maximum swap per process

[Langlais Benoit]

On a 1Gb ram, we added 4 swap units of 2Gb each. That makes roughly 8Gb of available memory. However I can't achieve in using more than (roughly) 2.5 Gb by a single process (I managed to run 3 codes of 2Gb in the mean time). My problem is that I want my process to use between 4 and 7 Gb. Is there a way to increase the maximum memory per process?
I'm on RedHat 7.2 with kernel 2.4.9-31

[Stuart Browne]

What does 'ulimit -a' report for the user you are running thse tests as?

And why are you trying to get a user to use swap? It will only slow it down (for normal processes).

[Langlais Benoit]

The results of limit are:
cputime unlimited
filesize unlimited
datasize unlimited
stacksize 8192 kbytes
coredumpsize 0 kbytes
memoryuse unlimited
descriptors 1024
memorylocked unlimited
maxproc 3584
openfiles 1024
The process I want to run is a scientific code. I know the swap will slow down the results, but the code is quide fast, so the swap-slow issue is not a real problem. Any idea?

[Stuart Browne]

Not really.. Those details look pretty normal. You might want to find a newsgroup reguarding Linux Kernel code and ask in there if there are any 2gig limitations on Swap space utilisation.

Unfortunately, I haven't heard of any such limitations. By the same token, I've not had any app running under Linux that uses more than about 400Mb at any given moment..

Sorry.

[Zeev Fisher]

Since the x86 is a 32 bit machine, we are confined to 4 GB of address space. Because of specific x86 MMU weaknesses we have to split up this space between virtual and physical space. This means that when we choose a larger physical space (to support more RAM) the
maximum size of an individual program gets smaller.

Linux currenly uses a 3:1 virtual:physical split, meaning that the kernel can use a maximum of 1 GB (minus 64 MB administrational overhead) RAM and the maximum
program size is 3 GB.

( taken from linux-mm.org )

So you have actually nothing to do but wait/buy 64bit Linux versions


Zeev

[Langlais Benoit]

Zeev,
I guess you refer to this page http://www.linux-mm.org/more_than_1GB.shtml. However it is written 'This HOWTO is obsoleted by kernel 2.3.24'. And I am using a 2.4 kernel.

But maybe this is not obsolete. There's something I don't understand. Is the 3Gb a limit for a single process, or the limit for all the processes? I guess this page refer to the first case. Moreover, I've been able to run two simultaneous codes each using 2.6Gb.

Do you know when the 64bit versions of linux will be available?

thanks

Benoit