Re: hammer: MAP_32BIT

Ulrich Drepper (drepper@redhat.com)
Fri, 09 May 2003 16:24:49 -0700


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Timothy Miller wrote:

> Why does there ever need to be an explicit HINT that you would prefer a
> <32 bit address, when it's known a priori that <32 is better? Why
> doesn't the mapping code ALWAYS try to use 32-bit addresses before
> resorting to 64-bit?

Because not all memory is addressed via GDT entries. In fact, almost
none is, only thread stacks and similar gimicks. If all mmap memory
would by default be served from the low memory pool you soon run out of
it and without any good reason.

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Ulrich Drepper \ ,-----------------' \ Mountain View, CA 94041 USA
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