Path: utzoo!attcan!uunet!lll-winken!ncis.tis.llnl.gov!helios.ee.lbl.gov!pasteur!ucbvax!POSTGRES.BERKELEY.EDU!dillon
From: dillon@POSTGRES.BERKELEY.EDU (Matt Dillon)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Virtual Memory / doable 1.4 request
Message-ID: <8905181640.AA07562@postgres.Berkeley.EDU>
Date: 18 May 89 16:40:08 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 18

:article, but there is a problem.  Neglecting chip RAM, the reason a
:task needs physical memory is to guarantee fixed execution time for
:instructions, and for calls to AllocMem.  Now, you can lock the page
:frames occupied by the code at load time, but if you allow AllocMem
:to kick out a VM page, and the page is dirty, then you have to wait
:for the pager to run and write the page out to disk.  I can think of
:a couple of solutions to this, but none are much better than
:statically partitioning memory.  Of course, if you don't run any
:real-time programs, then the idea remains elegant, and I'm glad I had
:it first. :-)

	Well, the particular task which had the page fault will 'block'
waiting for the page to come in, but remember this is a multitasking system!
Other tasks will still run.  Page outs wouldn't occur all that much unless
you are running more active processes than you have memory for so it is
pretty much restricted to the 'beginning to overload the machine' case.

					-Matt