🎯 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.

————————————

🧪 LAB 0 — Prerequisites

————————————

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)

————————————

🧪 LAB 1 — Launch Resource Monitor

————————————

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

————————————

🧪 LAB 2 — Monitor CPU Usage of .NET App

————————————

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

————————————

🧪 LAB 3 — Memory Analysis for .NET App

————————————

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.

————————————

🧪 LAB 4 — Disk I/O Analysis for .NET

————————————

This is crucial for:

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

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

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)

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

Interpretation

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

————————————

🧪 LAB 5 — Network Analysis for .NET

————————————

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

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).

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)

Advanced Scenario

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

• Outgoing IP
• Latency issues
• Failed connections

————————————

🧪 LAB 6 — Isolate and Focus on a Single Process

————————————

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.

————————————

🧪 LAB 7 — Detect Thread Starvation / Deadlocks

————————————

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

————————————

🧪 LAB 8 — Performance Optimization Decision Points

————————————

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

————————————

🧪 LAB 9 — Final Validation

————————————

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

————————————

LAB END: Summary

————————————

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.

Rajesh Kumar

I’m Rajesh Kumar, a DevOps, SRE, DevSecOps, Cloud, and Platform Engineering expert passionate about sharing practical knowledge, real-world experiences, and industry best practices. I have worked at Cotocus and regularly write about technology, travel, investing, health, product reviews, and digital marketing through my various platforms.

I publish technical articles at DevOps School, travel stories at Holiday Landmark, stock market insights at Stocks Mantra, health and fitness guidance at My Medic Plus, product reviews at TrueReviewNow, and SEO and digital marketing strategies at Wizbrand.