Allocation techniques, Operating System

Since most of the programs require a lot of memory allocation/deallocation, we expect the memory management to be fast, to have low fragmentation, make good use of locality, and be scalable to multiple processors. Newer issues include security from attacks (e.g. use randomization of locations to minimize effect of buffer-over?ow attacks) as well as reliability in the face of errors (e.g. detecting double free()'s and buffer overruns).

In analyzing the speed of an allocator, the key components are the cost of malloc, the cost of free, and the cost of getting the size of an object (for realloc). In certain types of programs, for instance those with a lot of graphics manipulation, allocators can become the performance bottleneck, and so speed is important.

We say that fragmentation occurs when the heap, due to characteristics of the allocation algorithm, gets "broken up" into several unusable spaces, or when the overall utilization of the memory is compromised. External fragmentation happens when there is waste of space outside (i.e. in between) allocated objects; internal fragmentation happens when there is waste of space inside an allocated area.

Remember that the allocator might at any single time have several pages with unused space, from which it could draw pieces of memory to give to requesting programs. There are several ways to decide what are the good spots, among those with free memory, from which to take memory. The ?rst-?t method ?nds the ?rst chunk of desired size and returns it; it is generally considered to be very fast; best-?t ?nds the chunk that wastes the least of space; and worst-?t takes memory from the largest existent spot, and as a consequence maximizes the free space available. As a general rule, ?rst-?t is faster, but increases fragmentation. One useful technique that can be applied with these methods is always to coalesce free adjacent objects into one big free object.

Posted Date: 3/12/2013 6:05:35 AM | Location : United States







Related Discussions:- Allocation techniques, Assignment Help, Ask Question on Allocation techniques, Get Answer, Expert's Help, Allocation techniques Discussions

Write discussion on Allocation techniques
Your posts are moderated
Related Questions
Page fault is a trap to the software gained by the hardware when a process accesses a page that is goes in the virtual address space, but not added in physical memory. In the har

Windows admin need it Project Description: We want to protect an executable on operating system level , so the process could be visible among all users while the executable r

What are batch systems? Early computers were physically huge machines run from a console. The general input devices were card readers and tape drivers. The common output device

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.

Why is rotational latency usually not considered in disk scheduling? How would you modify SSTF, SCAN, and C-SCAN to include latency optimization? Most disks do not export their

Problem: (a) Based on your experience in setting up Windows 2003 Server operating system, briefly describe the twelve different steps in which the installation is conducted du

Q. Describe the three main architectural layers of Windows XP? Answer: (1) The HAL (Hardware Abstraction Layer) creates operating system portability by hiding hardware differ

Locality of reference entails that the page reference being made by a processĀ  Locality of reference entails that the page reference being made by a process is similarly to be

Do you have writers that can use the software AIMMS version 3.9?

explain any four types of operating system feature and structure(design)