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

Benefits of virtual memory, Q.  When virtual memory is executed in a comput...

Q.  When virtual memory is executed in a computing system there are convinced costs associated with the technique and certain benefits. List the costs as well as the benefits. Is i

Write a program to demonstrate the memory leak problem, Write a program (wi...

Write a program (with the programming language and on the platform of your choice) to demonstrate the memory leak problem (see http://en.wikipedia.org/wiki/Memory_leak for detail

Protection, Can you please explain in easy words how input output protectio...

Can you please explain in easy words how input output protection works

Explain page-replacement algorithms, Q. Consider the following page-replac...

Q. Consider the following page-replacement algorithms. Rank the algorithms on a five-point scale from "bad" to "perfect" according to their page-fault rate. Detach those algorithm

Explain optimal page replacement, Optimal page replacement An optimal ...

Optimal page replacement An optimal page replacement algorithm has the least page fault rate of all algorithms. The algorithm states that a 'replace the page that will not be

List out the advantages of windows 2000 file management, List out the advan...

List out the advantages of windows 2000 file management. Permits detailed security for individual folders and files. Built-in granular compression capabilities

Information system, using the transformation process model and system think...

using the transformation process model and system thinking concepts explain the key operation of TGL works.

In which page replacement policy balady’s anomaly occurs, In which page rep...

In which page replacement policy Balady’s anomaly occurs? FIFO (First in First Out)

Determine what the expansion of nested macro calls follows, Determine what ...

Determine what the expansion of nested macro calls follows  The expansion of nested macro calls follows the Last in First out (LIFO) rule.

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