CSCE611-OS-Project02-Frame Manager

CSCE611-OS-MP02-Frame-Manager

Github Link: https://github.com/tamu-edu-students/CSCE410-611-Spring2024-Hanzhong_Liu

Files I modified:

• cont_frame_pool.H
• cont_frame_pool.C
• copykernel.sh
  • Modified to fit Mac OS
• makefile
  • Add a new item make run to make it easier to start the kernel

    run: copy start_vm
    copy: 
    	./copykernel.sh
    start_vm:
    	bochs -f bochsrc.bxrc

Memory Structure

Design of memory pools:

Design of the bitmap:
I used two bits to store the status of a frame. The first bit indicates whether the frame is used and the second bit indicates whether the frame is the head of a frame sequence. So, we have the follows:

• [0,x] : Not Used (x is 0 or 1)
• [1,1] : Used and this frame is the head of a sequence
• [1,0] : Used and this frame is not the head of a sequence

Get Frames

unsigned long ContFramePool::get_frames(unsigned int _n_frames);

• The function first determines if there are enough frames to allocate, then iterates through the bitmap, looking for appropriate frames, and returns the frame’s id.

Release Frames

void release_frames_internel(unsigned long _first_frame_no);

ContFramePool*        next_pool;  // next pool
static ContFramePool* pools_head; // head point of all polls
static void release_frames(unsigned long _first_frame_no);

• release_frames_internel: An internal function to release frames starting from a given frame number within a specific pool.
• next_pool: A pointer to the next memory frame pool, enabling a linked list structure for pool management.
• pools_head: A static pointer that serves as the head of the list of all memory frame pools.
• release_frames: A static function that releases frames by locating the correct pool using the frame’s ID and then invoking release_frames_internel for that pool.

Release process:

• release_frames is a static function which has only one parameter _first_frame_no
• release_frames first determines which pool the frame belongs to, and then use global_kernel_memory_pool and global_process_memory_pool to releases it.
• Since one sequence of frames needs to be released, the release process constantly determines whether a new head (Frame with Used_Head tag in bitmap) has been encountered. If so, the release_frames_internel will finish the release process and return.

Output/Test