From owner-freebsd-current  Wed Jun  6  7:19: 1 2001
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From: Mikhail Teterin <mi@aldan.algebra.com>
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Subject: mdconfig and _virtual_ memory
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Date: Wed, 6 Jun 2001 10:19:34 -0400 (EDT)
Cc: phk@freebsd.org
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Hi!

For years of  using MFS I presumed,  that it used virtual  memory -- RAM
and swap to store the file system -- using RAM for speed of MFS and swap
when RAM was needed by others.

When I moved  to mdconfig, I figured  I have to use ``-t  swap'' for the
same effect, but it seems, I was wrong -- apparently, ``swap'' means the
filesystem will always hit  the disk, even if there is  plenty of RAM to
go around. My suspicion was further confirmed, by disabling the swapping
at  all --  the  mdconfig-ed  device stopped  working  -- disklabel  got
ENOMEM.

Now I use  ``-t malloc'', but I  suspect, this will never  hit the disk,
even if there is where to swap and more memory can be used elsewhere. It
seems, ``-t malloc'' simply bites a chunk of RAM away...

Is it  possible to make md-devices  backed by _virtual memory_?  Did the
old MFS do that? Where else am I wrong in this letter?

Thanks! Yours,

	-mi

P.S. Where is that new mount_mfs wrapper?

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