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

Compare user threads and kernel threads, Compare user threads and kernel th...

Compare user threads and kernel threads. User threads:- User threads are supported above the kernel and are executed by a thread library at the user level. Thread creation

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

Difference among pre-emptive and non pre-emptive scheduling, Q. Define the ...

Q. Define the difference among pre-emptive and non pre-emptive scheduling. Answer: Pre-emptive scheduling permits a process to be interrupted in the midst of its execution ta

Briefly explain process management in windows 2000., Briefly explain proces...

Briefly explain process management in Windows 2000. The Windows 2000 process manager provides for deleting, creating and using threads and processes. It has no knowledge about

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

What is the cache coherency problem, Question: (a) Modern processors op...

Question: (a) Modern processors operate in one of two modes: one for the operating system and one for applications. What is the purpose of having these two modes? What are

How the nested macro calls are expanded, How the Nested Macro calls are exp...

How the Nested Macro calls are expanded LIFO (Last in First out)

Explain secondary-storage management, What are the three main activities of...

What are the three main activities of an operating system in regard to secondary-storage management? a) Free-space management. b) Storage allocation. c) Disk scheduling.

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