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SubjectRe: Virtual memory stuff and Reiserfs
On Thu, 5 Mar 1998, Hans Reiser wrote:

> There is a difference between a 4G file limit and a 4G mmap limit.
>
> The 4G mmap limit is an inherent mm issue, and nothing I do can fix it.
> Or am I wrong?

In the struct_page there's a off_t page->offset member
to indicate the file offset _from the start of the file_
when mmap()ing a file.
This means that everything over the 2g mark can't
be mmap()ed...
If you want to support larger files, you'd also want a
trick to mmap them (maybe two offset members, so you can
shift the 4g 'window' over the file?)

> What are you doing that isn't already size increased in 2.1?

We recently shrunk the struct_page. Kswapd is getting
more efficient. Euhm...

Rik.
+-----------------------------+------------------------------+
| For Linux mm-patches, go to | "I'm busy managing memory.." |
| my homepage (via LinuxHQ). | H.H.vanRiel@fys.ruu.nl |
| ...submissions welcome... | http://www.fys.ruu.nl/~riel/ |
+-----------------------------+------------------------------+


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