Don’t be silly, turn Debug off
The number 2 rule of performance testing is “never test in Debug mode” (rule number 1 is “don’t optimize what you don’t need“).
Well, I was reminded today this is not limited to compiling your application in Release mode. A process I’m developing showed about 10 times worse performance than our initial testing showed. I began to think about optimizations and introducing parallelism, when a I stumbled on the real answer:
log4net logging level was on “Debug”. D’oh!