Messages in this thread | | | Date | Mon, 16 Jan 2006 14:06:49 +0100 | From | Andrea Arcangeli <> | Subject | differences between MADV_FREE and MADV_DONTNEED |
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Now that MADV_REMOVE is in, should we discuss MADV_FREE?
MADV_FREE in Solaris is destructive and only works on anonymous memory, while MADV_DONTNEED seems to never be destructive (which I assume it means it's a noop on anonymous memory).
Our MADV_DONTNEED is destructive on anonymous memory, while it's non-destructive on file mappings.
Perhaps we could move the destructive anonymous part of MADV_DONTNEED to MADV_FREE?
Or we could as well go relaxed and define MADV_FREE and MADV_DONTNEED the same way (that still leaves the question if we risk to break apps ported from solaris where MADV_DONTNEED is apparently always not destructive).
I only read the docs, I don't know in practice what MADV_DONTNEED does on solaris (does it return -EINVAL if run on anonymous memory or not?).
http://docs.sun.com/app/docs/doc/816-5168/6mbb3hrgk?a=view
BTW, I don't know how other specifications define MADV_FREE, but besides MADV_REMOVE I've also got the request to provide MADV_FREE in linux, this is why I'm asking. (right now I'm telling them to use #ifdef __linux__ #define MADV_FREE MADV_DONTNEED but that's quite an hack since it could break if we make MADV_DONTNEED non-destructive in the future)
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