27 Feb
2025
27 Feb
'25
10:06 p.m.
Arrigo Triulzi wrote:
“Digital UNIX has two paging modes, lazy and
conservative. Conservative means that paging space is allocated as memory is allocated,
guaranteeing that there is always somewhere to page to. This limits VM to the size of the
paging partitions, but makes for a very robust system. Lazy is more like what people are
used to with Unix - paging space is allocated when needed for paging out, you can run more
jobs, but you're in big trouble when everything fills up.
My recall is that 4.2BSD would only give you (writable) memory it
could allocate swap space for.
I think of the penchant for "overcommitting" memory
(and the cold hand of the OOM killer) as Linuxisms