US 6,636,948 B2 · Method and system for a processor to gain assured ownership of an up-to-date copy of data

Abstract

A performance enhancing change-to-dirty operation (CTD) is disclosed wherein contention among several processors trying to gain ownership of a block of data is obviated by arranging the CTD to always succeed. A method and a system are disclosed where a processor in a multiprocessor system having a copy of data gains assured ownership of data that the processor may then write. The method provides for the possibilities of conditions that may exist and provides a scenario that the requesting processor may have to wait for the ownership. Conditions are handled where the memory is the “owner” of the data and where other processor are requesting ownership, and where copies of the data exist at other processors. The method provides for messages to other processor having copies of the data informing them that the data is now invalid.

Claims12

Dependent claims

A method for a processor to gain assured ownership and an up-to-date copy of data, wherein the processor is part of a multiprocessor system, the method comprising the steps of:

keeping track of locations of the up-to-date data and ownership thereof,
a first processor, having a copy of the data but not ownership, issuing a change-to-dirty command, CTD, that requests ownership of the data by the first processor,
responding to the CTD command by,
returning a success response, CTD-success, to the first processor if the first processor is unambiguously determined to have an up-to-date copy of the data, and
updating only the ownership of the data while not sending data, and
returning a wait for success response, CTD-check-OK, to the first processor if the first processor is not unambiguously determined to have an up-to-date copy of the data,
issuing a command wherein the up-to-date copy of the data is sent to the first processor, and
updating the ownership of the data.

5 more elements

Dependencies are inferred from the claim text.

Method and system for a processor to gain assured ownership of an up-to-date copy of data

Life of this patent

Method and system for a processor to gain assured ownership of an up-to-date copy of data

Life of this patent

Abstract

Claims12