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Re: PAE code ?



On 10/11/2011 01:07 AM, Jean-Yves Migeon wrote:
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.
Strange that the option is available in the 5.1 kernel source-code. I will try to re-build the kernel today and see if it works or not because I've come to the constatation that the i386 5.1 daily build with the latest security patches had some problems with the code base that seemed odd to me. so I went back to the standard 5.1 build and compiled from source like the SA reports indicated.

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).
I was just thinking out loud on this issue and just wordered if it was possible. You are right I didn't consider the memory management issues. Also I might got things confused by thinking this is what XEN does ... I've got no experience with system virtualisation outside of playing with opensolaris zones and that is a while back.


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).

Okey thanks.

Michael

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