Subj : Re: programming with large memory requirements
To   : comp.programming
From : Randy Howard
Date : Wed Sep 28 2005 05:17 pm

Ben Pfaff wrote
(in article <87oe6d9re5.fsf@benpfaff.org>):

>>> A brief scan through the Linux 2.6 ramdisk driver doesn't show
>>> any arbitrary limits.  It's based out of the page cache, which is
>>> itself not limited to 4 GB on 32-bit boxes.
>> 
>> http://www.ussg.iu.edu/hypermail/linux/kernel/0407.0/0586.html


> Hmm.  Well, that's disappointing, 

But about what I expected when I went googling.  32-bit 
platforms rarely deal with anything above 4GB and sometimes 2GB 
in a consistent way.  If you want to make effective use of 10GB 
of RAM, you run a 64-bit OS.  To do otherwise may be a fun 
afternoon diversion, but apart from that it's just silly.

> but there are two approaches to
> dodging the problem mentioned in that thread: use ramfs instead
> of a ramdisk, 

Something other than a ramdisk, and have you tried it?  I don't 
have a spare 10GB system laying around to play with.

Nevermind that the Linux fs buffer cache achieves most of this 
on its own, especially in a machine with lots of free ram, for 
no extra cost in terms of work or overhead.  

The folks in Windows land aren't so lucky, but that has always 
been the case, and is likely to remain so.

> or concatenate multiple 1 GB ram disks using a raid
> driver.  Either one would allow the effect of a 9 GB ram disk.

Actually, this one is likely to have some measurable overhead, 
if it does work.  At the end of the day, no great answer is 
available on 32-bit boxes.
 



-- 
Randy Howard (2reply remove FOOBAR)

.