Date: Sat, 15 May 1999 15:32:24 -0500 (CDT) From: Christopher Palmer <cpalmer@jig.ordway.org> To: matt <matt@mlink.net>, freebsd-questions@freebsd.org Subject: Re: swap.. Message-ID: <Pine.BSF.4.10.9905151522440.2390-100000@jig.ordway.org> In-Reply-To: <Pine.BSF.4.10.9905151617200.3171-100000@ns-1.ccia.cc>
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On Sat, 15 May 1999, matt wrote: > Well, this is totally my *PERSONAL* opinion of using OSs before where you > COULD turn off swap. Some OSs like linux, once they get into swap, they > bog down they get slow, they seem not to want to release swap.. Well, of course they get slow. As for not releasing the space, I think that's due to the way Linux was designed -- on purpose. I'm no kernel hacker, but I know that Linux (2.2 especially) is real aggressive about file cacheing. This means that even after you exit programs that were using lots of memory, they may stay in memory for a while (until something pushes them out) so that you can restart them more quickly next time. From a certain point of view, this is Good and Desirable. My Linux system at home (running kernel 2.2, 64MB RAM) usually has a couple hundred KB in swap, and occasionally as much as several MB. I don't see that it slows my machine down at all. In fact, when I upgraded to 2.2 from 2.0.36, I noticed a remarkable speed improvement -- and I note that one of the big changes from 2.0 to 2.2 was the memory management. So. As for FreeBSD, there was a thread here a while back about FreeBSD also being real aggressive about using available memory (although in a different way than Linux; again, Good and Desirable from a certain pov). It was suggested that people allocate more space for swap than they think they need, because FreeBSD is going to hit swap hard. My experience with FreeBSD is that this is true. And FreeBSD is also very fast on this modest hardware. So. From the point of view of processes, disk and memory are the same. It's up to the kernel to know the difference and make things appear fast for users and processes. FreeBSD and Linux both do excellent jobs of this, in different ways. Christopher Palmer Assistant Systems Administrator, Ordway Music Theatre cpalmer@jig.ordway.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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