CS 422 Distributed Computing Processes

Flashcards for review

A __ provides a set of instructions along with the capability of automatically executing a series of those instructions.

PROCESSOR

A __ is a minimal software processor in whose context a series of instructions can be executed.

THREAD

A __ is a software processor in whose context one or more threads may be executed.

PROCESS

Saving a thread __ implies stopping the current execution and saving all the data needed to continue the execution at a later stage.

context

A __ is the unit of execution within a process performing a task.

thread

In a __, both the process and thread are same.

single-threaded process

A __ can perform multiple tasks at the same time.

multi-threaded process

__ are capable of running more than one process or thread at the same time.

Multi-core processors

__ allow pausing and resuming without losing data.

CONTEXTS

__ is the minimal collection of values stored in the registers of a processor used for the execution of a series of instructions.

PROCESSOR CONTEXT

__ is the minimal collection of values stored in registers and memory, used for the execution of a series of instructions.

THREAD CONTEXT

__ is the minimal collection of values stored in registers and memory, used for the execution of a thread.

PROCESS CONTEXT

Threads share the same __.

address space

__ is generally (somewhat) more expensive as it involves getting the OS in the loop, i.e., trapping to the kernel.

Process switching

Threads are __ units of execution that allow efficient multitasking within a process.

lightweight

Processes are __, independent units of execution that require more overhead for creation, switching, and destruction.

heavier

In a multi-threaded process, the operating system can switch the CPU to another thread in that process to avoid ___.

NEEDLESS BLOCKING

The threads in a __ process can be scheduled to run in parallel on a multiprocessor or multicore processor.

multi-threaded

One of these is a trade-off of using threads: Threads use the same __: more prone to errors.

address space

A Main Issue with threads and Operating Systems is - Should an OS kernel provide threads, or should they be implemented as __ packages?

user-level

All services provided by the kernel are done on behalf of the process in which a thread resides, so if the kernel decides to block a thread, the __ will be blocked.

entire process

Operations that block a thread are no longer a problem under __ solution because the kernel schedules another available thread within the same process.

Kernel

Basic idea of __ Introduce a two-level threading approach: lightweight processes that can execute user-level threads.

Lightweight Processes

User-level thread does a system call implies __ that is executing that thread, blocks.

The LWP

__ scans an incoming HTML page and finds that more files need to be fetched.

The web browser

Most servers have high __ demands.

I/O

___programs tend to be smaller and easier to understand due to simplified flow of control.

Multithreaded

The __ tier is generally responsible for passing requests to an appropriate server: request dispatching.

first

What type of instruction may affect the configuration of a machine, may trap?

Control-sensitive instruction

A virtual machine monitor may be constructed if the set of sensitive instructions for that computer is a subset of the set of __ instructions.

privileged

Name the three types of cloud services: __.

INFRASTRUCTURE-AS-A-SERVICE; PLATFORM-AS-A-SERVICE; SOFTWARE-AS-A-SERVICE

A cloud provider will rent out a VM (or VMM) that may possibly be sharing a physical machine with other customers under __.

IaaS

__ Each new application must implement its own protocol logic, leading to higher development effort and less reuse.

Application-level

__ Promotes code reuse, interoperability, and simplifies development by abstracting network details from the application.

Middleware-level

Conceal resource access using client-side stubs for RPCs is called __ transparency.

Access

Conceal resource location and let client-side software keep track of the actual location is called __ transparency.

Location/migration

Multiple invocations handled by the client stub where clients do not see replicas is called __ transparency.

Replication

Mask server and communication failures transparency is called __.

Failure transparency

A __ implementing a specific service on behalf of a collection of clients.

process

__ server: The server handles the request before attending the next request.

Iterative

__ server: Uses a dispatcher, which picks up an incoming request that is then passed on to a separate thread/process.

Concurrent

Most services are tied to a __.

specific port

Should an urgent message come in to a server then associated request is put on hold under __ communication.

out-of-band

__ servers Never keep accurate information about the status of a client after having handled a request.

Stateless

__ servers keeps track of the status of its clients.

Stateful

What is the first tier generally responsible for?

passing requests to an appropriate server: request dispatching

With the TCP __: the selected server takes over the connection and continues communication with the client.

handoff

When servers are spread across the Internet a common approach is used: __.

DNS

To keep the client unaware of distribution, let the __ act on behalf of the client.

DNS resolver

Different organizations contribute machines, which they subsequently share for various experiments using __.

PlanetLab

__ Independent and protected environment with its own libraries, server versions, and so on.

Vserver

Migration in heterogeneous systems can be achieved only via __.

abstract machine implemented on different platforms

___ is the process of moving executable code from one machine to another in a distributed system to improve performance, efficiency, or flexibility.

Code migration

Moving code to a client when needed increases __.

Flexibility

Moving code from client to server is __.

Remote Evaluation

Moving code from server to client is __.

Code on Demand

What kind of mobility moves only the code and data segment (and reboot execution)?

Weak mobility

What kind of mobility moves the component, including execution state?

Strong mobility

Pushing memory pages to the new machine and resending the ones that are later modified during the migration process is a method of __.

Migrating images

For migrating images:stopping the current virtual machine; migrate memory, and start the new virtual machine is a __ Downtime.

High

__: modify guest OS, either by preventing nonprivileged sensitive instructions, or making them nonsensitive (i.e., changing the context)

Paravirtualization