Messages in this thread | | | Date | Thu, 24 Feb 2000 13:24:07 +0100 (MET) | From | Richard Guenther <> | Subject | Re: mmap/munmap semantics |
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On Thu, 24 Feb 2000, Stephen C. Tweedie wrote:
> Hi, > > On Thu, 24 Feb 2000 03:35:02 +0100, Jamie Lokier > <lk@tantalophile.demon.co.uk> said: > > > I don't think MADV_DONTNEED actually drops privately modified data does > > it? > > Yes, it does. From the DU man pages: > > MADV_DONTNEED > Do not need these pages > > The system will free any whole pages in the specified > region. All modifications will be lost and any swapped > out pages will be discarded. Subsequent access to the > region will result in a zero-fill-on-demand fault as > though it is being accessed for the first time. > Reserved swap space is not affected by this call.
Ah, this is cool - exactly what we need. I.e. an madvise(MADV_DONTNEED) and a subsequent munmap should not generate any disk io?
> Regarding the other half of the problem --- zeroing out a portion of a > file without further IO --- the splice code I hope to have using kiobufs > in 2.5 will allow this to be done very easily. You'll be able to take a > region of /dev/zero and splice it into your open file with zero-copy.
Cool, too. So for now we will stay with zeroing by reading from /dev/zero which does vm tricks in linux already.
Richard.
> --Stephen > > _______________________________________________ > glame-devel mailing list > glame-devel@lists.sourceforge.net > http://lists.sourceforge.net/mailman/listinfo/glame-devel >
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