I know several chats in linkedin

Java Performance Professionals – https://www.linkedin.com/groups/105986/
High Performance & Super Computing – https://www.linkedin.com/groups/95317/
Performance Testers – https://www.linkedin.com/groups/132947/
Performance Testing (2059820) – https://www.linkedin.com/groups/2059820/
Application Performance Monitoring – https://www.linkedin.com/groups/1780239/
Performance Specialists – https://www.linkedin.com/groups/104350/
JMeter Threads – https://www.linkedin.com/groups/2017104/
IT Load Testing and Performance Professionals – https://www.linkedin.com/groups/1863069/
Spring Users – https://www.linkedin.com/groups/46964/
Java Virtual Machine Internals ( JVM ) – https://www.linkedin.com/groups/3866887/
High Performance Computing (HPC) – https://www.linkedin.com/groups/87791/
SQL SERVER Performance Tuning – https://www.linkedin.com/groups/2794259/
Performance Test Specialists India – https://www.linkedin.com/groups/4884353/
Performance Testing/Automation Testing – https://www.linkedin.com/groups/88217/
Load & performance testing – https://www.linkedin.com/groups/107497/
…