International Business Machines Corporation

Jochen Liedtke

Trent Ray Jaeger

Nayeem Islam

Vsevolod V Panteleenko

Rangachari Anand

Marc Alan Auslander

Frederique-Anne Giraud

There is provided a method for representing unvalues in an unvalue-unaware memory of a computer processing system. The method includes the step of selecting arbitrary bit combinations to represent the unvalues, upon startup of the system. Upon performing a read operation from the memory, a read value is interpreted as an unvalue, when the read value matches at least one of the bit combinations. Upon performing a write operation to the memory, a value-unvalue-collision exception is raised, when a valid value is written to the memory and the valid value matches at least one of the bit combinations.

Unvalue-tagged memory without additional bits

A server complex including at least one hit server with item cache, used to process read and write operations relating to cached items from clients, and at least one miss server, serving as a link to other servers (e.g., web servers, file system servers, and databases) for receiving requests relayed from the hit server(s) which relate to non-cached items and for responding to same. The hit server is a general-purpose, generic, component, which is independent of concrete applications and is basically responsible for the performance; while a miss server is a highly-customizable component, which is responsible for flexibility, and is application specific. The inventive architecture provides improved performance whereby a server complex achieves exceptionally high throughput rates for local services (i.e., services using items in the local item cache); flexibility, whereby a server complex can support the enforcement of a variety of application-specific policies for item management, authentication, and item consistency; security, whereby a server complex can enable the verification of the source, integrity, and freshness of communications over untrusted links; and, scalability, whereby a server complex is expandable by adding server components and implementing customized item consistency policies.

Powerful and flexible server architecture

A system and method for enabling applications to pin a set of pages in memory for a predetermined duration in time. An application submits a request for pinning its memory for certain duration. As a compensation the applications may offer other currently mapped pages for replacement. The request may also include number of pages and duration of time. The request is granted with the constraint policies which the application is to follow. Such constraint policies include number of pages and length of time the pages may remain pinned in memory. When compensation pages are offered, those pages are replaced in place of the pages which are granted the privileged of being pinned. The present invention also provides page coloring compensation by including a compensation pool from where a compensation page having the same color as the one picked for replacement may be selected. The compensation pages offered by the application which are not used for compensating are returned subsequently to the application.

Schedulable dynamic memory pinning

A cache system in accordance with the present invention consists of one or more cache components and a set of one or more consistency-replacement functions. A cache component caches one or more items in its one or more cache entries. Items that hit in the cache can result in corresponding cache entries being read or written. Any valid entry in a cache component includes status information reflecting whether the entry has been accessed and whether it has been modified, and is linked to a consistency-action matrix that, in correspondence with the entry's status information and access type (i.e. read or write), determines what consistency action has to be executed in conjunction with the current entry access. Consistency actions and the consistency-action matrix are the inventive mechanisms for implementing cache-coherency and cache-replacement policies. Any valid entry in a cache is linked to a consistency-replacement function that implements one or more consistency and/or replacement policies. Consistency-replacement functions are application-specific and are implemented by means of the consistency-action matrix.

Flexible cache-coherency mechanism

A dynamic derivation mechanism is defined which enables limited permissions to be dynamically and flexibly derived for executables based upon their authenticated description. The dynamic derivation mechanism uses the authenticated description to determine the maximal permissions that individual principals can delegate to the content. A principal's maximal permissions for content define a superset of the rights that that principal will actually delegate to that content. Although the maximal permissions are derived from predefined specifications, the specifications can be sensitive to runtime state on the downloader's system or previous delegations to enable the dynamic (i.e., runtime) derivation. Multiple principals can delegate a subset of their maximal permissions for the executable content. The mechanism uses policy for combining the delegated permissions into the content's runtime permissions.

Flexible and dynamic derivation of permissions

A cache system in accordance with the present invention consists of one or more cache components and a set of one or more consistency-replacement functions. A cache component caches one or more items in its one or more cache entries. Items that hit in the cache can result in corresponding cache entries being read or written. Any valid entry in a cache component includes status information reflecting whether the entry has been accessed and whether it has been modified, and is linked to a consistency-action matrix that, in correspondence with the entry's status information and access type (i.e. read or write), determines what consistency action has to be executed in conjunction with the current entry access. consistency actions and the consistency-action matrix are the inventive mechanisms for implementing cache-coherency and cache-replacement policies. Any valid entry in a cache is linked to a consistency-replacement function that implements one or more consistency and/or replacement policies. Consistency-replacement functions are application-specific and are implemented by means of the consistency-action matrix.

Growing community of inventors

Ossining, NY, United States of America

Jochen Liedtke