Shared memory multiprocessors leonid ryzhyk april 21, 2006 1 introduction the hardware evolution has reached the point where it becomes extremely dif. The term processor in multiprocessor can mean either a central processing unit cpu or an inputoutput processor iop. Addressing partitioned arrays in distributed memory. The implication of our work is that efficient synchronization algorithms can be constructed in software for shared memory multiprocessors. Fast synchronization on sharedmemory multiprocessors.
An architectural approach zhen fang1, lixin zhang2, john b. Parallelization of nas benchmarks for shared memory. Research on the automatic distribution of data has been done for messagepassing, nonshared memory sys tems, e. Buffering, however, can cause logical problems in multiprocessors. Parallel implementation of the finite element method on. Scalable readerwriter synchronization for sharedmemory. Memory consistency models for sharedmemory multiprocessors.
Memory consistency models for sharedmemory multiprocessors kourosh gharachorloo december 1995 also published as stanford university technical report csltr95685. Smps dominate the server market, and are the building blocks for larger systems. Busbased shared memory multiprocessors symmetric memory multiprocessors smps. A distributed memory multiprocessor dmm is built by connecting nodes, which consist of uniprocessors or of shared memory multiprocessors smps, via a network, also called interconnection network in or switch. Multiprocessors are classified by the way their memory is organized. Scalable shared memory multiprocessors distribute memory among the processors and use scalable interconnection networks to provide high bandwidth and low latency communication. In a shared memory multiprocessor such as that shown in figure 1, private data caches have been shown to be quite effective in reducing the average delay to access the shared memory gottlieb1982, pfister1985. They provide a shared address space, and each processor has its own cache.
In a shared memory multiprocessor, there are more advantages in buffering memory requests, since each memory access has to traverse the memory processor interconnection and has to compete with memory requests issued by different processors. In these architectures a large number of processors share memory to support efficient and flexible communication within and between processes running on one or more operating systems. There are two basic types of mimd or multiprocessor architectures, commonly called shared memory and distributed memory multiprocessors. Barriers, likewise, are frequently used between brief phases of dataparallel algorithms e, g.
Performance evaluation of numa and coma distributed shared. The main task of the interconnection network is to figure 2. Speeding up unparallelized execution onshared memory multiprocessors conference paper pdf available may 1999 with 30 reads how we measure reads. Consider the purported solution to the producerconsumer problem shown in example 95. Shared memory multiprocessors issues for shared memory systems. Modeling sharedmemory multiprocessor systems with aadl. Shared memory multiprocessors can provide high processing power at relatively low cost.
Chapter 5 multiprocessors and threadlevel parallelism. A computer system in which two or more cpus share full access to a common ram 4 multiprocessor. Distributed shared memory dsm systems are becoming increasingly popular in high performance computing. Citeseerx memory consistency and event ordering in scalable. Greg plaxton department of computer science, university of texas at austin. We aim to derive from this general recommendations concerning the implementation of similar computations on shared memory multiprocessors. Thread scheduling for multiprogrammed multiprocessors nimar s. Algorithms for scalable synchronization on sharedmemory. Shared memory is physically distributed locally among processors nodes.
Exploration of distributed shared memory architectures for nocbased multiprocessors matteo monchiero gianluca palermo cristina silvano oreste villa dipartimento di elettronica e informazione politecnico di milano, milano, italy email. Numerous designs on how to interconnect the processing nodes and memory modules were published in the literature. A multiprocessor system is an interconnection of two or more cpus with memory and inputoutput equipment. The processors share a common memory address space and communicate with each other via memory. The effects of latency and occupancy in distributed shared. Lkerlevel interprocess communication for shared memory multiprocessors brian n. In addition, memory accesses are cached, buffered, and pipelined to bridge the gap between slow shared memory and fast processors. Owing to this architecture, these systems are also called symmetric sharedmemory multiprocessors smp hennessy. Programmers should be aware of the differences between the memory models of a multiprocessor and a uniprocessor. Information can therefore be shared among the cpus.
In this paper, we present hoard, an allocator for shared memory multiprocessors that combines the best features of monolithic and pureprivate heaps allocators. Time in multiprocessor system zlocal time 9program order 9interval between instructions elastic. Network function virtualization and messaging for non. Another type is the distributed memory or looselycoupled system. In a tightly coupled multiprocessor, a central memory system provides the same access time for each processor. In con trast, our work is oriented toward scalable shared memory multiprocessors. In this paper, we analyze the benefits and problems associated with the buffering of memory requests in shared memory multiprocessors. Shared memory multiprocessors are widely used as platforms for technical and commercial computing 2. Designing memory consistency models for shared memory multiprocessors by sarita vikram adve a thesis submitted in partial ful. Multiprocessors multiprocessors characteristics of. Exploration of distributed shared memory architectures for. A sharedmemory multiprocessor or just multiprocessor henceforth is a computer system in which two or more cpus share full access to a common.
The continuous growth in complexity of systems is making this task increasingly complex 7. 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. Previous results have suggested that the best policy choice often depends on the application. Another name for shared memory processors is parallel random access machine pram. Performance of multiprocessor interconnection networks computer. Memory access buffering in multiprocessors proceedings. The term also refers to the ability of a system to support more than one processor or the ability to allocate tasks between them. 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. Shared memory shared memory is more intuitive, but creates problems for both the programmer memory consistency, requiring synchronization and the architect cache coherency.
Noncoherent shared memory multiprocessors there are a number of advantages to multiprocessor hardware architectures that share memory. Scalable parallel sparse lu factorization methods on. Of the major design goals and key issues in multiprocessor operating systems. A surprisingly large fraction of os time 79% is spent on memory system stalls. Shared memory multiprocessors obtained by connecting full processors together processors have their own connection to memory processors are capable of independent execution and control thus, by this definition, gpu is not a multiprocessor as the gpu cores are not. Reducing contention in sharedmemory multiprocessors computer. A multiprocessor with local and global memory modules. Symmetric multiprocessors smp small number of cores share single memory with uniform memory latency distributed shared memory dsm memory distributed among processors nonuniform memory access latency numa processors connected via direct switched and nondirect multihop. Information can be passed by placing that in common global memory. Characteristics of multiprocessors university of babylon.
Distributed memory multiprocessors in fpgas francisco jos e alves correia pires thesis to obtain the master of science degree in electrical and computer engineering supervisor. Multithreading gives the illusion of multiprocessing including, in many cases, the performance with very little additional hardware. Userlevel interprocess communication for shared memory. The effects of latency and occupancy in distributed shared memory multiprocessors chris holt, mark heinrich, jaswinder pal singh, edward rothberg, and john hennessy submitted to jpdc, also stanford university technical report csltr95660 abstract. Memory architecture is an important component in a distributed shared memory parallel computer. Hybrid memory management for parallel execution of prolog. In a multiprocessor system all processes on the various cpus share a unique logical address space, which is mapped on a physical memory that can be. In addition, memory accesses are cached, buffered, and pipelined to bridge the gap between the slow shared memory and the fast processors. The main point of dsm is that it spares the programmer the concerns of message passing when writing applications that might otherwise have to use it.
Although this program works on current sparcbased multiprocessors, it assumes that all multiprocessors have strongly ordered memory. Carter1, liqun cheng1, michael parker3 1 school of computing university of utah salt lake city, ut 84112, u. Performance evaluation is a key technology for design in computer architecture. Extend from definitions in uniprocessors to those in multiprocessors memory operation. Hardware and software bottlenecks on largescale shared. This type of central memory system is often called main memory, shared memory, or global memory. A multiprocessor system with common shared memory is classified as a shared memory or tightly coupled multiprocessor. If this is occurring at the hardware level, then if processor p3 issues a memory read instruction for location 200, and processor p4 does the same, they both will be referring to the same physical memory cell. On a machine in which shared memory is distributed e. Large multiprocessors with numa many local memory accesses with the ability of bus snoop, an explicit directory about cache state can be used 222011 csc 258458 spring 2011 15. The study of operating systems level memory management policies for nonuniform memory access time numa shared memory multiprocessors is an area of active research. Cache coherence in busbased shared memory multiprocessors. Program transformations for cache locality enhancement on shared memory multiprocessors naraig manjikian doctor of philosophy graduate department of electrical and computer engineering university of toronto 1997 this dissertation proposes and evaluates compiler techniques that enhance cache locality. The term processor in multiprocessor can mean either a central processing unit.
The next wave of multiprocessors relied on distributed memory, where processing nodes have access only to their local memory, and access to remote data was accomplished by request and reply messages. Memory consistency models for shared memory multiprocessors kourosh gharachorloo december 1995 also published as stanford university technical report csltr95685. Cache coherency and memory consistency in noc based. Addressing partitioned arrays in distributed memory multiprocessors the software virtual memory approach rajeev barua david kranz anant agarwal laboratory for computer science massachusetts institute of technology cambridge, ma 029 may 6, 1996 abstract partitioning distributed arrays to ensure locality of reference is widely recognized as. A program running on any of the cpus sees a normal usually paged virtual address space. Thread scheduling for multiprogrammed multiprocessors. Sharedmemory multiprocessors multithreaded programming guide. Shared memory and distributed shared memory systems. Characteristics of multiprocessors computer organization. Working with multiprocessors multithreaded programming guide. Memory consistency and event ordering in scalable shared.
Optimizing ipc performance for sharedmemory multiprocessors. These structures are representative of the system structures for shared memory multiprocessors. We find that our version of unix accounts for 24% of the workloads total execution time. Compilelime optimization of nearneighbor communication for. The primary focus of this dissertation is the au tomatic derivation of computation and data partitions for regular scientific applications on scalable shared memory multiprocessors.
Levy university of washington interprocess communication ipc, in particular ipc oriented towards local cornmzmzcation. No coherence problem and hence no false sharing either. Lowlatency sharing and prefetching across processors. This thesis studies three shared memory architecturesnonuniform memory access numa with fullmapped directories, cacheonly memory architecture coma with fullmapped directories, and coma with directories based on a new design using binomial trees. The performance of spin lock alternatives for shared. This design is very different from earlier busbased multiprocessors and requires substantial modifications to the operating system to efficiently utilize the. Designing memory consistency models for sharedmemory. Algorithms for scalable synchronization on shared memory multirocessors o 23 be executed an enormous number of times in the course of a computation. In addition to this central memory also called main memory, shared memory, global memory, etc.
Download fulltext pdf download fulltext pdf optimizing ipc performance for shared memory multiprocessors article pdf available december 1995 with 197 reads. A shared memory multiprocessor is a computer system composed of multiple independent processors that execute different instruction streams. 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. The performance of spin lock alternatives for shared memory multiprocessors author. Owing to this architecture, these systems are also called symmetric shared memory multiprocessors smp hennessy. Multithreading lets you take advantage of multiprocessors, primarily through parallelism and scalability.
Sharedmemory multiprocessors 5 symmetric multiprocessors smps are the most common multiprocessors. The node controller handles all the memory coherency and io traffic going through the node. Numa and uma and shared memory multiprocessors computer. In contrast to message passing systems, shared memory multiprocessors allow for efficient data sharing, and thus are more suitable for execution models that exploit medium grain parallelism. This article gives guidelines to represent, with aadl, sharedmemory multiprocessing systems and their memory hierarchies while keeping a high level model of.
Using flynnss classification 1, an smp is a multipleinstruction multipledata mimd architecture. Shared versus distributed memory multiprocessors dtic. In addition to digital equipments support, the author was partly supported by darpa contract n00039. Memory consistency is directly interrelated to the processor interrogating memory. In fact, most commercial tightly coupled tightly coupled multiprocessors provide a cache memory with each cpu. Bus and cache memory organizations for multiprocessors by donald charles winsor chairman. All processors and memories attach to the same interconnect, usually a shared bus. Multiprocessors a sharedmemory multiprocessor is a computer system composed of multiple independent processors that execute different instruction streams. Shared memory multiprocessors 14 an example execution. Boosting the performance of shared memory multiprocessors.
A coherence protocol tomasevic93 is required in order. The implications of cache affinity on processor scheduling. The impact of memory models on software reliability in. Scalable readerwriter synchronization for shared memory multiprocessors john m. Bin lin department of computer science nov 25, 20 bin lin department of computer science cs533 fall 20 nov 25, 20 1 31. Its worstcase memory fragmentation is asymptotically equivalent to that of an optimal uniprocessor allocator.
Multiprocessing is the use of two or more central processing units cpus within a single computer system. Different solutions for smps and mpps cis 501martinroth. Additionally, dsm systems offer the ease of programming due to a global address spaces, similar to smps. Such systems can be considered scalable alternatives of conventional symmetric multiprocessors smps due to distributed memory. The only unusual property this system has is that the cpu can. A cache memory contributes in both hiding memory latency and reducing the traffic on the processor interconnection network of shared memory multiprocessors but it causes the coherence problem. Shared memory multiprocessors obtained by connecting full processors together processors have their own connection to memory processors are capable of independent execution and control thus, by this definition, gpu is not a. No all multiprocessors use shared bus for memory access it d t l. Program transformations for cache locality enhancement. Shared memory multiprocessors mem cis 501 martinroth.
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