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Re: New Cygwin family member
Hi guys,
On Feb 8 14:55, Corinna Vinschen wrote:
> Another problem is the memory layout (the "fork" problem). Fortunately
> we have a 43 bit address space now. Here's is our current model, still
> open for discussion:
>
> - Keep clear of memory from 0x0 up to 0x0:7fffffff, and from
> 0x700:00000000 up to 0x7ff:ffffffff since these areas are used
> by the OS for ... everything.
>
> - Cygwin thread stacks will be located between 0x0:80000000 and
> 0x0:ffffffff. With a default stack size of 1 Meg, we have room for
> 2048 threads.
>
> - The Cygwin executables will be loaded to 0x1:00400000.
>
> - The Cygwin DLL will be loaded to 0x1:80040000. That leaves 2 Gigs of
> space for the executable. The space from 0x1:8000000 up to
> 0x1:80040000 will be used for Cygwin's shared memory areas.
A slight change to the memory model occured to me, which should drop
the potential DLL collisions even more:
> - Other Cygwin distro DLLs are supposed to be rebased to the area
> between 0x2:00000000 up to 0x3:ffffffff. This is an area of 8 Gigs
> for DLLs. That should be enough for a while, I guess.
The memory slot from 0x2:00000000 up to 0x4:00000000 == 8 Gigs will be
used by rebase{all}...
...while ld's --auto-image-base will use the region from 0x4:00000000 up
to 0x6:00000000.
This means, rebased DLLs will never collide with auto-image-based DLLs,
and both types of DLLs have a full 8 Gigs space each, which should be
enough for the forseeable future.
> - The heap will be located at 0x4:00000000, and it will be 512Megs by
> default.
The heap will then be located at 0x6:00000000, of course.
> - Then ... a big void ...
>
> - Eventually, mmap's will be allocated from 0x700:00000000 downwards.
This means the VM space left for heap and mmaps is a mere 7152 Gigabyte,
about 7 Terabytes. I hope that's ok, even for our friends on the
Fortran frontier.
Comments?
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Maintainer cygwin AT cygwin DOT com
Red Hat