Links for using Performance Counters (perfmon) while troubleshooting SQL Server related issues
Understanding Performance Counters data while troubleshooting Performance issues in SQL Server: https://blogs.technet.com/vipulshah/archive/2006/11/30/understanding-perfmon-counters-while-troubleshooting-sql-server-performance-issues.aspx
External Links:
https://www.extremeexperts.com/SQL/Articles/SQLCounters.aspx
https://www.sqlservercentral.com/articles/Administering/performancemonitoringbasiccounters/1348/
User Settable queries: