Re: Virtual memory stuff and Reiserfs

Rik van Riel (
Thu, 5 Mar 1998 12:08:19 +0100 (MET)

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...

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