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Date:      03 Nov 2001 14:05:48 -0800
From:      swear@blarg.net (Gary W. Swearingen)
To:        "Mark Hughes" <mark@dvdnews.co.uk>
Cc:        <freebsd-questions@freebsd.org>
Subject:   Re: Swap space with 3GB RAM
Message-ID:  <critcrbjcz.tcr@localhost.localdomain>
In-Reply-To: <008601c1642e$7138ddf0$0200a8c0@mark2>
References:  <008601c1642e$7138ddf0$0200a8c0@mark2>

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"Mark Hughes" <mark@dvdnews.co.uk> writes:

> So, that given, any problems putting the swap space at the end of the
> partition table instead of near the start as one normally would?

I'm no kernel expert, but lots of reading has never uncovered a problem
with that.  I think the only reason for putting it first is to try to
place it on the outer disk tracks which sometimes xfr data faster. My
current swap FreeBSD partition is in the second 1/4 of my 40 GB disk.

P.S. I wouldn't use swap at all in your case, though I've yet to be that
RAM-rich to do without it.  I think you read too much into tuning(7)'s
words "perform best".  I'm fairly sure that it's just referring to
performance in paging/swapping situations that you will not have.  Maybe
you could benchmark a kernel build, say, with and without the swap and
let us know for sure so others don't feel the need to be so wasteful of
disk.  Rememeber, it only says it "can" lead to inefficiencies:

  Configuring too little swap can lead to inefficiencies in the VM
  page scanning code as well as create issues later on if you add 
  more memory to your machine.

Actually, by having swap, the kernel may waste time paging stuff out
that it has no need to page out. (It sometimes does this to prepare
for future needs that it guesses might occur, but which won't occur
on your system from what you said.  I think it tries to do this at
opportune times, but I'm sure it can't be 100% successful.)

I'm sure others will disagree.  It'd be nice to know for sure.

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