Date: Tue, 21 Jul 1998 11:31:36 +0300 (IDT)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: Martin Str|mberg <ams AT ludd DOT luth DOT se>
cc: djgpp AT delorie DOT com
Subject: Re: EMM386 limiting memory to 32Mb
In-Reply-To: <6p0gvp$q7m$1@news.luth.se>
Message-ID: <Pine.SUN.3.91.980721113118.6992R-100000@is>
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On 20 Jul 1998, Martin Str|mberg wrote:

> : IMHO, that's a bad idea.  Swap file should be at least twice the
> : installed RAM size, which is impossible with a RAM disk.
> 
> Where do you get such a strange idea from?

From my experience, where else?  It could be that my experience is
skewed, but that shouldn't be a reason to get angry.

> Suppose I have 512MB RAM, then I need 1GB swap space?

When the garden-variety desktop PC will have 512MB of main memory, I
assure you I will revise my views.  Nowadays, 16-32MB are the usual
numbers, and some people have less than that.  For such systems, I
think that twice those numbers (i.e., at least 64MB of swap) is a good
rule of thumb.

The reason is that you can easily have two programs in memory, each
one using memory close to these numbers (for example, GCC which runs
under Emacs, or 2 compilations in two DOS boxes), and you don't want
to run out of VM in that case.

> No. You need as much swap space as you need. Suppose you need 128MB
> for a certain (in your setting) worst case

Many people have hard time estimating the worst case.  That's where
rules of thumb come in handy.

> The problem here (in this thread) is evidently most versions of EMM386
> won't let you use more than 32MB, hence you need to start swapping
> prematurely. So what should we do with the X MB more than 32MB? If
> it's enough you _could_ use it a as RAMDISK to swap on to overcome
> EMM386 limitations.

I agree this is a good advice--for those who have 512MB of RAM ;-).