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

Explain drawbacks of fixed partitioning, The drawbacks of fixed partitionin...

The drawbacks of fixed partitioning are: The number of partitions are précised at system generation time limits the number of active processes in the system. For the re

Explain combined ult/klt approaches, COMBINED ULT/KLT APPROACHES Idea i...

COMBINED ULT/KLT APPROACHES Idea is to merge the best of both approaches Solaris is an illustration of an OS that combines both ULT and KLT  Thread creation complete i

List operations to be performed on directories, List operations to be perfo...

List operations to be performed on directories. Search for a file, delete a file, create a file, list a directory, rename a file, and traverse the file system.

Disk scheduling algorithms-first come, FCFS (First Come, First Served) Per...

FCFS (First Come, First Served) Perform operations in order requested No reordering of work queue No starvation every demand is serviced Poor performance

What is contiguous allocation, What is contiguous allocation? Allocati...

What is contiguous allocation? Allocation of a group of consecutive sectors for a one file.

How many disks can be used effectively by one fast wide bus, Q. More than ...

Q. More than one disk drive is able to be attached to a SCSI bus. Especially a fast wide SCSI-II bus can be connected to at most 15 disk drives. Remember that this bus has a bandw

Protection, protection in operating system

protection in operating system

Split the hexadecimal format, The following is a dump of a TCP header in h...

The following is a dump of a TCP header in hexadecimal format: 00CD0018 00000EF1 00000D5D 502200D1 01BF0010 We need to first split the above hex as such 00 CD 00 18 00 00

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