full RAM size not recognized after applying rt patch
 

I use 32bit powerpc with the linux 4.1.8 kernel and just applied the full rt patch which turned off the CONFIG_HIGHMEM configuration in menuconfig.

Following that my RAM size halved. the kernel recognizes only 766MB out of 1.5GB.

I saw there is a patch for restoring CONFIG_HIGHMEM configuration while still appliying the rt patch but its working for ARM only.

How can i change the settings in order the kernel to recognize the whole RAM without using high memory area. (maybe create more zone_normal? more nodes? or just extend the low memory area?) thanks!

How many Address lines is there on your powerpc? There's various software bodges to get around lack of address Your limits (with all address lines at 1) are 256k, 512k, 1024k, so it's odd that your limits are at 766MB.

Member Response
 

Hi,

Since the early PPC Mac is a RISC (32 bit) based system then you will need to use a distribution that will address that. Look at this to help you;Installing Linux on PowerPC Macs | Low End Mac
Hope this helps.
Have fun & enjoy!
:hattip:

thanks for the help.
After reading some articles and posts , the answer is that the linux 32bit OS supports only 1GB RAM size as long as CONFIG_HIGHMEM turned off and you use 3GB/1GB user/kernel virtual address space split.

In order to use more than 1GB you have to turn on the CONFIG_HIGHMEM or change the split (2GB/2GB for example) or use 64bit OS.