637 research outputs found
A Survey of Techniques for Architecting TLBs
“Translation lookaside buffer” (TLB) caches virtual to physical address translation information and is used
in systems ranging from embedded devices to high-end servers. Since TLB is accessed very frequently
and a TLB miss is extremely costly, prudent management of TLB is important for improving performance
and energy efficiency of processors. In this paper, we present a survey of techniques for architecting and
managing TLBs. We characterize the techniques across several dimensions to highlight their similarities and
distinctions. We believe that this paper will be useful for chip designers, computer architects and system
engineers
A Survey on Cache Management Mechanisms for Real-Time Embedded Systems
© ACM, 2015. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM Computing Surveys, {48, 2, (November 2015)} http://doi.acm.org/10.1145/2830555Multicore processors are being extensively used by real-time systems, mainly because of their demand for
increased computing power. However, multicore processors have shared resources that affect the predictability
of real-time systems, which is the key to correctly estimate the worst-case execution time of tasks. One of
the main factors for unpredictability in a multicore processor is the cache memory hierarchy. Recently, many
research works have proposed different techniques to deal with caches in multicore processors in the context
of real-time systems. Nevertheless, a review and categorization of these techniques is still an open topic and
would be very useful for the real-time community. In this article, we present a survey of cache management
techniques for real-time embedded systems, from the first studies of the field in 1990 up to the latest research
published in 2014. We categorize the main research works and provide a detailed comparison in terms of
similarities and differences. We also identify key challenges and discuss future research directions.King Saud University
NSER
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PebblesDB : building key-value stores using fragmented log-structured merge trees
Key-value stores such as LevelDB and RocksDB offer excellent write throughput, but suffer high write amplification. The write amplification problem is due to the Log-Structured Merge Trees data structure that underlies these key-value stores. To remedy this problem, this thesis presents a novel data structure that is inspired by Skip Lists, termed Fragmented Log- Structured Merge Trees (FLSM). FLSM introduces the notion of guards to organize logs (sstables or files containing the data on storage), and avoids rewriting data in the same level. Theoretically, we show how FLSM can address the problem of write amplification. We build PebblesDB, a high-performance key-value store, by modifying HyperLevelDB to use the FLSM data structure. We evaluate PebblesDB using micro-benchmarks and show that for write-intensive workloads, PebblesDB reduces write amplification by 2.4-3x compared to RocksDB, while increasing write throughput by 6.7x. We evaluate PebblesDB extensively under a variety of benchmarks, workload patterns, and environmental factors and analyze how it performs in different scenarios. We modify two widely-used NoSQL stores, MongoDB and HyperDex, to use PebblesDB as their underlying storage engine. Evaluating these applications using the YCSB benchmark shows that throughput is increased by 18-105% when using PebblesDB (compared to their default storage engines) while write IO is decreased by 35-55%.Computer Science
Subheap-Augmented Garbage Collection
Automated memory management avoids the tedium and danger of manual techniques. However, as no programmer input is required, no widely available interface exists to permit principled control over sometimes unacceptable performance costs. This dissertation explores the idea that performance-oriented languages should give programmers greater control over where and when the garbage collector (GC) expends effort. We describe an interface and implementation to expose heap partitioning and collection decisions without compromising type safety. We show that our interface allows the programmer to encode a form of reference counting using Hayes\u27 notion of key objects. Preliminary experimental data suggests that our proposed mechanism can avoid high overheads suffered by tracing collectors in some scenarios, especially with tight heaps. However, for other applications, the costs of applying subheaps---in human effort and runtime overheads---remain daunting
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