Reference counting, Operating System

Assignment Help:

The idea of reference counting is to maintain, for every object, the total number of references to that object, i.e. the number of "incoming" pointers. Whenever the number of references is zero we know that the object is not accessible through any pointers, and thus it is garbage. Also, whenever we choose to delete some useless object,we have to recursively check that object to see if it contains pointers to other objects; if so, we have decrement the reference counters for those objects as well. One problem of reference counting, though, is how to deal with cycles. Suppose object A points to B, and B points to A. If these objects can only be reached through each other, we have to free them too, even though their counters are not zero! Note that cycles can common inmany data structures; for example, consider a doubly-linked list. The commonly adopted solution to this problem is to run mark-sweep now and then, in order to remove cyclic references, and then run normal reference counting on the rest of the time.


Related Discussions:- Reference counting

Explain swapping technique used in pre-3bsd unix systems?, What are the dis...

What are the disadvantages of swapping technique used in pre-3BSD UNIX systems? If there is excessively much memory contention, processes are swapped out until sufficient

Deadlocks, At the end of this lecture, and into the next lecture, we will d...

At the end of this lecture, and into the next lecture, we will discuss the last major type of logical error that can occurwhen programming with threads. A deadlock occurswhen two t

Merits of device controller in the kernel, Q. State three merits of placing...

Q. State three merits of placing functionality in a device controller rather than in the kernel and State three disadvantages. Answer: Three advantages: Bugs are less probabl

What are the objectives of operating system?, What are the objectives of op...

What are the objectives of operating system? Objectives of OS 1.      Convenience: An OS makes a computer more suitable to use. 2.      Efficiency : An OS allows t

When page fault frequency in an operating system is reduced, When the Page ...

When the Page fault frequency in an operating system is reduced Locality of reference is appropriate to the process

Packets and time division multiplexing (tdm), Broken data into small packet...

Broken data into small packets allow time division multiplexing. In TDM every packet leaves the sender and is switched on the shared interaction channel through a multiplexer. At t

Life of a page, Suppose your process starts up, and allocates some memory w...

Suppose your process starts up, and allocates some memory with malloc(). The allocator will then give part of a memory page to your process. The OS then updates the corresponding p

How many disk operations are needed to fetch the i-node, How many disk oper...

How many disk operations are needed to fetch the i-node for the file /usr/ast/courses/os/handout.t? Assume that the i-node for the root directory is in memory, but nothing else alo

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