Date: Mon, 1 Apr 1996 08:40:48 -0500 (EST) From: "John S. Dyson" <toor@dyson.iquest.net> To: lehey.pad@sni.de (Greg Lehey) Cc: joerg_wunsch@uriah.heep.sax.de, freebsd-hackers@freebsd.org Subject: Re: Virtual Memory system (was: Interesting IDE perf results) Message-ID: <199604011340.IAA01196@dyson.iquest.net> In-Reply-To: <199604010933.LAA02889@nixpbe.pdb.sni.de> from "Greg Lehey" at Apr 1, 96 01:02:49 pm
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> > On an allied subject, I get the impression that the current VM system > wastes a fair amount of memory. I have a window which displays the > current vmstat statistics every 5 seconds, and I can't recall ever > having seen less than 3 MB free (this is on a 32 MB system). BSD/386 > will go down to 200 kB before starting to page furiously. > > Obviously it makes some sense not to take free memory down too low, > but isn't it possible that the current tuning errs a bit too much on > the side of free memory? > On a FreeBSD-current (and probably 2.1) system it will start paging at about 100K. Is "free" measured by adding "cache+free"? -- cached pages are similar to the free list on other OSes -- the pages haven't lost their identity, but are available for immediate allocation. Old 4.4Lite VM systems (who includes everyone else) free is really free and without identity. It is critical to limit the number of free pages in that case. John
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