Determining cache performance using a ghost cache list indicating tracks demoted from a cache list of tracks in a cache

Abstract

Provided are a computer program product, system, and method for determining cache performance using a ghost cache list. Tracks in the cache are indicated in a cache list. A track demoted from the cache is indicated in a ghost cache list in response to demoting the track in the cache. The demoted track is not indicated in the cache list. During caching operations, information is gathered on a number of cache hits comprising accesses to tracks indicated in the cache list and a number of ghost cache hits comprising accesses to tracks indicated in the ghost cache list. The gathered information on the cache hits and the ghost cache hits is used 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.