Re: Tree based scheduling

Felix Schroeter (felix@mamba.pond.sub.org)
02 Feb 1998 20:03:14 +0100


Hello!

erik@arbat.com (Erik Corry) writes:

> Most Unixes differentiate between paging (where individual
> pages are sent to backing store) and swapping (where the
> entire process is sent to backing store). Swapping can
> [...]

In fact, the difference between swapping and paging in BSD has become
marginal too.

If a process is swapped out, it is marked non-runnable (because
swapped out), then the u-pages (where mostly the kernel mode stack for
that process resides) are un-wired (made pageable). The rest is
handled by the pageout code.

IMO the main use of swapping is to free the u-pages in addition to the
already pageable user memory pages when in need of free memory.

Regards, Felix.