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Date:      Wed, 11 Aug 1999 11:51:11 -0700 (PDT)
From:      brooks@one-eyed-alien.net
To:        David Gilbert <dgilbert@velocet.ca>
Cc:        "'freebsd-security@FreeBSD.ORG '" <freebsd-security@FreeBSD.ORG>
Subject:   Re: 4 Swap partitions limit (was  Re: RE: Little question (offtopic))
Message-ID:  <Pine.GSO.4.10.9908111146001.13541-100000@orion.ac.hmc.edu>
In-Reply-To: <14257.50009.162402.381699@trooper.velocet.ca>

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On Wed, 11 Aug 1999, David Gilbert wrote:

> One curious aspect of FreeBSD that I havn't explained to my own
> satisfaction is why it appears to consume more swap than linux.  I see 
> a lot of linux installations running on 32 or 64M of swap, but I'm
> loathe to set up BSD boxes with less than 256M of swap.
> 
> Not that I have scientific evidence of this, but it has been a general 
> feeling of a number of people I know.

Lots of people get this feeling, which is why it's a FAQ :-):

--cut--
12.1: FreeBSD uses far more swap space than Linux. Why?

FreeBSD only appears to use more swap than Linux. In actual fact, it
does not. The main difference between FreeBSD and Linux in
this regard is that FreeBSD will proactively move entirely idle, unused
pages of main memory into swap in order to make more
main memory available for active use. Linux tends to only move pages to
swap as a last resort. The perceived heavier use of swap is
balanced by the more efficient use of main memory.

Note that while FreeBSD is proactive in this regard, it does not
arbitrarily decide to swap pages when the system is truely idle. Thus
you will not find your system all paged out when you get up in the morning
after leaving it idle overnight.
--cut--

-- Brooks

P.S. trimmed the CC list since this wasn't very on-topic.



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