Physical Memory Management

Question about which tools to use, bugs, the best way to implement a function, etc should go here. Don't forget to see if your question is answered in the wiki first! When in doubt post here.
Post Reply
User avatar
mduft
Member
Member
Posts: 46
Joined: Thu Jun 05, 2008 9:23 am
Location: Austria

Physical Memory Management

Post by mduft »

Hi

I have spend a day writing a physical memory manager for my kernel using a bitmap to keep track of allocations.

To further tweak what i wrote, i wanted to get some comments from you guru's :)

The implementation does (seems to) work, but i'm unsure if i haven't left some concrete blocks in it slowing me down :) And i'm not sure if all my calculations for addresses/offsets/etc. are correct, so that i may miss some areas of memory while searching for free pages, etc.

i attached both the header and c file, maybe somebody has some time to look at it. if not, maybe the code is good enough, to help others out writing their own physical memory manager....

how i use it:

i call SxPhysMemInit(), then i call SxPhysMemAddRegion for each of the mmap entries with type 1 reported by GRUB.

i maybe have to also mention that i use Microsofts Visual C++ to compile this ;) so maybe gcc will not work out of the box...
Attachments
physmem.tar.gz
memory manager sources (c/h)
(2.23 KiB) Downloaded 121 times
Top
User avatar
mutex
Member
Member
Posts: 131
Joined: Sat Jul 07, 2007 7:49 pm

Re: Physical Memory Management

Post by mutex »

Hi,

I took a quick look at your code, and i have some comments.

In my design i have a allocpage() and freepage() wich just returns / frees 1 physical page at the time. These functions are in my code 1 line statements. Very easy code. Then i have a vmalloc & vfree on top of that.

My vmalloc and vfree contains a self maintainable linked list of areas in vmem that are allocated, and the routines update the asking process pdir and ptab with the info. All pages are set to non-present so that i dont do a allocpage() befor i get a PF for a request to one of the addresses in the allocated vm region.

I have also a Flag attribute to my malloc to force it to do allocpage() on vmalloc. I have also a few flags for having malloc() do zerofill.

Just want to comment on your use of Vc++ for doing stuff like this. I do the same. For code with liked lists, bit-fippling etc its very good to debug code in Vc++ i use it alot.

Good luck with your coding!

-
Thomas
Top
Post Reply

Return to “OS Development”