OS-Memory_Allocator

chunk header結構

1. prev chunk: long int(8-byte)
2. next chunk: long int(8-byte)
3. prev chunk size: int(31-bit)
   • 指的是所有切割出來的chunk(allocated, free)中，相鄰自己，地址較低的chunk的size(有可能是allocated, free)
4. allocated flag: int(1-bit)
5. current chunk size: int(31-bit)
6. mmap flag: int(1-bit)

• chunk header結構為: 1.2.(3.4.)(5.6.)，共24-byte
• 3,4合併為一個int，5,6合併為一個int(前31個bit是size部分，最後一個bit是flag)
• 所以int=(size<<1)+flag bit

執行指令

1. $./hw4_mm_test
2. cat testfile.txt|./hw4_mm_test>outputfile.txt
3. astyle --style=kr --indent=spaces=4 --suffix-none hw4_mm_test.c (used after programming)

指令說明

指令:

1. alloc N
   • N is the bytes
   • if N>32*1024-24, use mmap
   • else if use heap
   • Return value:
     • mmap: actual data address
     • heap: relative data address
2. free ADDRESS
   • ADDRESS is the data address
     • mmap: actual data address
     • heap: relative data address
   • you can input any address, if the ADDRESS is not allocated or illegal, I'll tell you
3. print BIN[i]
   • i can be 0 to 10
   • return value is an actual data address
4. print mmap_alloc_list
   • return value is an actual data address

Note

1. 今天有一個地址A，今天若A=A+8，則結果A=A+sizeof(A)*8，不是單純的+8，如果想要單純的+8則寫成:A=(void*)A+8
2. a<<1+1，等同於a<<(1+1)，括號要記得: (a<<1)+1

Reference

1. Dynamic Memory Management