Date: Tue, 06 Jan 1998 01:05:02 -0800 From: David Greenman <dg@root.com> To: Julian Elischer <julian@whistle.com> Cc: "John S. Dyson" <toor@dyson.iquest.net>, cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG, cvs-sys@FreeBSD.ORG Subject: Re: John's latest VM commit. Message-ID: <199801060905.BAA27275@implode.root.com>
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>>> It would probably be a good thing to make all caching in our system VM object
>>> based. Then buffers will degrade into a structure used to communicate with
>>> I/O devices. I would not like to see the terrible mess that SVR4 has, with
>>> various types of vnode like structures in order to represent swap, filesystem,
>>> device files.
>>But every VM object needs an associated VNODE that represents the methods
>>and data needed to access teh real backing store.
I said:
> Actually, this isn't true. Most VM objects in the system are not vnode
>objects and thus have no vnode associated with them. Most of the vnode
>objects are actually containers for 'anonymous' memory that either has
>no backing ('default pager') or is swap backed. It could be argued that
After thinking about what I said for a bit, I think I might be exagerating
a little - on some systems where the vnode/object cache is sufficiently
large, you could easily have more of those than default/swap objects. It
depends on the processes - how many, memory mappings, etc., and how many
cached files are in the system. It would be more accurate to say simply that
there are a sizeable number of non-vnode objects...
-DG
David Greenman
Core-team/Principal Architect, The FreeBSD Project
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