[svlug] memory allocation of more than 2G per process possible?

Jeffrey Siegal jbs at quiotix.com
Mon Oct 27 18:21:44 PST 2003


Karsten M. Self wrote:
> on Mon, Oct 27, 2003 at 03:55:32PM -0800, Jeffrey Siegal (jbs at quiotix.com) wrote:
> 
>>Roland Krause wrote:
>>
>>>Under Linux, can I allocate more than 2Gig of memory in one single
>>>process on Intel 32bit x86 architecture?
>>>Roland
>>
>>That depends how your kernel is compiled.  It is possible to configure 
>>the kernel for 1GB, 2GB, 3GB or 4GB of user-mode address space per process.
> 
> 
> See /usr/src/linux/Documentation/Configure.help.
> 
> For 2.4.2x, it appears a single process can address at most 3 GiB of
> virtual memory:

That is the current limit for the standard 2.4.x kernels.  Red Hat has a 
patch in their 2.4.x enterprise kernel that raises the limit to 4GB.  I 
don't remember if this feature is in the standard 2.6.x pre-releases or not.

>     If you are compiling a kernel which will never run on a machine with
>     more than 960 megabytes of total physical RAM, answer "off" here
>     (default choice and suitable for most users). This will result in a
>     "3GB/1GB" split: 3GB are mapped so that each process sees a 3GB
>     virtual memory space and the remaining part of the 4GB virtual
>     memory space is used by the kernel to permanently map as much
>     physical memory as possible.
> 
> Peace.
> 
> 
> 
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