Date: Fri, 17 Aug 2007 11:07:14 -0400 From: Andy Greenwood <greenwood.andy@gmail.com> To: Jerry McAllister <jerrymc@msu.edu> Cc: Nicholas Wieland <nicholas.wieland@gmail.com>, freebsd-questions@freebsd.org Subject: Re: Swap size Message-ID: <46C5B9A2.3020305@gmail.com> In-Reply-To: <20070817145551.GA27837@gizmo.acns.msu.edu> References: <098C8817-8D41-4D94-96E2-97D4310B0BAE@gmail.com> <20070817145551.GA27837@gizmo.acns.msu.edu>
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Jerry McAllister wrote: > On Fri, Aug 17, 2007 at 02:05:57AM +0200, Nicholas Wieland wrote: > > >> I was reading tuning(7), and I found that I should size my swap >> double the size of my physical memory. >> AFAIK that was true some years ago, when memory was not as cheap as >> now, and following that guideline I should set my swap to 2GB, which >> seems far too much for swap (at least to me ...). I will never need >> this much memory as 1GB RAM and 2GB swap. >> Is it still correct ? How can I resize with bsdlabel if I already >> used all my disk space during install ? >> > > Remember, disk sizes have shot up too. > No, 2 GB is not excessive. You can get by with less, but you're > not likely to be using proportionately as much disk now as you used > to by going with 2X - I aim for a little over 2X. > > Remember that swap gets used for crash dumps and also for paging. > Now, you may think that you want to keep your machine from paging > and in one sense that is true. If you are so memory bound that > it has to page just to run, you're going to be so slow that it > seems to have froze (by today's standards). But, the system does > write stuff to page space and for processes that are often called > it can speed things up. > > So, it is not really a waste to assign that much to swap. > > ////jerry > > >> TIA, >> ngw >> >> -- >> Nicholas Wieland >> nicholas.wieland@gmail.com >> >> >> >> _______________________________________________ >> freebsd-questions@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-questions >> To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org" >> > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org" > My understanding was that you should estimate swap size based on the sizes of the programs which might be paged out. However, when I first set up my system, I didn't know this and created 1G swap slices (one on each disk) but I am not convinced that this was the best thing to do, since my system almost never uses a noticible percentage of the swap space. right now, I've got [andy@zeus fusefs-sshfs]$ swapinfo Device 1K-blocks Used Avail Capacity /dev/ad0s1b.eli 1048576 1148 1047428 0% /dev/ad1s1b.eli 1048576 1096 1047480 0% Total 2097152 2244 2094908 0% And the system is under normal load. This system has 1G of RAM. Is there any sense in having this much swap space when it's not being used?
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