From: ujlh@pool.info.sunyit.edu (James Henrickson)
Subject: Re: Up and Running linux
Organization: State University of New York -- Institute of Technology
Distribution: usa
Date: Sat, 29 Aug 1992 02:53:17 GMT

In article <MebGaou00Vp=EHMFNy@andrew.cmu.edu> Frank T Lofaro <fl0p+@andrew.cmu.edu> writes:
>Excerpts from comp.os.linux (USENET): 26-Aug-92 Re: Up and Running linux
> ujlh@pool.info.sunyit.edu (James Henrickson) (2551)
>
>>It is not a pretty sight.  I just installed Linux on a second machine, a
>>386SX-25 with 2 MB of RAM.  I have 880K free after the kernel is loaded,
>>and bash takes a huge chunk of that.  I can run kermit but not shell out
>>very often because I usually get a lot of "out of memory" errors.  (Swapping
>>doesn't seem to eliminate these error messages, maybe my "working set" is
>>too big to fit in 880K.)  When I *AM* able to run a command from within 
>>kermit, it is S-L-O-W.
>
>	Unless my understanding of VM is severly flawed (I hope not), having
>very low physical memory should *NOT* cause errors (as long as the
>kernel fits in memory, but it does, since it boots), as long as physical
>memory+swap space is sufficient and swapping is on. You should even be
>able to run a program that in and of itself is larger than all of the
>available physical memory. This assumes that VM on your setup and on
>Linux in general is working right (and that I'm not confused about VM :)
>
>A couple of questions:
>
>1. Are you sure you have enough swap space on disk?

Yes, 8 MB swap partition.

>2. Did you properly set up the swap partition (set partition id to swap,
>mkswap) or swap file (using mkswap)?

Yes, Partition ID: swap

>3. Did you remember to enable swapping (using swapon) in /etc/rc or on
>the command line?

Yes, in fact I have to do it before I "fsck" my Linux partition because
otherwise it pukes over the lack of memory.  (The fsck pukes, the rest
of /etc/rc is still executed.)
 
>If the answers to these are all yes:
>
>4. Are you using a SCSI disk? (I heard there were problems with SCSI and
>VM, but I could be off-base here).

Nope, IDE.

>I'd like to know for myself: Is there any difference, as far as a user
>should be concerned, between swap and physical memory, other than
>performance, and assuming that swapping is enabled? Do some programs
>*need* a certain amount of real, physical memory?
 
Beyond a certain point, the "working set" of the executing programs
can not be held in memory and the system would thrash big time, doing
so much swapping it isn't funny.  So much so, in fact, that in extreme
cases I don't think anything would get done.  I don't know exactly how
Linux handles this, though.  It might also be a problem with bash.

Another thing I failed to point out was that I was also getting a lot
of "fork failed, try again" messages (or something like that) during
that same time.  Another problem was that I was waiting quite a while
for an "ls" when the only thing I had running was seven getty's on
unused VC's and just bash on the one I was using.  Each time I had
these memory shortages, the disk was active for quite a while so I
believe it was swapping.  Unless, of course, if the swapping wasn't
working as intended.

I wonder if anyone else with 2 MB has run into these problems?

I have since upgraded my RAM.  Not to the 6 MB that I had planned on,
but to the full 8 that the board would hold.  All of these problems
have gone away and the 386SX-25 acts like it has a life now.  :-)

An unrelated question:  was the one line patch part of patch2?  I
originally deleted that one "i++" line as instructed by Linus, but
I reinstalled the kernel code about a week ago with virgin 0.97 and
the two patches.  I didn't see any mention of the one line fix in
the patch2 announcement.

[Excuse any typographiccccal errors, I'm tired.]  :-)  


-- 
Jim H.
*
* James L. Henrickson
* ujlh@sunyit.edu        "Some day I might have a real .signature!"
Newsgroups: comp.os.linux