16,651 research outputs found
Towards a Scalable Dynamic Spatial Database System
With the rise of GPS-enabled smartphones and other similar mobile devices,
massive amounts of location data are available. However, no scalable solutions
for soft real-time spatial queries on large sets of moving objects have yet
emerged. In this paper we explore and measure the limits of actual algorithms
and implementations regarding different application scenarios. And finally we
propose a novel distributed architecture to solve the scalability issues.Comment: (2012
Incremental Consistency Guarantees for Replicated Objects
Programming with replicated objects is difficult. Developers must face the
fundamental trade-off between consistency and performance head on, while
struggling with the complexity of distributed storage stacks. We introduce
Correctables, a novel abstraction that hides most of this complexity, allowing
developers to focus on the task of balancing consistency and performance. To
aid developers with this task, Correctables provide incremental consistency
guarantees, which capture successive refinements on the result of an ongoing
operation on a replicated object. In short, applications receive both a
preliminary---fast, possibly inconsistent---result, as well as a
final---consistent---result that arrives later.
We show how to leverage incremental consistency guarantees by speculating on
preliminary values, trading throughput and bandwidth for improved latency. We
experiment with two popular storage systems (Cassandra and ZooKeeper) and three
applications: a Twissandra-based microblogging service, an ad serving system,
and a ticket selling system. Our evaluation on the Amazon EC2 platform with
YCSB workloads A, B, and C shows that we can reduce the latency of strongly
consistent operations by up to 40% (from 100ms to 60ms) at little cost (10%
bandwidth increase, 6% throughput drop) in the ad system. Even if the
preliminary result is frequently inconsistent (25% of accesses), incremental
consistency incurs a bandwidth overhead of only 27%.Comment: 16 total pages, 12 figures. OSDI'16 (to appear
The Iray Light Transport Simulation and Rendering System
While ray tracing has become increasingly common and path tracing is well
understood by now, a major challenge lies in crafting an easy-to-use and
efficient system implementing these technologies. Following a purely
physically-based paradigm while still allowing for artistic workflows, the Iray
light transport simulation and rendering system allows for rendering complex
scenes by the push of a button and thus makes accurate light transport
simulation widely available. In this document we discuss the challenges and
implementation choices that follow from our primary design decisions,
demonstrating that such a rendering system can be made a practical, scalable,
and efficient real-world application that has been adopted by various companies
across many fields and is in use by many industry professionals today
Basis Token Consistency: A Practical Mechanism for Strong Web Cache Consistency
With web caching and cache-related services like CDNs and edge services playing an increasingly significant role in the modern internet, the problem of the weak consistency and coherence provisions in current web protocols is becoming increasingly significant and drawing the attention of the standards community [LCD01]. Toward this end, we present definitions of consistency and coherence for web-like environments, that is, distributed client-server information systems where the semantics of interactions with resource are more general than the read/write operations found in memory hierarchies and distributed file systems. We then present a brief review of proposed mechanisms which strengthen the consistency of caches in the web, focusing upon their conceptual contributions and their weaknesses in real-world practice. These insights motivate a new mechanism, which we call "Basis Token Consistency" or BTC; when implemented at the server, this mechanism allows any client (independent of the presence and conformity of any intermediaries) to maintain a self-consistent view of the server's state. This is accomplished by annotating responses with additional per-resource application information which allows client caches to recognize the obsolescence of currently cached entities and identify responses from other caches which are already stale in light of what has already been seen. The mechanism requires no deviation from the existing client-server communication model, and does not require servers to maintain any additional per-client state. We discuss how our mechanism could be integrated into a fragment-assembling Content Management System (CMS), and present a simulation-driven performance comparison between the BTC algorithm and the use of the Time-To-Live (TTL) heuristic.National Science Foundation (ANI-9986397, ANI-0095988
The End of a Myth: Distributed Transactions Can Scale
The common wisdom is that distributed transactions do not scale. But what if
distributed transactions could be made scalable using the next generation of
networks and a redesign of distributed databases? There would be no need for
developers anymore to worry about co-partitioning schemes to achieve decent
performance. Application development would become easier as data placement
would no longer determine how scalable an application is. Hardware provisioning
would be simplified as the system administrator can expect a linear scale-out
when adding more machines rather than some complex sub-linear function, which
is highly application specific.
In this paper, we present the design of our novel scalable database system
NAM-DB and show that distributed transactions with the very common Snapshot
Isolation guarantee can indeed scale using the next generation of RDMA-enabled
network technology without any inherent bottlenecks. Our experiments with the
TPC-C benchmark show that our system scales linearly to over 6.5 million
new-order (14.5 million total) distributed transactions per second on 56
machines.Comment: 12 page
Concurrent Access Algorithms for Different Data Structures: A Research Review
Algorithms for concurrent data structure have gained attention in recent years as multi-core processors have become ubiquitous. Several features of shared-memory multiprocessors make concurrent data structures significantly more difficult to design and to verify as correct than their sequential counterparts. The primary source of this additional difficulty is concurrency. This paper provides an overview of the some concurrent access algorithms for different data structures
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