[vm_snapshot_analysis] Improve compare command

Add breakdown by node type when this information is available.

Change-Id: If2d477d0720aff69e3a168b9520fc3c2ccd153c1
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/153767
Commit-Queue: Vyacheslav Egorov <[email protected]>
Reviewed-by: Martin Kustermann <[email protected]>

Author: mraleph

pkg/vm_snapshot_analysis/CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## 0.5.0
+
+- `compare` command now prints difference breakdown by node type when this
+information is available.
+
 ## 0.4.0
 
 - Add `buildComparisonTreemap` for constructing treemap representing the diff

pkg/vm_snapshot_analysis/lib/src/commands/compare.dart

@@ -144,10 +144,33 @@ precisely based on their source position (which is included in their name).
     print('Comparing ${oldJson.path} (old) to ${newJson.path} (new)');
     print('Old   : ${totalOld} bytes.');
     print('New   : ${totalNew} bytes.');
-    print('Change: ${totalDiff > 0 ? '+' : ''}${totalDiff} bytes.');
+    print('Change: ${totalDiff > 0 ? '+' : ''}${totalDiff}'
+        ' (${formatPercent(totalDiff, totalOld, withSign: true)}) bytes.');
 
     if (oldSizes.snapshotInfo != null) {
       print(bucketLegend);
+      print('\nBreakdown by object type:');
+      final oldTypeHistogram =
+          computeHistogram(oldSizes, HistogramType.byNodeType);
+      final newTypeHistogram =
+          computeHistogram(newSizes, HistogramType.byNodeType);
+
+      final diffTypeHistogram = Histogram.fromIterable(
+          Set<String>()
+            ..addAll(oldTypeHistogram.buckets.keys)
+            ..addAll(newTypeHistogram.buckets.keys),
+          sizeOf: (bucket) =>
+              (newTypeHistogram.buckets[bucket] ?? 0) -
+              (oldTypeHistogram.buckets[bucket] ?? 0),
+          bucketFor: (bucket) => bucket,
+          bucketInfo: oldTypeHistogram.bucketInfo);
+
+      printHistogram(oldSizes, diffTypeHistogram,
+          prefix: diffTypeHistogram.bySize
+              .where((bucket) => diffTypeHistogram.buckets[bucket] != 0),
+          maxWidth: maxWidth);
+
+      print(bucketLegend);
     }
   }
 }

pkg/vm_snapshot_analysis/lib/utils.dart

@@ -47,6 +47,12 @@ Future<Map<String, dynamic>> buildComparisonTreemap(File oldJson, File newJson,
   return treemapFromInfo(diff, format: format);
 }
 
+String formatPercent(int value, int total, {bool withSign = false}) {
+  final p = value / total * 100.0;
+  final sign = (withSign && value > 0) ? '+' : '';
+  return '${sign}${p.toStringAsFixed(2)}%';
+}
+
 void printHistogram(ProgramInfo info, Histogram histogram,
     {Iterable<String> prefix = const [],
     Iterable<String> suffix = const [],
@@ -61,10 +67,14 @@ void printHistogram(ProgramInfo info, Histogram histogram,
     if (wasFiltered) Text.right('Of total'),
   ], maxWidth: maxWidth);
 
-  String formatPercent(int value, int total) {
-    final p = value / total * 100.0;
-    return p.toStringAsFixed(2) + "%";
-  }
+  final visibleRows = [prefix, suffix].expand((l) => l).toList();
+  final visibleSize =
+      visibleRows.fold(0, (sum, key) => sum + histogram.buckets[key]);
+  final numRestRows = histogram.length - (suffix.length + prefix.length);
+  final hiddenRows = Set<String>.from(histogram.bySize)
+      .difference(Set<String>.from(visibleRows));
+  final interestingHiddenRows =
+      hiddenRows.any((k) => histogram.buckets[k] != 0);
 
   if (prefix.isNotEmpty) {
     for (var key in prefix) {
@@ -76,15 +86,10 @@ void printHistogram(ProgramInfo info, Histogram histogram,
         if (wasFiltered) formatPercent(size, totalSize),
       ]);
     }
-    table.addSeparator(
-        prefix.length < histogram.length ? Separator.Wave : Separator.Line);
+    table.addSeparator(interestingHiddenRows ? Separator.Wave : Separator.Line);
   }
 
-  final visibleSize = [prefix, suffix]
-      .expand((l) => l)
-      .fold(0, (sum, key) => sum + histogram.buckets[key]);
-  final numRestRows = histogram.length - (suffix.length + prefix.length);
-  if (numRestRows > 0) {
+  if (interestingHiddenRows) {
     final totalRestBytes = histogram.totalSize - visibleSize;
     table.addTextSeparator(
         '$numRestRows more rows accounting for ${totalRestBytes}'

pkg/vm_snapshot_analysis/pubspec.yaml

@@ -1,6 +1,6 @@
 name: vm_snapshot_analysis
 description: Utilities for analysing AOT snapshot size.
-version: 0.4.0
+version: 0.5.0
 
 homepage: https://github.com/dart-lang/sdk/tree/master/pkg/vm_snapshot_analysis