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Old 02-06-2008, 12:19 AM   #1
pankaj.bhamare
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PAE enable


hi,
My present hardware is as follows :
CPU dual core 2.8 GHz
RAM 4 GB
OS Redhat linux (kernel 2.6.9) (32 bit)

My requirement :
I want to access 64 GB virtual address space by using PAE. I don't know how to enable PAE on linux please suggest

Thanks in advance
 
Old 02-06-2008, 12:52 AM   #2
syg00
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You misunderstand PAE. It allows you to access more REAL RAM (on the motherboard). The 32-bit address space remains at 4 Gig - of which (usually) 1 Gig is kernel reserved.
 
Old 02-06-2008, 01:18 AM   #3
pankaj.bhamare
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Quote:
Originally Posted by syg00 View Post
You misunderstand PAE. It allows you to access more REAL RAM (on the motherboard). The 32-bit address space remains at 4 Gig - of which (usually) 1 Gig is kernel reserved.
thanks for reply,
I understood the concept

Now i need to use physical RAM more than 4GB.
On windows we can achieve the same by using VirualAlloc (along with other required hacks).

How can we do the same on Linux? I need my process to allocate more than 4GB (7GB for instance).

What are the required changes for the same in terms of CODE, COMPILATION, LINKING and other OS booting options.
 
Old 02-06-2008, 01:34 AM   #4
Micro420
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1) enable PAE in motherboard BIOS
2) enable PAE in kernel
3) may require PAE in GRUB entry
 
Old 02-06-2008, 02:31 AM   #5
pankaj.bhamare
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Quote:
Originally Posted by Micro420 View Post
1) enable PAE in motherboard BIOS
2) enable PAE in kernel
3) may require PAE in GRUB entry
thanks for reply

But i don't know how to check PAE is enable or not and also
how to enable PAE in kernel and GRUB.

Also want to know that is there is any compilation and linking option required to set so that my process can allocate more than 4GB. I have 4GB of RAM for my linux machine
 
Old 02-06-2008, 03:07 AM   #6
pankaj.bhamare
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I have also check in path

/usr/src/kernels/2.6.9-42.EL-smp-i686
grep CONFIG_HIGHMEM64G .config
got result
CONFIG_HIGHMEM64G=y
So i think PAE is enable in kernel
i have 4GB of RAM may be problem is because of that
I want my process to allocate 7GB
please help me

Thank in advance
 
Old 04-15-2009, 02:46 AM   #7
vishwas786
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Smile

I am a newbie in Linux.

[QUOTE=Micro420;3047585]1) enable PAE in motherboard BIOS

I wonder, there is a option to enable PAE from the BIOS. (It might be possible, that the same is present in other systems).

If this issue is only related to the use of memory more than 4GB, then, Why don't u try to setup the PAE kernel itself in the system.

On my system,I successfully built a PAE kernel, the issue got resolved. The steps I used:

cd /usr/src/sys/i386/conf
config PAE
cd ../compile/PAE
make cleandepend && make depend
make
The next steps would be to run "make install", which would install the kernel and then to reboot.

The PAE kernel configuration file is included with the distribution, you don't need to create it.

Regards,
newbie

Comments from senior members is needed. This will encourage me. Thanks
 
Old 04-15-2009, 05:14 AM   #8
otoomet
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How to detect the PAE: if you have 4G installed memory, look what the tools (e.g. top) tell you. It may be 1G (non extended memory support), about 3.2G (extended but not PAE) or 4G (PAE enabled). Of course, you may as well check kernel config...

You have to enable it in kernel (i.e. compile new kernel).

BIOS may enable more memory automatically.

Even in case of PAE, a single process cannot take over 2G memory AFAIK. You need 64bit system if your process needs 7G. However, there may be some tricks available.

2.6.9 kernel is pretty old. If you need memory a lot, I would recommend to install a 64-bit distro.

Best,
Ott
 
  


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