Re: hammer: MAP_32BIT

[Ulrich Drepper <drepper@redhat.com>]

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Timothy Miller wrote:

> If your program is capable of handling an address with more than 32
> bits, what point is there giving a hint?  Either your program can handle
> 64-bit pointers or it cannot.  Any program flexible enough to handle
> either size dynamically would expend enough overhead checking that it
> would be worse than if it just made a hard choice.

Look at the x86-64 context switching code.  If memory addressed by the
GDT entries has a 32-bit address it uses a different method than for
cases where the virtual address has more than 32 bits.  This way of
handling GDT entries is faster according to ak.  So, it's not a
correctness thing, it's a performance thing.

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