "histograms": histograms,
"seconds": after["updated"] - before["updated"]}
def percentiles(histogram: Dict[int, int], bucket_ms: float) -> Dict[str, Any]:
"""p50/p95/p99/max from a sparse histogram, as each bucket's upper edge."""
count = sum(histogram.values())
if not count:
return {}
out = {}
targets = {"p50": 0.50, "p95": 0.95, "p99": 0.99}
running = 0
for index in sorted(histogram):
running += histogram[index]
for name, fraction in list(targets.items()):
if running >= fraction * count:
out[name] = _edge(index, bucket_ms)
del targets[name]
out["max"] = _edge(max(histogram), bucket_ms)
return out
def _edge(index: int, bucket_ms: float):
if index >= BUCKET_COUNT - 1:
return f">={index * bucket_ms:g}"
return round((index + 1) * bucket_ms, 2)
def op_rows(totals: Dict[str, Any]) -> Dict[str, Dict[str, Any]]:
"""Per kind of noted render-thread work: how often its frame was late.
A kind's frames are the ones presented straight after that work ran (see
"Operations" in src/common/frame_timing.py). Stats from a recorder that
predates the counters have none, and give an empty table.
"""
frames = totals.get("op_frames") or {}
late = totals.get("late_op_frames") or {}
freezes = totals.get("op_freezes") or {}
moved = totals.get("op_bytes") or {}
rows = {}
for kind in sorted(set(frames) | set(freezes)):
count = frames.get(kind, 0)
if not count and not freezes.get(kind, 0):
continue
rows[kind] = {
"frames": count,
"late": late.get(kind, 0),
"late_pct": (round(100.0 * late.get(kind, 0) / count, 3)
if count else None),
"freezes": freezes.get(kind, 0),
"bytes": moved.get(kind, 0),
}
return rows
def gc_window(before: Dict[str, Any], after: Dict[str, Any]) -> Optional[Dict[str, Any]]:
"""Garbage collection over the run, or None from a service without the
monitor. The counters are cumulative since the service started, so they
are differenced like the totals; the longest is since the start."""
ga = after.get("gc")
if not ga:
return None
gb = before.get("gc") or {}
def minus(key):
return [a - b for a, b in zip(ga.get(key, []),
gb.get(key) or [0] * len(ga.get(key, [])))]
seconds = minus("seconds")
return {
"collections": minus("collections"),
"ms": [round(x * 1000.0, 1) for x in seconds],
"long_pauses": ga.get("long_pauses", 0) - gb.get("long_pauses", 0),
"long_ms": round((ga.get("long_seconds", 0.0)
- gb.get("long_seconds", 0.0)) * 1000.0, 1),
"threshold_ms": ga.get("threshold_ms"),
"max_ms_since_start": ga.get("max_ms"),
}
def build_report(before, after, preview: bool) -> Dict[str, Any]:
delta = diff(before, after)
totals = delta["totals"]
frames = totals["scroll_frames"]
# The rates are over frames judged against a known refresh period. Stats
# from a recorder that predates the count fall back to every frame.
timed = totals.get("timed_frames", frames) if "timed_frames" in totals else frames
hours = delta["seconds"] / 3600.0 if delta["seconds"] > 0 else 0.0
bucket_ms = after.get("bucket_ms", 0.25)
report = {
"seconds": round(delta["seconds"], 1),
"preview": preview,
"info": after.get("info"),
"binding_releases_gil": after.get("binding_releases_gil"),
"measured_refresh_hz": after.get("measured_refresh_hz"),
"scroll_frames": frames,
"static_frames": totals["static_frames"],
"late_frames": totals["late_frames"],
"timed_frames": timed,
"late_pct": round(100.0 * totals["late_frames"] / timed, 3) if timed else None,
"missed_refreshes": totals["missed_refreshes"],
"late_by": totals["late_by"],
"early_frames": totals.get("early_frames", 0),
"early_pct": (round(100.0 * totals.get("early_frames", 0) / timed, 3)
if timed else None),
"freeze_by": totals.get("freeze_by", {}),
"freezes": totals["freezes"],
"freezes_per_hour": round(totals["freezes"] / hours, 1) if hours else None,
"freeze_seconds": round(totals["freeze_seconds"], 2),
# None from a service that predates the count: its handovers are
# among the freezes above.
"handover_freezes": totals.get("handover_freezes"),
"worst_interval_ms": (round(totals["worst_interval_ms"], 1)
if totals["worst_interval_ms"] else None),
"timing_ms": {name: percentiles(h, bucket_ms)
for name, h in delta["histograms"].items()},
"ops": op_rows(totals),
"gc": gc_window(before, after),
}
# The rate the panel held while rendering: the typical frame's interval
# per refresh held. A few percent under the idle rate is normal (the Pi is
# bit-banging the panel and pushing frames at once); a widening gap between
# the two is a render-cost regression even when nothing is late.
typical = (report["timing_ms"].get("interval_per_hold") or {}).get("p50")
# percentiles() reports a bucket's upper edge; the midpoint is the better
# estimate, and half a 0.25ms bucket is already ~1% at 100Hz -- the size
# of the idle-vs-held gap this number exists to show.
if isinstance(typical, (int, float)) and typical > bucket_ms / 2:
report["held_refresh_hz"] = round(1000.0 / (typical - bucket_ms / 2), 1)
else:
report["held_refresh_hz"] = None
return report
def print_report(report: Dict[str, Any], limit: float) -> None:
info = report.get("info") or {}
size = "{}x{}".format(
(info.get("cols") or 0) * (info.get("chain_length") or 1),
(info.get("rows") or 0) * (info.get("parallel") or 1))
gil = {True: "releases the GIL", False: "STOCK (holds the GIL in SwapOnVSync)",
None: "unknown"}[report.get("binding_releases_gil")]
print(f"Rig {info.get('pi_model') or 'unknown'}")
print(f"Panel {size} chain {info.get('chain_length')} x parallel "
f"{info.get('parallel')} pwm_bits {info.get('pwm_bits')} "
f"slowdown {info.get('gpio_slowdown')} mapping {info.get('hardware_mapping')}")
print(f"Refresh {report.get('measured_refresh_hz') or '?'} Hz measured, "
f"cap {info.get('limit_refresh_rate_hz')}")
print(f"Binding {gil}")
print(f"Run {report['seconds']:.0f}s, preview "
f"{'open (simulated)' if report['preview'] else 'as-is'}")
print()
frames = report["scroll_frames"]
print(f"Scrolling frames {frames}")
if frames:
late_by = report["late_by"]
print(f"Late frames {report['late_frames']} ({report['late_pct']}%)"
f" missed refreshes {report['missed_refreshes']}"
f" [by 1: {late_by['1']}, 2: {late_by['2']}, "
f"3-5: {late_by['3-5']}, 6+: {late_by['6+']}]")
if report["early_frames"]:
print(f"Early frames {report['early_frames']} "
f"({report['early_pct']}%) swaps returned a refresh early")
print(f"Freezes >=250ms {report['freezes']}"
f" ({report['freezes_per_hour']}/h, {report['freeze_seconds']}s total)"
f" worst gap since start {report['worst_interval_ms'] or '-'} ms")
if report["freezes"]:
print(" by length: " + ", ".join(
f"{k}: {v}" for k, v in report["freeze_by"].items()))
if report.get("handover_freezes") is not None:
print(f"Handover gaps {report['handover_freezes']}"
" >=250ms before a new screen's first frame; not in the freezes")
gc_stats = report.get("gc")
if gc_stats:
counts, ms = gc_stats["collections"], gc_stats["ms"]
print(f"Garbage collection gen0/1/2 {counts[0]}/{counts[1]}/{counts[2]}"
f" ({ms[0]}/{ms[1]}/{ms[2]} ms) >={gc_stats['threshold_ms']:g}ms: "
f"{gc_stats['long_pauses']} ({gc_stats['long_ms']} ms)"
f" longest since start {gc_stats['max_ms_since_start']} ms")
print()
print(f"{'ms':<18}{'p50':>8}{'p95':>8}{'p99':>8}{'max':>8}")
for name in ("blit", "wait", "work", "interval_per_hold"):
row = report["timing_ms"].get(name) or {}
print(f"{name:<18}" + "".join(f"{str(row.get(k, '-')):>8}"
for k in ("p50", "p95", "p99", "max")))
print()
ops = report.get("ops") or {}
if ops:
# Frames presented straight after render-thread work of each kind. A
# late rate well above the overall one points at that work.
print(f"{'after work':<18}{'frames':>8}{'late':>8}{'late %':>8}"
f"{'freezes':>9}{'MB moved':>10}")
for kind, row in ops.items():
pct = "-" if row["late_pct"] is None else f"{row['late_pct']:g}"
print(f"{kind:<18}{row['frames']:>8}{row['late']:>8}{pct:>8}"
f"{row['freezes']:>9}{row['bytes'] / 1e6:>10.2f}")
print()
if report["late_pct"] is None:
print("RESULT nothing scrolled - no verdict")
elif not locked(report, limit):
ceiling = refresh_ceiling(report)
if (report.get("early_pct") or 0.0) > limit:
why = (f"{report['early_pct']}% of frames came a refresh early, so the "
"swaps were not waiting for the panel")
else:
why = (f"frames arrived at {report['measured_refresh_hz']}Hz, faster than "
f"the panel can refresh ({ceiling:g}Hz)")
print(f"RESULT FAIL NOT LOCKED: {why}, and the late count means nothing")
elif report["late_pct"] <= limit:
print(f"RESULT PASS {report['late_pct']}% late <= {limit}%")
else:
print(f"RESULT FAIL {report['late_pct']}% late > {limit}%")
#: How far over the panel's rate frames may arrive before the loop cannot have
#: been waiting for it. The margin covers the refresh wandering a little.
CEILING_MARGIN = 1.05
def refresh_ceiling(report: Dict[str, Any]) -> Optional[float]:
"""The fastest the panel can refresh, as far as this run knows.
The benchmark measures it (``idle_refresh_hz``); the service only knows its
cap. With neither, there is no ceiling to check against.
"""
idle = report.get("idle_refresh_hz")
if idle:
return float(idle)
cap = (report.get("info") or {}).get("limit_refresh_rate_hz")
try:
cap = float(cap)
except (TypeError, ValueError):
return None
return cap if cap > 0 else None
def locked(report: Dict[str, Any], limit: float) -> bool:
"""Whether the loop was paced by the panel at all.
Two ways it is not. Frames a whole refresh early mean some swaps did not
wait. And a loop that never waited at all -- the dirty-tracking skip firing
mid-scroll let one free-run at 827fps -- looks self-consistent to a refresh
estimate taken from its own frames, so nothing registers as early; what
gives it away is a "refresh" faster than the panel can physically do.
"""
if (report.get("early_pct") or 0.0) > limit:
return False
ceiling = refresh_ceiling(report)
measured = report.get("measured_refresh_hz")
return not (ceiling and measured and measured > ceiling * CEILING_MARGIN)
def passed(report: Dict[str, Any], limit: float) -> bool:
return (report["late_pct"] is not None and locked(report, limit)
and report["late_pct"] <= limit)
def touch_marker() -> bool:
try:
with open(VIEWER_MARKER, "a"):
pass
os.utime(VIEWER_MARKER, None)
return True
except OSError:
return False
def wait_for_fresh(path: str, timeout: float) -> Optional[Dict[str, Any]]:
"""The first snapshot written after now, so both ends of the run are exact."""
first = load(path)
deadline = time.time() + timeout
while time.time() < deadline:
current = load(path)
if current and (first is None or current["updated"] != first["updated"]):
return current
time.sleep(0.5)
return None
def main(argv=None) -> int:
parser = argparse.ArgumentParser(description=__doc__.split("\n")[0])
parser.add_argument("--duration", type=float, default=600.0,
help="seconds to soak (default 600)")
parser.add_argument("--preview", action="store_true",
help="keep the web-preview viewer marker fresh, as an "
"open preview tab does")
parser.add_argument("--max-late-pct", type=float, default=0.1,
help="fail above this percentage of late frames (default 0.1)")
parser.add_argument("--stats", default=default_stats_path(),
help="stats file written by the display service")
parser.add_argument("--json", metavar="PATH",
help="also write the report as JSON")
parser.add_argument("--show", action="store_true",
help="print totals since the service started and exit")
args = parser.parse_args(argv)
current = load(args.stats)
if current is None:
print(f"No frame stats at {args.stats}. Is the display service running a "
"build with frame timing, and has anything scrolled for ~10s?",
file=sys.stderr)
return 2
if time.time() - current["updated"] > STALE_SECONDS:
print(f"Frame stats are {time.time() - current['updated']:.0f}s old: nothing "
"has been presented recently (static screen, or the service stopped).",
file=sys.stderr)
if not args.show:
return 2
if args.show:
empty = json.loads(json.dumps(current))
for key, value in empty["totals"].items():
empty["totals"][key] = ({k: 0 for k in value} if isinstance(value, dict)
else 0)
empty["histograms"] = {}
empty["updated"] = current["started"]
report = build_report(empty, current, preview=False)
print_report(report, args.max_late_pct)
return 0
if args.preview and not touch_marker():
print(f"Cannot touch {VIEWER_MARKER}; run as the web service's user to "
"simulate an open preview.", file=sys.stderr)
return 2
print(f"Waiting for a fresh baseline from {args.stats} ...", flush=True)
before = wait_for_fresh(args.stats, timeout=60.0)
if before is None:
print("The stats file stopped updating.", file=sys.stderr)
return 2
end = time.time() + args.duration
next_progress = time.time() + 60.0
while time.time() < end:
if args.preview:
touch_marker()
time.sleep(1.0)
if time.time() >= next_progress:
now = load(args.stats)
if now and now.get("pid") == before["pid"]:
done = now["totals"]["scroll_frames"] - before["totals"]["scroll_frames"]
late = now["totals"]["late_frames"] - before["totals"]["late_frames"]
print(f" {int(end - time.time())}s left: {done} scrolling frames, "
f"{late} late", flush=True)
next_progress += 60.0
after = wait_for_fresh(args.stats, timeout=60.0)
if after is None:
print("The stats file stopped updating during the run.", file=sys.stderr)
return 2
if after.get("pid") != before.get("pid"):
print("The display service restarted during the run; results discarded.",
file=sys.stderr)
return 2
report = build_report(before, after, preview=args.preview)
print()
print_report(report, args.max_late_pct)
if args.json:
with open(args.json, "w", encoding="utf-8") as handle:
json.dump(report, handle, indent=2)
if report["late_pct"] is None:
return 2
return 0 if passed(report, args.max_late_pct) else 1
if __name__ == "__main__":
sys.exit(main())