Even with today's large caches, the increasing performance gap between processors and memory systems imposes a memory bottleneck for many important scientific and commercial applications. This bottleneck is intensified in shared-memory multiprocessors by contention and the effects of cache coherency. Under heavy memory contention, the memory latency may increase 2 or 3 times. Nonethless, as more sophisticated techniques are used to hide latency and increase bandwidth, measuring memory performance has become increasingly difficult. Previous simple methods to measure memory performance can overestimate uniprocessor memory latency and underestimate bandwidth by tens of percent. This paper introduces a micro benchmark suite that measures memory hierarchy performance in light of both uniprocessor optimizations and the contention and coherence effects of multiprocessors. The benchmark suite has been used to improve the memory system performance of the SGI Origin multiprocessor.

article Free AccessExtended ephemeral logging: log storage management for applications with long lived transactions Authors: John S. Keen Silicon Graphics, Mountain View, CA Silicon Graphics, Mountain View, CAView Profile , William J. Dally Massachusetts Institute of Technology, Cambridge, MA Massachusetts Institute of Technology, Cambridge, MAView Profile Authors Info & Claims ACM Transactions on Database SystemsVolume 22Issue 1pp 1–42https://doi.org/10.1145/244810.244811Published:01 March 1997Publication History 5citation636DownloadsMetricsTotal Citations5Total Downloads636Last 12 Months13Last 6 weeks2 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

Extended ephemeral logging (XEL) is a more general variation of the ephemeral logging (EL) technique for managing a log of database activity on disk; it does not require a timestamp to be maintained with each object in the database. XEL does not require periodic checkpoints and does not abort lengthy transactions as frequently as traditional firewall logging for the same amount of disk space. Therefore, it is well suited for concurrent databases and applications which have a wide distribution of transaction lifetimes.

Ephemeral logging (EL) is a new technique for managing a log of database activity on disk. It does not require periodic checkpoints and does not abort lengthy transactions as frequently as traditional firewall logging for the same amount of disk space. Therefore, it is well suited for highly concurrent databases and applications which have a wide distribution of transaction lifetimes.This paper briefly explains EL and then analyzes its performance. Simulation studies indicate that it can offer significant savings in disk space, at the expense of slightly higher bandwidth for logging and more main memory. The reduced size of the log implies much faster recovery after a crash as well as cost savings.EL is the method of choice in some but not all situations. We assess the limitations of our current knowledge about EL and suggest promising directions for further research.

A description is given of the Message-Driven Processor (MDP), an integrated multicomputer node. It incorporates a 36-bit integer processor, a memory management unit, a router for a 3D mesh network, a network interface, a 4K*36-bit word static RAM (SRAM), and an ECC dynamic RAM (DRAM) controller on a single 1.1 M-transistor VLSI chip. The MDP is not specialized for a single model of computation. Instead, it incorporates efficient primitive mechanisms for communication, synchronization, and naming. These mechanisms support most proposed parallel programming models. Each processing node of the MIT J-Machine consists of an MDP with 1 Mbit of DRAM.>