> First, there's no POSIX standard way to communicate this scheduling request to the kernel. So you either have to add a new API or add some "secret knock" to an existing API that will trigger the desired behavior. Neither of these encourage portable code, and neither help existing, deployed applications, which would have to be modified to get the desired result.

Linux doesn't fully comply with posix and has many of it's own apis. Cross platform applications either abstract this away themselves or libraries do it for them. I doubt a database doesn't use a lot of os specific features.