Re: PAE code ?

[Jean-Yves Migeon <jeanyves.migeon%free.fr@localhost>]

On 11.10.2011 00:19, Michael C. Vergallen wrote:
> Hi,
>
> Anyone got the PAE code working under the netbsd-5.1.0_PATCH kernel ? I
> would like to use it on a HP-DL580-G2 with 8 GB Ram and 4 cpu's but the
> compile stops at the x86 code.

I am not sure that the PAE code has been backported to NetBSD-5. It 
requires a couple of changes in x86 kernel code, especially for MP 
systems. The changes are intrusive to x86 virtual memory code, making 
the overall thing very unlikely for a backport.

> And as I don't know the netbsd kernel
> code I can't seem to get the thing working. Also I don't understand why
> the kernel dous not allocate a certain amount of memory to each cpu thus
> making it possible to use all the physical memory to the system and
> allowing userland to utilize all physical memory available by binding
> certain processes to a certain cpu.

What memory are you talking about? The memory resource is managed at 
system level, pinning memory to a CPU would be a waste of resource as 
you cannot tell in advance where it will be required. No decent modern 
OS should do that, except for very specific reasons like NUMA (and even 
there, it's more a matter of locality rather than allocation).

PAE is a 36 bits physical address scheme, virtual memory addressing 
remains at 32 bits. You will _not_ get additional virtual memory 
addressable for a given process (it stays at 3GiB), you just can run 
more of them before you hit the physical limit (2^36).

--
Jean-Yves Migeon
jeanyves.migeon%free.fr@localhost