US 9,811,474 B2
Determining cache performance using a ghost cache list indicating tracks demoted from a cache list of tracks in a cache
Kevin J. Ash, Tucson, AZ (US); Matthew G. Borlick, Tucson, AZ (US); Lokesh M. Gupta, Tucson, AZ (US); and Juan A. Yanes, Tucson, AZ (US)
Assigned to INTERNATIONAL BUSINESS MACHINES CORPORATION, Armonk, NY (US)
Filed by INTERNATIONAL BUSINESS MACHINES CORPORATION, Armonk, NY (US)
Filed on Oct. 30, 2015, as Appl. No. 14/928,948.
Prior Publication US 2017/0124001 A1, May 4, 2017
Int. Cl. G06F 12/12 (2016.01); G06F 13/00 (2006.01); G06F 12/128 (2016.01)
CPC G06F 12/128 (2013.01) [G06F 2212/621 (2013.01); G06F 2212/69 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A computer program product for managing a cache in a computer system to cache tracks stored in a storage, the computer program product comprising a computer readable storage medium having computer readable program code embodied therein that when executed performs operations, the operations comprising:
indicating tracks in the cache in a cache list;
indicating a demoted track comprising a track demoted from the cache in a ghost cache list in response to demoting the demoted track in the cache, wherein the demoted track is not indicated in the cache list;
during caching operations, gathering information on a number of cache hits comprising accesses to the tracks indicated in the cache list and a number of ghost cache hits comprising accesses to tracks indicated in the ghost cache list; and
using the gathered information on the number of cache hits and the number of ghost cache hits to generate information on cache performance improvements that would occur if the cache was increased in size to cache tracks in the ghost cache list by:
determining a cache service time based on the number of cache hits which indicates an estimated time to service an access request with the cache; and
determining a ghost cache service time based on the number of cache hits and the number of ghost cache hits, which indicates an estimated time to service an access request if the cache was increased in size to have space to store the tracks indicated in the ghost cache list.