Ulrich Drepper wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 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.
Alright. Sounds great. So my next question is this:
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?
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to email@example.com
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Thu May 15 2003 - 22:00:32 EST