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Date:      Sun, 14 Dec 2014 10:09:46 -0800
From:      Alfred Perlstein <bright@mu.org>
To:        Ian Lepore <ian@freebsd.org>
Cc:        FreeBSD Stable <freebsd-stable@freebsd.org>
Subject:   Re: i386 PAE kernel works fine on 10-stable
Message-ID:  <DB7FB000-9A82-41F5-A4BD-6806AF218F01@mu.org>
In-Reply-To: <1418579278.2026.9.camel@freebsd.org>
References:  <1418579278.2026.9.camel@freebsd.org>

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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).
>=20
> 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.
>=20
> 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:
>=20
>  option  KVA_PAGES=3D768	    # Default is 512
>=20
> 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.
>=20

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




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