How to get to the bottom of Sitecore Performance issues?

The idea is to give the quicklinks to gather data for performance issue analysis. Most of us may not be aware about the intrinsic .net framework and internal of CLR in details as we more focus on implementations and make use of features. This is where actual concept comes into play.

Debugging TOOL

1. DebugDiag

https://channel9.msdn.com/Shows/Defrag-Tools/Defrag-Tools-122-DebugDiag-Part-2
Performance counters
Proc Dump

2. Debugging Production Environment Windbg & SOS

https://channel9.msdn.com/Series/-NET-Debugging-Stater-Kit-for-the-Production-Environment/Windbg--SOS-03

3. Sons of Strike- SOS.dll

https://msdn.microsoft.com/en-us/library/bb190764(v=vs.110).aspx

If you really want to deep dive further refer Tezz Fernandez blogs and articles.

A long story short, if you are into critical production performance issue, sitecore support team may need your help to get certain process stats and data here are the few links that you must go through to nail down the issues.
https://blogs.msdn.microsoft.com/tess/

Some unanswered Questions?

Q.1  How to collect memory dumps using Task Manager ?
https://kb.sitecore.net/articles/758511

Q.2. How to collect memory dumps using ProcDump ?
https://kb.sitecore.net/articles/253710

Q.3. How to identify Sitecore process in Performance Monitor ?
https://kb.sitecore.net/articles/931689

Q.3. How to collect memory dumps using Managed GC Aware Dump ?
https://kb.sitecore.net/articles/284285

Q.4. How to collect memory dumps ?
https://kb.sitecore.net/articles/488758