Re: [9fans] Virtual memory in BSD and Plan9

["rob pike" <rob@plan9.bell-labs.com>]

I'm a radical here, but I think if a machine is paging, you've lost.
To me, VM is a pretty technique for memory management in the kernel,
something distinct from paging, which is a way to get the system
through temprorary overshoots in memory demand.

My boss when the first Plan 9 kernel was being written was Sandy
Fraser, who had worked on Atlas, one of the first VM systems.  When he
heard that I was putting VM into Plan 9 (a situation more accurately
described as building Plan 9's original memory manager around a VM
model), he literally called me on the carpet.  He said that he hated
VM bitterly because of the Atlas days, in which nothing got done
because the system was always thrashing.  I pointed out the
distinction between VM and paging, explained that I was implementing
VM but not paging (Phil W. put paging in a few years later), and
justified my decision by pointing out that with memory so cheap today,
there was really no reason to depend on the paging system to manage
your working set except for the occasional brief overrun on demand.

-rob