In uniform memory access, bandwidth is restricted or limited rather than non uniform memory access. Physically centralized memory, uniform memory access uma a. In a uma architecture, access time to a memory location is independent of which processor makes the request or which memory chip contains the transferred data. Cpus share full access to a common ram multiprocessor system two types of multiprocessor systems uniform memory access uma all memory addresses are reachable as fast as any other address nonuniform memory access numa some memory addresses are slower than others. Wisconsin csece 752 advanced computer architecture i prof. Although all multiprocessors have the property that every cpu can address all of memory, some. Today, the most common form of uma architecture is the symmetric multiprocessor smp machine, which consists of multiple identical processors with equal level. Each processor has equal memory accessing time latency and access speed. Such machines are called nonuniform memory access numa. For optimal performance, the kernel needs to be aware of where memory is located, and keep memory used as close as possible to the user of the memory. Chapter 7 multicores, multiprocessors, and clusters. Shared memory multiprocessors tightly coupled systems 2. Multiprocessors 1 umd department of computer science. Uniform memory access uma in this model, all the processors share the physical memory uniformly.
Implicit transactional memory in kiloinstruction multiprocessors. Multiprocessors and multithreading computer science. In contrast, numa nonuniform memory access multiprocessors do not have this property. Numa, or non uniform memory access, is a shared memory architecture that. Sharedmemory multiprocessors are differentiated by the relative time to access the common memory blocks by their processors. Uma uniform memory access system is a shared memory architecture for the multiprocessors. Processors have faster access to memory modules that are closest. Numa non uniform memory access is a method of configuring a cluster of microprocessor in a multiprocessing system so that they can share memory locally, improving performance and the ability of the system to be expanded. It is applicable for general purpose applications and timesharing applications. Explicit synchronization can be used to control access to kernel data structures. Kernelkernel communication in a sharedmemory multiprocessor. The total memory is 232bytes, divided up into 226cache lines of 64 bytes each. In this model, a single memory is used and accessed by all the processors present the multiprocessor system with the help of the interconnection network.
All the processors in the uma model share the physical memory uniformly. Nonuniform memory access numa is a computer memory design used in multiprocessing. Cpu cpu cpu cpu main memory cache cache cache cache all main memory takes the same time to access scales only to 4, 8 processors. Smp physically distributed memory, nonuniform memory access numa note. Chapter 9 multiprocessors and clusters matter which word is requested. Multiprocessors distributed operating systems distributed operating systems types of distributed computes multiprocessors memory architecture nonuniform memory architecture threads and multiprocessors multicomputers network io remote procedure calls distributed systems distributed file systems 4 42 weve been encountering them all semester. Mem cpu cpu cpu cpu cache mem cache mem cache mem cache rarer and more. Non uniform memory access numa is a computer memory design used in multiprocessing, where the memory access time depends on the memory location relative to the processor. Numa multiprocessors shared memory one logical address space can be treated as shared memory use synchronization e. Todays largescale numa machines use multistage interconnection networks instead of bus. Shared memory parallel architecture multiprocessor.
Multiprocessors and clusters rosehulman institute of. A smp is a system architecture in which all the processors can access each memory block in the same amount of time. All the processors have equal access time to all the memory words. Simple but effective techniques for numa memory management. In the second style, some memory accesses are faster than others depending on which processor asks for which word. Memory management for largescale numa multiprocessors abstract largescale shared memory multiprocessors such as the bbn butterily and ibm rp3 introduce a new level in the memory hierarchy. A taxonomy of parallel computers uma uniform memory access. The memory is statically allocated among the nodes, with 016m in node 0, 16m32m in node 1, and so on. These machines are called uma uniform memory access multiprocessors. In an uma architecture, access time to a memory location is independent of which processor makes the request or which memory chip contains the transferred data. Memory system performance in a numa multicore multiprocessor pdf. Pdf system design of a ccnuma multiprocessor architecture. Smp physically distributed memory, non uniform memory access numa note. Memory access between processor core to main memory is not.
Winter 2006 cse 548 multiprocessors 9 mimd highend higher bandwidth, multiplepath interconnect more scalable more complex cache coherency protocol if shared memory longer latencies physically distributed memory nonuniform memory access numa machine could have processor clusters. Why this difference exists will become clear later. Three most common shared memory multiprocessors models are. Difference between uniform memory access uma and non. Such machines are called uniform memory access uma multiprocessors or symmetric multiprocessors smp. The two basic types of shared memory architectures are uniform memory access uma and non uniform memory access numa, as shown in fig. For example, in uniform memory access uma multiprocessors, it is easy for all processors to share the code and data of the operating system. The nodes are connected by an interconnection network, as shown in fig. The second group consists of machines with physically distributed.
Multiprocessors two main kinds of shared memory multiprocessor. Shared memory multiprocessors slides developed by amir roth of university of pennsylvania with sources that included university of wisconsin slides by mark hill, guri sohi, jim smith, and david wood. Largescale shared memory multiprocessors such as the bbn butterfly and ibm rp3 introduce a new level in the memory hierarchy. One reason for the success of shared memory multiprocessors, as opposed to other parallel architecture styles, is their intuitive programming style and relatively low parallelization effort. This type of centralized shared memory architecture is currently by far the most popular organization. Oct 25, 2018 uma uniform memory access system is a shared memory architecture for the multiprocessors. Today, the most common form of uma architecture is the symmetric multiprocessor smp machine, which consists of multiple identical processors with equal level of access and access time to the shared memory. Multiprocessors with nonuniform memory access times introduce the problem of placing data near the processes that use them, in order to improve performance. Large count multiprocessors are being built with nonuniform memory access numa times access times that are dependent upon where within the machine a piece of memory physically resides.
Shared memory is more intuitive, but creates problems for both the programmer memory consistency, requiring synchronization and the architect cache coherency. Definition of uma uma uniform memory access system is a shared memory architecture for the multiprocessors. Difference between uma and numa with comparison chart. Parallel processing and multiprocessors why parallel processing. Main memory if present is equally far from all processors, but caches are not, and caches are the dominant determinant of memory performance. Chapter 8 multiprocessors umas for uniform memory access. Hence, not all processors have equal access times to the memories of all smps. Numa and uma and shared memory multiprocessors computer. Bus and cache memory organizations for multiprocessors by donald charles winsor chairman. Pdf memory management for largescale numa nonuniform. Multiprocessors can be categorized into three sharedmemory model which are. Parallel computer architecture models tutorialspoint. As chip multiprocessors cmps pick up steam as the mainstream processor design choice, how non uniform distribution of memory accesses across cache sets affects the cache management of cmps is. Under numa, a processor can access its own local memory faster than nonlocal memory memory local to another processor or memory shared between processors.
Multithreading gives the illusion of multiprocessing including, in many cases, the performance with very little additional hardware. An operating system for these numa nonuniform memory access. This architecture is used by symmetric multiprocessor smp computers. There are 3 types of buses used in uniform memory access which are. This capability is often referred to as uma or uniform memory access. Also symmetric multiprocessors smp uniform memory access uma all memory locations have similar latencies data sharing through memory readswrites p1 can write data to a physical address a, p2 can then read physical address a to get that data problem. Trevor mudge the single shared bus multiprocessorhas been the most commerciallysuccessful multiprocessorsystem design up to this time, largely because it permits the implementation of ef. All memory units are associated with processors to retrieve information from another processors memory a message must be sent there uniform memory all processors take the same time to reach all memory locations nonuniform numa memory memory access is not uniform characteristics of multiprocessors. Another name for shared memory processors is parallel random access machine pram.
Numa multiprocessors example of cm in cmu cm is the oldest known example of numa architecture. Coherence controller architectures for smpbased ccnuma multiprocessors. Understanding how nonuniform distribution of memory accesses. Uma is a shared memory architecture used in parallel computers. Shared memory multiprocessors recall the two common organizations. The architecture of such multiprocessors is the topic of section 8. Shared memory shared memory is more intuitive, but creates problems for both the programmer memory consistency, requiring synchronization and the architect cache coherency. Uniform memory access uma is a shared memory architecture used in parallel computers. Multiprocessor, parallel processing oakland university. An experimental evaluation of processor poolbased scheduling for.