Managing storage units in multi-core and multi-threaded systems

A method of managing at least one storage unit in a data processing apparatus, said data processing apparatus comprising processing circuitry for executing multiple program threads including at least one high priority program thread and at least one lower priority program thread, said at least one storage unit being shared between the multiple program threads and comprising multiple entries, each entry for storing a storage item for reference by the processing circuitry when executing said program threads, each storage item being either a high priority storage item associated with said at least one high priority program thread or a lower priority storage item associated with said at least one lower priority program thread, said method comprising the steps of:

• retaining a history field for each of a plurality of blocks of the storage unit, each block comprising one or more of said entries;
• detecting an evicted high priority storage item being evicted from an entry of the storage unit as a result of allocation to that entry of an allocated lower priority storage item;
• on said detection populating the history field for the block containing that entry with an indication of said evicted high priority storage item;
• and
• when an allocated high priority storage item is allocated to a selected entry of the storage unit, performing a comparison operation between the high priority storage item and the indication in the history field for the block containing the selected entry, and on detection of a match condition setting a lock indication associated with said selected entry to inhibit further eviction of said allocated high priority storage item.

A data processing apparatus comprising:

• processing means for executing multiple program threads including at least one high priority program thread and at least one lower priority program thread;
• at least one storage means shared between the multiple program threads and comprising multiple entries, each entry for storing a storage item for reference by the processing means when executing said program threads, each storage item being either a high priority storage item associated with said at least one high priority program thread or a lower priority storage item associated with said at least one lower priority program thread;
• history storage means for retaining a history field for each of a plurality of blocks of the storage unit, each block comprising one or more of said entries;
• and
• control means for, on detection of an evicted high priority storage item being evicted from an entry of the storage means as a result of allocation to that entry of an allocated lower priority storage item, populating the history field for the block containing that entry with an indication of the evicted high priority storage item,
• the control means being further for performing, when an allocated high priority storage item is allocated to a selected entry of the storage means, a comparison operation between the allocated high priority storage item and the indication in the history field for the block containing the selected entry, and on detection of a match condition said control means setting a lock indication associated with said selected entry to inhibit further eviction of said allocated high-priority storage item.