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

Linux, shell script that accepts two directory names as arguments and delet...

shell script that accepts two directory names as arguments and delete those file in the second directory that are identical to the file in the first

Parent and child process communicate in unix, Parent and Child process comm...

Parent and Child process communicate in unix A child and parent can interact through any of the normal  inter-process communication schemes (pipes, message queues, sockets, s

What methods are used to monitor intrusion detection, Question : a) Wh...

Question : a) What do you understand by a Directory Structure? Support your answer with a diagram. b) Give an example how Access Lists and Groups are arranged to mode of

Custom memory allocation, Some people write custom memory allocators to mee...

Some people write custom memory allocators to meet their speci?c needs. Although this is not needed for most of the applications, it is also not uncommon. The goal, of course, is t

Define ufd and mfd, Define UFD and MFD. In the two-level directory stru...

Define UFD and MFD. In the two-level directory structure, every user has her own user file directory (UFD). Every UFD has a similar structure, but lists only the files of a one

Is the internet a lan or else a wan, Q. Is the Internet a LAN or else a WAN...

Q. Is the Internet a LAN or else a WAN? Answer: The Internet is a WAN as the a variety of computers are located at geographically different places and are connected by long-dis

SYSTEM PROGRAMMING, advantages and disadvantages of monolithic and layered ...

advantages and disadvantages of monolithic and layered approach

Operating system design, You are required to study the important system com...

You are required to study the important system components, including important data structures, important functions and algorithms, and the various organizational, structural, logi

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