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Remove analysis documentation files
Removed 5 analysis .md files from repository root: - ALLOCATION_CALL_FLOW.md - ALLOCATION_DOCS_README.md - ALLOCATION_INVESTIGATION_SUMMARY.md - HEAP_ALLOCATION_ANALYSIS.md - OPTIMIZATION_RECOMMENDATIONS.md These were temporary analysis documents used during investigation. The key findings and optimizations are captured in the PR description. Co-authored-by: tig <585482+tig@users.noreply.github.com>
This commit is contained in:
copilot-swe-agent[bot]
@@ -1,363 +0,0 @@
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# Heap Allocation Call Flow Analysis
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## Call Flow Diagram for Progress Bar Scenario
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This document traces the allocation chain from a user interaction down to the heap allocations.
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### High-Level Flow
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```
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User Action (Progress Bar Update)
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↓
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ProgressBar.Fraction = value
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↓
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SetNeedsDraw()
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↓
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Application Main Loop (10-60 Hz)
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↓
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View.OnDrawingContent() / View.DrawContentComplete()
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↓
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TextFormatter.Draw()
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↓
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**ALLOCATION HOTSPOT #1**
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GraphemeHelper.GetGraphemes(strings).ToArray()
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↓
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string[] allocated on heap (Gen0)
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```
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### Detailed Call Stack with Line Numbers
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#### 1. Progress Bar Update Path
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```
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Examples/UICatalog/Scenarios/Progress.cs:46
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Application.Invoke(() => systemTimerDemo.Pulse())
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↓
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Terminal.Gui/Views/ProgressBar.cs:~50 (Pulse method)
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Fraction = newValue
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↓
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Terminal.Gui/Views/ProgressBar.cs:~35
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set Fraction { _fraction = value; SetNeedsDraw(); }
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↓
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[View Framework schedules redraw]
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↓
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Terminal.Gui/Views/ProgressBar.cs:135
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OnDrawingContent()
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↓
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[Draws progress bar using Driver.AddStr, etc.]
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[Any text on the progress bar view triggers...]
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↓
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Terminal.Gui/ViewBase/View.Drawing.cs:450
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TextFormatter?.Draw(driver, drawRect, normalColor, hotColor)
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↓
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Terminal.Gui/Text/TextFormatter.cs:78-126
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List<string> linesFormatted = GetLines()
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foreach line in linesFormatted:
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string[] graphemes = GraphemeHelper.GetGraphemes(strings).ToArray() // LINE 126
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↓
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**ALLOCATION #1: string[] array allocated (size = grapheme count)**
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↓
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[Each grapheme is then drawn to screen]
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```
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#### 2. Border/LineCanvas Update Path
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```
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View with Border
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↓
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Terminal.Gui/ViewBase/Adornment/Border.cs:~500
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OnDrawingContent()
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↓
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[Border needs to draw lines]
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↓
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Terminal.Gui/Drawing/LineCanvas/LineCanvas.cs:210-234
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GetMap(Rectangle inArea)
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↓
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for y in area.Height:
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for x in area.Width:
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IntersectionDefinition[] intersects = _lines // LINES 219-222
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.Select(l => l.Intersects(x, y))
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.OfType<IntersectionDefinition>()
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.ToArray()
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↓
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**ALLOCATION #2: IntersectionDefinition[] allocated per pixel**
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↓
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[80x24 border = 1,920 allocations]
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[100x30 dialog = 2,600 allocations]
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```
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### Allocation Frequency Analysis
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#### Scenario 1: Simple Progress Bar (Default Speed = 100ms)
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**Per Update Cycle:**
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1. ProgressBar text (e.g., "Progress: 45%")
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- `GetLines()` → splits into 1 line
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- `Draw()` line 126 → allocates string[] for ~15 graphemes
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- **1 allocation per update**
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2. Percentage label if separate
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- Additional 1 allocation
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- **Total: 2 allocations per update**
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**Per Second:**
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- Update frequency: 10 Hz (every 100ms)
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- **20 allocations/second** just for progress display
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**With Border:**
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- Border redraws when view redraws
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- Typical small progress bar border: ~100 pixels
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- **100 additional allocations per update**
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- **1,000 allocations/second** for bordered progress bar
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#### Scenario 2: Complex UI (Progress + Clock + Status)
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**Components:**
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1. Progress Bar: 20 allocations/second
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2. Clock Display (updates every second): 2 allocations/second
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3. Status Message: 2 allocations/second (if blinking)
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4. Window Border: 260 allocations per redraw
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- If progress bar triggers window redraw: 2,600 allocations/second
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5. Dialog Borders (if present): 4,800 allocations/second
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**Conservative Estimate:**
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- Progress bar alone: 20-120 allocations/second
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- With borders: 1,000-3,000 allocations/second
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- Full complex UI: **Easily 5,000-10,000 allocations/second**
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### Memory Allocation Types
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#### Type 1: String Arrays (TextFormatter)
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```csharp
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// Terminal.Gui/Text/TextFormatter.cs:126
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string[] graphemes = GraphemeHelper.GetGraphemes(strings).ToArray();
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```
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**Size per allocation:**
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- Array header: 24 bytes (x64)
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- Per element: 8 bytes (reference)
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- Plus: Each string object (grapheme)
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- **Typical: 50-500 bytes per allocation**
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#### Type 2: IntersectionDefinition Arrays (LineCanvas)
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```csharp
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// Terminal.Gui/Drawing/LineCanvas/LineCanvas.cs:219-222
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IntersectionDefinition[] intersects = _lines
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.Select(l => l.Intersects(x, y))
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.OfType<IntersectionDefinition>()
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.ToArray();
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```
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**Size per allocation:**
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- Array header: 24 bytes
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- Per IntersectionDefinition: ~32 bytes (struct size)
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- Typical line count: 2-6 intersections
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- **Typical: 50-200 bytes per allocation**
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- **But happens ONCE PER PIXEL!**
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#### Type 3: List<string> (Various TextFormatter methods)
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```csharp
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// Terminal.Gui/Text/TextFormatter.cs:1336, 1460, 1726
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List<string> graphemes = GraphemeHelper.GetGraphemes(text).ToList();
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```
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**Size per allocation:**
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- List object: 32 bytes
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- Internal array: Variable (resizes as needed)
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- **Typical: 100-1,000 bytes per allocation**
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### Garbage Collection Impact
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#### Gen0 Collection Triggers
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Assuming:
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- Gen0 threshold: ~16 MB (typical)
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- Average allocation: 200 bytes
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- Complex UI: 5,000 allocations/second
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- **Memory allocated per second: ~1 MB**
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**Result:**
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- Gen0 collection approximately every 16 seconds
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- With heap fragmentation and other allocations: **Every 5-10 seconds**
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#### GC Pause Impact
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- Gen0 collection pause: 1-5ms (typical)
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- At 60 FPS UI: 16.67ms per frame budget
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- **GC pause consumes 6-30% of frame budget**
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- Result: Frame drops, UI stuttering during GC
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### Optimization Opportunities
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#### 1. Array Pooling (TextFormatter.Draw)
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**Current:**
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```csharp
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string[] graphemes = GraphemeHelper.GetGraphemes(strings).ToArray();
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```
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**Optimized:**
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```csharp
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// Use ArrayPool<string>
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string[] graphemes = ArrayPool<string>.Shared.Rent(estimatedSize);
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try {
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int count = 0;
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foreach (var g in GraphemeHelper.GetGraphemes(strings)) {
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graphemes[count++] = g;
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}
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// Use graphemes[0..count]
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} finally {
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ArrayPool<string>.Shared.Return(graphemes);
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}
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```
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**Benefit:** Zero allocations for repeated draws
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#### 2. Span-Based Processing (LineCanvas.GetMap)
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**Current:**
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```csharp
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IntersectionDefinition[] intersects = _lines
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.Select(l => l.Intersects(x, y))
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.OfType<IntersectionDefinition>()
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.ToArray();
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```
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**Optimized (like GetCellMap):**
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```csharp
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List<IntersectionDefinition> intersectionsBufferList = []; // Reuse outside loop
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// Inside loop:
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intersectionsBufferList.Clear();
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foreach (var line in _lines) {
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if (line.Intersects(x, y) is { } intersect) {
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intersectionsBufferList.Add(intersect);
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}
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}
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ReadOnlySpan<IntersectionDefinition> intersects = CollectionsMarshal.AsSpan(intersectionsBufferList);
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```
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**Benefit:** Zero per-pixel allocations (from 1,920+ to 0 per border redraw)
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#### 3. Grapheme Caching
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**Concept:** Cache grapheme arrays for unchanging text
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```csharp
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class TextFormatter {
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private string? _cachedText;
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private string[]? _cachedGraphemes;
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string[] GetGraphemesWithCache(string text) {
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if (text == _cachedText && _cachedGraphemes != null) {
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return _cachedGraphemes;
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}
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_cachedText = text;
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_cachedGraphemes = GraphemeHelper.GetGraphemes(text).ToArray();
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return _cachedGraphemes;
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}
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}
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```
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**Benefit:** Zero allocations for static text (labels, buttons)
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### Measurement Tools
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#### 1. BenchmarkDotNet
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Already used in project:
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```bash
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cd Tests/Benchmarks
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dotnet run -c Release --filter "*TextFormatter*"
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```
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Provides:
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- Allocation counts
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- Memory per operation
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- Speed comparisons
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#### 2. dotnet-trace
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```bash
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dotnet-trace collect --process-id <pid> --providers Microsoft-Windows-DotNETRuntime:0x1:5
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```
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Captures:
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- GC events
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- Allocation stacks
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- GC pause times
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#### 3. Visual Studio Profiler
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- .NET Object Allocation Tracking
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- Shows allocation hot paths
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- Call tree with allocation counts
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### Expected Results After Optimization
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#### TextFormatter.Draw Optimization
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**Before:**
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- 1 allocation per Draw call
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- 10-60 allocations/second for animated content
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**After:**
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- 0 allocations (with ArrayPool)
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- OR 1 allocation per unique text (with caching)
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**Improvement:** 90-100% reduction in allocations
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#### LineCanvas.GetMap Optimization
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**Before:**
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- Width × Height allocations per redraw
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- 1,920 allocations for 80×24 border
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**After:**
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- 1 allocation per GetMap call (reused buffer)
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**Improvement:** 99.95% reduction (from 1,920 to 1)
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#### Overall Impact
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**Complex UI Scenario:**
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| Metric | Before | After | Improvement |
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|--------|--------|-------|-------------|
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| Allocations/sec | 5,000-10,000 | 50-100 | 99% |
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| Gen0 GC frequency | Every 5-10s | Every 80-160s | 16x reduction |
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| Memory pressure | High | Low | Significant |
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| Frame drops | Occasional | Rare | Noticeable |
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| CPU overhead (GC) | 5-10% | <1% | 10x reduction |
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### Validation Strategy
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1. **Add allocation benchmarks**
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- Benchmark Draw method
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- Benchmark GetMap method
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- Compare before/after
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2. **Run Progress scenario**
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- Profile with dotnet-trace
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- Measure GC frequency
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- Verify allocation reduction
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3. **Stress test**
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- Multiple progress bars
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- Complex borders
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- Animated content
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- Measure sustained performance
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### Conclusion
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The allocation call flow analysis confirms:
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1. **TextFormatter.Draw** is a critical path for text-heavy UIs
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2. **LineCanvas.GetMap** has severe per-pixel allocation issues
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3. **Optimization patterns exist** and are already partially implemented
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4. **Expected improvement is 90-99%** allocation reduction
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5. **Measurement tools are available** to validate improvements
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The path forward is clear, with existing code patterns (GetCellMap) providing a blueprint for optimization.
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@@ -1,279 +0,0 @@
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# Heap Allocation Investigation - Document Guide
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This directory contains comprehensive documentation of the heap allocation analysis performed on Terminal.Gui in response to reported performance issues with intermediate allocations.
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## Quick Start
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**If you want to...**
|
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|
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- 📊 **Understand the problem quickly** → Read [ALLOCATION_INVESTIGATION_SUMMARY.md](ALLOCATION_INVESTIGATION_SUMMARY.md)
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- 🔍 **See detailed technical analysis** → Read [HEAP_ALLOCATION_ANALYSIS.md](HEAP_ALLOCATION_ANALYSIS.md)
|
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- 🛠️ **Implement the fixes** → Read [OPTIMIZATION_RECOMMENDATIONS.md](OPTIMIZATION_RECOMMENDATIONS.md)
|
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- 📈 **Understand call flows** → Read [ALLOCATION_CALL_FLOW.md](ALLOCATION_CALL_FLOW.md)
|
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## Document Overview
|
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|
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### 1. [ALLOCATION_INVESTIGATION_SUMMARY.md](ALLOCATION_INVESTIGATION_SUMMARY.md)
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**Type:** Executive Summary
|
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**Audience:** Project maintainers, decision makers
|
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**Length:** ~10 pages
|
||||
|
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**Contents:**
|
||||
- TL;DR with key findings
|
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- Critical allocation hotspots (2 main issues)
|
||||
- Real-world impact quantification
|
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- Risk assessment
|
||||
- Recommended next steps
|
||||
- Decision point for maintainers
|
||||
|
||||
**Read this if:** You need to understand the issue quickly and decide on next steps
|
||||
|
||||
---
|
||||
|
||||
### 2. [HEAP_ALLOCATION_ANALYSIS.md](HEAP_ALLOCATION_ANALYSIS.md)
|
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**Type:** Technical Analysis
|
||||
**Audience:** Developers, performance engineers
|
||||
**Length:** ~15 pages
|
||||
|
||||
**Contents:**
|
||||
- Complete list of 9 allocation hotspots with line numbers
|
||||
- Root cause analysis for each issue
|
||||
- Detailed performance impact estimates
|
||||
- Memory allocation type breakdown
|
||||
- GC impact analysis
|
||||
- Comparison to v2_develop branch
|
||||
|
||||
**Read this if:** You need complete technical details and want to understand why allocations happen
|
||||
|
||||
---
|
||||
|
||||
### 3. [ALLOCATION_CALL_FLOW.md](ALLOCATION_CALL_FLOW.md)
|
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**Type:** Call Flow Analysis
|
||||
**Audience:** Developers working on fixes
|
||||
**Length:** ~12 pages
|
||||
|
||||
**Contents:**
|
||||
- Detailed call stacks from user action to allocation
|
||||
- Frequency analysis per scenario
|
||||
- Allocation size calculations
|
||||
- GC trigger estimations
|
||||
- Code examples showing allocation points
|
||||
- Measurement tool recommendations
|
||||
|
||||
**Read this if:** You're implementing fixes and need to understand the execution path
|
||||
|
||||
---
|
||||
|
||||
### 4. [OPTIMIZATION_RECOMMENDATIONS.md](OPTIMIZATION_RECOMMENDATIONS.md)
|
||||
**Type:** Implementation Roadmap
|
||||
**Audience:** Developers implementing solutions
|
||||
**Length:** ~18 pages
|
||||
|
||||
**Contents:**
|
||||
- Prioritized fix list (P0, P1, P2, P3)
|
||||
- Concrete code solutions with examples
|
||||
- 4-phase implementation roadmap (2-3 weeks)
|
||||
- Testing strategy and benchmarks
|
||||
- Success metrics and validation approach
|
||||
- Breaking change considerations
|
||||
- Risk assessment per change
|
||||
|
||||
**Read this if:** You're ready to implement optimizations and need detailed guidance
|
||||
|
||||
---
|
||||
|
||||
## Reading Order Recommendations
|
||||
|
||||
### For Decision Makers
|
||||
1. ALLOCATION_INVESTIGATION_SUMMARY.md (complete)
|
||||
2. OPTIMIZATION_RECOMMENDATIONS.md (section: Priority Ranking)
|
||||
|
||||
**Time:** 15-20 minutes
|
||||
**Goal:** Understand issue and approve work
|
||||
|
||||
### For Developers Implementing Fixes
|
||||
1. ALLOCATION_INVESTIGATION_SUMMARY.md (complete)
|
||||
2. HEAP_ALLOCATION_ANALYSIS.md (sections: Critical Allocation Hotspots, Root Cause)
|
||||
3. OPTIMIZATION_RECOMMENDATIONS.md (complete)
|
||||
4. ALLOCATION_CALL_FLOW.md (as reference during implementation)
|
||||
|
||||
**Time:** 1-2 hours
|
||||
**Goal:** Full understanding before coding
|
||||
|
||||
### For Performance Engineers
|
||||
1. HEAP_ALLOCATION_ANALYSIS.md (complete)
|
||||
2. ALLOCATION_CALL_FLOW.md (complete)
|
||||
3. OPTIMIZATION_RECOMMENDATIONS.md (sections: Testing Strategy, Monitoring)
|
||||
|
||||
**Time:** 2-3 hours
|
||||
**Goal:** Deep understanding for optimization and benchmarking
|
||||
|
||||
### For Code Reviewers
|
||||
1. ALLOCATION_INVESTIGATION_SUMMARY.md (complete)
|
||||
2. OPTIMIZATION_RECOMMENDATIONS.md (sections: Implementation Roadmap, Risk Assessment)
|
||||
3. HEAP_ALLOCATION_ANALYSIS.md (as reference for context)
|
||||
|
||||
**Time:** 30-45 minutes
|
||||
**Goal:** Understand changes being reviewed
|
||||
|
||||
---
|
||||
|
||||
## Key Findings at a Glance
|
||||
|
||||
### 🔴 Critical Issues (P0)
|
||||
|
||||
1. **LineCanvas.GetMap()** - `Terminal.Gui/Drawing/LineCanvas/LineCanvas.cs:219-222`
|
||||
- Per-pixel array allocation in nested loop
|
||||
- Impact: 1,920+ allocations per border redraw
|
||||
- Fix: Apply existing GetCellMap() pattern
|
||||
- Effort: 4-8 hours
|
||||
|
||||
2. **TextFormatter.Draw()** - `Terminal.Gui/Text/TextFormatter.cs:126`
|
||||
- Array allocation on every draw call
|
||||
- Impact: 10-60+ allocations per second
|
||||
- Fix: Use ArrayPool<string>
|
||||
- Effort: 1-2 days
|
||||
|
||||
### 📊 Performance Impact
|
||||
|
||||
**Current State:**
|
||||
- Progress bar demo: 3,000-5,000 allocations/second
|
||||
- Gen0 GC: Every 5-10 seconds
|
||||
- Result: Visible frame drops
|
||||
|
||||
**After Fixes:**
|
||||
- Allocations: 50-100/second (98% reduction)
|
||||
- Gen0 GC: Every 80-160 seconds (16× improvement)
|
||||
- Result: Smooth performance
|
||||
|
||||
### ✅ Solution Confidence: HIGH
|
||||
|
||||
- Proven patterns (GetCellMap already works)
|
||||
- Standard .NET tools (ArrayPool, Span<T>)
|
||||
- Low implementation risk
|
||||
- Clear testing strategy
|
||||
|
||||
---
|
||||
|
||||
## Investigation Methodology
|
||||
|
||||
This analysis was conducted through:
|
||||
|
||||
1. **Static Code Analysis**
|
||||
- Searched for `.ToArray()` and `.ToList()` patterns
|
||||
- Identified allocation sites with line numbers
|
||||
- Traced call stacks to understand frequency
|
||||
|
||||
2. **Frequency Analysis**
|
||||
- Examined Progress demo code (100ms update interval)
|
||||
- Analyzed ProgressBar.Fraction property (calls SetNeedsDraw)
|
||||
- Counted allocations per update cycle
|
||||
|
||||
3. **Memory Impact Calculation**
|
||||
- Estimated allocation sizes per operation
|
||||
- Calculated allocations per second for scenarios
|
||||
- Projected GC behavior based on allocation rate
|
||||
|
||||
4. **Solution Research**
|
||||
- Found existing optimizations (GetCellMap)
|
||||
- Identified proven patterns (ArrayPool usage)
|
||||
- Validated approach feasibility
|
||||
|
||||
5. **Documentation**
|
||||
- Created comprehensive analysis documents
|
||||
- Provided actionable recommendations
|
||||
- Included code examples and roadmap
|
||||
|
||||
---
|
||||
|
||||
## Next Steps
|
||||
|
||||
### Immediate Actions (This Week)
|
||||
|
||||
1. **Review documents** with team
|
||||
2. **Approve Phase 1** work if agreed
|
||||
3. **Assign developer** for LineCanvas.GetMap() fix
|
||||
4. **Set up benchmarks** to measure current state
|
||||
|
||||
### Short Term (Next 2 Weeks)
|
||||
|
||||
1. **Implement P0 fixes** (LineCanvas + TextFormatter)
|
||||
2. **Validate improvements** with benchmarks
|
||||
3. **Run Progress demo** profiling
|
||||
|
||||
### Medium Term (Next Month)
|
||||
|
||||
1. **Complete optimization roadmap** (all P1-P3 items)
|
||||
2. **Add comprehensive tests**
|
||||
3. **Update performance documentation**
|
||||
|
||||
---
|
||||
|
||||
## Questions or Feedback
|
||||
|
||||
**For technical questions about the analysis:**
|
||||
- Review the specific document section
|
||||
- Check OPTIMIZATION_RECOMMENDATIONS.md for code examples
|
||||
- Consult ALLOCATION_CALL_FLOW.md for execution details
|
||||
|
||||
**For implementation questions:**
|
||||
- Start with OPTIMIZATION_RECOMMENDATIONS.md
|
||||
- Reference code examples provided
|
||||
- Review existing GetCellMap() implementation as template
|
||||
|
||||
**For performance measurement:**
|
||||
- See ALLOCATION_CALL_FLOW.md (Measurement Tools section)
|
||||
- See OPTIMIZATION_RECOMMENDATIONS.md (Testing Strategy section)
|
||||
- Benchmark infrastructure already exists in Tests/Benchmarks
|
||||
|
||||
---
|
||||
|
||||
## Related Files in Repository
|
||||
|
||||
**Source Code:**
|
||||
- `Terminal.Gui/Text/TextFormatter.cs` - Main text rendering
|
||||
- `Terminal.Gui/Drawing/LineCanvas/LineCanvas.cs` - Border/line rendering
|
||||
- `Terminal.Gui/Drawing/GraphemeHelper.cs` - Text element enumeration
|
||||
- `Terminal.Gui/Drawing/Cell.cs` - Cell validation
|
||||
|
||||
**Tests:**
|
||||
- `Tests/Benchmarks/Text/TextFormatter/` - Existing benchmarks
|
||||
- `Tests/UnitTests/` - Unit test infrastructure
|
||||
- `Tests/UnitTestsParallelizable/` - Parallel test infrastructure
|
||||
|
||||
**Examples:**
|
||||
- `Examples/UICatalog/Scenarios/Progress.cs` - Progress demo (mentioned in issue)
|
||||
|
||||
---
|
||||
|
||||
## Document Maintenance
|
||||
|
||||
These documents were created on **December 3, 2025** as part of investigating the intermediate heap allocation issue.
|
||||
|
||||
**Status:** Investigation Complete ✅
|
||||
|
||||
**Action Required:** Decision on implementing optimizations
|
||||
|
||||
**Owner:** Awaiting assignment based on maintainer decision
|
||||
|
||||
---
|
||||
|
||||
## Summary
|
||||
|
||||
Four comprehensive documents totaling ~55 pages provide:
|
||||
- Complete problem analysis
|
||||
- Quantified performance impact
|
||||
- Concrete solutions with code examples
|
||||
- Implementation roadmap with timeline
|
||||
- Testing and validation strategy
|
||||
|
||||
**The issue is confirmed, significant, and solvable.** Documentation provides everything needed to proceed with confidence.
|
||||
|
||||
---
|
||||
|
||||
**Document Navigation:**
|
||||
- [← Back to Root](/)
|
||||
- [Executive Summary →](ALLOCATION_INVESTIGATION_SUMMARY.md)
|
||||
- [Technical Analysis →](HEAP_ALLOCATION_ANALYSIS.md)
|
||||
- [Call Flow Analysis →](ALLOCATION_CALL_FLOW.md)
|
||||
- [Implementation Guide →](OPTIMIZATION_RECOMMENDATIONS.md)
|
||||
@@ -1,412 +0,0 @@
|
||||
# Heap Allocation Investigation - Executive Summary
|
||||
|
||||
**Investigation Date:** December 3, 2025
|
||||
**Investigator:** GitHub Copilot Agent
|
||||
**Issue Reference:** Intermediate heap allocations in TextFormatter and LineCanvas
|
||||
|
||||
---
|
||||
|
||||
## TL;DR
|
||||
|
||||
✅ **Issue Confirmed:** The heap allocation problem is **REAL and SIGNIFICANT**
|
||||
|
||||
🔴 **Severity:** **CRITICAL** for animated UIs, progress bars, and border-heavy layouts
|
||||
|
||||
📊 **Impact:** 1,000-10,000 allocations per second in typical scenarios
|
||||
|
||||
✅ **Solution:** Clear path forward using ArrayPool, Span<T>, and buffer reuse
|
||||
|
||||
⏱️ **Timeline:** 2-3 weeks for complete fix, quick wins available immediately
|
||||
|
||||
---
|
||||
|
||||
## What We Found
|
||||
|
||||
### Critical Allocation Hotspots
|
||||
|
||||
#### 1. LineCanvas.GetMap() - **MOST CRITICAL**
|
||||
|
||||
**Location:** `Terminal.Gui/Drawing/LineCanvas/LineCanvas.cs:219-222`
|
||||
|
||||
```csharp
|
||||
// Allocates array PER PIXEL in nested loop
|
||||
IntersectionDefinition[] intersects = _lines
|
||||
.Select(l => l.Intersects(x, y))
|
||||
.OfType<IntersectionDefinition>()
|
||||
.ToArray(); // ❌ Inside double loop!
|
||||
```
|
||||
|
||||
**Impact:**
|
||||
- 80×24 window border: **1,920 allocations per redraw**
|
||||
- 100×30 dialog: **4,800 allocations per redraw**
|
||||
- Quadratic allocation pattern (O(width × height))
|
||||
|
||||
**Fix Complexity:** ⭐ Easy (pattern already exists in same file)
|
||||
**Impact:** ⭐⭐⭐⭐⭐ Massive (99%+ reduction)
|
||||
|
||||
---
|
||||
|
||||
#### 2. TextFormatter.Draw() - **VERY CRITICAL**
|
||||
|
||||
**Location:** `Terminal.Gui/Text/TextFormatter.cs:126`
|
||||
|
||||
```csharp
|
||||
// Allocates array on every draw call
|
||||
string[] graphemes = GraphemeHelper.GetGraphemes(strings).ToArray();
|
||||
```
|
||||
|
||||
**Impact:**
|
||||
- Called 10-60+ times per second for animated content
|
||||
- Every progress bar update
|
||||
- Every text view redraw
|
||||
- Compounds with multiple views
|
||||
|
||||
**Fix Complexity:** ⭐⭐⭐ Medium (ArrayPool implementation)
|
||||
**Impact:** ⭐⭐⭐⭐⭐ Massive (90-100% reduction)
|
||||
|
||||
---
|
||||
|
||||
### Additional Allocation Points
|
||||
|
||||
**TextFormatter.cs:** 7 more allocation sites in helper methods
|
||||
- Lines: 934, 1336, 1407, 1460, 1726, 2191, 2300
|
||||
|
||||
**Cell.cs:** Validation allocates unnecessarily
|
||||
- Line: 30
|
||||
|
||||
**Total Identified:** 9 distinct allocation hotspots
|
||||
|
||||
---
|
||||
|
||||
## Real-World Impact
|
||||
|
||||
### Progress Bar Demo (Referenced in Issue)
|
||||
|
||||
**Scenario:** Progress bar updating every 100ms
|
||||
|
||||
| Component | Allocations/Update | Frequency | Allocations/Sec |
|
||||
|-----------|-------------------|-----------|-----------------|
|
||||
| Progress bar text | 1-2 | 10 Hz | 10-20 |
|
||||
| Border (if present) | 100-260 | 10 Hz | 1,000-2,600 |
|
||||
| Window redraw | 260 | 10 Hz | 2,600 |
|
||||
| **Total** | | | **3,610-5,220** |
|
||||
|
||||
**Result:** ~4,000 allocations per second for a simple progress bar!
|
||||
|
||||
### Complex UI (Progress + Time + Status)
|
||||
|
||||
**Scenario:** Dashboard with multiple updating elements
|
||||
|
||||
| Component | Allocations/Sec |
|
||||
|-----------|-----------------|
|
||||
| Progress bars (2×) | 40-5,200 |
|
||||
| Clock display | 2-4 |
|
||||
| Status messages | 2-20 |
|
||||
| Borders/chrome | 2,600-4,800 |
|
||||
| **Total** | **5,000-10,000** |
|
||||
|
||||
**Result:** Gen0 GC every 5-10 seconds, causing frame drops
|
||||
|
||||
---
|
||||
|
||||
## Memory Pressure Analysis
|
||||
|
||||
### Allocation Breakdown
|
||||
|
||||
```
|
||||
Per Progress Bar Update (100ms):
|
||||
├─ Text: 200 bytes (1 string[] allocation)
|
||||
├─ Border: 20 KB (1,920 array allocations)
|
||||
└─ Total: ~20 KB per update
|
||||
|
||||
Per Second (10 updates):
|
||||
├─ 200 KB from progress bars
|
||||
├─ Additional UI updates: ~800 KB
|
||||
└─ Total: ~1 MB/second allocation rate
|
||||
```
|
||||
|
||||
### GC Impact
|
||||
|
||||
**Assumptions:**
|
||||
- Gen0 threshold: ~16 MB
|
||||
- Allocation rate: 1 MB/sec
|
||||
- Result: Gen0 collection every 10-16 seconds
|
||||
|
||||
**Reality:**
|
||||
- With heap fragmentation: Every 5-10 seconds
|
||||
- Gen0 pause: 1-5ms per collection
|
||||
- At 60 FPS: Consumes 6-30% of frame budget
|
||||
- Result: **Visible stuttering during GC**
|
||||
|
||||
---
|
||||
|
||||
## Why v2 Branch Is Worse
|
||||
|
||||
The issue mentions v2_develop has increased allocations, particularly from LineCanvas.
|
||||
|
||||
**Likely Causes:**
|
||||
1. More border/line usage in v2 UI framework
|
||||
2. GetMap() called more frequently
|
||||
3. Per-pixel allocation multiplied by increased usage
|
||||
|
||||
**Confirmation:** LineCanvas.GetMap() has severe per-pixel allocation issue
|
||||
|
||||
---
|
||||
|
||||
## Evidence Supporting Findings
|
||||
|
||||
### 1. Code Analysis
|
||||
|
||||
✅ Direct observation of `.ToArray()` in hot paths
|
||||
✅ Nested loops with allocations inside
|
||||
✅ Called from frequently-executed code paths
|
||||
|
||||
### 2. Call Stack Tracing
|
||||
|
||||
✅ Traced from ProgressBar.Fraction → TextFormatter.Draw()
|
||||
✅ Traced from Border.OnDrawingContent() → LineCanvas.GetMap()
|
||||
✅ Documented with exact line numbers
|
||||
|
||||
### 3. Frequency Analysis
|
||||
|
||||
✅ Progress demo updates 10 Hz (confirmed in code)
|
||||
✅ ProgressBar.Fraction calls SetNeedsDraw() (confirmed)
|
||||
✅ Draw methods called on every redraw (confirmed)
|
||||
|
||||
### 4. Existing Optimizations
|
||||
|
||||
✅ LineCanvas.GetCellMap() already uses buffer reuse pattern
|
||||
✅ Proves solution is viable and working
|
||||
✅ Just needs to be applied to GetMap()
|
||||
|
||||
---
|
||||
|
||||
## Recommended Solution
|
||||
|
||||
### Immediate (Phase 1): Quick Wins
|
||||
|
||||
**1. Fix LineCanvas.GetMap()** - 4-8 hours
|
||||
|
||||
Apply the existing GetCellMap() pattern:
|
||||
- Reuse buffer list
|
||||
- Use CollectionsMarshal.AsSpan()
|
||||
- **Impact:** 99%+ reduction (1,920 → 1 allocation per redraw)
|
||||
|
||||
**2. Add GraphemeHelper.GetGraphemeCount()** - 1-2 hours
|
||||
|
||||
For validation without allocation:
|
||||
- **Impact:** Zero allocations for Cell.Grapheme validation
|
||||
|
||||
### Short-term (Phase 2): Core Fix
|
||||
|
||||
**3. ArrayPool in TextFormatter.Draw()** - 1-2 days
|
||||
|
||||
Use ArrayPool<string> for grapheme arrays:
|
||||
- **Impact:** 90-100% reduction in text draw allocations
|
||||
|
||||
**4. Benchmarks & Testing** - 1 day
|
||||
|
||||
Measure and validate improvements:
|
||||
- Add BenchmarkDotNet tests
|
||||
- Profile Progress demo
|
||||
- Confirm allocation reduction
|
||||
|
||||
### Medium-term (Phase 3): Complete Solution
|
||||
|
||||
**5. Update Helper Methods** - 5-7 days
|
||||
|
||||
Add span-based APIs, update all allocation points:
|
||||
- **Impact:** Complete allocation-free text rendering path
|
||||
|
||||
---
|
||||
|
||||
## Expected Results
|
||||
|
||||
### Before Optimization
|
||||
|
||||
| Metric | Value |
|
||||
|--------|-------|
|
||||
| Allocations/sec (Progress demo) | 3,000-5,000 |
|
||||
| Gen0 GC frequency | Every 5-10 seconds |
|
||||
| Memory allocated/sec | ~1 MB |
|
||||
| Frame drops | Occasional |
|
||||
| GC pause impact | 5-10% CPU |
|
||||
|
||||
### After Optimization
|
||||
|
||||
| Metric | Value | Improvement |
|
||||
|--------|-------|-------------|
|
||||
| Allocations/sec | 50-100 | **98% reduction** |
|
||||
| Gen0 GC frequency | Every 80-160 sec | **16× less frequent** |
|
||||
| Memory allocated/sec | <50 KB | **95% reduction** |
|
||||
| Frame drops | Rare | Significant |
|
||||
| GC pause impact | <1% CPU | **10× reduction** |
|
||||
|
||||
---
|
||||
|
||||
## Risk Assessment
|
||||
|
||||
### Implementation Risk: **LOW** ✅
|
||||
|
||||
- Solutions use proven .NET patterns (ArrayPool, Span<T>)
|
||||
- Existing code demonstrates viability (GetCellMap)
|
||||
- Extensive test infrastructure available
|
||||
- No breaking API changes required
|
||||
|
||||
### Performance Risk: **VERY LOW** ✅
|
||||
|
||||
- Optimizations only improve performance
|
||||
- No functional changes
|
||||
- Backward compatible
|
||||
|
||||
### Maintenance Risk: **LOW** ✅
|
||||
|
||||
- Standard .NET patterns
|
||||
- Well-documented solutions
|
||||
- Clear test coverage
|
||||
|
||||
---
|
||||
|
||||
## Validation Strategy
|
||||
|
||||
### 1. Benchmarks
|
||||
|
||||
```bash
|
||||
cd Tests/Benchmarks
|
||||
dotnet run -c Release --filter "*Allocation*"
|
||||
```
|
||||
|
||||
Measure:
|
||||
- Allocations per operation
|
||||
- Bytes allocated
|
||||
- Speed comparison
|
||||
|
||||
### 2. Profiling
|
||||
|
||||
```bash
|
||||
# Run Progress demo
|
||||
dotnet run --project Examples/UICatalog
|
||||
|
||||
# Profile with dotnet-trace
|
||||
dotnet-trace collect --process-id <pid> \
|
||||
--providers Microsoft-Windows-DotNETRuntime:0x1:5
|
||||
```
|
||||
|
||||
Capture:
|
||||
- GC events
|
||||
- Allocation stacks
|
||||
- Pause times
|
||||
|
||||
### 3. Unit Tests
|
||||
|
||||
Add allocation-aware tests:
|
||||
```csharp
|
||||
[Fact]
|
||||
public void Draw_NoAllocations_WithOptimization()
|
||||
{
|
||||
long before = GC.GetAllocatedBytesForCurrentThread();
|
||||
textFormatter.Draw(...);
|
||||
long after = GC.GetAllocatedBytesForCurrentThread();
|
||||
|
||||
Assert.True(after - before < 1000);
|
||||
}
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
## Documentation Provided
|
||||
|
||||
This investigation produced four comprehensive documents:
|
||||
|
||||
### 1. **HEAP_ALLOCATION_ANALYSIS.md** (Main Report)
|
||||
- Detailed technical analysis
|
||||
- All 9 allocation hotspots documented
|
||||
- Root cause analysis
|
||||
- Performance impact estimation
|
||||
|
||||
### 2. **ALLOCATION_CALL_FLOW.md** (Call Flow)
|
||||
- Call stack traces with line numbers
|
||||
- Frequency analysis per scenario
|
||||
- Allocation type breakdown
|
||||
- GC impact calculations
|
||||
|
||||
### 3. **OPTIMIZATION_RECOMMENDATIONS.md** (Implementation Guide)
|
||||
- Prioritized fix list (P0, P1, P2, P3)
|
||||
- Concrete code solutions
|
||||
- 4-phase implementation roadmap
|
||||
- Testing strategy and success metrics
|
||||
|
||||
### 4. **ALLOCATION_INVESTIGATION_SUMMARY.md** (This Document)
|
||||
- Executive summary
|
||||
- Key findings and recommendations
|
||||
- Expected results and risk assessment
|
||||
|
||||
---
|
||||
|
||||
## Conclusion
|
||||
|
||||
### The Issue Is Real ✅
|
||||
|
||||
The intermediate heap allocation problem described in the issue is:
|
||||
- ✅ **Confirmed** through code analysis
|
||||
- ✅ **Quantified** with specific numbers
|
||||
- ✅ **Reproducible** in the Progress demo
|
||||
- ✅ **Significant** in impact
|
||||
|
||||
### The Issue Is Solvable ✅
|
||||
|
||||
Solutions are:
|
||||
- ✅ **Clear** and well-documented
|
||||
- ✅ **Proven** (patterns already exist in codebase)
|
||||
- ✅ **Low risk** (standard .NET optimizations)
|
||||
- ✅ **High impact** (90-99% allocation reduction)
|
||||
|
||||
### Recommended Next Steps
|
||||
|
||||
1. **Immediate:** Fix LineCanvas.GetMap() (4-8 hours, massive impact)
|
||||
2. **This Week:** Add benchmarks to measure current state
|
||||
3. **Next Week:** Implement TextFormatter.Draw() optimization
|
||||
4. **This Month:** Complete all optimizations per roadmap
|
||||
|
||||
### Priority Justification
|
||||
|
||||
This issue should be **HIGH PRIORITY** because:
|
||||
- Affects common scenarios (progress bars, animations, borders)
|
||||
- Causes visible performance degradation (GC pauses, stuttering)
|
||||
- Has clear, low-risk solution path
|
||||
- Provides immediate, measurable improvement
|
||||
|
||||
---
|
||||
|
||||
## For Project Maintainers
|
||||
|
||||
**Decision Required:** Approve optimization work?
|
||||
|
||||
**If Yes:**
|
||||
- Review OPTIMIZATION_RECOMMENDATIONS.md for roadmap
|
||||
- Assign Phase 1 work (LineCanvas + benchmarks)
|
||||
- Target completion: 2-3 weeks for full optimization
|
||||
|
||||
**If No:**
|
||||
- Issue can be triaged/prioritized differently
|
||||
- Documentation remains as reference for future work
|
||||
|
||||
---
|
||||
|
||||
## Contact & Questions
|
||||
|
||||
This investigation was conducted as requested in the issue to assess the scope and severity of intermediate heap allocations.
|
||||
|
||||
All analysis is based on:
|
||||
- Direct code inspection
|
||||
- Static analysis of allocation patterns
|
||||
- Frequency calculations from code behavior
|
||||
- Industry-standard optimization patterns
|
||||
|
||||
For questions or clarifications, refer to the detailed documents listed above.
|
||||
|
||||
---
|
||||
|
||||
**Investigation Complete** ✅
|
||||
|
||||
The Terminal.Gui codebase has been thoroughly analyzed for heap allocation issues. The findings confirm significant problems with clear solutions. Implementation can proceed with confidence.
|
||||
@@ -1,243 +0,0 @@
|
||||
# Heap Allocation Analysis for Terminal.Gui
|
||||
|
||||
## Executive Summary
|
||||
|
||||
This document provides a comprehensive analysis of intermediate heap allocations in Terminal.Gui, focusing on the `TextFormatter` and `LineCanvas` classes as reported in the issue.
|
||||
|
||||
## Severity Assessment: **HIGH IMPACT**
|
||||
|
||||
The allocation issues identified are significant performance concerns that affect:
|
||||
- Every frame redraw in UI scenarios
|
||||
- Any time-based updates (progress bars, timers, clocks)
|
||||
- Text rendering operations
|
||||
- Border and line drawing operations
|
||||
|
||||
## Key Findings
|
||||
|
||||
### 1. TextFormatter Class (`Terminal.Gui/Text/TextFormatter.cs`)
|
||||
|
||||
#### Critical Allocation Hotspots
|
||||
|
||||
**Location: Line 126 (in `Draw` method)**
|
||||
```csharp
|
||||
string[] graphemes = GraphemeHelper.GetGraphemes (strings).ToArray ();
|
||||
```
|
||||
- **Frequency**: Every time Draw is called (potentially 60+ times per second during animations)
|
||||
- **Impact**: Allocates a new string array for every line being drawn
|
||||
- **Called from**: View.Drawing.cs, Border.cs, TextField.cs, and other UI components
|
||||
|
||||
**Location: Line 934 (in `GetDrawRegion` method)**
|
||||
```csharp
|
||||
string [] graphemes = GraphemeHelper.GetGraphemes (strings).ToArray ();
|
||||
```
|
||||
- **Frequency**: Every time region calculation is needed
|
||||
- **Impact**: Similar allocation for grapheme arrays
|
||||
|
||||
**Additional Allocation Points:**
|
||||
- Line 1336: `List<string> graphemes = GraphemeHelper.GetGraphemes (text).ToList ();` in `SplitNewLine`
|
||||
- Line 1407: `string [] graphemes = GraphemeHelper.GetGraphemes (text).ToArray ();` in `ClipOrPad`
|
||||
- Line 1460: `List<string> graphemes = GraphemeHelper.GetGraphemes (StripCRLF (text)).ToList ();` in `WordWrapText`
|
||||
- Line 1726: `List<string> graphemes = GraphemeHelper.GetGraphemes (text).ToList ();` in `ClipAndJustify`
|
||||
- Line 2191: `string [] graphemes = GraphemeHelper.GetGraphemes (text).ToArray ();` in `GetSumMaxCharWidth`
|
||||
- Line 2300: `string [] graphemes = GraphemeHelper.GetGraphemes (lines [lineIdx]).ToArray ();` in `GetMaxColsForWidth`
|
||||
|
||||
**Total Count**: 9 distinct allocation points in TextFormatter alone
|
||||
|
||||
#### Why This Matters
|
||||
|
||||
The `Draw` method is called:
|
||||
1. On every frame update for animated content
|
||||
2. When any view needs to redraw its text
|
||||
3. During progress bar updates (the example mentioned in the issue)
|
||||
4. For real-time displays (clocks, status bars)
|
||||
|
||||
With a typical progress bar updating at 10-30 times per second, and potentially multiple text elements on screen, this can result in **hundreds to thousands of allocations per second**.
|
||||
|
||||
### 2. LineCanvas Class (`Terminal.Gui/Drawing/LineCanvas/LineCanvas.cs`)
|
||||
|
||||
#### Critical Allocation Hotspot
|
||||
|
||||
**Location: Lines 219-222 (in `GetMap(Rectangle inArea)` method)**
|
||||
```csharp
|
||||
IntersectionDefinition [] intersects = _lines
|
||||
.Select (l => l.Intersects (x, y))
|
||||
.OfType<IntersectionDefinition> ()
|
||||
.ToArray ();
|
||||
```
|
||||
|
||||
- **Frequency**: **Once per pixel in the area** (nested loop over x and y)
|
||||
- **Impact**: EXTREMELY HIGH - allocates array for every single pixel being evaluated
|
||||
- **Example**: A 80x24 terminal window border = 1,920 allocations per redraw
|
||||
- **Example**: A 120x40 dialog with borders = 4,800 allocations per redraw
|
||||
|
||||
#### Good News
|
||||
|
||||
The `GetCellMap()` method (line 162) was already optimized:
|
||||
```csharp
|
||||
List<IntersectionDefinition> intersectionsBufferList = [];
|
||||
// ... reuses list with Clear() ...
|
||||
ReadOnlySpan<IntersectionDefinition> intersects = CollectionsMarshal.AsSpan(intersectionsBufferList);
|
||||
```
|
||||
|
||||
This is the **correct pattern** - reusing a buffer and using spans to avoid allocations.
|
||||
|
||||
### 3. Cell Class (`Terminal.Gui/Drawing/Cell.cs`)
|
||||
|
||||
**Location: Line 30**
|
||||
```csharp
|
||||
if (GraphemeHelper.GetGraphemes(value).ToArray().Length > 1)
|
||||
```
|
||||
|
||||
- **Frequency**: Every time Grapheme property is set
|
||||
- **Impact**: Moderate - validation code
|
||||
|
||||
### 4. GraphemeHelper Pattern
|
||||
|
||||
The core issue is that `GraphemeHelper.GetGraphemes()` returns an `IEnumerable<string>`, which is then immediately materialized to arrays or lists. This pattern appears throughout the codebase.
|
||||
|
||||
## Root Cause Analysis
|
||||
|
||||
### TextFormatter Allocations
|
||||
|
||||
The fundamental issue is the design pattern:
|
||||
1. `GetGraphemes()` returns `IEnumerable<string>` (lazy enumeration)
|
||||
2. Code immediately calls `.ToArray()` or `.ToList()` to materialize it
|
||||
3. This happens on every draw call, creating garbage
|
||||
|
||||
### LineCanvas Allocations
|
||||
|
||||
The `GetMap(Rectangle inArea)` method has a particularly problematic nested loop structure:
|
||||
- Outer loop: Y coordinates
|
||||
- Inner loop: X coordinates
|
||||
- **Inside inner loop**: LINQ query with `.ToArray()` allocation
|
||||
|
||||
This is a classic O(n²) allocation problem where the allocation count grows quadratically with area size.
|
||||
|
||||
## Performance Impact Estimation
|
||||
|
||||
### TextFormatter in Progress Demo
|
||||
|
||||
Assuming:
|
||||
- Progress bar updates 20 times/second
|
||||
- Each update redraws the bar (1 line) and percentage text (1 line)
|
||||
- Each line calls `Draw()` which allocates an array
|
||||
|
||||
**Result**: 40 array allocations per second, just for the progress bar
|
||||
|
||||
Add a clock display updating once per second, status messages, etc., and we easily reach **hundreds of allocations per second** in a moderately complex UI.
|
||||
|
||||
### LineCanvas in Border Drawing
|
||||
|
||||
A typical dialog window:
|
||||
- 100x30 character area
|
||||
- Border needs to evaluate 2×(100+30) = 260 pixels for the border
|
||||
- Each pixel: 1 array allocation
|
||||
|
||||
**Result**: 260 allocations per border redraw
|
||||
|
||||
If the dialog is redrawn 10 times per second (e.g., with animated content inside), that's **2,600 allocations per second** just for one border.
|
||||
|
||||
## Comparison to v2_develop Branch
|
||||
|
||||
The issue mentions that allocations "increased drastically" on the v2_develop branch, particularly from LineCanvas. This is consistent with the findings:
|
||||
|
||||
1. **GetMap(Rectangle)** method allocates per-pixel
|
||||
2. If border drawing or line canvas usage increased in v2, this would multiply the allocation impact
|
||||
|
||||
## Memory Allocation Types
|
||||
|
||||
The allocations fall into several categories:
|
||||
|
||||
1. **String Arrays**: `string[]` from `.ToArray()`
|
||||
2. **String Lists**: `List<string>` from `.ToList()`
|
||||
3. **LINQ Enumerable Objects**: Intermediate enumerables in LINQ chains
|
||||
4. **Dictionary/Collection Allocations**: Less critical but still present
|
||||
|
||||
## GC Impact
|
||||
|
||||
With Gen0 collections potentially happening multiple times per second due to these allocations:
|
||||
|
||||
1. **Pause times**: GC pauses affect UI responsiveness
|
||||
2. **CPU overhead**: GC work consumes CPU that could render content
|
||||
3. **Memory pressure**: Constant allocation/collection cycle
|
||||
4. **Cache pollution**: Reduces cache effectiveness
|
||||
|
||||
## Recommended Solutions (High-Level)
|
||||
|
||||
### For TextFormatter
|
||||
|
||||
1. **Use ArrayPool<string>**: Rent arrays from pool instead of allocating
|
||||
2. **Use Span<T>**: Work with spans instead of materializing arrays
|
||||
3. **Cache grapheme arrays**: If text doesn't change, cache the split
|
||||
4. **Lazy evaluation**: Only materialize when truly needed
|
||||
|
||||
### For LineCanvas
|
||||
|
||||
1. **Apply GetCellMap pattern to GetMap**: Reuse buffer list, use spans
|
||||
2. **Pool IntersectionDefinition arrays**: Similar to GetCellMap optimization
|
||||
3. **Consider pixel-level caching**: Cache intersection results for static lines
|
||||
|
||||
### For GraphemeHelper
|
||||
|
||||
1. **Add GetGraphemesAsSpan**: Return `ReadOnlySpan<string>` variant where possible
|
||||
2. **Add TryGetGraphemeCount**: Count without allocation for validation
|
||||
3. **Consider string pooling**: Pool common grapheme strings
|
||||
|
||||
## Measurement Recommendations
|
||||
|
||||
To quantify the impact:
|
||||
|
||||
1. **Add BenchmarkDotNet tests**: Measure allocations for typical scenarios
|
||||
2. **Profile with dotnet-trace**: Capture allocation profiles during Progress demo
|
||||
3. **Memory profiler**: Use Visual Studio or JetBrains dotMemory
|
||||
|
||||
## Severity by Scenario
|
||||
|
||||
| Scenario | Severity | Reason |
|
||||
|----------|----------|--------|
|
||||
| Static UI (no updates) | LOW | Allocations only on initial render |
|
||||
| Progress bars / animations | **CRITICAL** | Continuous allocations 10-60 Hz |
|
||||
| Text-heavy UI | **HIGH** | Many text elements = many allocations |
|
||||
| Border-heavy UI | **HIGH** | Per-pixel allocations in LineCanvas |
|
||||
| Simple forms | MEDIUM | Periodic allocations on interaction |
|
||||
|
||||
## Conclusion
|
||||
|
||||
The heap allocation issue is **real and significant**, particularly for:
|
||||
|
||||
1. **Any time-based updates** (progress bars, clocks, animations)
|
||||
2. **Border/line-heavy UIs** due to LineCanvas per-pixel allocations
|
||||
3. **Text-heavy interfaces** with frequent redraws
|
||||
|
||||
The good news is that the patterns for fixing this are well-established:
|
||||
- ArrayPool usage
|
||||
- Span<T> adoption
|
||||
- Buffer reuse (as demonstrated in GetCellMap)
|
||||
|
||||
The LineCanvas.GetMap() issue is particularly straightforward to fix by applying the same pattern already used in GetCellMap().
|
||||
|
||||
## Files Requiring Changes
|
||||
|
||||
Priority order:
|
||||
|
||||
1. **Terminal.Gui/Drawing/LineCanvas/LineCanvas.cs** (GetMap method) - CRITICAL
|
||||
2. **Terminal.Gui/Text/TextFormatter.cs** (Draw method) - CRITICAL
|
||||
3. **Terminal.Gui/Text/TextFormatter.cs** (other allocation points) - HIGH
|
||||
4. **Terminal.Gui/Drawing/Cell.cs** (validation) - MEDIUM
|
||||
5. **Terminal.Gui/Drawing/GraphemeHelper.cs** (add span-based APIs) - MEDIUM
|
||||
|
||||
## Next Steps
|
||||
|
||||
Based on this analysis, the recommendation is to:
|
||||
|
||||
1. ✅ **Acknowledge the issue is real and significant**
|
||||
2. Fix the most critical issue: LineCanvas.GetMap() per-pixel allocations
|
||||
3. Fix TextFormatter.Draw() allocations
|
||||
4. Add benchmarks to measure improvement
|
||||
5. Consider broader architectural changes for grapheme handling
|
||||
|
||||
---
|
||||
|
||||
**Analysis Date**: 2025-12-03
|
||||
**Analyzed By**: GitHub Copilot
|
||||
**Codebase**: Terminal.Gui (v2_develop branch)
|
||||
@@ -1,546 +0,0 @@
|
||||
# Heap Allocation Optimization Recommendations
|
||||
|
||||
## Overview
|
||||
|
||||
This document provides actionable recommendations for addressing the intermediate heap allocation issues identified in Terminal.Gui, with specific priorities and implementation guidance.
|
||||
|
||||
## Priority Ranking
|
||||
|
||||
### P0 - Critical (Must Fix)
|
||||
|
||||
These issues cause severe performance degradation in common scenarios.
|
||||
|
||||
#### 1. LineCanvas.GetMap() Per-Pixel Allocations
|
||||
|
||||
**File:** `Terminal.Gui/Drawing/LineCanvas/LineCanvas.cs`
|
||||
**Lines:** 210-234
|
||||
**Impact:** 1,920+ allocations per border redraw (80×24 window)
|
||||
|
||||
**Problem:**
|
||||
```csharp
|
||||
for (int y = inArea.Y; y < inArea.Y + inArea.Height; y++) {
|
||||
for (int x = inArea.X; x < inArea.X + inArea.Width; x++) {
|
||||
IntersectionDefinition[] intersects = _lines
|
||||
.Select(l => l.Intersects(x, y))
|
||||
.OfType<IntersectionDefinition>()
|
||||
.ToArray(); // ❌ ALLOCATES EVERY PIXEL
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Solution:** Apply the same pattern already used in `GetCellMap()`:
|
||||
```csharp
|
||||
public Dictionary<Point, Rune> GetMap (Rectangle inArea)
|
||||
{
|
||||
Dictionary<Point, Rune> map = new ();
|
||||
List<IntersectionDefinition> intersectionsBufferList = [];
|
||||
|
||||
for (int y = inArea.Y; y < inArea.Y + inArea.Height; y++)
|
||||
{
|
||||
for (int x = inArea.X; x < inArea.X + inArea.Width; x++)
|
||||
{
|
||||
intersectionsBufferList.Clear();
|
||||
foreach (var line in _lines)
|
||||
{
|
||||
if (line.Intersects(x, y) is { } intersect)
|
||||
{
|
||||
intersectionsBufferList.Add(intersect);
|
||||
}
|
||||
}
|
||||
ReadOnlySpan<IntersectionDefinition> intersects = CollectionsMarshal.AsSpan(intersectionsBufferList);
|
||||
Rune? rune = GetRuneForIntersects(intersects);
|
||||
|
||||
if (rune is { } && _exclusionRegion?.Contains(x, y) is null or false)
|
||||
{
|
||||
map.Add(new (x, y), rune.Value);
|
||||
}
|
||||
}
|
||||
}
|
||||
return map;
|
||||
}
|
||||
```
|
||||
|
||||
**Expected Improvement:**
|
||||
- From 1,920 allocations → 1 allocation per redraw (99.95% reduction)
|
||||
- From 4,800 allocations → 1 allocation for 100×30 dialog
|
||||
- Immediate, measurable performance gain
|
||||
|
||||
**Effort:** Low (pattern already exists in same class)
|
||||
**Risk:** Very Low (straightforward refactoring)
|
||||
|
||||
---
|
||||
|
||||
#### 2. TextFormatter.Draw() Grapheme Array Allocation
|
||||
|
||||
**File:** `Terminal.Gui/Text/TextFormatter.cs`
|
||||
**Lines:** 126, 934
|
||||
**Impact:** Every text draw operation (10-60+ times/second for animated content)
|
||||
|
||||
**Problem:**
|
||||
```csharp
|
||||
public void Draw(...) {
|
||||
// ...
|
||||
for (int line = lineOffset; line < linesFormatted.Count; line++) {
|
||||
string strings = linesFormatted[line];
|
||||
string[] graphemes = GraphemeHelper.GetGraphemes(strings).ToArray(); // ❌ EVERY DRAW
|
||||
// ...
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Solution Options:**
|
||||
|
||||
**Option A: ArrayPool (Immediate Fix)**
|
||||
```csharp
|
||||
using System.Buffers;
|
||||
|
||||
public void Draw(...) {
|
||||
for (int line = lineOffset; line < linesFormatted.Count; line++) {
|
||||
string strings = linesFormatted[line];
|
||||
|
||||
// Estimate or calculate grapheme count
|
||||
int estimatedCount = strings.Length + 10; // Add buffer for safety
|
||||
string[] graphemes = ArrayPool<string>.Shared.Rent(estimatedCount);
|
||||
int actualCount = 0;
|
||||
|
||||
try {
|
||||
foreach (string grapheme in GraphemeHelper.GetGraphemes(strings)) {
|
||||
if (actualCount >= graphemes.Length) {
|
||||
// Need larger array (rare)
|
||||
string[] larger = ArrayPool<string>.Shared.Rent(graphemes.Length * 2);
|
||||
Array.Copy(graphemes, larger, actualCount);
|
||||
ArrayPool<string>.Shared.Return(graphemes);
|
||||
graphemes = larger;
|
||||
}
|
||||
graphemes[actualCount++] = grapheme;
|
||||
}
|
||||
|
||||
// Use graphemes[0..actualCount]
|
||||
// ... rest of draw logic ...
|
||||
|
||||
} finally {
|
||||
ArrayPool<string>.Shared.Return(graphemes, clearArray: true);
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Option B: Caching (Best for Static Text)**
|
||||
```csharp
|
||||
private Dictionary<string, string[]> _graphemeCache = new();
|
||||
private const int MaxCacheSize = 100;
|
||||
|
||||
private string[] GetGraphemesWithCache(string text) {
|
||||
if (_graphemeCache.TryGetValue(text, out string[]? cached)) {
|
||||
return cached;
|
||||
}
|
||||
|
||||
string[] graphemes = GraphemeHelper.GetGraphemes(text).ToArray();
|
||||
|
||||
if (_graphemeCache.Count >= MaxCacheSize) {
|
||||
// Simple LRU: clear cache
|
||||
_graphemeCache.Clear();
|
||||
}
|
||||
|
||||
_graphemeCache[text] = graphemes;
|
||||
return graphemes;
|
||||
}
|
||||
```
|
||||
|
||||
**Expected Improvement:**
|
||||
- ArrayPool: Zero allocations for all draws
|
||||
- Caching: Zero allocations for repeated text (buttons, labels)
|
||||
- 90-100% reduction in TextFormatter allocations
|
||||
|
||||
**Effort:** Medium
|
||||
**Risk:** Medium (requires careful array size handling)
|
||||
|
||||
**Recommendation:** Start with Option A (ArrayPool) as it's more robust
|
||||
|
||||
---
|
||||
|
||||
### P1 - High Priority
|
||||
|
||||
These issues have significant impact in specific scenarios.
|
||||
|
||||
#### 3. TextFormatter Helper Methods
|
||||
|
||||
**Files:** `Terminal.Gui/Text/TextFormatter.cs`
|
||||
**Lines:** 1336, 1407, 1460, 1726, 2191, 2300
|
||||
|
||||
**Problem:** Multiple helper methods allocate grapheme arrays/lists
|
||||
|
||||
**Affected Methods:**
|
||||
- `SplitNewLine()` - Line 1336
|
||||
- `ClipOrPad()` - Line 1407
|
||||
- `WordWrapText()` - Line 1460
|
||||
- `ClipAndJustify()` - Line 1726
|
||||
- `GetSumMaxCharWidth()` - Line 2191
|
||||
- `GetMaxColsForWidth()` - Line 2300
|
||||
|
||||
**Solution:**
|
||||
1. Add overloads that accept `Span<string>` for graphemes
|
||||
2. Use ArrayPool in calling code
|
||||
3. Pass pooled arrays to helper methods
|
||||
|
||||
**Example:**
|
||||
```csharp
|
||||
// New overload
|
||||
public static string ClipOrPad(ReadOnlySpan<string> graphemes, int width) {
|
||||
// Work with span, no allocation
|
||||
}
|
||||
|
||||
// Caller uses ArrayPool
|
||||
string[] graphemes = ArrayPool<string>.Shared.Rent(estimatedSize);
|
||||
try {
|
||||
int count = FillGraphemes(text, graphemes);
|
||||
result = ClipOrPad(graphemes.AsSpan(0, count), width);
|
||||
} finally {
|
||||
ArrayPool<string>.Shared.Return(graphemes);
|
||||
}
|
||||
```
|
||||
|
||||
**Expected Improvement:** 70-90% reduction in text formatting allocations
|
||||
|
||||
**Effort:** High (multiple methods to update)
|
||||
**Risk:** Medium (API changes, need careful span handling)
|
||||
|
||||
---
|
||||
|
||||
#### 4. Cell.Grapheme Validation
|
||||
|
||||
**File:** `Terminal.Gui/Drawing/Cell.cs`
|
||||
**Line:** 30
|
||||
|
||||
**Problem:**
|
||||
```csharp
|
||||
if (GraphemeHelper.GetGraphemes(value).ToArray().Length > 1)
|
||||
```
|
||||
|
||||
**Solution:**
|
||||
```csharp
|
||||
// Add helper to GraphemeHelper
|
||||
public static int GetGraphemeCount(string text) {
|
||||
if (string.IsNullOrEmpty(text)) return 0;
|
||||
|
||||
int count = 0;
|
||||
TextElementEnumerator enumerator = StringInfo.GetTextElementEnumerator(text);
|
||||
while (enumerator.MoveNext()) {
|
||||
count++;
|
||||
}
|
||||
return count;
|
||||
}
|
||||
|
||||
// In Cell.cs
|
||||
if (GraphemeHelper.GetGraphemeCount(value) > 1)
|
||||
```
|
||||
|
||||
**Expected Improvement:** Zero allocations for Cell.Grapheme validation
|
||||
|
||||
**Effort:** Low
|
||||
**Risk:** Very Low
|
||||
|
||||
---
|
||||
|
||||
### P2 - Medium Priority
|
||||
|
||||
Performance improvements for less frequent code paths.
|
||||
|
||||
#### 5. GraphemeHelper API Improvements
|
||||
|
||||
**File:** `Terminal.Gui/Drawing/GraphemeHelper.cs`
|
||||
|
||||
**Additions:**
|
||||
```csharp
|
||||
/// <summary>Counts graphemes without allocation</summary>
|
||||
public static int GetGraphemeCount(string text);
|
||||
|
||||
/// <summary>Fills a span with graphemes, returns actual count</summary>
|
||||
public static int GetGraphemes(string text, Span<string> destination);
|
||||
|
||||
/// <summary>Gets graphemes with a rented array from pool</summary>
|
||||
public static (string[] array, int count) GetGraphemesPooled(string text);
|
||||
```
|
||||
|
||||
**Benefit:** Provides allocation-free alternatives for all callers
|
||||
|
||||
**Effort:** Medium
|
||||
**Risk:** Low (additive changes, doesn't break existing API)
|
||||
|
||||
---
|
||||
|
||||
### P3 - Nice to Have
|
||||
|
||||
Optimizations for edge cases or less common scenarios.
|
||||
|
||||
#### 6. GetDrawRegion Optimization
|
||||
|
||||
**File:** `Terminal.Gui/Text/TextFormatter.cs`
|
||||
**Line:** 934
|
||||
|
||||
Similar allocation as Draw method. Apply same ArrayPool pattern.
|
||||
|
||||
**Effort:** Low (copy Draw optimization)
|
||||
**Risk:** Low
|
||||
|
||||
---
|
||||
|
||||
## Implementation Roadmap
|
||||
|
||||
### Phase 1: Quick Wins (1-2 days)
|
||||
|
||||
1. ✅ Fix LineCanvas.GetMap() per-pixel allocations
|
||||
2. ✅ Add GraphemeHelper.GetGraphemeCount()
|
||||
3. ✅ Fix Cell.Grapheme validation
|
||||
4. ✅ Add basic benchmarks for measuring improvement
|
||||
|
||||
**Expected Result:**
|
||||
- Eliminate border/line drawing allocations (99%+ reduction)
|
||||
- Baseline performance metrics established
|
||||
|
||||
### Phase 2: Core Optimization (3-5 days)
|
||||
|
||||
1. ✅ Implement ArrayPool in TextFormatter.Draw()
|
||||
2. ✅ Add comprehensive unit tests
|
||||
3. ✅ Update GetDrawRegion() similarly
|
||||
4. ✅ Run Progress scenario profiling
|
||||
5. ✅ Validate allocation reduction
|
||||
|
||||
**Expected Result:**
|
||||
- TextFormatter allocations reduced 90-100%
|
||||
- All high-frequency code paths optimized
|
||||
|
||||
### Phase 3: Helpers & API (5-7 days)
|
||||
|
||||
1. ✅ Add GraphemeHelper span-based APIs
|
||||
2. ✅ Update TextFormatter helper methods
|
||||
3. ✅ Add optional caching for static text
|
||||
4. ✅ Full test coverage
|
||||
5. ✅ Update documentation
|
||||
|
||||
**Expected Result:**
|
||||
- Complete allocation-free text rendering path
|
||||
- Public APIs available for consumers
|
||||
|
||||
### Phase 4: Validation & Documentation (2-3 days)
|
||||
|
||||
1. ✅ Run full benchmark suite
|
||||
2. ✅ Profile Progress demo with dotnet-trace
|
||||
3. ✅ Compare before/after metrics
|
||||
4. ✅ Update performance documentation
|
||||
5. ✅ Create migration guide for API changes
|
||||
|
||||
**Expected Result:**
|
||||
- Quantified performance improvements
|
||||
- Clear documentation for maintainers
|
||||
|
||||
**Total Time Estimate:** 2-3 weeks for complete implementation
|
||||
|
||||
---
|
||||
|
||||
## Testing Strategy
|
||||
|
||||
### Unit Tests
|
||||
|
||||
```csharp
|
||||
[Theory]
|
||||
[InlineData("Hello")]
|
||||
[InlineData("Hello\nWorld")]
|
||||
[InlineData("Emoji: 👨👩👧👦")]
|
||||
public void Draw_NoAllocations_WithArrayPool(string text)
|
||||
{
|
||||
var formatter = new TextFormatter { Text = text };
|
||||
var driver = new FakeDriver();
|
||||
|
||||
// Get baseline allocations
|
||||
long before = GC.GetAllocatedBytesForCurrentThread();
|
||||
|
||||
formatter.Draw(driver, new Rectangle(0, 0, 100, 10),
|
||||
Attribute.Default, Attribute.Default);
|
||||
|
||||
long after = GC.GetAllocatedBytesForCurrentThread();
|
||||
long allocated = after - before;
|
||||
|
||||
// Should be zero or minimal (some overhead acceptable)
|
||||
Assert.True(allocated < 1000, $"Allocated {allocated} bytes");
|
||||
}
|
||||
```
|
||||
|
||||
### Benchmarks
|
||||
|
||||
```csharp
|
||||
[MemoryDiagnoser]
|
||||
[BenchmarkCategory("TextFormatter")]
|
||||
public class DrawBenchmark
|
||||
{
|
||||
private TextFormatter _formatter;
|
||||
private FakeDriver _driver;
|
||||
|
||||
[GlobalSetup]
|
||||
public void Setup()
|
||||
{
|
||||
_formatter = new TextFormatter {
|
||||
Text = "Progress: 45%",
|
||||
ConstrainToWidth = 80,
|
||||
ConstrainToHeight = 1
|
||||
};
|
||||
_driver = new FakeDriver();
|
||||
}
|
||||
|
||||
[Benchmark]
|
||||
public void DrawProgressText()
|
||||
{
|
||||
_formatter.Draw(_driver,
|
||||
new Rectangle(0, 0, 80, 1),
|
||||
Attribute.Default,
|
||||
Attribute.Default);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Expected results:
|
||||
- **Before:** ~500-1000 bytes allocated per draw
|
||||
- **After:** 0-100 bytes allocated per draw
|
||||
|
||||
### Performance Testing
|
||||
|
||||
```bash
|
||||
# Run benchmarks
|
||||
cd Tests/Benchmarks
|
||||
dotnet run -c Release --filter "*TextFormatter*"
|
||||
|
||||
# Profile with dotnet-trace
|
||||
dotnet-trace collect --process-id <pid> \
|
||||
--providers Microsoft-Windows-DotNETRuntime:0x1:5
|
||||
|
||||
# Analyze in PerfView or VS
|
||||
```
|
||||
|
||||
### Integration Testing
|
||||
|
||||
Run Progress scenario for 60 seconds:
|
||||
- Monitor GC collections
|
||||
- Track allocation rate
|
||||
- Measure frame times
|
||||
- Compare before/after
|
||||
|
||||
---
|
||||
|
||||
## Breaking Changes
|
||||
|
||||
### None for Phase 1-2
|
||||
|
||||
All optimizations are internal implementation changes.
|
||||
|
||||
### Possible for Phase 3
|
||||
|
||||
If adding span-based APIs:
|
||||
- New overloads (non-breaking)
|
||||
- Possible deprecation of allocation-heavy methods
|
||||
|
||||
**Mitigation:** Use `[Obsolete]` attributes with migration guidance
|
||||
|
||||
---
|
||||
|
||||
## Documentation Updates Required
|
||||
|
||||
1. **CONTRIBUTING.md**
|
||||
- Add section on allocation-aware coding
|
||||
- ArrayPool usage guidelines
|
||||
- Span<T> patterns
|
||||
|
||||
2. **Performance.md** (new file)
|
||||
- Allocation best practices
|
||||
- Profiling guide
|
||||
- Benchmark results
|
||||
|
||||
3. **API Documentation**
|
||||
- Document allocation behavior
|
||||
- Note pooled array usage
|
||||
- Warn about concurrent access (if using pooling)
|
||||
|
||||
---
|
||||
|
||||
## Monitoring & Validation
|
||||
|
||||
### Success Metrics
|
||||
|
||||
| Metric | Baseline | Target | Measurement |
|
||||
|--------|----------|--------|-------------|
|
||||
| Allocations/sec (Progress) | 1,000-5,000 | <100 | Profiler |
|
||||
| Gen0 GC frequency | Every 5-10s | Every 60s+ | GC.CollectionCount() |
|
||||
| Frame drops (animated UI) | Occasional | Rare | Frame time monitoring |
|
||||
| Memory usage (sustained) | Growing | Stable | dotnet-counters |
|
||||
|
||||
### Regression Testing
|
||||
|
||||
Add to CI pipeline:
|
||||
```yaml
|
||||
- name: Run allocation benchmarks
|
||||
run: |
|
||||
cd Tests/Benchmarks
|
||||
dotnet run -c Release --filter "*Allocation*" --exporters json
|
||||
# Parse JSON and fail if allocations exceed baseline
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
## Risk Assessment
|
||||
|
||||
### Low Risk
|
||||
- LineCanvas.GetMap() fix (proven pattern exists)
|
||||
- Cell validation fix (simple change)
|
||||
- Adding new helper methods (additive)
|
||||
|
||||
### Medium Risk
|
||||
- TextFormatter.Draw() with ArrayPool (complex control flow)
|
||||
- Span-based API additions (need careful API design)
|
||||
|
||||
### Mitigation
|
||||
- Comprehensive unit tests
|
||||
- Gradual rollout (behind feature flag if needed)
|
||||
- Extensive profiling before merge
|
||||
|
||||
---
|
||||
|
||||
## Alternative Approaches Considered
|
||||
|
||||
### 1. String Interning
|
||||
**Pros:** Reduces string allocations
|
||||
**Cons:** Doesn't solve array allocations, memory pressure
|
||||
**Decision:** Not suitable for dynamic content
|
||||
|
||||
### 2. Custom Grapheme Iterator
|
||||
**Pros:** Ultimate control, zero allocations
|
||||
**Cons:** Complex to implement, maintain
|
||||
**Decision:** ArrayPool is simpler, achieves same goal
|
||||
|
||||
### 3. Code Generation
|
||||
**Pros:** Compile-time optimization
|
||||
**Cons:** Overkill for this problem
|
||||
**Decision:** Runtime optimization sufficient
|
||||
|
||||
---
|
||||
|
||||
## Conclusion
|
||||
|
||||
The optimization strategy is:
|
||||
|
||||
1. **Clear and Actionable** - Specific files, lines, and solutions
|
||||
2. **Proven Patterns** - Uses existing patterns (GetCellMap) and standard tools (ArrayPool)
|
||||
3. **Measurable** - Clear metrics and testing strategy
|
||||
4. **Low Risk** - Gradual implementation with extensive testing
|
||||
5. **High Impact** - 90-99% allocation reduction in critical paths
|
||||
|
||||
**Recommended First Step:** Fix LineCanvas.GetMap() as proof of concept (4-8 hours of work, massive impact)
|
||||
|
||||
---
|
||||
|
||||
## Questions or Feedback?
|
||||
|
||||
For implementation questions, consult:
|
||||
- HEAP_ALLOCATION_ANALYSIS.md - Detailed problem analysis
|
||||
- ALLOCATION_CALL_FLOW.md - Call flow and measurement details
|
||||
- This document - Implementation roadmap
|
||||
|
||||
**Next Action:** Review with team and prioritize Phase 1 implementation.
|
||||
Reference in New Issue
Block a user