Subject: Re: RD53s and swapping
To: Lord Isildur <mrfusion@crue.jdwarren.com>
From: Johnny Billquist <bqt@Update.UU.SE>
List: port-vax
Date: 01/25/1999 22:37:14
On Mon, 25 Jan 1999, Lord Isildur wrote:

> but shared texts (which weve enjoed since very early BSD releases) does
> the same thing! the real selling point of shared libs is to save disk,
> to be able to update your programs wihtout recompiling them by updating 
> a library instead. with shared text only one copy of the text is resident
> anyways! 
> ok ok ok ill grant ya that  there is the one copy of a lib function at a time
> in memory, but that payoff isnt that big.. its in disk where it saves a lot of
> space... 

But shared text, as done in BSD of old, isn't the same thing!

Assuming you have two copies of emacs, you will only have on copy of libc,
and all that stuff in memory, but if you start vi, it will have it's own
libc, which isn't shared with the libc that is linked into the emacs
image.

I hope you understand the difference here. Now, if shared libraries really
keeps the number of copies of that specific library to one in memory,
total, then you have a real memory gain. But I can't really understant how
the system does it, but then again, there are new stuff in BSD that I'm
not all familiar with.

Now, under RSX (a real to God operating system), I could tell you how this
is done, and RSX really only keeps one copy of a shared library in memory,
no matter how many or different programs that are using it. :-)

	Johnny

Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt@update.uu.se           ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol