Date: Sat, 13 Aug 2005 18:32:57 +1000 From: Peter Jeremy <PeterJeremy@optushome.com.au> To: Chris <chris@childeric.freeserve.co.uk> Cc: freebsd-stable@freebsd.org Subject: Re: Memory requirements between releases Message-ID: <20050813083257.GB13959@cirb503493.alcatel.com.au> In-Reply-To: <42FD08D3.2080300@childeric.freeserve.co.uk> References: <42FD08D3.2080300@childeric.freeserve.co.uk>
next in thread | previous in thread | raw e-mail | index | archive | help
On Fri, 2005-Aug-12 21:38:43 +0100, Chris wrote: >The installation notes for 4.11 say, referring to i386 platform >" ...after installation, FreeBSD itself can be run in 4-8MB of RAM with >a pared-down kernel" > >The installation notes for 5.4 and 6 (the floppies README.TXT) say >"FreeBSD for the i386 requires ...at least 24 MB of RAM". > >Did the memory requirement really jump that much or is something >different being measured? As Kris said, you are measuring two different things. Note the phrase "after installation" in your first quote. Installation takes substantially more memory because FreeBSD needs to load a full-sized GENERIC kernel, allocate space for a RAM disk to hold the installation filesystem process and have enough RAM left over to actually run the installaton processes. Once you've installed FreeBSD, you can prune down the kernel and you don't need the RAM disk. That said, 5.x is larger than 4.x (which is larger than 3.x, etc). >I have on old tosh 110CT laptop with 24mb memory I want to set up as a >wireless router/NAT box but would prefer to use 6 or 5.4. Can I reduce >the amount of memory required? I have compiled a reduced kernel but it >swaps like mad when compiling. Kismet and deps took over 12 hours. Just >after boot and not doing anything it has about 2mb free and 17 processes >running. 24MB should be adequate as a SOHO wireless router/NAT box but doing compilations will stress it significantly (as you've noticed). It would be too small if you were going to run lots of applications (named, squid etc) 2MB free sounds about right. The Unix kernel sees free space as wasted space and tries to avoid having too much of it. You can add "inactive" to the free memory to get a better idea of how much RAM isn't being used, and the cache will shrink if processes need for RAM. As long as your system isn't paging during normal operation (normal operation for a firewall excludes compiling ports or the kernel), then you have enough RAM. 17 processes sounds a bit high. You can probably find some that aren't necessary - in particular, you probably only want one or two gettys. -- Peter Jeremy
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20050813083257.GB13959>