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🎯 Lab Objective

By the end of this lab, you will be able to:

✔ Launch and use Resource Monitor
✔ Analyze CPU, Memory, Disk, and Network usage for a .NET application
✔ Identify performance bottlenecks
✔ Detect high CPU, memory leaks, disk thrashing, and network issues
✔ Use Resource Monitor to troubleshoot real-time .NET app problems

This lab is hands-on, and every step includes expected results + observations.

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🧪 LAB 0 — Prerequisites

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Before starting:

✔ Windows 10/11 or Windows Server

✔ .NET 6 or .NET 7 runtime installed

✔ A sample .NET app (API, console, or background worker)

If you don’t have one, you can create a quick sample API:

dotnet new webapi -n DemoApi
cd DemoApi
dotnet run
Code language: JavaScript (javascript)

This will run on:
http://localhost:5000 or http://localhost:5241 (depending on your version)

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🧪 LAB 1 — Launch Resource Monitor

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Step 1: Open ResMon

Press:

Win + R → resmon

OR

Ctrl + Shift + Esc → Task Manager → Performance → Open Resource Monitor

Expected Output

You see an interface with tabs:

• Overview
• CPU
• Memory
• Disk
• Network

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🧪 LAB 2 — Monitor CPU Usage of .NET App

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Step 1: Run your .NET application

Example:

dotnet run

Step 2: Open Resource Monitor → CPU Tab

Step 3: Filter by the .NET process

Look for:

• dotnet.exe
• w3wp.exe (if IIS hosted)
• yourapp.exe (self-contained builds)

Check these fields:

• Image
• PID
• Threads
• CPU %
• Average CPU

Step 4: Simulate load

Use a separate terminal:

for /l %i in (1,1,1000) do curl http://localhost:5000/weatherforecast
Code language: JavaScript (javascript)

Or use Postman runner.

Observe:

• CPU usage rises
• Thread count increases
• Your .NET process moves to the top of the CPU list

Step 5: Analyze Wait Chain for Deadlocks

Right-click your .NET process →
Analyze Wait Chain

Expected Result

• No wait chain = no deadlock
• If threads wait for each other → potential deadlock

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🧪 LAB 3 — Memory Analysis for .NET App

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Step 1: Open Memory tab

Filter your .NET process.

Look at:

• Commit (KB)
• Working Set (KB)
• Private (KB)
• Shareable
• Hard Faults/sec

Step 2: Trigger .NET memory usage

Modify API or run a loop:

var data = new List<byte[]>();
for(int i=0; i<50000; i++)
{
    data.Add(new byte[1024 * 50]); // 50 KB
}
Code language: PHP (php)

Run load test again.

Expected Observations

• Working Set increases
• Commit size increases
• Hard Faults/sec spikes if system memory is low

Step 3: Identify memory leak behavior

If Working Set grows continuously without dropping → possible memory leak.

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🧪 LAB 4 — Disk I/O Analysis for .NET

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This is crucial for:

• Logging-heavy applications
• APIs that write large files
• Upload/download endpoints
• Apps with heavy DB operations

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Step 1: Open Disk tab

Filter by your dotnet.exe process.

Observe:

• Read (B/sec)
• Write (B/sec)
• Total (B/sec)
• Disk Queue Length
• Response Time
• File path being accessed

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Step 2: Simulate Disk Load

Create a .NET endpoint that writes files:

[HttpGet("write")]
public IActionResult WriteDemo()
{
    System.IO.File.WriteAllText("test_" + Guid.NewGuid() + ".txt", new string('A', 1000000));
    return Ok();
}
Code language: PHP (php)

Call it multiple times:

for /l %i in (1,1,200) do curl http://localhost:5000/write
Code language: JavaScript (javascript)

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Expected Observations

• Disk write activity spikes
• Resource Monitor shows file names like:
  C:\path\yourapp\test_*.txt
• Disk Queue Length increases
• Response Time shows milliseconds → indicates I/O latency

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Interpretation

• High queue length → Disk bottleneck
• High response time → slow disk (SSD/HDD issue)
• Heavy writes → Logging too much

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🧪 LAB 5 — Network Analysis for .NET

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Step 1: Go to Network Tab

Filter by your .NET process.

Observe:

• Send (B/sec)
• Receive (B/sec)
• Total bytes/sec
• Remote Address
• Port
• TCP connections
• Failures

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Step 2: Simulate High Network Load

Run:

for /l %i in (1,1,300) do curl http://localhost:5000/weatherforecast
Code language: JavaScript (javascript)

Or:

Use Postman runner (10–100 requests/sec).

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Expected Observations

• Network usage increases
• You can see your API responding on port:
  • 5000
  • 5241
  • custom hosted port
• TCP connections show:
  • Local Address
  • Remote Address
  • State (Established)

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Advanced Scenario

If your .NET app calls external APIs, you can see:

• Outgoing IP
• Latency issues
• Failed connections

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🧪 LAB 6 — Isolate and Focus on a Single Process

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Resource Monitor allows FILTERING by process.

Step 1: Check the box next to dotnet.exe

Now the entire UI filters:

✔ CPU → Only your threads
✔ Disk → Only your files
✔ Network → Only your connections
✔ Memory → Only your segments

This is the most powerful feature in Resource Monitor.

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🧪 LAB 7 — Detect Thread Starvation / Deadlocks

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Step 1: CPU Tab → Expand Threads

Look for:

• A single thread using high CPU
• Many threads blocked

Step 2: Right-click → Analyze Wait Chain

Expected

• App may show:
  “One or more threads are waiting on each other” → Deadlock

This helps catch:

• async/await deadlocks
• database blocking
• file I/O blocking
• network blocking

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🧪 LAB 8 — Performance Optimization Decision Points

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Using Resource Monitor, collect findings:

1. CPU Bottleneck → Optimize

• Reduce JSON serialization
• Optimize LINQ projections
• Use async I/O
• Reduce heavy loops
• Add caching

2. Memory Bottleneck → Optimize

• Fix memory leaks
• Reduce LOH allocations
• Use pooling
• Dispose unmanaged resources

3. Disk Bottleneck → Optimize

• Reduce logging
• Use async disk I/O
• Move logs to separate drive
• Optimize temp-file usage

4. Network Bottleneck → Optimize

• Add connection pooling
• Reduce large payloads
• Enable compression
• Optimize external API calls

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🧪 LAB 9 — Final Validation

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After optimization:

Re-run load

• Use curl/Postman
• Generate real load

Re-check Resource Monitor

• CPU should stabilize
• Disk writes reduced
• Hard faults minimized
• Network calls optimized
• Memory usage flattened

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LAB END: Summary

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After completing this lab, you can:

✔ Use Resource Monitor to analyze:

• CPU
• Memory
• Disk
• Network

✔ Filter by .NET process
✔ Identify bottlenecks
✔ Detect deadlocks, file locks, port usage
✔ Optimize .NET application performance using real-time signals

Resource Monitor is a real-time diagnostic powerhouse for Windows and crucial for effective .NET performance optimization.

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