vovaer.blogg.se - Cache coherence in shared memory multiprocessor

#CACHE COHERENCE IN SHARED MEMORY MULTIPROCESSOR PORTABLE#
#CACHE COHERENCE IN SHARED MEMORY MULTIPROCESSOR SOFTWARE#

In contrast, the object based approach organizes the shared memory region as an abstract space for storing shareable objects of variable sizes. The page based approach organizes shared memory into pages of fixed size.

#CACHE COHERENCE IN SHARED MEMORY MULTIPROCESSOR SOFTWARE#

Software DSM systems also have the flexibility to organize the shared memory region in different ways. Processes should execute at the same timeĮxecuting the processes may happen with non-overlapping lifetimes Processes could cause error by altering data Processes are protected by having private address space Programmers need to understand consistency models to write correct programsĬomparison with message passing Message passing.Little programmer control over actual messages being generated.Must provide additional protection against simultaneous accesses to shared data.Generally slower to access than non-distributed shared memory.Shield programmers from sending or receiving primitives.

#CACHE COHERENCE IN SHARED MEMORY MULTIPROCESSOR PORTABLE#

Programs are more portable due to common programming interfaces.

Generally cheaper than using a multiprocessor system.

Can handle complex and large databases without replication or sending the data to processes.

Scales well with a large number of nodes.

Object-based approach, ideally accessing shared data through object-oriented discipline.

Shared-variable approach using routines to access shared variables.

Page-based approach using virtual memory.

There are three ways of implementing DSM: Hardware examples include cache coherence circuits and network interface controllers. A DSM system implements the shared-memory model on a physically distributed memory system.ĭSM can be achieved via software as well as hardware.

However, these systems offer a more portable approach to DSM system implementations. In contrast, software DSM systems implemented at the library or language level are not transparent and developers usually have to program them differently. When implemented in the operating system, such systems are transparent to the developer which means that the underlying distributed memory is completely hidden from the users. Software DSM systems can be implemented in an operating system, or as a programming library and can be thought of as extensions of the underlying virtual memory architecture. : 201 Distributed global address space ( DGAS), is a similar term for a wide class of software and hardware implementations, in which each node of a cluster has access to shared memory in addition to each node's private (i.e., not shared) memory.Ī distributed-memory system, often called a multicomputer, consists of multiple independent processing nodes with local memory modules which is connected by a general interconnection network. The term "shared" does not mean that there is a single centralized memory, but that the address space is shared-i.e., the same physical address on two processors refers to the same location in memory. In computer science, distributed shared memory ( DSM) is a form of memory architecture where physically separated memories can be addressed as a single shared address space. For the DGA awards, see Directors Guild of America Award.