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

What is single-level directory, What is Single-level Directory All file...

What is Single-level Directory All files are constrained in the similar directory, which is simple to support and understood. One limitation is when the number of files enhance

Explain lru approximation page replacement in detail, LRU approximation pag...

LRU approximation page replacement In this we utilize the reference bit associated with the page entry to choose a page to be removed. The various algorithms used for the imp

Explain worst fit algorithm, Worst Fit Algorithm Here we obtain the la...

Worst Fit Algorithm Here we obtain the largest space available for the smallest. Therefore after that process entered there will be much more space remaining. In this space we

What are the various page replacement algorithms, What are the various page...

What are the various page replacement algorithms used for page replacement? FIFO page replacement Optimal page replacement LRU page replacement LRU approximat

How file record length should be chosen, How File record length should be c...

How File record length should be chosen File record length should be selected to match the data characteristics

Explain medium term scheduling, Medium term scheduling This is componen...

Medium term scheduling This is component of the swapping function. Usually the swapping in decision is based on the need to manage the degree of multiprogramming. At a system t

Could you replicate a multilevel directory structure, Q. Could you replica...

Q. Could you replicate a multilevel directory structure with a single-level directory structure in which arbitrarily long names can be used? If your answer is yes describe how you

Cache replacement policies, The physical memory acts as a cache backed by t...

The physical memory acts as a cache backed by the disk. When the physical memory is full, and we want to read in another page from disk, we have to evict a page from physical memor

Linux, what is I/O management Linux

what is I/O management Linux

Request or response interface - interaction using message, Explain the Requ...

Explain the Request or Response interface The Request/Response interface is ideal for a message based client-server interaction. By modeling components to interact via a reque

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