Virtualization and Cloud

Question 1

Hypervisor should have full control of virtualized resources

Answer 1

Safety in VM

Question 1

Behavior of a program should be the same as running program on baremetal

Answer 1

Fidelity in VM

Question 2

Much of the code in VM should run without intervention

Answer 2

Efficiency in VM

Question 3

Can directly access resources of underlying machine and implement resource allocation strategies to service VMs

Answer 3

Type 1 hypervisor

Question 4

Must negotiate resources with base operating system

Answer 4

Type 2 hypervisor

Question 5

Only uses hypercalls to get system services like I/O

Answer 5

microkernel

Question 6

Modify sourcecode of guest operating system

Answer 6

paravirtualization

Question 7

Executes hypercalls, defined in API and exposed to guest OS

Answer 7

paravirtualization

Question 8

When sensitive instruction occurs, trap in host OS and delegate to hypervisor

Answer 8

true virtualization

Question 9

Generic set of procedures that can be executed by any hypervisor

Answer 9

Virtual machine interface

Question 10

• On demand service
• Broad network access
• Resource pooling
• Rapid elasticity
• Measured service

Answer 10

Requirements of cloud platform

Question 11

any x86 OS any app can run without modification

Answer 11

Challenges in virtualization of x86 - compatability

Question 12

performs all UI functions, starts VM and performs most drive emulation, as well as proxying calls to base OS

Answer 12

VMX

Question 13

Small kernel-mode driver that is installed alongside host OS to allow VMM to run by briefly suspending OS

Answer 13

VMX driver

Question 14

Holds all software to multiplex CPU and memory, including exception handlers, trap and emulate handlers, etc

Answer 14

Virtual memory manager

Question 15

Context of VMM changes from host OS to VMM

Answer 15

World switch

Question 16

Swaps all memory and registers, including exception handlers and privileged requests

Answer 16

world switch

Question 17

VMWare’s type 1 hypervisor

Answer 17

ESX server

Question 18

Baremetal hypervisor with VMM that allows for multiple virtual machines

Answer 18

ESX server

Question 19

• CPU scheduler ensures each virtual machine gets a fair share of CPU
• Memory manager optimized for scalability, even when VM requests more memory than available
• File system optimized for VM images and high I/O throughput
• Easy to extend capabilities and enable plugins

Answer 19

ESX server benefits

Question 20

Each word in memory can be read as fast as any other word

Answer 20

Uniform memory access

Question 21

Multiprocessor with single bus, used by all cores

Answer 21

UMA with bus-based architecture

Question 22

Leads to issues when one CPU core is using bus more than others

Answer 22

Issues with UMA and bus-based architecture

Question 23

Block can either be read-only, allowing it to be in multiple cache lines at same time, or read-write, where it can be in only one cache at a time

Answer 23

UMA with bus-based architecture

Question 24

At each intersection of horizontal and vertical lines is a crosspoint, either in an open or closed state

Answer 24

UMA with crossbar switches

Question 25

Crossbar switches are ______, so CPU is never denied connection

Answer 25

UMA with crossbar switches

Question 26

Based on 2x2 switch, message arriving on any input can be swapped to any output

Answer 26

UMA with multistage switching

Question 27

Still vulnerable to blocking if data is being read / written using same bus at same time

Answer 27

UMA with multistage switching

Question 28

Access to local slice of memory is faster than accessing remote memory

Answer 28

NUMA multiprocessor

Question 29

• Single address space visible to all CPUs
• Access to remote memory via LOAD and STORE instructions
• Access to remote memory is slower than access to local memory

Answer 29

Characteristics of NUMA

Question 30

• Each CPU has own private OS
• Multiprocess memory partitioned amongst CPUs, but share underlying OS
• Process makes syscall that is handled by own CPU. No processes shared.
• No sharing of physical pages
• Inconsistency can result if two CPUs attempt to modify same data

Answer 30

Each CPU has own OS

Question 31

• One copy of each operating system on master
• All syscalls are directed to master
• When CPU goes idle, prompt master for next process
• One buffer cache, master delegates pages

Answer 31

Master-slave multiprocessing

Question 32

• One copy of OS in memory, but any system can access
• When syscall made, CPU executing process will trap to kernel and process syscall
• Multiple mutexes in kernel, divided into submodules to ensure CPUs cannot access same resource at same time

Answer 32

Symmetric multiprocessing

Question 33

Using TSL for multiprocessing will lead to

Answer 33

spin lock

Question 34

CPU is blocked from accessing bus will constantly request lock

Answer 34

spin lock

Question 35

Give CPU each own private lock variable in unusued cache block. Check cache for any other CPU requesting resource and give access to that CPU

Answer 35

TSL cache thrashing

Question 36

Partition CPU into blocks. Only execute threads once there are enough free CPUs in partition

Answer 36

Space sharing

Question 37

Groups of threads scheduled as a unit. All members run at once on different timeshared CPUs. All members start and end time slices together

Answer 37

Gang scheduling

Question 38

Limited from doing anything on CPU until send/receive is finishd

Answer 38

Blocking calls

Question 39

Transfer control to kernel temporarily, then return before actual call is finished

Answer 39

Nonblocking calls

Question 40

Each machine has own VM and page table. When need page that CPU does not have, OS traps and asks CPU to hold page to unpage and send to requesting CPU

Answer 40

Distributed shared memory

Question 41

In multi-computer approach, when a CPU only needs part of page and constantly has to unpage and page with CPU that needs other part of page

Answer 41

false sharing