Subject: Re: Swap overcommit (was Re: Replacement for grep(1) (part 2))
To: Noriyuki Soda <email@example.com>
From: Matthew Dillon <firstname.lastname@example.org>
Date: 07/15/1999 11:25:39
:: -s Print summary information about total swap
:: space usage and availability:
:: allocated The total amount of swap space
:: (in 1024-byte blocks)
:: currently allocated for use as
:: backing store.
:: reserved The total amount of swap space
:: (in 1024-bytes blocks) not
:: currently allocated, but
:: claimed by memory mappings for
:: possible future use.
:: used The total amount of swap space
:: (in 1024-byte blocks) that is
:: either allocated or reserved.
It would be really easy to test this.
Write a program that malloc's 32MB of space and touches it,
then sleeps 10 seconds and forks, with both child and parent
sleeping afterwords. ( the parent and the forked child should
not touch the memory after the fork occurs ).
Do a pstat -s before, after the initial touch, and after
the fork. If you do not see the reserved swap space jump
by 32MB after the fork, it isn't what you thought it was.