Read-write locks, Operating System

Assignment Help:

Consider a large web-based database. In some sense, Google is sort of like this. There might be many users who want to read from the database, but only a few users who are allowed to write to the database. If we use standard locks to control access to the database, the application will be much slower than it could be with a more clever type of lock.

Suppose we have one object that is shared among several threads. Suppose also that each thread is either a reader or a writer. Readers only read data but never modify it, while writers read and modify data. If we know which threads are reading and which ones are writing, what can we do to increase concurrency?

First, we have to prevent two writers from writing at the same time. In addition, a reader cannot read while a writer is writing. There is no problem, however in allowing lots of readers to read at the same time. Read-write locks achieve this, and can greatly improve performance for this sort of application.

Note that the lock is the same for both readers andwriters (called 'rw' in the slides), but the readers use an rlock() on the lock and writers use a wlock() on the same lock. Writers requesting a wlock() will have to wait until all readers and writers have released the lock. Readers requesting a rlock() can acquire it even if other readers are holding the lock. Readers however will still have to wait until any writer holding the lock releases the lock.


Related Discussions:- Read-write locks

How can the deadlock be prevented-safe state, How can the deadlock be preve...

How can the deadlock be prevented-Safe State Safe state : A state is safe if the system is able to allocate resources to each process in some order and still avoid deadlock.

Nachos file system, File System Interface and Implementation The Nachos ...

File System Interface and Implementation The Nachos file system, as distributed, uses a single-level index allocation method for data allocation of files. In the current design,

Server thread, Extend task 1 so that the requests are issued by the clients...

Extend task 1 so that the requests are issued by the clients instead of the server. The server now do not use the "all_requests.dat" file. Instead every client thread reads from

What is the use of boot block, What is the use of boot block? For a com...

What is the use of boot block? For a computer to begin running when powered up or rebooted it requires having an initial program to run. This bootstrap program tends to be easy

unix script command and echo command, Objectives 1.    Login to UNIX ...

Objectives 1.    Login to UNIX system and logout 2.    Learn features of the vi editor and to use online help (main pages).  Gain experience using them to create a document

Process abstraction in operating systems, Many early operating systems rega...

Many early operating systems regarded processes as different timesharing users. The process abstraction is a popular way to organize concurrent programs, but it is not the only cho

Describe the differences among short-term and medium-term, Describe the dif...

Describe the differences among short-term, medium-term, and long-term scheduling.   Short-term (CPU scheduler)-selects from jobs in memory those jobs that are ready to execu

Write a note on the usage of semaphores, Write a note on the usage of semap...

Write a note on the usage of semaphores. Semaphore is a synchronization tool and it is a variable having integer values. It is accessed only by two standard atomic operations w

Define inter process communication (ipc), The term IPC (Inter-Process Commu...

The term IPC (Inter-Process Communication) defines several paths by which different process executing on some operating system interact between each other.

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd