Optimizing space utilization by retaining metadata in cache

A computerized apparatus, comprising control circuitry that includes a set of processing units coupled to memory, the control circuitry constructed and arranged to:

• during a first cache processing cycle, (i) place M compressed blocks of the data in a segment of storage space, (ii) populate M entries of a mapping structure in cache for mapping the M compressed blocks in the segment, the mapping structure having space for N entries, N>M, with N−M locations of the mapping structure remaining unpopulated, and (iii), apply a hold to the mapping structure in the cache to ensure that the mapping structure is retained in the cache;
• during a second cache processing cycle, (i) place between 1 and N−M additional compressed blocks in the segment and (ii) populate an additional location in the mapping structure for each additional compressed block placed or to be placed in the segment;
• and
• during or after the second cache processing cycle, release the hold on the mapping structure.

A computer program product including a set of non-transitory, computer-readable media having instructions which, when executed by control circuitry of a computerized apparatus, cause the control circuitry to perform a method of managing data received for writing, the method comprising:

• during a first cache processing cycle, (i) placing M compressed blocks of the data in a segment of storage space, (ii) populating M entries of a mapping structure in cache for mapping the M compressed blocks in the segment, the mapping structure having space for N entries, N>M, with N−M locations of the mapping structure remaining unpopulated, and (iii), applying a hold to the mapping structure in the cache to ensure that the mapping structure is retained in the cache;
• during a second cache processing cycle, (i) placing between 1 and N−M additional compressed blocks in the segment and (ii) populating an additional location in the mapping structure for each additional compressed block placed or to be placed in the segment;
• and
• during or after the second cache processing cycle, releasing the hold on the mapping structure.