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SubjectRe: Virtual memory stuff and Reiserfs
Date
> 
> 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?)

The 386 (at least) is capable of addressing 64TB of virtual memory, isn't
mmap implemented as a demand page loading of VM??? That's how
I'd implement it.

>
> > 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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Perry Harrington Linux rules all OSes. APSoft ()
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