Does anyone know the max memory a process can use?

A_quest_guy · 07-17-2002, 08:34 PM

I need to know how much memory a single process can use in a Linux (RedHat 7.2 or later) machine. We run very large simulations that take upwards of 4GB of memory for the process and need to know if Linux is a viable solution. Any Help is greatly appreciated!!!!!

trickykid · 07-17-2002, 09:09 PM

I don't think there is a limit if you have the RAM/Memory to back it up. I just know there is a default limit to the number of processes which is usually at 4094 for a user.

A_quest_guy · 07-18-2002, 07:50 AM

I have heard and read somewhere that the system can only use 3.8GB of memory. That is for the entire system, but someone has told me that a single process has a 2GB limit. Thanks for the reply though!!!

Half_Elf · 07-18-2002, 02:37 PM

Pfff this is not true. Just take a look into the kernel, you can activate "high memory support" up to 24GB... I don't know if a process can take more than 2Gb, but the system can go farther!

A_quest_guy · 07-18-2002, 02:47 PM

Half_Elf is that any release of Red Hat, thought that was reserved for "ADvanced Server" 7 and Above.

trickykid · 07-18-2002, 03:54 PM

Quote:

Originally posted by A_quest_guy
Half_Elf is that any release of Red Hat, thought that was reserved for "ADvanced Server" 7 and Above.

As Half_Elf stated, it all depends on the kernel, not the distro. At most all you would have to do if your current kernel does not support is update and compile. Usually by default it won't recognize any RAM more than 4GB with the 2.4.x kernel series but that is fixed with a simple recompile.

A_quest_guy · 07-18-2002, 05:46 PM

Thanks for the information, hate to be a bug, but does anyone know about a single process? That is the real issue since the systems that we are looking at using will only have 4GB of Memory. I know with some of the versions of solaris there is a change that you have to do to the "ulimit" to allow the use of more then 2GB.

jeremy · 07-18-2002, 06:37 PM

The answer to your question depends on the arch you are using. On x86 the max is 4GB per process, but the top 1GB of that is mapped as kernel space, so the app can only use 3GB. To get around this you would need to use a 64-bit processors, such as Sparc or Alpha.

BTW, I *think* there is a kernel patch floating around to work around this, but I have never used it so I cannot comment on it.

--jeremy