http://hawxchen.blogspot.tw/2012/08/talk-memory-allocation-in-classic.html I presented this slide at COSCUP 2012 with 907 attendees in Taiwan.

1. Memory Allocation
In
Classic Monolithic Kernel
And
Classic Micro Kernel
陳膺正 (Hawx Chen )
yingjheng.chen@gmail.com
http://gplus.to/HawxChen
http://hawxchen.blogspot.tw
Presented at COSCUP2012- JuluOS Workshop/JuluOSDev http://www.juluos.org/

2. Who Am I
• Experience
– 2008 NCTU CS Bachelor
– 2010 NTU CSIE Master
– 2010~presnet Mstar Semiconductor
• Senior software engineer
• Open Source
– https://github.com/HawxChen/MIT-6.828-
Adventure Enjoy to implement OS

3. Memory Management
• Importance of History.
• Based Arch:
– Classic Monolithic: UNIX v6
– Classic Microkernel: MINIX
• UNIX
– Kernel(Physical) Memory Allocator
– User(virtual) Memory Allocator
• MINIX
– Kernel(Physical) Memory Allocator
– User Memory Allocator

4. Memory Management
• Importance of History.
• Based Arch:
– Classic Monolithic: UNIX v6
– Classic Microkernel: MINIX
• UNIX
– Kernel(Physical) Memory Allocator
– User(virtual) Memory Allocator
• MINIX
– Kernel(Physical) Memory Allocator
– User Memory Allocator

5. Importance of History
• Computer
programmming is Art?
From
http://www2.uwstout.edu/content/profdev/images/kelly_art_history.jpg
http://www.informit.com/ShowCover.aspx?isbn=0201485419

7. Importance of history
• Having an understanding of the battles
fought in the past will give you the
ammunition for your current battles
了解過去的戰場在爭什麼，會讓你得到現
行戰場的火藥。

8. Importance of history

9. Importance of history

10. Memory Management
• Importance of History.
• Based Arch:
– Classic Monolithic: UNIX v6
– Classic Microkernel: MINIX
• UNIX
– Kernel(Physical) Memory Allocator
– User(virtual) Memory Allocator
• MINIX
– Kernel(Physical) Memory Allocator
– User Memory Allocator

11. UNIX Arch
User Process
System Call
Process
Management I/O Services
Device
Drivers
Scheduler
Hardware
I/O Buffers
Memory
Management File
System
Kernel Space
Interface (Library Routines)
User Process

12. MINIX Arch
Kernel Space

13. MINIX Scheduling
• When to run each component?
• Scheduler
– Multilevel Queue
– Lazy scheduling

14. Memory Management
• Importance of History.
• Based Arch:
– Classic Monolithic: UNIX v6
– Classic Microkernel: MINIX
• UNIX
– Kernel(Physical) Memory Allocator
– User(virtual) Memory Allocator
• MINIX
– Kernel(Physical) Memory Allocator
– User Memory Allocator
• How to start

15. Some UNIX v6 Features
HW: PDP machine
• 2Byte (1 Word) Alignment
• Block Addressed: 64 Bytes
KISA0 KISD0 UISA0 UISD0

16. UNIX Kernel Addressing Space
Physical
• Kernel segment registers
Loader/
initialized at m40.S INT&Trap
– KISA0 ~ KISA5 : 0~48KB functions
– KISA6 KISD6: Per process data and
structure. Kernel context
– KISA7 KISD7: IO Segment
Kernel
data/bss
u per-process
data
• #0 system process(scheduler) IO address
space
• #1 init process

17. UNIX Kernel Addressing Space
• Kernel segment registers
initialized at m40.S
– KISA0 ~ KISA5 : 0~48KB
– KISA6 KISD6: Per process data and
structure.
– KISA7 KISD7: IO Segment
stack
kernel stack
u per-
process data
1K
struct user data structure
• #0 system process(scheduler)
• #1 init process

18. UNIX Kernel Memory Allocation
• coremap counted from *ka6+USIZE
Loader/
INT&Trap
functions
Kernel context
First Fit Avail Memory
Kernel
data/bss
u per-process 48K
data stack
struct user
Avail
Memory
49K
IO address
space

19. UNIX User Memory Allocation
• User segment registers initialized at main
– UISA/UISD
– Text+Data(BSS)+Stack + U(Kernel Stack/Internal PCB) <=
64KB
0
Virtual Physical
0
Context
Context
Data
Data
Stack
unmapped
64KB Stack 256KB

20. Memory Management
• Importance of History.
• Based Arch:
– Classic Monolithic: UNIX v6
– Classic Microkernel: MINIX
– UNIX
– Kernel(Physical) Memory Allocator
– User(virtual) Memory Allocator
• MINIX
– Kernel(Physical) Memory Allocator
– User Memory Allocator

21. MINIX Kernel Address Space
• Kernel don’t use any dynamic
memory
• Hardware independent
• View entire available memory
as CLIKCS (1024 Byte)

22. MINIX Memory Manager
PM
Mm Pm
• Almost hardware
independent
• User mode

23. MINIX Physical Memory Manager
• Hole List manager Hole structure
hole_head
Base1 Base1 Base1 BaseN
Size1 Size1 Size1 … SizeN
…

24. MINIX User Memory Allocation
• Holes: Free memory slot
– Unit: # clicks (1024 Bytes)
0x25863
• Size calculated from file
header Context
• Gap: Available memory Data 0x25863
• No memory
relocation(Before swapped
0x31945
out) Gap
• No memory expansion Gap
– Gap adjustment Stack
• No memory translation
0x31945
– No virtual memory
(Before 3.1.4)

25. Something I want to convey!

26. • History is the ONE PIECE.
• How to start to implement OS?
– What’s the most important?
– Keep others to be as simple as possible.
• Join us.

28. Reference