Re: [bigmem-patch] 4GB with Linux on IA32

Stephen C. Tweedie
1999-08-19T16:49:11Z

Hi,

On Thu, 19 Aug 1999 13:33:32 +0000, Thierry Vignaud
<tvignaud@mandrakesoft.com> said:

> since only recent motherboard support more than 512Mb RAM, and since
> they used i686 (PPro, P2, P3), why not use the pse36 extension of
> these cpu that enable to stock the segment length on 24bits, which
> give 64To when mem unit is 4b page. this'll make the limit much
> higher (say 128Mb RAM for the kernel space memory and 15,9To for the
> user space).

The PAE36 extensions let you address 64GB of physical memory, but don't
change the fact that you still have a 32-bit user address space: the
user space is still limited to 3GB.

> This would break some api, but why not add foo_64 for each foo()
> function as glibc does for big files ? As for standard api such as of
> libc, i don't think wa have to worry about. There are few Programs
> which want a lot of memory such as oracle. For these, we may find a
> special way of accessing the mem (64bits pointers, 64bit mmap, ...)

The CPU doesn't support 64 bit pointers. Kind of makes it a bit
inefficient to access the user memory if you have to make a system call
every time. :)

--Stephen