Messages in this thread | | | Date | Tue, 2 Oct 2007 13:19:15 +0100 (BST) | From | Hugh Dickins <> | Subject | Re: [PATCH] Inconsistent mmap()/mremap() flags |
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On Tue, 2 Oct 2007, Thayne Harbaugh wrote: > On Tue, 2007-10-02 at 07:15 +0200, Andi Kleen wrote: > > > For mmap you can emulate it by passing a low hint != 0 (e.g. getpagesize()) > > in address but without MAP_FIXED and checking if the result is not beyond > > your range. > > Cool. That's a much better solution for multiple reasons - like you > mention, MAP_32BIT is only 2GB as well as it's only available on x86_64. > > > > > Given for mremap() it is not that easy because there is no "hint" argument > > > > without MREMAP_FIXED; but unless someone really needs it i would prefer > > > > to not propagate the hack. If it's really needed it's probably better > > > > to implement a start search hint for mremap()
I think you can do it already, without us complicating mremap further with such a start search hint.
First call mmap with a low hint address, the new size you'll be wanting from the mremap, PROT_NONE, MAP_ANONYMOUS, -1, 0. Then call mremap with old address, old size, new size, MREMAP_MAYMOVE|MREMAP_FIXED, and new address as returned by the preparatory mmap.
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