Are new kernels compiled with PAE (Physical Address Extension)?

mibadt · 2010-07-23 02:40:48

Hi,
As far as I know, Arch 32b kernels are not compiled with that option, and, as a consequence are limited to using a max 3 GB of memory.
If that's indeed the case, in view of current RAM prices and typical modern PC configuration, I'd rather have that option turned ON in future kernel upgrades.

Can anybody confirm the fact and explain why current 32b kernels are compiled that way in the first place?

Thanks

Last edited by mibadt (2010-07-23 02:41:17)

karol · 2010-07-23 02:56:17

http://www.freebsd.org/doc/en/books/faq … emory.html
It's for FreeBSD so I'm not sure it applies to Linux (almost surely doesn't apply)

Edit: http://en.wikipedia.org/wiki/Physical_A … sion#Linux
http://groups.google.com/group/linux.ke … 254a092330

Last edited by karol (2010-07-23 03:02:12)

Allan · 2010-07-23 03:31:33

You can easily check this out for yourself:

> grep "HIGHMEM" /var/abs/core/kernel26/config
# CONFIG_NOHIGHMEM is not set
CONFIG_HIGHMEM4G=y
# CONFIG_HIGHMEM64G is not set
CONFIG_HIGHMEM=y
# CONFIG_DEBUG_HIGHMEM is not set

So it is not enabled... you can compile your own kernel with and adjusted config file if you want. Or build kernel25-pae from the AUR. Or if you system supports x86_64 then use the x86_64 kernel, or switch to x86_64 completely.

That should be enough options for you.

alexandrite · 2010-07-23 04:17:04

Out of curiosity, what exactly is the justification for not compiling PAE into the arch kernel by default?

Allan · 2010-07-23 04:32:30

Performance loss. On average it is ~1%, but worst case scenario is a 10% loss.

ngoonee · 2010-07-24 02:38:51

Allan wrote:

Performance loss. On average it is ~1%, but worst case scenario is a 10% loss.

And the fact that you should really be running 64-bit anyway if you have more than 32 GB of ram.

fukawi2 · 2010-07-24 05:42:23

ngoonee wrote:

And the fact that you should really be running 64-bit anyway if you have more than 32 GB of ram.

s/32/4/g

ngoonee · 2010-07-24 15:26:29

Oops. I think my brain (and motor control) needs more RAM.....

Arch Linux

#1 2010-07-23 02:40:48

Are new kernels compiled with PAE (Physical Address Extension)?

#2 2010-07-23 02:56:17

Re: Are new kernels compiled with PAE (Physical Address Extension)?

#3 2010-07-23 03:31:33

Re: Are new kernels compiled with PAE (Physical Address Extension)?

#4 2010-07-23 04:17:04

Re: Are new kernels compiled with PAE (Physical Address Extension)?

#5 2010-07-23 04:32:30

Re: Are new kernels compiled with PAE (Physical Address Extension)?

#6 2010-07-24 02:38:51

Re: Are new kernels compiled with PAE (Physical Address Extension)?

#7 2010-07-24 05:42:23

Re: Are new kernels compiled with PAE (Physical Address Extension)?

#8 2010-07-24 15:26:29

Re: Are new kernels compiled with PAE (Physical Address Extension)?

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