Newer generations of Intel processors often provide a feature called hyperthreading, which splits each physical processor core into two virtual cores. Historically, this was not well received, as benchmarks often illustrated performance degradation when the feature was enabled.
Since the introduction of Nehalem-based architecture in 2008, this is no longer the case. While doubling the processor count does not result in a doubling of throughput, we've run several tests that show up to 40 percent improvement over using physical cores alone. This may not be universal, but it does apply to PostgreSQL performance tests. What this means is that the commonly accepted formula for determining ideal connection count requires modification. ...
