International Business Machines Corporation

Brian J Smith

Bruce McNutt

Ahmad Zandi

Mark Anthony Sovik

Pong-sheng Wang

Nancy Y Young

David Alastair Short

A method for determining a single reference residency time of a cache comprises the steps of causing test data to be staged to the cache and measuring a response time after a wait time has elapsed. The measuring step is repeated for a plurality of values of wait time. The method also includes the step of determining a boundary value of the wait time. A wait time of less than or equal to the boundary value yields a corresponding response time representing a cache hit and a wait time of greater than the boundary value yields a corresponding response time representing a cache miss. The boundary value is an estimate of the single reference residency time of the cache.

Method and system for determining a cache single reference residency time

A cache having dynamic cache memory allocation is provided. A cache memory stores a plurality of data blocks, each block belonging to one of a plurality of data sets. A cache directory maintains a list of entries associated with the data blocks stored in the cache memory, wherein each entry corresponds to an individual data block and has fields for storing information including a designation of the data set to which the corresponding data block belongs. A directory controller generates each entry when the corresponding data block is loaded in the cache. The directory controller inserts the generated entry into the list at the optimal insertion point for the data block's data set, which is derived from a calculated optimal single-reference residency time for that data set. Further, the directory controller moves an entry in the list to the insertion point for the given data set of a corresponding data block when the corresponding data block is referenced in the cache. A storage control unit for storing data blocks within the cache memory replaces in the cache memory the data block corresponding to the bottom entry of the list with the data block corresponding to an entry inserted into the list.

Method and apparatus for dynamic cache memory allocation via

A computer system constructs a compression dictionary for compressing a character string by interrogating an initial substring portion to determine input string characteristics that are used to select one or more dictionary segments from a library of predetermined dictionary segments individually adapted for compressing strings with particular characteristics. The initial substring portion is dynamically determined during the interrogation. A first set of dictionary segments that meet predetermined automatic selection criteria are selected and a second set of candidate dictionary segments that meet second-level selection criteria are identified for a sampling phase. During the sampling phase, the candidate dictionary segments are alternately used to compress the initial substring portion and determine compression performance statistics. The performance of the dictionary segments in the sampling phase determines which candidate dictionary segments will be added to the first selected dictionary segments, within dictionary total size limits. The first selected dictionary segments and the identified segments constitute a system-built compression dictionary that is used to compress the remainder of the input string. In this way, predetermined compression dictionaries are selected for maximum efficiency in accordance with the data actually being compressed and compression can be carried out quickly and efficiently as input data is received.

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Brian J Smith