headsup: swap_pager.c

[Dan Nelson]

In the last episode (Aug 01), Poul-Henning Kamp said:
> In message <xzpel0568cn.fsf at dwp.des.no>, Dag-Erling =?iso-8859-1?q?Sm=F8rgrav?=
>  writes:
> >"Poul-Henning Kamp" <phk at phk.freebsd.dk> writes:
> >> The thing you overlook is that often when things gets paged out,
> >> the system is short on memory and therefore more likely to not do
> >> anything productive, whereas when things gets paged in, there are
> >> a better chance of some other process being able to use the CPU
> >> time productively. If we did predictive pageouts like some of the
> >> "serious" mainfram OS's this would be less true.
> >
> >How hard would it be to get the kernel to write the pages "most
> >likely to be swapped out" to swap in the idle loop, to save time if
> >/ when they actually need to be swapped out later?
> 
> I don't know :-)
> 
> Quite frankly, given the sizes of RAM we see these days, I think that
> paging optimizations may be largely a thing of the past.

RAM is like disk space; if it's there, users will consume it.  If you
have 8GB of RAM, someone will write a program that needs 2gb of RAM,
then someone else will decide to run that program in 5 vtys (speaking
from experience here).

Predictive swapping would be neat.

-- 
	Dan Nelson
	dnelson at allantgroup.com