Data cache with hybrid writeback and writethrough

A method for performing hybrid writeback and writethrough, the method comprising:

• writing data from a retired store queue entry to a hit cache line in a data cache, wherein the hit cache line is initially in a starting coherence state;
• writing the data to an allocated entry in a write buffer when the hit cache line is in the starting coherence state;
• receiving a downgrade to invalid coherence probe from:
• one of an entity not local to a processor associated with the data cache or a backing structure controller
• prior to at least one of upgrading the coherence state of the hit cache line or writing the data to a backing structure;
• downgrading the hit cache line to an invalid coherence state;
• deleting the data in hit cache line;
• downgrading the allocated entry to an invalid coherence state;
• and
• performing, by the write buffer, a writethrough of the data to the backing structure.

A method for performing hybrid writeback and writethrough, the method comprising:

• writing data to a hit cache line in a data cache from a store queue, wherein the hit cache line is initially in a starting coherence state;
• writing the data to an allocated entry in a write buffer when the hit cache line is in the starting coherence state, wherein the allocated entry is in a modified coherence state with data after writing of the data;
• tracking cache coherence states of the data cache by the write buffer;
• and
• responsive to receiving a downgrade to shared coherence probe from a non-local entity with respect to the write buffer:
• remaining, by the hit cache line, in the starting coherence state;
• downgrading the allocated entry to a shared coherence state with data;
• and
• performing, by the write buffer, a writethrough of the data to a memory.