L. Iftode, J.P. Singh, and K. Li. Scope consistency: A bridge between release consistency and entry consistency. In Proceedings of the 8th Symposium on Parallel Algorithms and Architecture, June 1996.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....consistency models can often be introduced without any or with only minor code changes. Relaxed consistency models have been extensively researched in the realm of Software Distributed Shared Memory (SW DSM) 13] 14] 15] and implemented in the form of relaxed consistency protocols [16] [17]. While latter ones are not applicable or necessary in HW DSM scenarios, the concept of relaxed consistency models can be applied in a rather straightforward way. The result for the programmer is a secure, global memory abstraction. III. LOCAL CONSISTENCY SCHEMES Based on these design ....

....when accessed outside a critical region, but rather between two barrier operations. Depending on a code s synchronization pattern, this can lead to fewer invalidations and improved performance. For the programmer, the result is a slightly more relaxed consistency model with two consistency scopes [17]. Due to the inherent separation between locks and barriers in most shared memory codes, however, it can be expected that the impact on the programming model will be negligible for most codes. This new scheme can be implemented by adding a second consistency flag to each cache line that mirrors ....

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L. Iftode, J. Singh, and L. Li, "Scope Consistency: A Bridge between Release Consistency and Entry Consistency," Theory of Computer Systems, vol. 31, pp. 451--473, 1998.

.... efficiently supported in software distributed shared memory (SDSM) systems [14] In an SDSM [11, 3, 10, 7] twodimensional distributions can cause a large amount of excess communication between nodes, even when using relaxed memory consistencies such as eager write shared [3] lazy write shared [10, 7, 8], or a hybrid [1] The primary problem is that two dimensional distributions force nodes to share data in two dimensions, but the data is organized in either a row or column major layout. Consequently, nodes share both rows and columns, meaning that every element in a page must be write shared, ....

L. Iftode, J. Pal Singh, and K. Li. Scope consistency: a bridge between release consistency and entry consistency. In Proceedings of the 8th Annual ACM Symposium on Parallel Algorithms and Architectures, June 1996.

....by looking at what other threads have read and written. The underlying protocol then flushes data only where needed and potentially only to those threads requiring that data. The release operation is a completely thread local operation requiring no interaction with main memory. Scope consistency [26] sends only the updates made within one (dynamic) scope to other threads. Updates made while in an outer scope remain cached. Again, the implementation is allowed to send updates to a variable early and an implementation is also allowed to prefetch over a scope entry point. Java supports a weakly ....

L. Iftode, J. P. Singh, and K. Li. Scope Consistency: A Bridge between Release Consistency and Entry Consistency. In Proceedings of the 8th ACM Annual Symposium on Parallel Algorithms and Architectures (SPAA'96), pages 277--287, Padua, Italy, 1996.

....the memory, which needs to be compensated in order to reach a stable and reliable environment for the user. This, however, can be easily accomplished by applying the formalism of relaxed consistency models, which are well known from the SW DSM domain [16, 18, 5] and research in this area (e.g. [13, 10, 21]) has shown that relaxed consistency models only lead to a minimal impact on the programmability. Hence, the ease of use is maintained despite the missing hardware coherency mechanisms. Non coherent systems, in coordination with an appropriate hardware coherency management, are therefore ....

....and retrieve remote data, an operation unnecessary in the approach discussed in this paper due to the assumed HW DSM capabilities. 4 Implementing Relaxed Consistency Models The work on SW DSM systems has lead to the definition and implementation of several different consistency models (e.g. [13, 10, 4]) Almost all of them, most prominently Release Consistency [13] can be implemented on non coherent hardware by combining the use of synchronization operations in user applications, like locks and barriers, with cache invalidations and write buffer flushes as introduced above. In the following, ....

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L. Iftode, J. Singh, and L. Li. Scope Consistency: A Bridge between Release Consistency and Entry Consistency. Theory of Computer Systems, 31:451--473, 1998.

.... Herlihy s thesis work [19] LOOM [24] and the more recent pickling (serialization) of Java [32] Several software only S DSM systems have proposed that programmers explicitly identify the data to be modified in a critical section, either directly [23, 20] or by explicit [36, 4] or implicit [22] association with a synchronization object (lock) In contrast to systems that maintain coherence at the level of virtual memory pages, software only S DSM is less vulnerable to false sharing. In a similar vein, views in InterWeave relieve the system of the need to inform processes of updates to ....

L. Iftode, J. P. Singh, and K. Li. Scope Consistency: A Bridge Between Release Consistency and Entry Consistency. In Proc. of the 8th Annual ACM Symp. on Parallel Algorithms and Architectures, pages 451--473, Padua, Italy, June 1996.

....access after an acquire, instead of at the time of the acquire, which leads to a reduced number of messages transferred over the network when compared with the earlier version of the RC models. Two more variations of the RC model have been proposed: entry consistency [18] and scope consistency [19] models. Unlike the four RC models stated earlier, these models support somewhat different programming paradigm, in which the shared data in the program must be specifically associated with the synchronization objects. The entry consistency(EC) model guarantees that shared data becomes consistent ....

L. Iftode, J.P. Singh, and K. Li, "Scope consistency: A bridge between release consistency and entry consistency," in In Proc. 8th ACM Annual Symp. on Parallel Algorithms and Architectures, pages 277-287, Jun. 1996.

....the synchronization variables are subject to consistency. The main problem with this approach is that the user explicitly identifies the synchronization variables, the shared data that needs consistency, and the binding between the shared data and the synchronization variables. Scope consistency [60] tries to make the binding between shared data and synchronization variables implicit. The synchronization variables define scopes through which the memory is viewed, and an implicit association of data (pages) with scopes is achieved dynamically when a write access occurs inside the scope. In ....

....work is to make parallelism implicit by using a suitable data layout and by automatically ensuring consistency, with system support. The data layout is based on a general partitioning and a relaxed consistency scheme. Work on relaxed consistency originates in the virtual shared memory techniques [21, 60,61,72, 94]. One way of relaxing a strict consistency model is to ensure consistency only at synchronization points. In a software maintained consistency, the synchronization points can be either indicated by the user (programmer) or discovered by a compiler. The first option allows for high optimizations, ....

[Article contains additional citation context not shown here]

L. Iftode, J. P. Singh, and K. Li. Scope consistency: A bridge between release consistency and entry consistency. In Proc. of the 8th ACM Annual Symp. on Parallel Algorithms and Architectures (SPAA'96), pages 277--287, 1996.

....directories. Since our approach extends data coherency techniques, they are applicable to both hardware and software DSM systems. We are continuing to investigate ways to reduce the overhead of our approach. One possibility is to extend our approach to relaxed memory consistency models ( 3][5][7] in which case coherency is maintained only on locks. In addition, it is also possible to limit the amount of rollback caused by errors. We propose barriers (Global and Partial) with communicating processes such that all processes synchronizing on a barrier maintain consistent checkpoints ....

L. Iftode, et. al. "Scope consistency: A bridge between Release consistency and Entry consistency", Proc of the 8 th Annl ACM Symposium on Parallel Algorithms and Architectures. 1996.

....memory model that we used in [27, 26] I include the computation centric theory in this dissertation because it introduces concepts, such as constructibility, that I think will be important to other researchers who want to improve upon location consistency and BACKER. Most existing memory models [47, 3, 70, 64, 90, 20, 84] are expressed in terms of processors acting on memory. We call these memory models processor centric; the memory model specifies what happens when a processor performs some action on memory. In contrast, the philosophy of the computation centric theory is to separate the logical dependencies ....

L. IFTODE,J.P.SINGH, AND K. LI, Scope consistency: A bridge between release consistency and entry consistency, in Proceedings of the Eighth Annual ACM Symposium on Parallel Algorithms and Architectures (SPAA), Padua, Italy, June 1996, pp. 277--287.

....such a history mechanism that does not depend on program data sets or user interaction to improve performance. A implcmctatio of software scopc cosistcc l. In order to address the preb leto of false sharing commonly found in DSM systems, we introduce a software variation of scope consistency [23] that has a performance advantage for spe cific classes of parallel programs. Additionally, the use of scope consistency facilitates the use of multicast for those programs that make use of small, inde pendent critical sections. A DSM s stem for Widows NT. Brazes represents the first ....

....performance tuning techniques outlined in Section 2.4. 2.3 Software Scope Consistency Scope consistency was introduced as an enhancement to the SHRIMP AURC sys tem [22] and is a refinement of release consistency. A discussion of scope consistency and its hardware implementation can be found in [23]. Basically, scope consistency divides the execution of a program into scopes, and shared data is only guaranteed to be consistent at the end of a scope. Scopes are characterized as global or local scopes. Global scope delimiters include global synchronization events such as barriers. After a ....

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L. Iftode, J. Singh, and K. Li. Scope consistency: A bridge between release con- sistency and entry consistency. In The $th Amual A CM S!/mposium o Parallel Algorithms ad Architectures, June 1996.

....to use release consistency. It implements multiple memory consistency protocols including sequential and release consistency. Entry consistency is first introduced in Midway system. Other relaxed memory consistency, like the lazy release consistency [41] used in TreadMark and the scope consistency [30], has no direct relation to our system and is not discussed. 7.1.4 Fault tolerant Computing Fault tolerant systems can be categorized according to their approach to handle failures: systems that are designed to handle failures as their first priority, and systems that provide fault tolerance as ....

L. Iftode, J. Singh, and K. Li. Scope consistency: A bridge between release consistency and entry consistency. In Proceedings of the ACM Symposium on Parallel Algorithms and Architectures, 1996.

....between the programmer and the SVM) This coherent modification of distributed data is achieved by a cache coherence protocol. As different applications require to manage data in different ways, several protocols have been proposed, like the lazy release consistency [12] or the scope consistency [11]. To implement a protocol, most software SVM use the paging mechanism of common processors to detect access to data. On each node, the address space elementary unit is a page (typically 4 to 8 Kbytes) Read and write access to a page can be individually set. If a SVM system must detect, for ....

L. Iftode, J. P. Singh, and K. Li. Scope consistency: A bridge between release consistency and entry consistency. In Proc. of the 8th ACM Annual Symp. on Parallel Algorithms and Architectures (SPAA'96), pages 277--287, June 1996.

....for optimization, the memory might enforce fewer guarantees. Or to make the programmer s job easier the memory might enforce more guarantees. Many choices have been made along this ease of use e#cient implementation continuum. The results are the consistency models described in the literature [5, 13, 18, 21, 22, 24, 25, 28, 29, 31, 34, 39] Application Program Consistency Model # # Read and Write Operations # # Values Returned by Reads Shared Memory API Memory Implementation (Black Box) Figure 1.1: Shared Memory as an API This leads to the idea of shared memory as an application programming interface (API) as shown in ....

....model, but sends updates as late as possible. The distinction between release and weak consistency is that release forces the program to give more detailed instructions on what must be up to date at a synchronization. This trend is continued with entry consistency [13] and scope consistency [29]. In entry consistency [13] each synchronization variable is associated with one or more ordinary variables. Acquires and releases only bring up to date those ordinary variables associated with a particular synchronization variable. In scope consistency [29] this set of variables is not static, ....

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L. Iftode, J. P. Singh, and K. Li. Scope consistency: A bridge between release consistency and entry consistency. Technical report, Princeton University, 1996. 86

....imposed by the different systems; the actual coherence actions taken by each system are only overviewed. 1 We claim that all our systems are based on the EC model, even though some researchers consider systems that transparently associate locks and data to be based on Scope Consistency (ScC) [7]. We belong to the group of researchers that prefer the more abstract definition of EC, under which the specific way the lock data association is accomplished is an implementation issue that is independent of the consistency model. Thus, we regard ScC as an implementation of EC, rather than a new ....

....as lock unlock and barrier. However, not all programs that execute correctly under other relaxed consistency models are guaranteed to execute correctly under EC, the consistency model of all systems in the AEC family. To run correctly under EC the application must satisfy the following conditions [7]: a) lockprotected modifications to shared data are not expected to be visible at processor p before at least one of the locks that protect the data is acquired by p; and (b) shared data modifications not protected by locks are not expected to be visible before the next barrier. Although program ....

[Article contains additional citation context not shown here]

L. Iftode, J.P. Singh, and K. Li. Scope Consistency: A Bridge Between Release Consistency and Entry Consistency. Theory of Computing Systems, 31:451--473, 1998.

....As the number of machines increases, providing consistency among the machines becomes more costly. Consequently, selection of the most appropriate consistency protocol becomes very important for large scale multicomputers. Past DSM research has resulted in a variety of consistency protocols [5, 6, 8, 13]. However, the most appropriate consistency protocol for a given application is difficult to identify and depends on a wide range of factors. In most systems, the application is stuck with whatever consistency protocol the DSM provides. Some recent work, however, has explored the concept of ....

Liviu Iftode, Jaswinder Pal Singh, and Kai Li. Scope consistency: A bridge between release consistency and entry consistency. In Proceedings of the Annual ACM Symposium on Parallel Algorithms and Architectures, Jun 1996.

....to shared pages) until lock release operations, so that messages can be coalesced and the negative impact of false sharing be alleviated. TreadMarks [19] and ADSM [20] delay the coherence transactions even further, until the next lock acquire operation. The Midway [4] and Scope Consistency (ScC) [13] systems also delay communication and coherence operations until a lock acquire transaction, but restrict these operations to the data that are associated with the lock variable. Although effective at improving the performance of software DSMs, these protocols still involve a substantial amount ....

....model must be synchronized with mutual exclusion lock and barrier primitives. However, not all programs that execute correctly under other relaxed consistency models are guaranteed to execute correctly under EC. To run correctly under EC the application must satisfy the following conditions [13]: ffl lock protected modifications to shared data are not expected to be visible at processor p before at least one of the locks that protect the data is acquired by p; and 6 ffl shared data modifications not protected by locks are not expected to be visible before the next barrier. Although ....

L. Iftode, J.P. Singh, and K. Li. Scope Consistency: A Bridge Between Release Consistency and Entry Consistency. Theory of Computing Systems, 31:451--473, 1998.

....implementation of the Entry Consistency model. The system is objectbased and requires the programmer to associate shared data with synchronization objects. This burden on the programmer led to the recent proposal of two variations derivations of the Entry Consistency model: Scope Consistency (ScC) [9] and Affinity Entry Consistency (AEC) 14] ADSM differs from these approaches in several ways, the most important of which are the programming 17 model, the details of the consistency model implemented, and the coherence strategy applied. We address each of these differences in turn. Just like ....

L. Iftode, J.P. Singh, and K. Li. Scope Consistency: A Bridge Between Release Consistency and Entry Consistency. In Proceedings of the 8th Annual ACM Symposium on Parallel Algorithms and Architectures, June 1996.

....performance to clients using them [15] These caches are limited to the consistency mechanisms provided by the Web, and are passive elements; they do not accept updates from clients. Distributed shared memory systems take advantage of locking mechanisms to optimize data movement and invalidation [2,8,12]. Programs that correctly lock data see pessimistic consistency semantics. Munin allows applications to annotate data to expose application knowledge to further optimize data movement [3] GeoCasting [17] provides broadcasts that are limited to a physical area. Distance based discovery combines ....

Iftode, L., J. P. Singh, and K. Li. Scope consistency: a bridge between release consistency and entry consistency. Eighth Annual ACM Symposium on Parallel Algorithms and Architectures, p.451-73. Jun 1996, Padua, Italy .

....programmers. A relaxed model can reduce data traffic in the netThe research was supported by the Hong Kong RGC grant HKU 7032 98E HKU RGC grant HKU 7030 97E. work while maintaining memory consistency. Examples are lazy release consistency (LRC) 1] in TreadMarks [7] or scope consistency (ScC) [2] in JIAJIA V1.1 [5] Other works try to reduce the data traffic by proposing efficient memory coherence protocols, like the home migration protocol in JIAJIA V2.1 [8] In this paper, we introduce the JUMP DP DSM system. It makes use of the migratinghome protocol to implement the ScC model. The ....

L. Iftode, J. P. Singh and K. Li. Scope Consistency: A Bridge between Release Consistency and Entry Consistency. In Proc. of the 8th ACM Annual Symposium on Parallel Algorithms and Architectures (SPAA'96), pages 277-287, June 1996.

....computing. Distributed systems constructed of industry standard multiprocessors and networks offer an excellent price to performance ratio compared with monolithic multiprocessor systems, especially for large systems. Advances in user level communication mechanisms [4] memory consistency models [12, 14], and network technologies (e.g. 4] and [9] have improved the performance of these systems significantly. However, several issues limit the widespread adoption of clustered multiprocessors for distributed parallel computing. First, clusters of multiprocessors have an increased risk of failure ....

....communication through false sharing. Shared memory coherence issues increase in complexity if relaxed consistency models are employed [23] For example, Brazos implements a multiple writer protocol and two relaxed memory consistency models: Release Consistency (RC) 8] and Scope Consistency (ScC) [12]. Both of these models allow multiple nodes to modify different portions of a virtual page concurrently, and only perform coherence or consistency actions at specific synchronization points. t1 x = 9 MigrateMe(2) t1 y = x y = 9 iff N1 and N2 synchronize before assignment Node N1 Node N2 ....

L. Iftode, J. P. Singh, and K. Li. Scope Consistency: A Bridge between Release Consistency and Entry Consistency. In Proceedings of the 8th Annual ACM Symposium on Parallel Algorithms and Architectures, pp. 277-287, June 1996.

....or switch between certain aspects of a protocol on the y, possibly even during runtime, i.e. between distinct stages of execution. The properties of a DSM protocol include the following aspects: The Consistency can be sequential, release, entry or scope, just to name the most popular ones [17, 14, 4, 12]. The Granularity of a DSM object can be at the level of a byte, a word, a page or an arbitrary size of an object. This is the level at which the internal DSM protocols handle objects. The Sharing Resolution within a DSM object may be at the level of a bit, a byte, a word or a double word. This ....

....DSM system have been realized for a number of consistency models, sometimes even with an object oriented approach. Implementations of sequential consistency, such as by Li and Hudak [17] were non object based. The models of release and scope consistency typically do not build on object either [15, 12]. Entry consistency, on the other hand, is often associated with the object oriented paradigm due to the granularity of the protocol [3, 7] The Panda system [2] used similar design goals but focused on transaction based DSMs and persistent objects based on C language extensions that were not as ....

Liviu Iftode, Jaswinder Pal Singh, and Kai Li. Scope consistency: a bridge between release consistency and entry consistency. In Symposium on Parallel Algorithms and Architectures, pages 277-287, June 1996.

....Athens, GA 30602. Email:dkl cs.uga.edu z Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, IN 46556. Email: vin cse.nd. edu 1 between nodes, even when using relaxed memory consistencies such as eager write shared [CBZ91] lazy write shared [KDCZ94, Ift98, IPL96] or a hybrid [ACL 99] The primary problem is that two dimensional distributions force nodes to share data in two dimensions, but the data is organized in either a row or column major layout. Consequently, nodes share both rows and columns, meaning that every element in a page must be ....

Liviu Iftode, Jaswinder Pal Singh, and Kai Li. Scope consistency: a bridge between release consistency and entry consistency. In Proceedings of the 8th Annual ACM Symposium on Parallel Algorithms and Architectures, June 1996.

....machines. As the number of machines increases, providing consistency among the machines becomes more costly. Consequently, selection of the most appropriate consistency model becomes very important for large scale multicomputers. Past DSM research has resulted in a variety of consistency models [5, 6, 8, 13]. However, the most appropriate consistency model for a given application is difficult to identify and depends on a wide range of factors. In most systems, the application is stuck with whatever consistency model the DSM provides. Some recent work, however, has explored the concept of adaptive ....

Liviu Iftode, Jaswinder Pal Singh, and Kai Li. Scope consistency: A bridge between release consistency and entry consistency. In Proceedings of the Annual ACM Symposium on Parallel Algorithms and Architectures, Jun 1996.

....encoding and decoding diffs in multiple writer protocol are time intensive, and virtual page protection and segment violation interrupt introduce much system overhead. Many new techniques have been proposed to reduce above two overheads in the past, such as relaxed memory consistency models [2, 3, 4] to reduce the frequency of communication, multiple writer protocol to reduce the effect of false sharing[5] and the help of hardware [6] et.al. The performance of recent software DSM systems made great progress in comparison with early systems[1] However, according to some recent performance ....

....processor. Reference to a non home page will cause the delivery of a SIGSEGV signal. The SIGSEGV handler then maps the faulting page to the global address of the page in local address space. Multiple writer technique is employed to alleviate false sharing. JIAJIA implements scope consistency (ScC)[4] which is even lazier than lazy release consistency (LRC) 2] ScC does not require to implement the complete happen before 1 relation. Instead, it only requires the last interval of the releaser to be visible to the acquiring processor on an acquire. The unique characteristic of JIAJIA is the ....

[Article contains additional citation context not shown here]

L. Iftode, J. P. Singh, and K. Li. Scope consistency: A bridge between release consistency and entry consistency. In Proc. of the 8th ACM Annual Symp. on Parallel Algorithms and Architectures (SPAA'96), pages 277--287, June 1996.

....in the local cache. If the number of locally kept remote pages is larger than the maximum number allowed, some aged cache pages must be replaced (unmapped) to make room for the new page. Multiple writer technique is employed to alleviate false sharing. JIAJIA implements the scope consistency (ScC)[8] which is even lazier than lazy release consistency (LRC) 11] JIAJIA provides three types of synchronization mechanisms: lock, barrier, and condition variables. Currently, home migration scheme is supported by JIAJIA, according to the information of access patterns counted by run time library. ....

L. Iftode, J. P. Singh, and K. Li. Scope consistency: A bridge between release consistency and entry consistency. Theory of Computing Systems, 31(4):451--473, July/August 1998.

....of the 10th ACM Symposium on Parallel Algorithms and Architectures (SPAA) June 28 July 2, 1998 online algorithm. The computation centric theory is based on the two concepts of a computation and an observer function. Most existing memory models [DSB86, AH90, Goo89, GLL 90, KCZ92, BZS93, ISL96] are expressed in terms of processors acting on memory. We call these memory models processor centric; the memory model specifies what happens when a processor performs some action on memory. In contrast, the philosophy of this paper is to separate the logical dependencies among instructions (the ....

Liviu Iftode, Jaswinder Pal Singh, and Kai Li. Scope consistency: A bridge between release consistency and entry consistency. In Proceedings of the Eighth Annual ACM Symposium on Parallel Algorithms and Architectures (SPAA), pages 277--287, Padua, Italy, June 1996.

....volume rendering algorithms on different hardware shared address space architectures, we explore both the old and new parallel shear warper on a SVM platform. 6.5. 1 SVM Experimental Environment We use the SVM platform simulating all software homebased lazy release consistency (HLRC) protocol [7]. It models an architecture of SMP nodes connected with a commodity interconnect Myrinet. Each node has 4 processors, and 1 I O bus network interface. It assumes 200MHz processors, 400MB sec memory buses and 100MB sec I O buses. The width of the memory and I O buses are 8 bytes and 4 bytes ....

Iftode L., Singh J. P., and Li K. Scope Consistency: a Bridge Between Release Consistency and Entry Consistency. In Proceedings of the 8th Annual ACM Symposium on Parallel Algorithms and Architectures, June 1996.

....that they do not fill in our experiments. Network links operate at processor speed and are 16 bits wide. We assume a fast messaging system [19] as the basic communication library. The all software SVM platform we use simulates an all software home based lazy release consistency (HLRC) protocol [33], which has memory overhead and scalability advantages over non home based protocols such as that in TreadMarks [43] The HLRC protocol assigns each page to a home node. To alleviate the false sharing problem at page granularity, HLRC implements a multiple writer protocol based on using twins ....

L. Iftode, J. P. Singh, and K. Li. Scope consistency: a bridge between release consistency and entry consistency. In Proceedings of the 8th Annual ACM Symposium on Parallel Algorithms and Architectures, June 1996.

....in SVM systems can bring prefetching to hide latency and amortize communication overhead if the whole page contains useful data. On the other hand, fragmentation and false sharing can easily occur due to the large page granularity of coherence. Protocols using relaxed memory consistency models [24, 45, 4, 32] are used to alleviate these interactions. The protocols delay the coherence transactions to synchronization events, thus reducing the frequency of protocol operations and page misses. As a result, however, this makes the synchronization expensive, as well as the protocol overheads. Moreover, ....

L. Iftode, J. P. Singh, and K. Li. Scope consistency: a bridge between release consistency and entry consistency. In Proceedings of the 8th Annual ACM Symposium on Parallel Algorithms and Architectures, June 1996.

....of such a system, several copies of a piece of data are made using caches. Therefore a cache coherence protocol is needed to guarantee a coherent view of the system. Since the first protocol, several ones have been proposed like the lazy release consistency [7] or the scope consistency [6]. However a protocol aims at optimizing a limited range a application sharing patterns. Therefore a general purpose SVM must integrate several protocols. However this static approach cannot take into account new technology like Remote Memory Access [5] Therefore protocols should be dynamically ....

L. Iftode, J. P. Singh, and K. Li. Scope Consistency: A Bridge between Release Consistency and Entry Consistency. In Proceedings of the 8th Anual ACM Symposium on Parallel Algorithms and Architectures, June 1996.

....supported by three different consistency protocols. The first consistency model offers the widely used though fairly inefficient sequential consistency [16] model. This model is supported by single writer as well as multiple writer protocols. Secondly, the distributed lock based scope consistency [14] is implemented. Our main goal in this project is to examine the impact of efficient distributed synchronization protocols to the performance of a SVM system. 4.2 Memory Consistency Models Uniprocessor systems present a simple model of the memory to the programmer. A read operation always ....

....the last written value until the next write operation occurs. When multiple processors are involved, the memory model becomes more complex because the definitions of last value written , subsequent read and next write become unclear. Hence, several consistency models have been proposed [5,6,10,14,15] that place specific requirements on the order that shared memory accesses from one processor are observed by other processors. In other words, memory consistency models define which orderings are legal Table 2: Run times (in seconds) for different benchmark problem (N states the total number of ....

[Article contains additional citation context not shown here]

Iftode, L.; Singh, J. P.; Li, K.: Scope Consistency: A Bridge between Release Consistency and Entry Consistency. In Proc. of the 8th ACM Annual Symp. on Parallel Algorithms and Architectures (SPAA`96), June 1996

....server push and append only data. While WebOS concentrates on the building blocks one might use to create an automatic replica management system, our concern is that system itself. Distributed shared memory systems take advantage of locking mechanisms to optimize data movement and invalidation [2,11,16]. Programs that correctly lock data see pessimistic consistency semantics. Munin [4] enables cooperative applications to annotate data to expose application knowledge to further optimize data movement. Khazana [5] is a distributed middleware service that provides an abstraction similar to ....

Iftode, L., J. P. Singh, and K. Li. Scope consistency: a bridge between release consistency and entry consistency. Eighth Annual ACM Symposium on Parallel Algorithms and Architectures, p.451-73. Jun 1996, Padua, Italy.

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L. Iftode, J. P. Singh and K. Li. Scope Consistency: A Bridge between Release Consistency and Entry Consistency. In Proc. of the 8th ACM Annual Symposium on Parallel Algorithms and Architectures (SPAA'96), pages 277-287, June 1996.

....consistency (EC) model [7] which is even weaker and appears to be more efficient than LRC. Unfortunately, the programming interface associated with EC is not easy to use, as it requires explicit binding between synchronization variables (locks) and shared memory variables. Scope consistency (ScC) [8] has thus been proposed, aiming at good programmability and high performance. Figure 1. The distributed shared memory abstraction: Each processor sees a shared address space, delineated by the dashed outline, rather than a collection of distributed address spaces. Apart from the use of relaxed ....

....the lazy release consistency model, JIAJIA used the home based approach to realize the scope consistency model. This results in a more efficient implementation, since scope consistency produces less data propagation than lazy release consistency at lock acquire or barrier synchronization [8]. Later versions of JIAJIA also adopt the concept of home migration of shared memory pages, in order to achieve better adaptation to the memory access patterns of DSM applications. One of them is the home migration protocol implemented by JIAJIA V2.1 [15] This protocol shares the same objective ....

L. Iftode, J. P. Singh and K. Li. Scope Consistency: A Bridge between Release Consistency and Entry Consistency. In Proc. of the 8th ACM Annual Symposium on Parallel Algorithms and Architectures (SPAA'96), pages 277-287, June 1996.

....models and providing access control at a ne granularity. Relaxed consistency models introduce additional programmer restrictions in exchange for (hopefully) better performance. Examples of relaxed consistency models include release consistency [10] entry consistency [2] scope consistency [13]. Lazy release consistency(LRC) 15] is a software implementation of release consistency which delays the coherence action until the acquire time. Most software shared systems today use LRC based protocols [14] 11] 30] 16] These consistency models employ sophisticated protocols to reduce false ....

.... (RC) 10] and its SVM implementation [5] delayed consistency model [8] and its SVM protocols [4, 9] multiple writer lazy release consistency (LRC) model [15] and implementation [14] entry consistency model and prototype [2] automatic update release consistency [11] scope consistency [13], home based lazy release consistency and its implementations [30] and single writer lazy release consistency [16] All prototypes based on relaxed consistency models use virtual memory page sizes as their coherence units. Another approach is to preserve the sequential consistency model and to ....

L. Iftode, J.P. Singh, and K. Li. Scope Consistency: a Bridge Between Release Consistency and Entry Consistency. In Proceedings of the 8th Annual ACM Symposium on Parallel Algorithms and Architectures, June 1996.

....all updates are propagated and from which all copies are derived. Unlike AURC, HLRC requires no specialized hardware support, using di s as in LRC for update detection and propagation. This idea of using a home based approach to build an all software protocol similar to AURC was introduced in [17]. Our second protocol, called Overlapped Home based LRC (OHLRC) takes advantage of the communication processor found on each node of the Paragon to o oad some of the protocol overhead of HLRC from the critical path followed by the compute processor. To evaluate the performance implications of ....

....recently proposed Automatic Update Release Consistency protocol (AURC) 15] is an LRC protocol that takes advantage of the automatic update mechanism in virtual memory mapped communication. The idea of using a home based approach to build an all software protocol similar to AURC was proposed in [17]. Our home based LRC protocols are based on the AURC protocol, but the updates are detected in software using di s, as in the standard LRC. A degree of overlapping similar to the one the automatic update mechanism provides is achieved in our Overlapped Home based LRC (OHLRC) protocol, where the ....

[Article contains additional citation context not shown here]

L. Iftode, J.P. Singh, and K. Li. Scope Consistency: a Bridge Between Release Consistency and Entry Consistency. In Proceedings of the 8th Annual ACM Symposium on Parallel Algorithms and Architectures, June 1996.

....from shared networks of workstations (e.g. NOW [2] to dedicated cluster machines as in the Beowulf [7] approach. Generally, cluster programming is done using message passing systems such as 3 PVM [17] MPI [20] and HPVM [11] although software based Distributed Shared Memory (DSM) systems (e.g. [31, 23, 24, 27]) have also been developed in an effort to simplify programming. At the implementation level, however, both message based and DSM systems depend on a priori knowledge of the identities of the machines that form a computing cluster 1 . The work presented in this paper dynamically selects the ....

L. Iftode, J. P. Singh, and K. Li. Scope Consistency: A Bridge Between Release Consistency and Entry Consistency. Theory of Computing Systems, 31(4):451-- 473, 1998.

No context found.

L. Iftode, J.P. Singh, and K. Li. Scope consistency: A bridge between release consistency and entry consistency. In Proceedings of the 8th Symposium on Parallel Algorithms and Architecture, June 1996.

No context found.

L. Iftode, J.P. Singh and K. Li: "Scope Consistency: A Bridge between Release Consistency and Entry Consistency", In Proc. of the 8th Annual ACM Symposium on Parallel Algorithms and Architectures, 1996.

No context found.

L. Iftode, J. Singh, and K. Li. Scope consistency: A bridge between release consistency and entry consistency. In Proc. of the 8th Annual ACM Symposium on Parallel Algorithms and Architectures, 1996.

No context found.

L. Iftode, J. Singh, and K. Li. Scope consistency: A bridge between release consistency and entry consistency. In Proc. of the 8th ACM Annual Symp. on Parallel Algorithms and Architectures (SPAA'96), pages 277--287, June 1996.

No context found.

L. Iftode, J. Singh, and K. Li. Scope consistency: A bridge between release consistency and entry consistency. In Proc. of the 8th ACM Annual Symp. on Parallel Algorithms and Architectures (SPAA'96), pages 277-287, June 1996.

No context found.

L. Iftode, J.P. Singh, and K. Li. Scope consistency: a bridge between release consistency and entry consistency. In Proceedings of the 8th Annual ACM Symposium on Parallel Algorithms and Architectures, June 1996.

No context found.

Iftode L., Singh J.P., Li K; Scope Consistency: A bridge between release consistency and entry consistency. Proceedings of the 8th ACM Annual Symposium on Parallel Algorithms and Architectures (SPAA'96), pp. 277-287, June, 1996.

No context found.

Liviu Iftode, Jaswinder Pal Singh, and Kai Li. Scope consistency: a bridge between release consistency and entry consistency. In Symposium on Parallel Algorithms and Architectures, pages 277-287, June 1996.

No context found.

Iftode, L., Singh, J. P., and Li, K. "Scope Consistency: A Bridge between Release Consistency and Entry Consistency" . Proc 8th ACM Annual Symp. on Parallel Algorithms and Architectures (SPAA'96), pages 277-287, June 1996.

No context found.

L. Iftode, J. Singh, and K. Li, "Scope Consistency: A Bridge between Release Consistency and Entry Consistency", In Proceedings of the 8th Annual ACM Symposium on Parallel Algorithms and Architectures, June 1996.

No context found.

Iftode, L. and Singh, J.P. and Li, K. Scope Consistency: A Bridge between Release Consistency and Entry Consistency. In Proceedings of the 8th Annual on ACM Symposium on Parallel Algorithms and Architectures, June 1996.

No context found.

L. Iftode, J. Singh, L. Li, Scope consistency: a bridge between release consistency and entry consistency, Theory Comput. Syst. 31 (1998) 451--473.

No context found.

Iftode, L., J.p. Singh, and K. Li. Scope Consistency: A Bridge between Release Consistency and Entry Consistency. in 8fi Annual ACM Symposium on Parallel Algorifims and Architectures. 1996.

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