Messages in this thread | | | Date | Thu, 24 Feb 2000 11:06:25 +0100 (MET) | From | Richard Guenther <> | Subject | Re: mmap/munmap semantics |
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On Wed, 23 Feb 2000, Benjamin C.R. LaHaise wrote:
> On Wed, 23 Feb 2000, Richard Guenther wrote: > > > 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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