Subject: Does NetBSD overcommit swap space?
To: None <>
From: Alan Barrett <>
List: tech-userlevel
Date: 07/15/1999 11:00:16
OK, so does NetBSD overcommit, or not?  Which man pages tell me?

The malloc(3) man page says

     The malloc() function conforms to ANSI X3.159-1989 (``ANSI C'').

Whether or not the ANSI C standard guarantees that malloc does not
overcommit memory might be an interesting topic for language lawyers,
but it is not something that we should expect random NetBSD users to

Easy stuff:

    It would be nice if NetBSD's malloc(3) and brk(2) man pages stated
    explicitly whether or not backing store is overcommitted, what
    happens when real memory and backing store are fully committed, and
    what processes can do to protect themselves against or recover from
    low memory.


    It might be useful if a process could ask the kernel something like
    "Please pretend to give me 1GB of space, but note that I intend to
    use it very sparsely; I promise not to touch more than 5000 512-byte
    pages within the 1GB block, and I want to receive a SIGDANGER signal
    if I don't keep this promise."

--apb (Alan Barrett)