Re: Memory limitations in Linux.

From: Jamie Lokier (
Date: Wed May 03 2000 - 10:40:17 EST

MNigel Jacob wrote:
> Are there any plans to increase the max per process memory
> limitation in Linux 2.4 from 2GB(as in Linux 2.2.*)to 4GB(or more)?
> Is there a patch or maybe an (experimental) kernel in existance that
> supports 4GB or memory?

Done already, long ago. Who said it only supports 2GB?

It defaults to 3GB per process on IA32 platforms (Pentium, Athlon etc.)

That's about as much as is practical without a severe performance
penalty. You can raise it closer to 4GB -- 3.75GB for example, but to
reach 4GB really slows the kernel down, and to go beyond it requires
special, very slow user space code and a special compiler. We don't
support either of those configurations.

On 64 bit platforms like Alpha and Sparc64, it's into the terabyte range
or beyond. The actual limit depends on the processor. (I understand
that 64 bit processors don't allow you to use all 64 bits as user
address space).

When AMD releases their IA32 processors with 64 bit extensions, perhaps
that will support more than 4GB per process too.

You can of course _access_ much more than that per process. And the
total RAM shared between all processes is not subject to the 4GB
limitation. On Pentium Pros you can use 64GB total RAM.

have a nice day,
-- Jamie

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