Re: excessive swap-in time

phil-news-nospam@xxxxxxxx wrote:
| You can think of obvious ways to tweak this to make this one case
| perform better, but you can think of cases that are made worse by
| those same tweaks.

Something has to be forced back out to swap in a process that becomes
active again. The question is which pages to select. Those of processes
that are recently inactive would be what ultimately would be swapped out.
Might as well go straight to them directly, rather than the newly active
process fighting against its own pages.


Nothing new in this discussion. The Linux people have always been of the
advice that, "if there is not enough memory, buy some more", while it is
well known and demonstrated that a system can very well function fine
and dandy with a constant stream of paging to swap. Of course, this
depends on proper selection of the pages to swap, and one of the main
point in Linux kerner 2.6 was the inclusion of a reasonable VM system
doing that correctly. A small discussion of the ideas around such
choices can be found here:
http://www.freebsd.org/doc/en_US.ISO8859-1/articles/vm-design/freeing-pages.html


--

Michel TALON

.