i386 PAE kernel works fine on 10-stable

[Alfred Perlstein]

On Dec 14, 2014, at 9:47 AM, Ian Lepore wrote:

> This is an out of the blue FYI post to let people know that despite all
> the misinformation you'll run across if you search for information on
> FreeBSD PAE support, it (still) works just fine.  I've been using it
> (for reasons related to our build system and products at $work) since
> 2006, and I can say unequivocally that it works fine on 6.x, 8.x, and
> now 10.x (and presumably on the odd-numbered releases too but I've never
> tried those).
> 
> In my most recent testing with 10-stable, I found it was compatible with
> drm2 and radeonkms drivers and I was able to run Xorg and gnome just
> fine.  All my devices, and apps, and even the linuxulator worked just
> fine.
> 
> One thing that changed somewhere between 8.4 and 10.1 is that I had to
> add a kernel tuning option to my kernel config:
> 
>  option  KVA_PAGES=768	    # Default is 512
> 
> I suspect that the most frequent use of PAE is on laptops that have 4gb
> and the default tuning is adequate for that.  My desktop machine has
> 12gb and I needed to bump up that value to avoid errors related to being
> unable to create new kernel stacks.
> 

There already is a #define that is bifurcated based on PAE in pmap.h:

#ifndef KVA_PAGES
#ifdef PAE
#define KVA_PAGES       512
#else
#define KVA_PAGES       256
#endif
#endif

Do you think it will harm things to apply your suggested default to this file?

-Alfred