Messages in this thread | | | Subject | Re: can we make anonymous memory non-EXECUTABLE? | From | Doug McNaught <> | Date | 09 Jan 2002 14:47:32 -0500 |
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Rob Landley <landley@trommello.org> writes:
> Glibc does mmap instead of brk because theoretically brk can leave wasted > memory between fragments, although apparently nobody's ever seen more than > 10% waste in a live program, and the speed penality of taking a soft page > fault at access time to muck about with the page tables is a LOT bigger than > 10%...
The other reason glibc uses mmap() is because your shared libraries are (usually) mapped smack dab in the middle of your address space. brk() assumes a contiguous heap, so when it hits your libraries, it has to stop, even if there is a gig of VM above the libs. mmap() can give you an arbitrary chunk of the address space, so glibc uses it for 'large' allocations.
-Doug -- Let us cross over the river, and rest under the shade of the trees. --T. J. Jackson, 1863 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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