Object-based client caching allows clients to keep more frequently accessed objects while discarding colder objects that reside on the same page. However, when these objects are modified and sent to the server, it may need to read the corresponding page from disk to install the update. These 'installation reads' are not required with a page-based cache because whole pages are sent to the server. The relative effectiveness of the two cache techniques depends crucially on the application workload and on the object layout on pages. In a large system, when many applications share data objects, customizing cache management to either an object-based or a page-based configuration may not be optimal to any of the applications. We describe a hybrid system that permits clients to cache objects and pages. The system uses a simple cache design that combines the best of object caching and page caching. The client increases its cache hit ratio as in object-based caching. The client avoids some installation reads by sending pages to the server when possible. Using simulated workloads, we explore the performance of our design and show that it can offer a significant performance improvement over both pure object caching and pure page caching on a range of workloads.

article Exokernel: an operating system architecture for application-level resource management Share on Authors: D. R. Engler M.I.T. Laboratory for Computer Science, Cambridge, MA M.I.T. Laboratory for Computer Science, Cambridge, MAView Profile , M. F. Kaashoek M.I.T. Laboratory for Computer Science, Cambridge, MA M.I.T. Laboratory for Computer Science, Cambridge, MAView Profile , J. O'Toole M.I.T. Laboratory for Computer Science, Cambridge, MA M.I.T. Laboratory for Computer Science, Cambridge, MAView Profile Authors Info & Claims ACM SIGOPS Operating Systems ReviewVolume 29Issue 5Dec. 3, 1995 pp 251–266https://doi.org/10.1145/224057.224076Online:03 December 1995Publication History 700citation13,300DownloadsMetricsTotal Citations700Total Downloads13,300Last 12 Months628Last 6 weeks58 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 SiteGet Access

We have implemented the first copying garbage collector that permits continuous unimpeded mutator access to the original objects during copying. The garbage collector incrementally replicates all accessible objects and uses a mutation log to bring the replicas up-to-date with changes made by the mutator. An experimental implementation demonstrates that the costs of using our algorithm are small and that bounded pause times of 50 milliseconds can be readily achieved.

We describe a replicating garbage collector for a persistent heap. The garbage collector cooperates with a transaction manager to provide safe and efficient transactional storage management. Clients read and write the heap in primary memory and can commit or abort their write operations. When write operations are committed they are preserved in stable storage and survive system failures. Clients can freely access the heap during garbage collection because the collector concurrently builds a compact replica of the heap. A log captures client write operations and is used to support both the transaction manager and the replicating garbage collector.Our implementation is the first to provide concurrent and compacting garbage collection of a persistent heap. Measurements show that concurrent replicating collection produces significantly shorter pause times than stop-and-copy collection. For small transactions, throughput is limited by the logging bandwidth of the underlying log manager. The results suggest that replicating garbage collection offers a flexible and efficient way to provide automatic storage management in transaction systems, object-oriented databases and persistent programming environments.

A semantic file system is an information storage system that provides flexible associative access to the system's contents by automatically extracting attributes from files with file type specific transducers. Associative access is provided by a conservative extension to existing tree-structured file system protocols, and by protocols that are designed specifically for content based access. Compatiblity with existing file system protocols is provided by introducing the concept of a virtual directory. Virtual directory names are interpreted as queries, and thus provide flexible associative access to files and directories in a manner compatible with existing software. Rapid attribute-based access to file system contents is implemented by automatic extraction and indexing of key properties of file system objects. The automatic indexing of files and directories is called "semantic" because user programmable transducers use information about the semantics of updated file system objects to extract the properties for indexing. Experimental results from a semantic file system implementation support the thesis that semantic file systems present a more effective storage abstraction than do traditional tree structured file systems for information sharing and command level programming.

We present the first type reconstruction system which combines the implicit typing of ML with the full power of the explicitly typed second-order polymorphic lambda calculus. The system will accept ML-style programs, explicitly typed programs, and programs that use explicit types for all first-class polymorphic values. We accomplish this flexibility by providing both generic and explicitly-quantified polymorphic types, as well as operators which convert between these two forms of polymorphism. This type reconstruction system is an integral part of the FX-89 programming language. We present a type reconstruction algorithm for the system. The type reconstruction algorithm is proven sound and complete with respect to the formal typing rules.