Re: top(1) and the meaning of columns

[Miles Bader <miles@gnu.org>]

Matus UHLAR - fantomas <uhlar@fantomas.sk> writes:
>> In this case it means that the processes are trying to use more memory
>> _actively_ than will fit in RAM, and you end up with a very high page
>> fault rate, meaning your system spends much more time doing disk I/O
>> to the swap area than it does actually computing.
>
> AFAIK it's usually called 'swapping', I dunno why someone called it
> 'thrashing' :)

Thrashing is basically when the system is paging so much it cannot get
any real work done.  E.g., process A needs more RAM, so the kernel pages
out lots of process B's memory -- but then process B immediately wants
more RAM too, perhaps to page in the just-paged-out pages, which the
kernel makes room for by paging out process A's memory ... which process
A immediately wants ... etc. etc., thrash thrash :-O

This is in contrast with "normal" paging, which only happens occasionally,
because the act of paging out memory frees up enough RAM so that normal
execution can continue _without_ paging for a while.

-Miles

-- 
Yo mama's so fat when she gets on an elevator it HAS to go down.