controller that tries to handle early invocations of the controller,
in other words, invocations before the expected end of the interval.
However, there were some calculation errors in this early invocation
case. Notably, if an early invocation occurred while the error was
negative, the derivative term was off by a large amount. One visible
effect of this error was that processes were being killed by the
virtual memory system's OOM killer when in fact there was plentiful
free memory.
Correct a couple minor errors in the sysctl descriptions, and apply
some style fixes.
Reviewed by: jeff, markj
use it to regulate page daemon output.
This provides much smoother and more responsive page daemon output, anticipating
demand and avoiding pageout stalls by increasing the number of pages to match
the workload. This is a reimplementation of work done by myself and mlaier at
Isilon.
Reviewed by: bsdimp
Tested by: pho
Sponsored by: Netflix, Dell/EMC Isilon
Differential Revision: https://reviews.freebsd.org/D14402
