Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uunet!microsoft!stevesc
From: stevesc@microsoft.UUCP (Steve Schonberger)
Newsgroups: comp.os.minix
Subject: filesystem cache blocks
Message-ID: <9374@microsoft.UUCP>
Date: 8 Dec 89 04:23:37 GMT
Reply-To: stevesc@microsoft.UUCP (Steve Schonberger)
Organization: Microsoft Corp., Redmond WA
Lines: 24

Is it possible to allow the filesystem process to use all (or most of)
free memory as disk cache?  (If it does that already, excuse the dumb
question; it's been a long time since I read the code from The Book,
and I've never seen the code from more recent versions.)  It seems
like something that could be done, and which would speed up the system
a great deal.  Of course, every time memory was allocated to a process
it would first have to be taken away from the cache block pool, but if
dirty blocks were one way or another kept out of the areas most likely
to be claimed by new processes (such as by allocating cache blocks for
files open for writing only in the fixed portion of the cache), taking
blocks away from the cache would just be a matter of marking them as
no longer cached.  Such an addition would take quite a bit of work on
the filesystem, and a little change to the memory manager (so that it
would tell the filesystem to release them before it gave them to
another process), and I think would be transparent elsewhere.

Are there any obvious problems with this other than the need for
someone to code it?  Any more subtle problems?  Has this been
discussed before so that I'm just wasting bandwidth bringing it up
again?

-- 
	Steve Schonberger	microsoft!stevesc@uunet.uu.net
	"Working under pressure is the sugar that we crave" --A. Lamb