PostgreSQL 12 High Availability Cookbook - Third Edition

Simultaneous multithreading 

Essentially, all modern server-class processors provide a feature that essentially splits each physical processor core into two virtual cores. Intel calls this hyper-threading, while AMD uses the standard Simultaneous Multithreading (SMT) terminology. Historically, this was not well received as benchmarks often illustrated performance degradation when the feature was enabled.

Recently, several security vulnerabilities have been discovered in SMT-enabled CPUs. Be sure to check for security advisories before enabling this feature in earnest.

Since the introduction of Intel's Nehalem-based architecture in 2008 and AMD's Ryzen architecture in 2017, this is no longer the case. While doubling the processor count does ...