[gentoo-user] Kernel doesn't use all of the available memory

[gentoo-user] Kernel doesn't use all of the available memory

[Helmut Jarausch]

Hi,

I see a strange effect which puzzles me.
I have two AMD64 (~amd64) Systems. Both have 8Gb memory installed
as reported by their BIOS as well as by lshw.
One is a somewhat older Opteron, the other one a recent Phenom II.
But the output of 'free -m' differs significantly

On the Phenom II       there a total of 7738 Mb
but on the old Opteron there a total of 6477 Mb only.

The 2.6.36 kernel is configured nearly identical (just a different SATA 
driver).

Has anybody an idea where this comes from?

Many thanks for a hint,
Helmut.

Re: [gentoo-user] Kernel doesn't use all of the available memory

[Michael Hampicke]

> One is a somewhat older Opteron, the other one a recent Phenom II.
> But the output of 'free -m' differs significantly
> *snip*
> Has anybody an idea where this comes from?

Maybe some of the system's memory is reserved as memory for a onboard
graphics card (on mainboard) which does not have it's own memory?

Re: [gentoo-user] Kernel doesn't use all of the available memory

[Volker Armin Hemmann]

On Thursday 09 December 2010, Helmut Jarausch wrote:
> Hi,
> 
> I see a strange effect which puzzles me.
> I have two AMD64 (~amd64) Systems. Both have 8Gb memory installed
> as reported by their BIOS as well as by lshw.
> One is a somewhat older Opteron, the other one a recent Phenom II.
> But the output of 'free -m' differs significantly
> 
> On the Phenom II       there a total of 7738 Mb
> but on the old Opteron there a total of 6477 Mb only.
> 
> The 2.6.36 kernel is configured nearly identical (just a different SATA
> driver).
> 
> Has anybody an idea where this comes from?

a) bios limitiation. Some bad bios implementations (even from expensive 
vendors) map the pci space into the 3.5-4gb or 7.5-8gb area. Stupid.

b) onboard devices.

Re: [gentoo-user] Kernel doesn't use all of the available memory

[Neil Bothwick]

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On Fri, 10 Dec 2010 16:47:18 +0100, Volker Armin Hemmann wrote:

> a) bios limitiation. Some bad bios implementations (even from expensive 
> vendors) map the pci space into the 3.5-4gb or 7.5-8gb area. Stupid.

Although you usually change the BIOS settings to not act broken just to
appease rubbish Windows drivers.


-- 
Neil Bothwick

If it's tourist season, why can't we shoot them?

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Re: [gentoo-user] Kernel doesn't use all of the available memory

[Volker Armin Hemmann]

On Friday 10 December 2010 23:07:10 Neil Bothwick wrote:
> On Fri, 10 Dec 2010 16:47:18 +0100, Volker Armin Hemmann wrote:
> > a) bios limitiation. Some bad bios implementations (even from expensive
> > vendors) map the pci space into the 3.5-4gb or 7.5-8gb area. Stupid.
> 
> Although you usually change the BIOS settings to not act broken just to
> appease rubbish Windows drivers.

if you have a bios that lets you change stuff like that.

Re: [gentoo-user] Kernel doesn't use all of the available memory

[Neil Bothwick]

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On Sun, 12 Dec 2010 00:25:16 +0100, Volker Armin Hemmann wrote:

> > Although you usually change the BIOS settings to not act broken just
> > to appease rubbish Windows drivers.  
> 
> if you have a bios that lets you change stuff like that.
> 

I meant to write "Although you CAN usually change the BIOS settings", so
yes, if your BIOS allows it (the ones I've tried do).


-- 
Neil Bothwick

Get your grubby hands off my tagline! I stole it first!

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Re: [gentoo-user] Kernel doesn't use all of the available memory

[meino.cramer]

Helmut Jarausch <jarausch@igpm.rwth-aachen.de> [10-12-10 01:09]:
> Hi,
> 
> I see a strange effect which puzzles me.
> I have two AMD64 (~amd64) Systems. Both have 8Gb memory installed
> as reported by their BIOS as well as by lshw.
> One is a somewhat older Opteron, the other one a recent Phenom II.
> But the output of 'free -m' differs significantly
> 
> On the Phenom II       there a total of 7738 Mb
> but on the old Opteron there a total of 6477 Mb only.
> 
> The 2.6.36 kernel is configured nearly identical (just a different SATA 
> driver).
> 
> Has anybody an idea where this comes from?
> 
> Many thanks for a hint,
> Helmut.
> 

(I dont know the exact core count of both processors...)

But may be additional cores of the Phenom II (x6?) will result
in more mem preallocated by the BIOS (may be without reason).

On my system (8GB,Phenom II X6 1090T, ASUS Crosshair IV Formula) 
there are 8184216 kB in total.

So even the  7738 Mb seems to be lesser than possible.

Only a shot into the dark...

mcc