freebsd stable - Jan 2018 - i386 with 4GB RAM: less than 2GB available on A2SAV (Intel Atom E3940)

On 28 Jan 2018, at 15:57, Andre Albsmeier <Andre.Albsmeier at 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.
> 
> 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:
> 
> FreeBSD 11.1-STABLE #0: Mon Jan 15 06:57:10 CET 2018
> ...
> real memory  = 4294967296 (4096 MB)
> avail memory = 1939558400 (1849 MB)
> ...
> 
> 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

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> On 28 Jan 2018, at 15:57, Andre Albsmeier <Andre.Albsmeier at
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.

		Mike

On 01/28/2018 10:05, Dimitry Andric wrote:
> On 28 Jan 2018, at 15:57, Andre Albsmeier <Andre.Albsmeier at
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.
>>
>> 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:
>>
>> FreeBSD 11.1-STABLE #0: Mon Jan 15 06:57:10 CET 2018
>> ...
>> real memory  = 4294967296 (4096 MB)
>> avail memory = 1939558400 (1849 MB)
>> ...
>>
>> 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.
sysctl machdep.smap on BIOS, machdep.efi_map on UEFI.

Eric

On Sun, 28-Jan-2018 at 17:05:54 +0100, Dimitry Andric
wrote:
> On 28 Jan 2018, at 15:57, Andre Albsmeier <Andre.Albsmeier at
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.
> > 
> > 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:
> > 
> > FreeBSD 11.1-STABLE #0: Mon Jan 15 06:57:10 CET 2018
> > ...
> > real memory  = 4294967296 (4096 MB)
> > avail memory = 1939558400 (1849 MB)
> > ...
> > 
> > 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
Yes, it does:

real memory  = 4294967296 (4096 MB)
Physical memory chunk(s):
0x0000000000001000 - 0x000000000009afff, 630784 bytes (154 pages)
0x0000000000100000 - 0x00000000003fffff, 3145728 bytes (768 pages)
0x0000000000c28000 - 0x000000001fffffff, 524124160 bytes (127960 pages)
0x0000000022151000 - 0x0000000075733fff, 1398681600 bytes (341475 pages)
0x000000007998e000 - 0x0000000079a5efff, 856064 bytes (209 pages)
0x000000007a151000 - 0x000000007a4bffff, 3600384 bytes (879 pages)
0x000000007a4eb000 - 0x000000007aae2fff, 6258688 bytes (1528 pages)
0x000000007aae5000 - 0x000000007afeffff, 5287936 bytes (1291 pages)
avail memory = 1939800064 (1849 MB)

	-Andre
> 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
> 


-- 
Win98: useless extension to a minor patch release for 32-bit extensions
       and a graphical shell for a 16-bit patch to an 8-bit operating
       system originally coded for a 4-bit microprocessor, written by
       a 2-bit company that can't stand for 1 bit of competition.

On Sun, 28-Jan-2018 at 10:32:44 -0600, Mike Karels
wrote:
> > On 28 Jan 2018, at 15:57, Andre Albsmeier <Andre.Albsmeier at
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.
Finally I found some time to play with the PAE option. I added

option     PAE
option     KVA_PAGES=1024

and the A2SAV booted and gave me

real memory  = 4294967296 (4096 MB)
avail memory = 4048207872 (3860 MB)

Very encouraging, this is double of what I had before! So I decided to try
this on my desktop machine which also boots but loading the i915kms and drm2
stuff fails with

info: [drm] Initialized drm 1.1.0 20060810
drmn0: <Intel IvyBridge> on vgapci0
error: [drm:pid949:i915_gem_gtt_init] *ERROR* Scratch setup failed
device_attach: drmn0 attach returned 12

The KMS stuff doesn't support the A2SAV anyway so I can't test how
it would behave there...