Here is the actual quote from Linus Torvalds and the other members of the kernel team. They certainly know far more about it than I do. From
http://kt.zork.net/kernel-traffic/kt20010126_104.html#2
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2. Greater 2.4 Swap Requirements
7 Jan 2001 - 18 Jan 2001 (100 posts) Archive Link: "Subtle MM bug"
Topics: Virtual Memory
People: Rik van Riel, Linus Torvalds, Eric W. Biederman, Zlatko Calusic
In the course of discussion, it became clear that Linux 2.4.x required more swap than previous versions. Rik van Riel mentioned, "2.4 keeps dirty pages in the swap cache, so you will need more swap to run the same programs..." He asked Linus Torvalds, "is this something we want to keep or should we give the user the option to run in a mode where swap space is freed when we swap in something non-shared ?" Linus replied:
I'd prefer just documenting it and keeping it. I'd hate to have two fairly different modes of behaviour. It's always been the suggested "twice the amount of RAM", although there's historically been the "Linux doesn't really need that much" that we just killed with 2.4.x.
If you have 512MB of RAM, you can probably afford another 40GB or so of harddisk. They are disgustingly cheap these days.
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Linus says that the idea that Linux does not need 2x RAM was killed by the 2.4 kernel.