On Sun, 2014-12-14 at 10:09 -0800, Alfred Perlstein
wrote:> 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?
>
I would have to defer to someone who actually understands just what that
parm is tuning. It was purely speculation on my part that the current
default is adequate for less memory than I have, and I don't know what
that downside might be for setting it too high.
-- Ian