Re: Stuck at 1GB again

From: Stephen C. Tweedie (
Date: Sun Sep 03 2000 - 06:10:35 EST


On Sat, Sep 02, 2000 at 11:50:32AM -0700, wrote:

> The kernel is compiled with the 4GB option. (which I think is
> the 2/2GB option from 2.2.x kernels). I believe the option is
> supposed to assign 2GB of address space to real memory, and
> 2GB to virtual memory (from a per process point of view).

No, it's much better than that in 2.4! The 2.4 4GB option still has
the 3+1 split, and only maps the first just-under-1GB of physical
memory into the kernel's permanent VA space. The rest of the memory
is mapped on demand.

> Without glibc 2.2 I should be able to get to 2GB of memory
> allocated via the heap. I only need glibc 2.2 to start
> mmap'ing malloc'able pools from VM. I.E. beyond 2GB of
> malloc'ed memory.

> My app running with 1 GB RAM under linux 2.2, with glibc 2.2
> successfully malloc's up to 3GB and the app works fine. (though
> swapping quite a bit).
> My app running with 2 GB RAM under linux 2.4.0-test7, with glibc 2.2
> dies at 1 GB of memory used. (it also dies at 1 GB using glibc 2.1.2).

What happens at this point? If you strace the binary, what fails?

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