>The process accounting code is old. It's at least as old as 7th Edition
>UNIX (that's where I saw it first, but then I never used V6; it's not in
>the V6 kernel source in the Lion's Book - I just checked), and back then,
>that's how things were done. No one has really felt the need to
>fundamentally change it since then.

You still have a copy of Lyon's book? Is that still legal?
If so, you just volunteered to write 6th or 7th Edition (no mpx)
emulation for NetBSD/vax and 11/750, 11/780, or 11/790 (aka 8600) ;).


Disk-swap times on PDP-11s means it's unappealing to use a user
process to log accounting info.  If the accounting process got swapped
out, your system is under heavy load, which means you may be
generating lots of accounting records. Some of which are likely to be
lost before the accoutning logger gets swapped in.  (no paging, remember!)

Cheaper all around to have the kernel accumulate records in a
disk buffer and write them out directly.

Of course these days, a user-configurable buffer (as enami suggests)
could be larger than the 64K kernel address space on an 11
(or D-space, with split I+D).