Date: Tue, 30 Jan 2018 07:09:44 -0700 From: Alan Somers <asomers@freebsd.org> To: Andre Albsmeier <Andre.Albsmeier@siemens.com> Cc: Mike Karels <mike@karels.net>, FreeBSD <freebsd-stable@freebsd.org>, Dimitry Andric <dim@freebsd.org> Subject: Re: i386 with 4GB RAM: less than 2GB available on A2SAV (Intel Atom E3940) Message-ID: <CAOtMX2jHSD0tSus0gjeHR5UERzgkK1%2BxYNd=Haz-EKVsZGZ8Fw@mail.gmail.com> In-Reply-To: <20180130071123.GB43715@bali> References: <FF56490E-BD56-4BF1-B1D7-866ACEB32DC4@FreeBSD.org> <201801281632.w0SGWiui055204@mail.karels.net> <20180130071123.GB43715@bali>
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On Tue, Jan 30, 2018 at 12:11 AM, Andre Albsmeier < Andre.Albsmeier@siemens.com> wrote: > On Sun, 28-Jan-2018 at 10:32:44 -0600, Mike Karels wrote: > > > On 28 Jan 2018, at 15:57, Andre Albsmeier <Andre.Albsmeier@siemens.com> > = > > > wrote: > > > > I have a lot of machines running with 4 GB physical RAM and, for > > > > some reasons, I still have to use a 32 bits OS. > > > >=20 > > > > All of them show something between 3 and 3.5 GB of RAM available > > > > in dmesg but the brand new Supermicro A2SAV really shocked me: > > > >=20 > > > > FreeBSD 11.1-STABLE #0: Mon Jan 15 06:57:10 CET 2018 > > > > ... > > > > real memory =3D 4294967296 (4096 MB) > > > > avail memory =3D 1939558400 (1849 MB) > > > > ... > > > >=20 > > > > So do people have any ideas how I might get a bit closer to at least > > > > 3 GB? I assume there are no FreeBSD knobs which might help but hope > > > > dies last... > > > > > This is a common problem on i386. Most likely some ranges are reserved > > > for I/O mappings, such as video cards. If you boot with -v, I think > the > > > kernel prints an overview of the physical ram chunks available? I > don't > > > know of any other way to get such an overview. > > > > > Another option is to try PAE, but I have no idea how stable that is... > > > > > -Dimitry > > > > I suspect that the unavailable RAM has been mapped above 4 GB by the > BIOS. > > > > About PAE: at $JOB, we have a FreeBSD 8.2 system that has been running > > PAE reliably since 8.2 was new. Also, we ship amd64 systems that run > > mostly 32-bit binaries, which works well. > > But can the entire userland be 32 bit only? > Sure. I do this with jails. It's no problem to have a 32-bit jail on a 64-bit kernel. Kernel modules would be an issue, though. If you need any, you'll have to find a way for the 64-bit machines to find 64-bit kernel modules. > > Maybe I'll try the PAE thing... >
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