slacker (sla@c.ker) on 5/13/07 wrote:
---------------------------
>Linus Torvalds (torvalds@osdl.org) on 5/13/07 wrote:
>---------------------------
>>The biggest single reason to go 64-bit is exactly
>>because of physical address space. Your virtual address
>>space needs to bea multiple of the physical one:
>>when you hit 1GB of RAM, 32-bit virtual memory is no longer
>>acceptable. You literally do need more virtual memory than
>>physical.
>
>Your virtual address space needs to be a multiple of the maximum resident set
>size of your applications. If you have a single application which is working
>with 1GB of physical memory, then you will need > 1GB (and likely > 4GB) of virtual memory.

Yhe kernel caches data as well, which was one of the points
(eg. about various kernel caches not being able to take
advantage of the physical memory without jumping through so
many hoops it isn't worthwhile).

PAE works "OK" if you include the kernel working set size
in that set. However clearly the best thing to do is avoid
all the ifs, buts, and maybes, and use a 64-bit virtual
address space for the kernel.