Re: [PATCH] 2.6: mmap complement, fdmap

[Matt Mackall <mpm@selenic.com>]

On Mon, Mar 22, 2004 at 12:14:56AM -0600, Matt Miller wrote:
> > On Sun, Mar 21, 2004 at 10:43:07PM -0600, Matt Miller wrote:
> > > 	``flags'' can be one of O_RDONLY, O_WRONLY, or O_RDWR.
> > >
> > > I have verified functionality on ia32 and sparc as these are the only
> > > architectures I currently have some type of access to.  To test, start the
> > > kernel configuration process and go under File systems/Pseudo filesystems
> > > and select this option:
> > >
> > > 	[*] Virtual memory file descriptor mapping support
> > >
> > > Please let me know about any and all suggestions/bugs/flames.  I tried to
> >
> > *boggle*
> >
> > a) what the hell for?
> 
> It's targetted mainly as a performance enhancer.  Some of the specific
> scenarios where it would be useful are:
> 
> a) When one cannot afford to take the performance hit of synchronizing
>    a memory range to disk due to disk size limitations or speed
>    requirements.
> b) Some things can benefit from the ability to interface with memory as a
>    file.
> 
> The specific reason for implementing this was to allow for loading dynamic
> libraries in the context of a process without having to write them to
> disk.

How about tmpfs/ramfs instead? Open a file on tmpfs and mmap it and
you've got the same thing without any of the nasty corner cases.
 
-- 
Matt Mackall : http://www.selenic.com : Linux development and consulting