Method and apparatus for scalable disambiguated coherence in shared storage hierarchies

An apparatus comprising:

• a first processor to transmit a first data request;
• a plurality of data storage units correspondingly coupled to the plurality of processors;
• a first data storage unit of the plurality of data storage units corresponding to the first processor, the first data storage unit having a first data portion to hold a first data encoding, a corresponding first status portion to hold a first status encoding, and a first storage control to transmit the first data encoding in response to the first data request if the first status encoding is one of a set of valid status encodings and to transmit a second data request if the first status encoding is one of a set of invalid status encodings;
• a second data storage unit coupled with the first processors, the second data storage unit having a second data portion to hold a second data encoding, a second status portion to hold a second status encoding of the corresponding second data portion, and a second storage control to receive the second data request and to transmit the second data encoding in response to the second data request if the second status encoding is one of a set of clean status encodings and to transmit a third data request if the second status encoding is one of a set of exclusive dirty status encodings;
• and
• a third data storage unit of the plurality of data storage units having a third data portion to hold a third data encoding and having a third storage control to transmit the third data encoding in response to the third data request.

An apparatus comprising:

• shared storage means for storing a data portion;
• shared status recording means for encoding an exclusive dirty status corresponding to the data portion;
• a plurality of private storage means for storing private copies of modified and unmodified data portions;
• control means for maintaining coherence of data portions between private storage means and shared storage means.

A method comprising:

• transmitting a data portion encoding in response to a first data request if a corresponding data portion status is one of a set of clean status encodings;
• transmitting a second data request if the corresponding data portion status is one of a set of exclusive dirty status encodings;
• transmitting an invalidation request according to a presence encoding of the corresponding data portion if the first data request is of a first request type and if the data portion status is one of a set of valid status encodings;
• and
• setting the data portion status to one of a set of dirty status encodings if the first data request is of the first request type.

A state machine executable encoding of a method comprising one or more code storage medium having executable encodings stored thereon which, when executed by one or more state machines, causes the one or more state machine to:

• transmit a data portion encoding in response to a first data request if a corresponding data portion status is one of a set of clean status encodings;
• transmit a second data request if the corresponding data portion status is one of a set of exclusive dirty status encodings;
• transmit an invalidation request if the first data request is of a first request type and if the data portion status is one of a set of valid status encodings;
• and
• set the data portion status to one of a set of dirty status encodings if the first data request is of the first request type.