Method and apparatus for improving the efficiency of cache memories using stored activity measures

A method for improving the efficiency of a cache memory system in which cache lines in a cache memory are transferred in a page between the cache memory and an underlying storage, the method comprising:

• (a) assigning to each cache line an activity measure that is indicative of the relative activity of the each cache line;
• and
• (b) using activity measures assigned to the cache lines to determine which cache lines to retain in the cache memory and which cache lines to remove from the cache memory including deriving a metric from each activity measure which metric orders all cache lines according to relative activity and using a metric associated with each cache line to determine which cache lines to include in a multi-line page that is transferred between the cache memory and the underlying storage.

Apparatus for improving the efficiency of a cache memory system in which cache lines in a cache memory are transferred in a multi-line page between the cache memory and an underlying storage, the apparatus comprising:

• a metric generator that, when a page is brought into the cache memory from the underlying storage, assigns to each cache line in the page an activity measure that is indicative of the time at which the page was brought into the cache memory and the number of times the each cache line was accessed since it was brought into the cache memory;
• and
• a memory control that uses activity measures assigned to the cache lines to determine which cache lines to retain in the cache memory and which cache lines to remove from the cache memory.

Apparatus for improving the efficiency of a cache memory system in which cache lines in a cache memory are transferred in a page between the cache memory and an underlying storage, the apparatus comprising:

• a metric generator that assigns to each cache line an activity measure that is indicative of the relative activity of the each cache line;
• and
• a memory control that uses activity measures assigned to the cache lines to determine which cache lines to retain in the cache memory and which cache lines to remove from the cache memory wherein the memory control comprises a computation mechanism that derives a metric from each activity measure which metric orders all cache lines according to relative activity and a metric handler that uses a metric associated with each cache line to determine which cache lines to include in a multi-line page that is transferred between the cache memory and the underlying storage.

A computer program product for improving the efficiency of a cache memory system in which cache lines in a cache memory are transferred in a multi-line page between the cache memory and an underlying storage, the computer program product comprising a computer usable medium having computer readable program code thereon, including:

• program code, operable when a page is brought into the cache memory from the underlying storage, for assigning to each cache line in the page an activity measure that is indicative of the time at which the page was brought into the cache memory and the number of times the each cache line was accessed since it was brought into the cache memory;
• and
• program code for using activity measures assigned to the cache lines to determine which cache lines to retain in the cache memory and which cache lines to remove from the cache memory.

A computer program product for improving the efficiency of a cache memory system in which cache lines in a cache memory are transferred in a page between the cache memory and an underlying storage, the computer program product comprising a computer usable medium having computer readable program code thereon, including:

• program code for assigning to each cache line an activity measure that is indicative of the relative activity of the each cache line;
• and
• program code for using activity measures assigned to the cache lines to determine which cache lines to retain in the cache memory and which cache lines to remove from the cache memory wherein program code for using activity measures comprises program code for deriving a metric from each activity measure which metric orders all cache lines according to relative activity and program code for using a metric associated with each cache line to determine which cache lines to include in a multi-line page that is transferred between the cache memory and the underlying storage.