Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!motcid!ibbotson
From: ibbotson@motcid.UUCP (Craig Ibbotson)
Newsgroups: comp.os.os2.misc
Subject: Paging in OS/2
Keywords: Paging in OS/2
Message-ID: <4298@amber7.UUCP>
Date: 25 Jul 90 15:43:25 GMT
Distribution: comp
Organization: Motorola Inc., Cellular Infrastructure Div., Arlington Heights, IL
Lines: 20

I have a question I was hoping an OS/2 expert might be able to answer for
me.

My understanding is that OS/2 uses a demand paging scheme, and advertises
it uses the Least Recently Used (LRU) algorithm as its page replacement
strategy.  However, systems rarely, if ever, use a true LRU implementation
and generally implement an approximation of the LRU algorithm; a true
LRU algorithm would require timestamping each page.  

Looking at the memory layout for a page, I see each page has a dirty bit and
an accessed bit.  This makes me think they are using the Not Used Recently
(NUR) approximation to the LRU algorithm, but I cannot find this documented
anywhere for certain.

Does anyone out there know if OS/2 uses the NUR approximation to the LRU 
algorithm?  If it doesn't use NUR, what does it use?

Thanks in advance -

Craig