50 percent swap used, but "ps auxww" output shows no processes swapped out

[Eugene Grosbein]

04.02.2018 5:32, Brandon Allbery wrote:

> Also worth noting is that likely candidates for such pageouts include
> long-lived daemons that are only needed, or which only need certain pages,
> during startup/shutdown. So evicting only those pages to swap allows
> optimal use of memory that would otherwise be wasted unnecessarily.
> 
> Studying demand paging and unified page management is worth the effort.
> Modern OSes, including Windows, make heavy use of this to optimize memory
> usage --- but it means that old-style notions of process memory usage will
> leave you wondering how the numbers make any sense. (I see this quite a
> lot; most people still seem to think the basic unit of memory management is
> a process, not a memory page, despite unified page management being over a
> decade old and basic demand paging going back to 4BSD days.)

FreeBSD kernel does not try to "swapout" even long-lived sleeping daemons as a whole 
when it needs some free pages. Even if it needs to free more pages by paging out
some of them, it tries to minimize such I/O operations by default
and writes only minimal necessary amount of pages keeping the rest intact,
when vm.swap_idle_enabled=0.