Date: Mon, 15 Sep 1997 20:08:27 +0200 From: lada@ws6303.gud.siemens.at (marino.ladavac@siemens.at) To: freebsd-questions@FreeBSD.ORG, psd@nev.ml.org Subject: Re: swap Message-ID: <199709151808.UAA04399@ws6423.gud.siemens.at>
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> From owner-freebsd-questions@FreeBSD.ORG Mon Sep 15 19:48:27 MET 1997 > Date: Mon, 15 Sep 1997 17:41:55 +0200 (MET DST) > From: Paul Dekkers <psd@nev.ml.org> > To: freebsd-questions@FreeBSD.ORG > Subject: swap > Mime-Version: 1.0 > X-Loop: FreeBSD.org > > Hi > > How can I see how much swap is used already? Swapon -s doesn't work, and I > don't think vmstat gives me that info (at least not the output of vmstat > as I saw it)... top gives you quite readable current values. > Does it matter how big your swapdrive is? I have currently a swapdisk of > 50MB, that's enough I think, but does it make the system slower the bigger > the swapslice is? How much swap do you need depends on the disparity of your RAM and total intended working set size--in other words if your apps require 100 Megs of memory, and you have only 20 Megs of RAM, you'd better have at least 80 Megs of swap. You might need even full 100 Megs of swap if the particular VM implementation reserves swap space for all potentially written RAM pages. The size of the swap area does imply an overhead consisting mainly of the free swap page list which is usually implemented as a bitmap. At 1 Byte per 32 KBype of swap (4 KByte page size is assumed), this overhead is rather negligible. There are some other issues (page identity lists, active working set) which are consequences of the computer usage patterns and not the swap size per se. /Marino > > -- > Paul Dekkers (psd@nev.ml.org or psd@dds.nl) > N.E.V - Nescio Ergo Valeo > >
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