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Distributed shred memory architecture
Distributed shared memory (DSM) is a memory architecture where physically separate memories can be addressed as a single logical address space. In a DSM system, data moves between nodes' main and secondary memories when a process accesses shared data. Each node has a memory mapping manager that maps the shared virtual memory to local physical memory. DSM provides advantages like shielding programmers from message passing, lower cost than multiprocessors, and large virtual address spaces, but disadvantages include potential performance penalties from remote data access and lack of programmer control over messaging.
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Distributed shred memory architecture
- 1. DSM architecture, advantages &disadvantages Subject: DOS CE-B Maulik togadiya
- 2. What is sharedmemory? On-Chip Memory CPU Memory CPU1 Memory CPU4 CPU2 CPU3 Chip package Address and data lines Connecting the CPU to the memory extension A single-chip computer A hypothetical shared-memory Multiprocessor.
- 3. Introduction Distributed sharedmemory (DSM) is a form of memory architecture where the (physically separate) memories can be addressed as one (logically shared) address space. Here, the term "shared" does not mean that there is a single centralized memory but "shared" means that the address space is shared. The shared memory model provides a virtual address space shared between all nodes. The overcome the high cost of communication in distributed systems, DSM systems move data to the location of access.
- 4. How it works? Data moves between main memory and secondary memory (within a node) and between main memories of different nodes. When a process accesses data in the shared address space, the mapping manager maps shared memory address to physical memory (local or remote).
- 5. DSM architecture Highspeed communication network is used for connecting nodes. A simple message passing system allows on different node to exchange message with each other. Memory mapping manager routine in each node maps local memory onto the shared virtual memory. For mapping operation, the shared memory space is partitioned into blocks. The main memory of individual nodes is used to cache of shared memory space.
- 6. Memory Mapping Manager Memory Mapping Manager Memory Mapping Manager Shared Memory NODE 1NODE 2 NODE 3 Communication network
- 7. Systems thatsupport DSM,data moves between secondary memory and main memory as well as between main memories of different nodes. When process access data in shared address space, a mapping manager maps the shared memory address to the physical memory. The mapping manager is layer of software implemented either in the operating kernel or as runtime library routine. DSM architecture
- 8. Advantages Shields programmerfrom send/receive primitives. DSM is usually cheaper than using multiprocessor system. DSM provides large virtual memory space. DSM programs portable as they use common DSM programming interface. It can handle complex and large data bases without replication or sending the data to processes. No memory access bottleneck.
- 9. Disadvantages Must providefor protection against simultaneous access to shared data such as lock.. It could cause a performance penalty. Little programmer control over actual messages being generated. Performance of irregular problems could be difficult. Programmers need to be understand consistency model to write correct programs.