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

Write a short note on pcb, Write a short note on PCB? Every process is ...

Write a short note on PCB? Every process is represented in the operating system by a process control block also called a task control block. It contains more information regard

Page fault handling , Page Fault Handling conditions like, where the copy...

Page Fault Handling conditions like, where the copy on write bit of a page is set and that page is send by more than one process, the Kernel assign new page and copies the conten

Explain wait for graph, Explain Wait for Graph a. Use a resource alloca...

Explain Wait for Graph a. Use a resource allocation graph to derive a wait-for graph.  b. Wait-for graph acquired by making an edge from p 1 to p 2 iff p 1 is waiting for

What are the operations that can be performed on a directory, What are the ...

What are the operations that can be performed on a directory? The operations that can be performed on a directory are Search for a file Create a file Delete a

What is a semaphore, What is a semaphore? A semaphore 'S' is a synchron...

What is a semaphore? A semaphore 'S' is a synchronization tool which is  an integer value that, apart from initialization, is accessed only by two standard atomic operations; w

What are the issues in designing a network, Normal 0 false fa...

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4

Concepts of an address - data and control bus, Let us consider the operatio...

Let us consider the operation of the EPROM device in more detail. Consider the pining details below again   Before we examine the interface means of the EPROM, it is worth

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