Mailinglist Archive: opensuse (794 mails)

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Re: [opensuse] Get an SSD just for swap?
  • From: "Carlos E. R." <robin.listas@xxxxxxxxxxxxxx>
  • Date: Thu, 30 Nov 2017 00:58:59 +0100 (CET)
  • Message-id: <alpine.LSU.2.21.1711300050360.31979@Telcontar.valinor>
Hash: SHA1

On Wednesday, 2017-11-29 at 15:16 -0500, David T-G wrote:

Please do not use a non-standard character, '%' to mark the quoted part. Please use '>'. Other mail programs do not recognize it.

Wol & Carlos, et al --

...and then Wol's lists said...
% On 29/11/17 14:12, Carlos E. R. wrote:
% >The rule of "twice the ram" was a Windows 3 rule. And it was a
% >There is no such rule in Linux; simply use as much as you need.
% And this "twice ram" predates Windows, let alone Windows 3.

And Linux, too.

% Try running a *vanilla* early 2.4 series kernel with swap == ram. As
% soon as the system even *touches* swap IT WILL CRASH.

In fact, try running a nice old SunOS 4.0 UNIX or, I think (but am not
sure) even classic ATT v7. The 2x rule is *very* old.

It was explained to me as the system first loading into memory a copy
of the executable and then running it from there, ostensibly to avoid
corrupting the copy on disk but perhaps also for speed reasons (although
swap was just as slow, so I never bought into that), which means both
the static and running copies == 2x the usage. In any case, nobody ever
had enough disk to spare to go more than 2x, and the OS didn't like it
at less than 2x, so 2x it always was :-)

Happy Holidays


When I used Windows 3 (call it swap or whatever, does not matter), of course I tried to use more than 2x ram. I had ample disk space, what I did not have was ram. Windows said, AFAIK, fine, but I will nevertheless not use more than 2x. I can't.

No, the code always runs from RAM.

One could set up 0.7 x RAM if so wished.

I never heard of that static and running copies theory. Certainly not true for Windows 3.

In fact, Windows had the trick of being able not to use swap for code: it likes to read again the excutable file instead, preserving swap space.

- -- Cheers,
Carlos E. R.
(from openSUSE 42.2 x86_64 "Malachite" at Telcontar)

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