Subject: Re: BUFFERCACHE, PR 1903
To: Michael L. VanLoon -- HeadCandy.com <michaelv@MindBender.serv.net>
From: John S. Dyson <email@example.com>
Date: 09/14/1996 12:09:56
> >I agree, if we are adding BUFFERCACHE to implement something similar
> >to NBUF/BUFPAGES, it will need to be documented to be useful, so why
> >not just document NBUF/BUFPAGES? On the other hand, hard-coding
> >the buffer cache can be real a pain when you pull out some RAM and don't
> >change the kernel! (ouch! I've been there) The ability for it to
> >dynamically resize (at boot) is a plus. Perhaps when the NKPDE
> >problem is fixed, something more dynamic will be implemented.
> That's one of the points of this patch. It doesn't hard code a fixed
> size for NBUF/BUFPAGES, it codes a percentage of available memory.
> So, if you plug it into a smaller machine, you're using the same
> percentage, but a smaller total amount of available RAM. That sounds
> failry dynamic to me.
Back before the FreeBSD merged VM/Buffer Cache, I had a dynamically sized
buffer cache implemented (never published.) It shouldn't be hard at all
to add that feature to NetBSD (before the NetBSD merged scheme comes out.)
The dynamic buffer cache notion got "bounced" in FreeBSD, but it isn't
hard to do (probably only a few day effort.) It is easy to maintain
machine independence, etc.
Just an idea (perhaps bad one :-)).