e09bd6ea71
The A/B harness used to measure the idle-sleep work that shipped in main (#2559): Measure-EventLoop.ps1 and measure-event-loop.sh drive CPU/lag comparisons across server.eventLoopIdleWaitMs settings, and HostLatencyProbe.cs measures what basic operations cost on a host. dev-docs/measuring-event-loop.md explains the method, the numbers that matter, and how to re-vendor IORingGroup for ring experiments. This branch is main plus this commit, rebased forward as main moves. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
131 lines
3.7 KiB
Bash
Executable file
131 lines
3.7 KiB
Bash
Executable file
#!/usr/bin/env bash
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# A/B measurement for the event loop scheduler, for macOS and Linux.
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#
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# Boots the shard twice against identical binaries -- once with idle sleeping disabled
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# (server.eventLoopIdleWaitMs = 0) and once with it enabled (= 2) -- and samples process CPU time
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# over a fixed window. Everything else is held constant, so the delta is the scheduler.
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#
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# The Windows equivalent is tools/Measure-EventLoop.ps1.
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#
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# Usage: ./tools/measure-event-loop.sh [warmup_seconds] [sample_seconds]
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set -euo pipefail
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WARMUP="${1:-45}"
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SAMPLE="${2:-60}"
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ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
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DIST="$ROOT/Distribution"
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CONFIG="$DIST/Configuration/modernuo.json"
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# The published binary has no extension on these platforms.
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EXE="$DIST/ModernUO"
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if [ ! -x "$EXE" ]; then
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echo "ModernUO not found at $EXE. Build with: dotnet build -c Release" >&2
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exit 1
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fi
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if [ ! -f "$CONFIG" ]; then
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echo "No configuration at $CONFIG. Start the shard once to generate it." >&2
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exit 1
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fi
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mkdir -p "$DIST/Logs"
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# python3 rather than sed: the value must be replaced inside JSON, and the file is the live
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# server configuration. macOS ships python3 with the developer tools.
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set_idle_wait() {
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python3 - "$CONFIG" "$1" <<'PY'
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import json, sys
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path, value = sys.argv[1], sys.argv[2]
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with open(path) as f:
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cfg = json.load(f)
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cfg.setdefault("settings", {})["server.eventLoopIdleWaitMs"] = value
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with open(path, "w") as f:
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json.dump(cfg, f, indent=2)
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PY
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}
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# Process CPU time in seconds. ps reports [[dd-]hh:]mm:ss, which needs unpacking.
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cpu_seconds() {
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local t
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t="$(ps -o time= -p "$1" | tr -d ' ')"
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python3 - "$t" <<'PY'
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import sys
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raw = sys.argv[1]
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days, _, rest = raw.rpartition('-')
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parts = [float(p) for p in rest.split(':')]
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total = 0.0
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for p in parts:
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total = total * 60 + p
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if days:
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total += float(days) * 86400
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print(total)
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PY
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}
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measure() {
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local idle="$1" label="$2"
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set_idle_wait "$idle"
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echo
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echo "=== $label (server.eventLoopIdleWaitMs = $idle) ==="
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# Redirect stdin from /dev/null so the server runs headless and never blocks on console input.
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"$EXE" < /dev/null > "$DIST/Logs/measure-$idle.out" 2> "$DIST/Logs/measure-$idle.err" &
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local pid=$!
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# shellcheck disable=SC2064
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trap "kill $pid 2>/dev/null || true" EXIT
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echo " pid $pid; warming up for ${WARMUP}s..."
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sleep "$WARMUP"
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if ! kill -0 "$pid" 2>/dev/null; then
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echo " server exited during warmup. See Logs/measure-$idle.err" >&2
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tail -20 "$DIST/Logs/measure-$idle.err" >&2 || true
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exit 1
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fi
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local before after wall_before wall_after
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before="$(cpu_seconds "$pid")"
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wall_before="$(date +%s)"
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echo " sampling for ${SAMPLE}s..."
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sleep "$SAMPLE"
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after="$(cpu_seconds "$pid")"
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wall_after="$(date +%s)"
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kill "$pid" 2>/dev/null || true
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wait "$pid" 2>/dev/null || true
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trap - EXIT
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python3 - "$before" "$after" "$wall_before" "$wall_after" <<'PY'
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import sys
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cpu = float(sys.argv[2]) - float(sys.argv[1])
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wall = float(sys.argv[4]) - float(sys.argv[3])
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pct = cpu / wall * 100 if wall > 0 else 0
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print(f" CPU: {pct:.2f}% of one core ({cpu:.1f}s CPU over {wall:.0f}s wall)")
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PY
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}
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measure 0 "Never sleep (max responsiveness)"
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measure 2 "Idle sleeping"
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echo
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echo "=== Result ==="
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echo " Compare the two CPU figures above."
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echo " Then read the loop: lines for what it cost in timer accuracy:"
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echo
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grep -h "loop: " "$DIST/Logs/measure-0.out" | tail -3 || true
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echo " ---"
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grep -h "loop: " "$DIST/Logs/measure-2.out" | tail -3 || true
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echo
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echo " missed16ms and sched are the health numbers. cpu alone does not tell you"
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echo " whether the trade was worth it."
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# Leave the configuration on the default.
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set_idle_wait 2
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