On Wed, 23 Feb 2000, Benjamin C.R. LaHaise wrote:

On Wed, 23 Feb 2000, Richard Guenther wrote:

quoted

So how can I throw away a dirty (shared) mapping of a file without
generating disk io? Remember, I do not care about the contents of the file
at the mmap place.
A possible solution would be to be able to convert a shared mapping to
a private one? If I'm the only user of the shared mapping (so its a
virtually private one) this should be easy - just "disconnect" it. In the
other case I do not really know how to handle this.

The most portable and easiest way to achieve this behaviour right now is
to use individual files or shm segments for the shared mappings.  Using
SysV shared memory will get you the most performance since it won't get
written back to disk early (like mmaped files).  If that doesn't give you
enough space, I strongly recommend using 1 file per shared "segment",
since the semantics you get by truncating and then extending the mapping
are exactly what you want.  As a bonus, this technique works on
filesystems that don't support files with holes =)

Yes, but unfortunately the individual file approach does not work in case
we (ideally) want to operate on a whole disk...

Richard.

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