Patent ID: 9372751
Filing Date: 2016-06-21
CPC Classification: G06F

Claim Text:
1. A computer program product for free space collection in a log structured storage system having segments, each segment including a plurality of tracks, the computer program product comprising one or more computer-readable tangible storage medium and program instructions stored on at least one of the one or more computer-readable tangible storage medium, the computer-readable tangible storage medium comprising: program instructions, in response to initially writing data to all the tracks of an empty one of the segments, to add an entry for the one segment to a stable segment list, the entry including a collection score value of zero; program instructions, in response to invalidating a track in one of the segments to which data has been written; program instructions to periodically determine a collection score value for each segment with a track in the ITL by calculating a cumulative sum of invalidation duration values corresponding to the durations that tracks belonging to the segment have remained on the ITL; program instructions, in response to determining that the collection score value for a track in the ITL is greater than a predetermined collection score threshold value, to set the collection score to the collection score threshold value and removing the track from the ITL; program instructions, in response to determining that a segment in the recently invalidated segment list has no associated tracks in the ITL, to move the segment from the recently invalidated segment list to the stable segment list; program instructions, in response to receiving a request to collect free space in the log structured storage system, to select for free space collection the segment in the recently invalidated segment list having the largest cumulative sum of invalidation duration values if this cumulative sum is larger than the cumulative sum of invalidation duration values for the segment in the stable segment list having the largest cumulative sum of invalidation duration values, otherwise, to select for free space collection the segment in the stable segment list having the largest cumulative sum of invalidation duration values; and program instructions to empty the selected segments, whereby the emptied segments become available for the writing of data to their tracks.