Path: utzoo!utgpu!watserv1!watmath!att!cbnewsh!dwc
From: dwc@cbnewsh.ATT.COM (Malaclypse the Elder)
Newsgroups: comp.unix.i386
Subject: Re: Question about memory
Keywords: memory, swap
Message-ID: <9567@cbnewsh.ATT.COM>
Date: 13 Apr 90 01:11:35 GMT
References: <1721@aber-cs.UUCP>
Organization: The Legion of Dynamic Discord
Lines: 30

In article <1721@aber-cs.UUCP>, pcg@aber-cs.UUCP (Piercarlo Grandi) writes:
> In article <156@cms2.UUCP> alan@cms2.UUCP (Alan McCain) writes:
>   Several weeks ago I saw a posting about a question someone had about the
>   memory in their system.  They said that when their system goes into swap it
>   never seems to come out of it completely, even when everyone logs off.  I
>   have the same situation.  Whey does this happen and can it be fixed?
>   
>   Email responses are fine.
> 
> No, no. This is a pet peeve of mine. The System V swapper stinks, as
> reported by Bach in his book.
> 
> In particular, on a 386, it will still do expansion out swaps. Having done
> them, it locks itself itself up waiting for the inswap.
> 

i don't have a copy of bach's book handy but i am pretty sure that
unix system v release 3 DOES NOT do expansion out swaps.  that is,
if by expansion out swaps, you mean that every process that does an
sbrk() to grow its data region gets swapped out first.  but swapping
CAN occur when an sbrk() is invoked.  if there is insufficient physically
contiguous memory for page tables to accomodate the growth in the
region, the process will roadblock on memory and the swapper awaken
(this is all from memory so some details may be off).

this doesn't mean that the SVR3 swapper doesn't 'stink'.  it could
be better.

danny chen
att!hocus!dwc