Below is the definitive, step-by-step list of PerfMon counters you must add for .NET / ASP.NET Core / API / Microservices performance optimization.

This is the same checklist used in enterprise performance engineering, load testing, and production diagnostics.

I will give you:

✔ Exact counters
✔ In step-by-step order
✔ Why each counter matters
✔ Which ones are optional vs mandatory
✔ What values are considered “bad”

This is your final PerfMon Counter Checklist for .NET performance.

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STEP-BY-STEP: Add These PerfMon Counters for .NET Application Performance Optimization

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🔵 STEP 1 — Add Essential CPU Counters (Mandatory)

✔ Processor

• % Processor Time — _Total
• % Privileged Time — _Total
• % Interrupt Time
• Processor Queue Length (from System)

✔ Process (for your app)

Select instance:
➡ dotnet, w3wp, or yourapp.exe

Add:

• % Processor Time
• Thread Count
• Handle Count
• Private Bytes
• Working Set
• IO Data Bytes/sec
• IO Read Bytes/sec
• IO Write Bytes/sec

Why CPU counters matter

• Detect CPU saturation (>80%)
• Find thread pool starvation
• Detect infinite loops, heavy JSON serialization, LINQ misuse
• Detect high kernel (privileged) usage → drivers, encryption, networking

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🟣 STEP 2 — Add Memory Counters (Mandatory)

✔ Memory

• Available MBytes
• % Committed Bytes in Use
• Pages/sec
• Page Reads/sec
• Cache Faults/sec
• Committed Bytes

✔ Process (your app)

• Private Bytes (memory leak indicator)
• Virtual Bytes
• Working Set
• Page Faults/sec

Why Memory counters matter

• Identify memory leaks
• Detect high paging → application slowdown
• Understand GC pressure
• Identify large object allocations

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🟢 STEP 3 — Add Disk I/O Counters (Mandatory)

✔ PhysicalDisk

(_Total)

• Avg. Disk Queue Length
• Avg. Disk sec/Read
• Avg. Disk sec/Write
• Disk Reads/sec
• Disk Writes/sec
• Current Disk Queue Length

✔ LogicalDisk

• % Free Space
• Free Megabytes

Why disk counters matter

• Identify disk bottlenecks
• Troubleshoot long API latency caused by slow file or database I/O.
• Detect heavy logging or temp file writes

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🟡 STEP 4 — Add Network Counters (Mandatory for API/Web App)

✔ Network Interface

• Bytes Total/sec
• Bytes Received/sec
• Bytes Sent/sec
• Output Queue Length
• Packets/sec
• Packets Outbound Errors
• Packets Received Errors

✔ TCPv4

• Connections Established
• Connection Failures
• Segments Retransmitted/sec

Why network counters matter

• Understand throughput
• Detect API congestion
• Detect retransmissions (network instability)

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🔴 STEP 5 — Add .NET CLR Counters (CRITICAL for .NET Performance)

➡ In PerfMon UI, expand:
“.NET CLR Memory”
“.NET CLR Exceptions”
“.NET CLR Jit”
“.NET CLR LocksAndThreads”
“.NET CLR Networking”

Select your instance:
dotnet, w3wp, or your application name.

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🍀 .NET CLR MEMORY (Very Important)

✔ Add these:

• % Time in GC
• Gen 0 Collections
• Gen 1 Collections
• Gen 2 Collections 🔥
• Large Object Heap Size 🔥
• # Bytes in all Heaps
• Promoted Memory/sec
• Finalization Survivors
• GC Handles

Interpretation:

Counter	Meaning
% Time in GC > 15%	Too much GC blocking = slow app
Frequent Gen 2 GC	Memory pressure / large objects
High LOH size	Large object allocations causing fragmentation
High Promoted MB/sec	Short-lived objects living too long

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🍀 .NET CLR EXCEPTIONS

Add:

• # of Exceptions Thrown/sec

This indicates:

• Poor coding practices
• Bad error handling
• Hidden exceptions killing performance

If > 100/sec consistently → WRONG code.

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🍀 .NET CLR LOCKS & THREADS

Add:

• # of current logical Threads
• # of current physical Threads
• Contention Rate/sec
• Queue Length

Indicates:

• Thread pool starvation
• Async deadlocks
• High locking contention

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🍀 .NET CLR JIT

Add:

• % Time in JIT
• IL Bytes Jitted/sec

JIT issues appear on:

• Cold starts
• Large reflection / dynamic LINQ usage

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🟤 STEP 6 — Add ASP.NET / IIS Counters (If Web App or API)

✔ ASP.NET Applications

(Select your app pool)

Add:

• Requests/Sec
• Requests Queued
• Requests Rejected
• Request Execution Time
• Pipeline Instance Count

✔ ASP.NET

• Application Restarts
• Worker Process Restarts

✔ Web Service

(For old .NET Framework)

• Total Method Requests/sec

✔ WinHTTP Proxy/Service

If using HttpClient extensively.

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🔵 STEP 7 — Add Kestrel & Hosting Counters (.NET Core Self-hosted)

If running on Kestrel (non-IIS):

✔ ASP.NET Core Hosting

• Current Requests
• Requests/sec
• Request Queue Length

✔ Kestrel

(Available in dotnet counters, but PerfMon may expose via EventSource)

• Connection queue length
• Active connections
• TLS handshake duration

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🟣 STEP 8 — Add SQL Server Counters (If Your App Uses DB)

Category: SQLServer:SQL Statistics

• Batch Requests/sec
• Compilations/sec
• Re-Compilations/sec

Category: SQLServer:Buffer Manager

• Buffer cache hit ratio
• Page life expectancy (PLE)

Category: SQLServer:General Statistics

• User Connections
• Processes blocked

Category: SQLServer:Wait Statistics

• Lock waits/sec
• Latch waits/sec

These help detect:

• Query bottlenecks
• High CPU SQL queries
• Plan cache issues
• Memory pressure

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🎯 FINAL: Complete List (Copy-Paste Checklist)

Here is the single list you can paste into training material:

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✔ CPU

• Processor → % Processor Time (_Total)
• Processor → % Privileged Time
• Processor → % Interrupt Time
• System → Processor Queue Length
• Process(dotnet/w3wp/app.exe) → % Processor Time
• Thread Count
• Handle Count

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✔ Memory

• Memory → Available MBytes
• Memory → % Committed Bytes
• Memory → Pages/sec
• Process → Private Bytes
• Process → Page Faults/sec
• Process → Working Set

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✔ Disk

• Avg. Disk Queue Length
• Avg. Disk sec/Read
• Avg. Disk sec/Write
• Disk Reads/sec
• Disk Writes/sec

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✔ Network

• Bytes Total/sec
• TCP Retransmissions/sec
• Connections Established
• Packets Errors

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✔ .NET CLR Memory

• % Time in GC
• Gen 0/1/2 Collections
• Promoted MB/sec
• Bytes in All Heaps
• LOH Size

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✔ .NET CLR Exceptions

• Exceptions/sec

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✔ .NET CLR LocksAndThreads

• Contention Rate/sec
• Logical Threads
• Physical Threads

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✔ ASP.NET / Hosting

• Requests/sec
• Current Requests
• Request Queue Length
• Request Execution Time

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✔ SQL Server

• Batch Requests/sec
• SQL Compilations/sec
• SQL Re-compilations/sec
• Buffer Cache Hit Ratio
• Page Life Expectancy

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