On 10/09/2012 01:07 AM, Mike Hommey wrote:
Note it doesn't have to be a vs. situation. madvise could be an additional way to interface with volatile ranges on a given fd. That is, madvise doesn't have to mean anonymous memory. As a matter of fact, MADV_WILLNEED/MADV_DONTNEED are usually used on mmaped files. Similarly, there could be a way to use madvise to mark volatile ranges, without the application having to track what memory ranges are associated to what part of what file, which the kernel already tracks.
Good point. We could add madvise() interface, but limit it only to mmapped tmpfs files, in parallel with the fallocate() interface.
However, I would like to think through how MADV_MARK_VOLATILE with purely anonymous memory could work, before starting that approach. That and Neil's point that having an identical kernel interface restricted to tmpfs, only as a convenience to userland in switching from virtual address to/from mmapped file offset may be better left to a userland library.
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