Variable cache data retention system

• US 7,769,953 B2
• Filed: 04/12/2008
• Issued: 08/03/2010
• Est. Priority Date: 08/17/2005
• Status: Active Grant

• Current Assignee: JP Morgan Chase Bank, N.A. (JP Morgan Chase & Co)
• Original Assignee: International Business Machines Corporation
• Inventors: Borlick, Matthew G.
• Primary Examiner(s): Elmore; Stephen C
• Application Number:
  US12/101,970
• Publication Number:
  US 20090228661A1
• Time in Patent Office: 843 Days
• Field of Search: 711/133, 711/159
• US Class Current: 711/133
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 12/121 using replacement algorithms

Abstract

A customizable cache discard policy is provided which reduces adverse consequences of conventional discard policies. In a data processing system, a cache controller invokes a cache data discard policy as the cache approaches its capacity. Using one possible policy, data having the shortest retrieval (fetch) time is discarded before data having longer retrieval times. In an alternative policy, data may be discarded based upon its source. Weightings may be applied based upon the distance from each source to the cache, may be based upon priorities assigned to each source, or may be based upon the type of each source.

Claims

1. A cache system, comprising:

a cache storage operable to store data from a plurality of data sources;

a lookup table configured to store an entry for each data source and an associated non-latency based weighting value; and

a cache manager configured to implement a cached data discard policy whereby, upon the cache storage reaching a predetermined capacity level, data from a data source having a first weighting value is retained in the cache longer than data from a data source having a lower weighting value.

2. The cache system of claim 1, wherein assigning each non-latency based weighting value comprises assigning a weighting value according to the geographic locations of each of the data sources.

3. The cache system of claim 2, wherein a data source having the first weighting value is geographically more distant from the cache than a data source having the lower weighting value.

4. The cache system of claim 1, wherein the cache manager is further configured to assign the weighting value according to a predetermined priority of data received from each data source.

5. The cache system of claim 4, wherein first data received from a data source having the first weighting value has a higher priority than second data received from a data source having a lower weighting value.

6. The cache system of claim 1, wherein the cache manager is further configured to:

maintain a log of the time required to receive data from each of the data sources;

assign to a data source a second weighting value corresponding to the time required to receive data from the data source relative to the time required to receive data from each of the other data sources; and

add the first and second weighting values to obtain a combined weighting value for each data source, whereby upon the cache reaching a predetermined capacity level, implementing a data discard policy whereby first data from a data source having a first combined weighting value is retained in the cache longer than second data from a data source having a second combined weighting value.

7. The cache system of claim 1, wherein the cache manager is further configured to, after retaining the first data in the cache, decrease the weighting value of the first data by a predetermined amount to decrease the chance that the first data will be retained in the cache when the cache next reaches the predetermined capacity level.