Method And Apparatus To Implement Lazy Flush In A Virtually Tagged Cache Memory

A system comprising:

• a processor that includes:
• an execution unit to execute one or more instructions;
• and
• a cache memory comprising:
• a plurality of cache lines to store data, wherein each cache line includes a corresponding stale indicator to indicate whether corresponding data stored in the cache line is stale, and also includes a corresponding virtual address;
• and
• a controller to update the stale indicator in each of the plurality of cache lines in response to execution of a lazy flush instruction, wherein the lazy flush instruction specifies that upon a data request, at most one cache line is to be flushed and replacement data is to be stored in the one cache line;
• a dynamic random access memory (DRAM) coupled to the processor to store data that is accessible to the execution unit.

A method comprising:

• in response to a trigger condition, executing a lazy flush instruction that updates a plurality of stale indicators to indicate that data stored in a corresponding plurality of cache lines of a cache memory is stale;
• after executing the lazy flush instruction, searching the cache memory to locate first data in response to a data request that includes a first virtual address;
• if the first data is located in the cache memory:
• replacing a virtual address in a foreground tag of a first cache line with the first virtual address;
• updating a first stale indicator associated with the first cache line storing the first data to indicate that the first data is not stale;
• and
• providing the first data in response to the request.