Physical memory manager about annos HOT 7 OPEN

I'd like to help with this issue. I'm learning about kernels and I really would like to help design one.

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Nice!

What are your ideas for this memory manager?

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I'm honestly not sure, would you be able to help me with designing it? I understand the theory behind memory management but I've yet to implement it. Do you have any suggestions?

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I was thinking about starting with a simple bitmap-based physical memory manager, just to get started, and improving it over time.

In it, each bit would represent a physical page of memory, 4kb.

I am still reading about it, but I think it's OK for a start...

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So it's going to be a heap of memory with each block pointing to 4KB of memory?

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No, more like this: http://wiki.osdev.org/Page_Frame_Allocation#Bitmap

Just a simple array for the bitmap. A heap would consume too much memory.

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I started doing the physical memory manager in a68ca7f.

It does basic things, but can be improved.

I did some TODO items in the PMM.cpp file, to be solved. I will replicate them here:

• Use allocation flags, for each one of the memory areas
  This envolves setting a flag for each area that belongs to a determined group, e.g, memory < 16 MB might be used by some old devices, like the floppy or old hardware, that can't use a bigger physical address

• The CheckPages() method.
  It's missing. We need a function that checks if we can allocate a big area. This is intended to be used by the VMM, that needs to allocate a certain quantity of memory, but it doesn't need to be physically contiguous. So, it can allocate, for example, 2 uncontiguous blocks of 8 pages if a single, contiguous block of 16 pages can't be allocated at once.

• Detect overlapping zones, alert the user and do something sane
  Some real hardware overlap memory zones, like an old computer I have. Maybe detect what types they are and do something.

• Merge contiguous zones with the same type
  This might be easy (I don't know, I didn't do it yet). Involves joining them if one ends where other starts and they have the same type.

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