fdab6db634
Sequential runs of same_blocks.dart disagreed by 70% between the first and third invocation on this box: schedutil plus boost ramp is a larger effect than any difference between levels. Interleaving one block from each file in turn puts that drift on every level equally.
91 lines
3 KiB
Dart
91 lines
3 KiB
Dart
// Times several extracted-block files against each other, interleaved, so that
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// CPU frequency drift lands on every file equally.
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//
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// dart compile exe levels.dart -o /tmp/levels && /tmp/levels a.blocks b.blocks
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//
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// Each file is the format benchmark/same_blocks.dart reads: uint32 count, then
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// per block a uint32 frame length, a uint32 decompressed size, and the frame.
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// Every file must hold the same number of blocks, of the same output size, so
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// the medians are like for like.
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import 'dart:io';
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import 'dart:typed_data';
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import 'package:pure_zstd/pure_zstd.dart';
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const int warmSeconds = 4;
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const int passes = 60;
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List<Uint8List> load(String path, List<int> sizes) {
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final bytes = File(path).readAsBytesSync();
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final data = ByteData.sublistView(bytes);
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final count = data.getUint32(0, Endian.big);
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final frames = <Uint8List>[];
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var at = 4;
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for (var i = 0; i < count; i++) {
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final length = data.getUint32(at, Endian.big);
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final size = data.getUint32(at + 4, Endian.big);
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if (sizes.length <= i) {
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sizes.add(size);
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} else if (sizes[i] != size) {
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throw StateError(
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'$path block $i is $size bytes out, expected ${sizes[i]}',
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);
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}
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at += 8;
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frames.add(Uint8List.sublistView(bytes, at, at + length));
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at += length;
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}
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return frames;
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}
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void main(List<String> args) {
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final sizes = <int>[];
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final sets = args.map((path) => load(path, sizes)).toList();
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for (final set in sets) {
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if (set.length != sets.first.length) {
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throw StateError('the files do not hold the same number of blocks');
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}
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for (var i = 0; i < set.length; i++) {
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if (zstdDecode(set[i]).length != sizes[i]) {
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throw StateError('block $i decoded to the wrong size');
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}
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}
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}
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// Spin long enough for the governor to raise the clock before anything is
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// timed, otherwise the first file measured pays for the ramp.
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final warm = Stopwatch()..start();
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while (warm.elapsed.inSeconds < warmSeconds) {
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for (final set in sets) {
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for (final frame in set) {
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zstdDecode(frame);
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}
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}
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}
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final micros = [for (final _ in sets) <int>[]];
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for (var pass = 0; pass < passes; pass++) {
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for (var b = 0; b < sets.first.length; b++) {
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for (var s = 0; s < sets.length; s++) {
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final watch = Stopwatch()..start();
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zstdDecode(sets[s][b]);
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watch.stop();
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micros[s].add(watch.elapsedMicroseconds);
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}
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}
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}
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for (var s = 0; s < sets.length; s++) {
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final xs = micros[s]..sort();
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double q(double f) => xs[(xs.length * f).floor()] / 1000;
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final median = q(0.5);
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final bytes = sizes.reduce((a, b) => a + b) / sizes.length;
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stdout.writeln(
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'${args[s].split('/').last.padRight(24)} n=${xs.length} '
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'median=${median.toStringAsFixed(3)}ms '
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'p10=${q(0.1).toStringAsFixed(3)} p90=${q(0.9).toStringAsFixed(3)} '
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'MBps=${(bytes / 1048576 / (median / 1000)).toStringAsFixed(0)} '
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'sweep113=${(median * 113).toStringAsFixed(0)}ms',
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);
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}
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}
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