1. Seoul National University
Virtualization

2. Virtualization History of Computing = History of Virtualization
Seoul National University
Virtualization
Illusion
History of Computing =
History of Virtualization
e.g., process abstraction, virtual memory, cache memory, virtual machine, simultaneous multithreading (SMT),…(the list goes on)

3. Virtualization Example: Process abstraction
Seoul National University
Virtualization Example: Process abstraction
Source:
CPU
Time Multiplexing of physical CPU within the operating system (OS) using timer circuit/interrupt + =
CPU
CPU
Single physical CPU
Multiple logical CPUs

4. Virtualization Example: Virtual Machine
Seoul National University
Virtualization Example: Virtual Machine
Thin software layer below operating system
Linux
Windows XP + =
. . .
e.g., VMware, VirtualPC, Connectix Virtual PC

5. Virtualization Example: Cache Memory
Seoul National University
Virtualization Example: Cache Memory
New Memory Technology
(Performance: SRAM)
(Cost: DRAM) + =
SRAM
DRAM

6. Virtualization Example: Virtual Memory
Seoul National University
Virtualization Example: Virtual Memory
Dedicated (virtual)
Memory for each process + =
Hard Disk
DRAM

7. Two Aspects of Virtualization
Seoul National University
Two Aspects of Virtualization
Functionality
Hardware: MMU (memory management unit) and exception mechanism (“page fault”)
Software: virtual memory management routines based on page tables, one for each process, in the operating system (OS)
Performance
Optimizing regular memory references
Temporal locality (locality in time)
If an item is referenced, it will tend to be referenced again soon.
Spatial locality (locality in space)
If an item is referenced, items whose addresses are close by will tend to be referenced soon.
Optimizing page table references
TLB (Translation Look-aside Buffer)

8. Typical Workload Pattern
Seoul National University
Typical Workload Pattern
Source: Glass & Cao (1997 ACM SIGMETRICS)