Re: How to set up a Linux machine that occupies the minimum memory footprint ?

From: Abdullah Ramazanoglu (abdullah_at_ramazanoglu.tr)
Date: 11/30/04 

Date: Tue, 30 Nov 2004 21:09:33 +0200

begin Penang dedi ki:
> Abdullah Ramazanoglu <abdullah@ramazanoglu.tr> wrote in message news:
 --8<--

> Are you saying that if I have a 4GB RAM memory,
> and I set up a 400MB (10%) of swap space, then
> Linux will somehow "know" that it doesn't have
> too much to play on, and it will "follow the
> line", so to speak, and not thrashing the disk
> for no apparent reason ?
>
> If so, what if my application suddenly needs
> 4.8 GB of memory, and since Linux and all the
> other overheads already occupied 100-200MB of
> memory, the actual Virtual Memory Space has
> only 4.2GB left. And if my application needs
> 4.8 GB of memory, my application will crash.
>
> Am I right ?

That's correct.

> Hmmm.... in that case, I think I better go the
> 8GB route, for I don't want a crash, any crash
> at all, in the middle of an intense rendering job.
>
>>> The software in question is a beast - originally run under Solaris -
>>> and although we've managed to ported it to run under Linux, we haven't
>>> have the chance to throw everything on it, yet.
>
>> Let us get it straight. You've said in another message that your app is
>> not 64-bit aware. But it works under 64-bit Sparc/Solaris with more than
>> 4GB of RAM, right? If so it will also run under Opteron/Linux with the
>> same amount of RAM.
>
> Originally it knew 64Bit, but when we ported back to Linux - that time
> AMD's 64bit thing didn't look very promising - we aimed for the IA32
> architecture - so now this beast only "see" 32Bit space.
>
> I dunno how tough it'd be to "change" the specs again for the beast to
> work in 64Bit environment, we'd try, but I dunno if that's going to
> have any negative effect or not. Very tight timeframe we're talking
> about.

If it was originally 64-bit, then it should be relatively easy to convert
back to 64 bit. Also, with 32-bit addressing, your app wouldn't be able to
use more than 4G even if you have 8G of RAM. So you may need to convert it
to 64 bit anyway.

  --8<--
>> All in all, the most straightforward way seems to be finding a
>> uniprocessor Athlon64 or Opteron board with more than 4GB RAM capability.
>
> I will. And if anyone reads this message, and has info on which mobo
> is best suitable, I'd be more than grateful for any suggestion.

Here are some links to socket-940 Opteron mainboards capable of 8-32GB RAM:

http://www.asus.com/prog/spec.asp?m=SK8V (Uni-CPU, 8GB)
http://www.asus.com/prog/spec.asp?m=SK8N (Uni-CPU, 8GB)
http://www.tyan.com/products/html/opteron.html (Uni to Quad, 8 to 32GB)

Unfortunately all of them need 2GB DIMM sticks for max memory, which seem
to be overly expensive (per MB). So I would consider getting a
uniprocessor 8GB board but populate it with 4x1G RAM sticks, and give it a
test run. If 4GB turns out to be too small, then I would swap the 1GB
DIMMs with 2GB ones, one at a time, and re-test. Thus I would have started
from 4G and gradually upgrade first to 5, then 6, then 7 and 8G depending
on tests. As for the abundant 1GB DIMMs, you can make use of them in other
machines, or buy them on the condition that you will have the option of
trading them later for 2GB DIMMs.

Another option is going for dual-CPU 16GB (8 DIMM slots) mainboard to be
able to use 1G DIMMS. But as I've said earlier, you should scrutinize
whether a single CPU would be able to use all the RAM installed. Also the
cost difference between uni and dual CPU mainboards is another factor.
There should also be other mainboards with more than 4GB capability. YMMV.

> All in all, many, MANY THANKS for your kind input.

My pleasure :) 

-- 
Abdullah        | aramazan@ |
Ramazanoglu     | myrealbox |
________________| D.0.T cöm |__

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