在Linux内核中修改Sysfs的/ sys / devices / system / memory /目录

Question

I am working on my course homework for modifying the memory directory of Sysfs in Linux Kernel. I am seeking help from people here after taking permission from my prof. Here's what I exactly want to do.

Background: If I have a 4 GB RAM I can have 4 X 1 GB DIMMS or 2X 2GB DIMMS on my motherboard. NUMA is supported in Linux by dividing this 4GB physical memory into many chunks with specific starting and ending physical address for each chunk. The 'devices' directory in Sysfs contains the global device hierarchy. This contains every physical device that has been discovered by the bus types registered with the kernel. Hence the details regarding the memory chunks are stored in the path '/sys/devices/system/memory/' of Linux Kernel. In this directory, we have a file called 'block_size_bytes' which decides how many parts my RAM can be split into. For example in my system it is 8000000 and hence the RAM is split into 32 memory folders from memory0 to memory43. Every 'memoryX' directory will have a file called 'state' which represents the online/offline state of the memory chunk. I can toggle between online/offline if I want to 'switch off' that particular chunk off memory.

So here's what I exactly want to do:

I want to modify this whole directory structure into 4 directories. Why 4? Because, I have 4 X 1GB DIMMS on my motherboard, so I want reduce these 32 memory chunks in to to 4 big chunks so that I can control whichever DIMM I want by toggling it's 'state' online/offline. So Basically I want to change the state of the memory on DIMM level.

That's pretty much my problem description.

My approach: I have read through the sysfs file system and tried to look up the kernel modules which are responsible for organizing the 'memory' directory of sysfs. I want to find the module and edit it as per my requirement and compile that module. It got increasingly difficult to find the specific documentation regarding this topic which lead me to ask this question. All I could find was that there this C programming file '/lib/modules/3.8.0-19-generic/source/drivers/base/memory.c' which has methods for setting the 'state' of the memory chunks, showing the starting and ending physical address of each memory section and many other methods. But I am not able to figure out where exactly these methods are being called or which module is utilizing this C file to set all the attributes.

Could you please let me know which exact module I need to look for? If you find my approach wrong, could you please point me in the right direction?

Thanks in advance :)

Answer 1

I just answer to this part of the question :

But I am not able to figure out where exactly these methods are being called or which module is utilizing this C file to set all the attributes.

You can use lxr to search in the kernel tree. Here an exemple with show_mem_state function.