thr3ads.net - Xen users - [Xen-users] 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE) [Mar 2008]

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Wouter de Geus

2008-Mar-11 11:48 UTC

[Xen-users] 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE)

Hello,

I have recently upgraded one of my machines, both in hardware and Xen version.
In the old situation it had 3GB of memory and Xen 3.1, worked like a charm.
After upgrading it has 4GB of memory and Xen 3.2.

However, only 3.5GB of the memory is available to xen.
(xm info gives
  total_memory           : 3573 )

I''ve read about the grub 0.97 bug, so I patched it.
However, that has absolutely no effect.

Grub output:
grub> displaymem 
 EISA Memory BIOS Interface is present
 Address Map BIOS Interface is present
 Lower memory: 640K, Upper memory (to first chipset hole): 3072K
 [Address Range Descriptor entries immediately follow (values are 64-bit)]
   Usable RAM:  Base Address:  0x0 X 4GB + 0x0,
      Length:   0x0 X 4GB + 0xa0000 bytes
   Reserved:  Base Address:  0x0 X 4GB + 0xa0000,
      Length:   0x0 X 4GB + 0x60000 bytes
   Usable RAM:  Base Address:  0x0 X 4GB + 0x100000,
      Length:   0x0 X 4GB + 0x300000 bytes
>From xm dmesg:(XEN) Xen-e820 RAM map:
(XEN)  0000000000000000 - 000000000009fc00 (usable)
(XEN)  000000000009fc00 - 00000000000a0000 (reserved)
(XEN)  00000000000e0000 - 0000000000100000 (reserved)
(XEN)  0000000000100000 - 00000000df65b000 (usable)
(XEN)  00000000df65b000 - 00000000df6e8000 (ACPI NVS)
(XEN)  00000000df6e8000 - 00000000df6ec000 (usable)
(XEN)  00000000df6ec000 - 00000000df6ff000 (ACPI data)
(XEN)  00000000df6ff000 - 00000000df700000 (usable)
(XEN) System RAM: 3573MB (3659772kB)

Does anyone have any idea what might make those extra 500-ish MBs available to
Xen? :)

Thanks for reading.

Wouter.
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Wouter de Geus

2008-Mar-11 16:40 UTC

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[Xen-users] 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE)

Hello,

(second attempt in sending this, messed up my from header ;))

I have recently upgraded one of my machines, both in hardware and Xen version.
In the old situation it had 3GB of memory and Xen 3.1, worked like a charm.
After upgrading it has 4GB of memory and Xen 3.2.

However, only 3.5GB of the memory is available to xen.
(xm info gives
  total_memory           : 3573 )

I''ve read about the grub 0.97 bug, so I patched it.
However, that has absolutely no effect.

Grub output:
grub> displaymem 
 EISA Memory BIOS Interface is present
 Address Map BIOS Interface is present
 Lower memory: 640K, Upper memory (to first chipset hole): 3072K
 [Address Range Descriptor entries immediately follow (values are 64-bit)]
   Usable RAM:  Base Address:  0x0 X 4GB + 0x0,
      Length:   0x0 X 4GB + 0xa0000 bytes
   Reserved:  Base Address:  0x0 X 4GB + 0xa0000,
      Length:   0x0 X 4GB + 0x60000 bytes
   Usable RAM:  Base Address:  0x0 X 4GB + 0x100000,
      Length:   0x0 X 4GB + 0x300000 bytes
>From xm dmesg:(XEN) Xen-e820 RAM map:
(XEN)  0000000000000000 - 000000000009fc00 (usable)
(XEN)  000000000009fc00 - 00000000000a0000 (reserved)
(XEN)  00000000000e0000 - 0000000000100000 (reserved)
(XEN)  0000000000100000 - 00000000df65b000 (usable)
(XEN)  00000000df65b000 - 00000000df6e8000 (ACPI NVS)
(XEN)  00000000df6e8000 - 00000000df6ec000 (usable)
(XEN)  00000000df6ec000 - 00000000df6ff000 (ACPI data)
(XEN)  00000000df6ff000 - 00000000df700000 (usable)
(XEN) System RAM: 3573MB (3659772kB)

Does anyone have any idea what might make those extra 500-ish MBs available to
Xen? :)

Thanks for reading.

Wouter.
-- 

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--[ UxBoD ]--

2008-Mar-11 16:48 UTC

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Re: [Xen-users] 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE)

32bit or 64bit Dom0 O/S ?

Regards,

-- 
--[ UxBoD ]--
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// Fingerprint: F57A 0CBD DD19 79E9 1FCC A612 CB36 D89D 2C5A 3A84
// Keyserver: www.keyserver.net Key-ID: 0x2C5A3A84
// Phone: +44 845 869 2749 SIP Phone: uxbod@sip.splatnix.net

----- "Wouter de Geus" <benv-xensource.com@junerules.com> wrote:
> Hello,
> 
> (second attempt in sending this, messed up my from header ;))
> 
> I have recently upgraded one of my machines, both in hardware and Xen
> version.
> In the old situation it had 3GB of memory and Xen 3.1, worked like a
> charm.
> After upgrading it has 4GB of memory and Xen 3.2.
> 
> However, only 3.5GB of the memory is available to xen.
> (xm info gives
>   total_memory           : 3573 )
> 
> I''ve read about the grub 0.97 bug, so I patched it.
> However, that has absolutely no effect.
> 
> Grub output:
> grub> displaymem 
>  EISA Memory BIOS Interface is present
>  Address Map BIOS Interface is present
>  Lower memory: 640K, Upper memory (to first chipset hole): 3072K
>  [Address Range Descriptor entries immediately follow (values are
> 64-bit)]
>    Usable RAM:  Base Address:  0x0 X 4GB + 0x0,
>       Length:   0x0 X 4GB + 0xa0000 bytes
>    Reserved:  Base Address:  0x0 X 4GB + 0xa0000,
>       Length:   0x0 X 4GB + 0x60000 bytes
>    Usable RAM:  Base Address:  0x0 X 4GB + 0x100000,
>       Length:   0x0 X 4GB + 0x300000 bytes
-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.


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Wouter de Geus

2008-Mar-11 17:16 UTC

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Re: [Xen-users] 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE)

Oh, I forgot to mention that ;)

My first try I used a non-PAE 32 bit kernel.
When I noticed the missing memory I figured I needed PAE.

So now I''m using a 32 bit PAE enabled kernel. (and obviously I rebuilt
Xen too).

Wouter.

* --[ UxBoD ]-- <uxbod@splatnix.net> [2008-03-11 16:48:35 +0000]:
> 32bit or 64bit Dom0 O/S ?
> 
> Regards,
> 
> -- 
> --[ UxBoD ]--
> // PGP Key: "curl -s http://www.splatnix.net/uxbod.asc | gpg
--import"
> // Fingerprint: F57A 0CBD DD19 79E9 1FCC A612 CB36 D89D 2C5A 3A84
> // Keyserver: www.keyserver.net Key-ID: 0x2C5A3A84
> // Phone: +44 845 869 2749 SIP Phone: uxbod@sip.splatnix.net
> 
> ----- "Wouter de Geus" <benv-xensource.com@junerules.com>
wrote:
> 
> > Hello,
> > 
> > (second attempt in sending this, messed up my from header ;))
> > 
> > I have recently upgraded one of my machines, both in hardware and Xen
> > version.
> > In the old situation it had 3GB of memory and Xen 3.1, worked like a
> > charm.
> > After upgrading it has 4GB of memory and Xen 3.2.
> > 
> > However, only 3.5GB of the memory is available to xen.
> > (xm info gives
> >   total_memory           : 3573 )
> > 
> > I''ve read about the grub 0.97 bug, so I patched it.
> > However, that has absolutely no effect.
> > 
> > Grub output:
> > grub> displaymem 
> >  EISA Memory BIOS Interface is present
> >  Address Map BIOS Interface is present
> >  Lower memory: 640K, Upper memory (to first chipset hole): 3072K
> >  [Address Range Descriptor entries immediately follow (values are
> > 64-bit)]
> >    Usable RAM:  Base Address:  0x0 X 4GB + 0x0,
> >       Length:   0x0 X 4GB + 0xa0000 bytes
> >    Reserved:  Base Address:  0x0 X 4GB + 0xa0000,
> >       Length:   0x0 X 4GB + 0x60000 bytes
> >    Usable RAM:  Base Address:  0x0 X 4GB + 0x100000,
> >       Length:   0x0 X 4GB + 0x300000 bytes
> 
> -- 
> This message has been scanned for viruses and
> dangerous content by MailScanner, and is
> believed to be clean.
> 
-- 
BenV / JuNe

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Brian A. Seklecki

2008-Mar-11 17:52 UTC

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Re: [Xen-users] 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE)

On Tue, 2008-03-11 at 12:48 +0100, Wouter de Geus wrote:> Hello,
> 
> I have recently upgraded one of my machines, both in hardware and Xen
version.
> In the old situation it had 3GB of memory and Xen 3.1, worked like a charm.
> After upgrading it has 4GB of memory and Xen 3.2.
> 
> However, only 3.5GB of the memory is available to xen.
> (xm info gives
>   total_memory           : 3573 )

Google something called PAE.  Then reinstall the amd64 / x86_64 version
of your distro.  Maybe include "uname -a" output when reporting bugs?

~BAS

> I''ve read about the grub 0.97 bug, so I patched it.
> However, that has absolutely no effect.
> 
> Grub output:
> grub> displaymem 
>  EISA Memory BIOS Interface is present
>  Address Map BIOS Interface is present
>  Lower memory: 640K, Upper memory (to first chipset hole): 3072K
>  [Address Range Descriptor entries immediately follow (values are 64-bit)]
>    Usable RAM:  Base Address:  0x0 X 4GB + 0x0,
>       Length:   0x0 X 4GB + 0xa0000 bytes
>    Reserved:  Base Address:  0x0 X 4GB + 0xa0000,
>       Length:   0x0 X 4GB + 0x60000 bytes
>    Usable RAM:  Base Address:  0x0 X 4GB + 0x100000,
>       Length:   0x0 X 4GB + 0x300000 bytes
> 
> >From xm dmesg:
> (XEN) Xen-e820 RAM map:
> (XEN)  0000000000000000 - 000000000009fc00 (usable)
> (XEN)  000000000009fc00 - 00000000000a0000 (reserved)
> (XEN)  00000000000e0000 - 0000000000100000 (reserved)
> (XEN)  0000000000100000 - 00000000df65b000 (usable)
> (XEN)  00000000df65b000 - 00000000df6e8000 (ACPI NVS)
> (XEN)  00000000df6e8000 - 00000000df6ec000 (usable)
> (XEN)  00000000df6ec000 - 00000000df6ff000 (ACPI data)
> (XEN)  00000000df6ff000 - 00000000df700000 (usable)
> (XEN) System RAM: 3573MB (3659772kB)
> 
> Does anyone have any idea what might make those extra 500-ish MBs available
to Xen? :)
> 
> Thanks for reading.
> 
> Wouter.

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Mark Williamson

2008-Mar-11 19:22 UTC

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Re: [Xen-users] 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE)

> Oh, I forgot to mention that ;)
>
> My first try I used a non-PAE 32 bit kernel.
> When I noticed the missing memory I figured I needed PAE.
>
> So now I''m using a 32 bit PAE enabled kernel. (and obviously I
rebuilt Xen
> too).
Do you definitely know that normal PAE Linux *can* access all 4GB on this 
system?  On some systems the chipset makes it impossible to access the full 
4GB, with or without PAE :-(

Cheers,
Mark
> Wouter.
>
> * --[ UxBoD ]-- <uxbod@splatnix.net> [2008-03-11 16:48:35 +0000]:
> > 32bit or 64bit Dom0 O/S ?
> >
> > Regards,
> >
> > --
> > --[ UxBoD ]--
> > // PGP Key: "curl -s http://www.splatnix.net/uxbod.asc | gpg
--import"
> > // Fingerprint: F57A 0CBD DD19 79E9 1FCC A612 CB36 D89D 2C5A 3A84
> > // Keyserver: www.keyserver.net Key-ID: 0x2C5A3A84
> > // Phone: +44 845 869 2749 SIP Phone: uxbod@sip.splatnix.net
> >
> > ----- "Wouter de Geus"
<benv-xensource.com@junerules.com> wrote:
> > > Hello,
> > >
> > > (second attempt in sending this, messed up my from header ;))
> > >
> > > I have recently upgraded one of my machines, both in hardware and
Xen
> > > version.
> > > In the old situation it had 3GB of memory and Xen 3.1, worked
like a
> > > charm.
> > > After upgrading it has 4GB of memory and Xen 3.2.
> > >
> > > However, only 3.5GB of the memory is available to xen.
> > > (xm info gives
> > >   total_memory           : 3573 )
> > >
> > > I''ve read about the grub 0.97 bug, so I patched it.
> > > However, that has absolutely no effect.
> > >
> > > Grub output:
> > > grub> displaymem
> > >  EISA Memory BIOS Interface is present
> > >  Address Map BIOS Interface is present
> > >  Lower memory: 640K, Upper memory (to first chipset hole): 3072K
> > >  [Address Range Descriptor entries immediately follow (values are
> > > 64-bit)]
> > >    Usable RAM:  Base Address:  0x0 X 4GB + 0x0,
> > >       Length:   0x0 X 4GB + 0xa0000 bytes
> > >    Reserved:  Base Address:  0x0 X 4GB + 0xa0000,
> > >       Length:   0x0 X 4GB + 0x60000 bytes
> > >    Usable RAM:  Base Address:  0x0 X 4GB + 0x100000,
> > >       Length:   0x0 X 4GB + 0x300000 bytes
> >
> > --
> > This message has been scanned for viruses and
> > dangerous content by MailScanner, and is
> > believed to be clean.


-- 
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Dimitri Puzin

2008-Mar-12 15:24 UTC

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Re: [Xen-users] 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE)

Wouter de Geus schrieb:> > Hello,Hi,
> >
> > I have recently upgraded one of my machines, both in hardware and
Xen version.> > In the old situation it had 3GB of memory and Xen 3.1, worked like a
charm.> > After upgrading it has 4GB of memory and Xen 3.2.[...]

Same thing here. I have a tyan S5112 which has 4 GB phys. RAM installed
however  the max. mem. size the system can address is limited to 4GB.
PAE doesn''t work. 64 bit systems don''t need PAE. They can
address all of
the RAM directly.

The PCI address space lies in the system addressable space in the upper
~768 MB, starting somewhere at 3.3 GB. The actual beginning may be a bit
different, depending on the installed components, BIOS/settings, etc. If
PAE (here I mean hardware support for PAE, which includes chipset
function) is available then the physical memory which collides with the
PCI addr range is remapped to another address, normally beginning
somewhere at 4096MB. However if PAE support isn''t available, then the
last ~768MB of RAM are hidden. Otherwise it would be impossible to
address any device in the system because of address space collision
between the virtual PCI address range and physical memory address range.

The exact specifics of the chipset and addressable memory are noted in
the manual of your mainboard. As a rule, I don''t buy/get any hardware
with max mem size equal to the mem size I intend to install.

Hope this could clear some things for you.


Regards,

Dimitri Puzin aka Tristan-777




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Xen users - Mar 2008 - 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE)

[Xen-users] 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE)

[Xen-users] 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE)

Re: [Xen-users] 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE)

Re: [Xen-users] 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE)

Re: [Xen-users] 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE)

Re: [Xen-users] 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE)

Re: [Xen-users] 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE)