Adding memory under linux

[Praetor]

I just dropped another 512 into my server. Running a sys info in php only shows 882.72 mb rather than 1024-ish.

Now, is this due to memory being subtracted and used for necessary system services, bad memory, or do I have to recompile the kernel and/or add new options to the boot loader?

Running a 2.6 P4-HT on an Intel 865PERL in dual-channel mode. 4 sticks of Crucial pc3200, Gentoo running kernel 2.6.10.

 

[xcript]

IIRC I had to enable HIGHMEM4G (Processor type and features ---> High Memory Support (4GB)) and recompile my kernel when I got another stick of 512.

 

[Praetor]

See, I remember in the old days, you had to do some serious voodoo magic when adding memory to get the system to boot. I just don't know if that's still the case.

I'll try that High Memory Support (even though I don't have enough memory for it to theoretically work) and see if that makes a difference.

Anyone other suggestions?

 

[xcript]

Originally posted by: linux-2.6.11-rc4

CONFIG_HIGHMEM4G:

• 
  Select this if you have a 32-bit processor and between 1 and 4
  gigabytes of physical RAM.

😛

 

[bersl2]

This is semi-OT, but you can actually run on bad memory.

 

[Nothinman]

I'll try that High Memory Support (even though I don't have enough memory for it to theoretically work) and see if that makes a difference.

You need to enable HIGHMEM4G and recompile to get over 896M memory to be available. That or you can change your kernel's __PAGE_OFFSET value to extend "low" memory and recompile without HIGHMEM4G.

 

[Praetor]

Originally posted by: Nothinman

I'll try that High Memory Support (even though I don't have enough memory for it to theoretically work) and see if that makes a difference.

You need to enable HIGHMEM4G and recompile to get over 896M memory to be available. That or you can change your kernel's __PAGE_OFFSET value to extend "low" memory and recompile without HIGHMEM4G.

Sweet. Working on recompiling the kernel now. Thanks for the suggestions and explanations!