Performance schema performance tuning One of the most important question users ask before deciding to use the performance schema is: what is the overhead ? The underlying concern of course is to make sure deploying the performance schema does not negatively impact production ("First, do no harm").
The question is simple, and yet the answer is not so simple, as it depends on so many things.
As seen in some benchmarks done already, the overhead when using the performance schema can vary a lot, and in some cases really causes degradations.
A lot of time has been spent investigating the root causes (note the plural form) for the performance schema overhead in general, so I think it is a good time to share current findings.

Server workload Analysing performances, and testing the effects of different code or configuration changes, can hardly be done in a vacuum. That's where benchmarks come in.
The problem with …