International Business Machines Corporation

Ross Evan Johnson

Richard James Eickemeyer

Steven R Kunkel

Eric L Barsness

Richard D Dettinger

George Wayne Nation

Mark Robert Funk

Timothy John Mullins

Harold F Kossman

James Allen Rose

Mikko Herman Lipasti

Kevin Curtis Griffin

William A Hammond, Jr

James L Denton

Sandra Kay Ryan

Multiple database queries are satisfied with the same data in a manner that assures the data is current and without having to interrogate the database for each query. In a first embodiment, all queries that are received during the processing of a first query after interrogation of the database has begun for the first query are evaluated to determine whether the result set returned for the first query will satisfy the queries received during processing of the first query. If so, the result set returned for the first query is used to generate result sets for the subsequent compatible queries received during the processing of the first query. In a second embodiment, queries are delayed and grouped, and a new query is then processed for each group that returns a result set that satisfies all of the queries in the group. In both cases, the result set for one query is used to generate a result set for a different query.

Processing database queries by returning results of a first query to subsequent queries

An apparatus, program product and method utilize a heuristic-based algorithm such as simulated annealing to order program code segments in a computer memory to provide improved computer performance in terms of memory access, e.g., by minimizing cache misses or other memory-related performance penalties that may be present in a multi-level memory architecture. Program code is ordered in a computer memory by selecting an ordering from among a plurality of orderings for a plurality of program code segments using a heuristic algorithm, and ordering the plurality of program code segments in a memory of a computer using the selected ordering.

Ordering of high use program code segments using simulated annealing

A method and system for enhanced performance multithread operation in a data processing system which includes a processor, a main memory store and at least two levels of cache memory. At least one instruction within an initial thread is executed. Thereafter, the state of the processor at a selected point within the first thread is stored, execution of the first thread is terminated and a second thread is selected for execution only in response to a level two or higher cache miss, thereby minimizing processor delays due to memory latency. The validity state of each thread is preferably maintained in order to minimize the likelihood of returning to a prior thread for execution before the cache miss has been corrected. A least recently executed thread is preferably selected for execution in the event of a nonvalidity indication in association with all remaining threads, in anticipation of a change to the valid status of that thread prior to all other threads. A thread switch bit may also be utilized to selectively inhibit thread switching where execution of a particular thread is deemed necessary.

Method and system for multi-thread switching only when a cache miss

A sorting algorithm is applied to an array data structure to arrange array elements according to the predicted frequency by which those array elements are likely to be modified. Higher modification frequency array elements are arranged proximate the end of the array to minimize the number of array elements that will typically need to be updated in response to modification of these array elements, reserving the modifications that require more array elements to be updated to those array elements that have a lower likelihood of modification. A sorting algorithm suitable for use in memory compression arranges blocks for a given page in reverse order since data located proximate the beginning of a page has a higher probability of being modified than the data proximate the end of the page.

Computer system and method which sort array elements to optimize array

Logic for decreasing the number of cache lines dedicated to user data. When pools for allocation are selected using a dynamic storage allocation procedure, the size of a data block is compared to the size of the allocated pool. If the comparison results meet a predetermined criterion, the logic aligns the data to the beginning of a cache line and places the header in a separate cache line that may be deallocated. And if the data will fit within one-half of a cache slot in the allocated pool, then the line or lines having the header data can be re-used as the header is deallocated. Otherwise, user data blocks are placed in cache lines that are spatially local.

System and method for increasing cache efficiency through optimized data

An apparatus and method in a data processing system for sending a data packet from a source node to a destination node. The data processing system includes a multi-segment network having at least two segments, wherein the source node and the destination node are located within different segments. Communication of a data packet from one segment to another segment is provided by an agent node. When a receiving node, which may be either an agent or a destination node, cannot accept a packet, it places a reservation tag of 'A' or 'B' in an echo packet. The retried packet then uses this reservation tag to gain priority for any available buffers in the agent or destination node. The receiving node toggles between accepting all the outstanding 'A' packets (when the receiving node is in the 'receiving A' state) and accepting all the outstanding 'B' packets (when the receiving node is in the 'receiving B' state) assuming that the receiving node has a free, unoccupied buffer for accepting the packet. The receiving node counts the number of outstanding 'A' reservations and the number of outstanding 'B' reservations. Any time the number of available buffers is greater than the number of outstanding 'A' packets (when the receiving node is in the receiving 'A' state) any 'new' packets or 'B' packets will be accepted. Analogously, any time the number of available buffers is greater than the number of outstanding 'B' packets (when the receiving node is in the receiving 'B' state) any 'new' packets or 'A' packets will be accepted.

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Rochester, MN, United States of America

Ross Evan Johnson