Quite some time ago I was trying to profile the kernel (in vax), and found that there are some places where the code implemented has ended up very inefficient. This is not noticed on any modern hardware, but the effect on vax is significant. IIRC one of the places was the in-kernel NTP code. Taking it out had a noticeable effect on kernel time used.Do you have measurements that show clock drift under load?I was assuming he had. But in a sense, it also wouldn't surprise me. When doing things, the amount of time in system mode these days for NetBSD/VAX really bothers me. Sometimes I can observe it being at over 50% system time for longer periods. And in Josh case, it's reporting over 50% in interrupt context, which *really* worries me, and suggests that would could easily be missing interrupts...
Is the in-kernel profiling code is still available for use? This was many years ago, I do not know what the state is now.Can also note that I once was trying to find what caused the clock drift (has been present for quite some time) by adding code that was checking for lost interrupts, but there were no missed clock interrupts seen. Did not search any deeper after that.
-- Ragge