US 5,313,647 AGranted

Digital data processor with improved checkpointing and forking

AssigneeKendall Square Research Corporation

InventorsMark A. Kaufman, Fernando Oliveira

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Abstract

A digital data processing apparatus includes a processing element that executes a process for generating requests for access to mapped data in a memory element. The apparatus also includes a fork/checkpoint-signalling element that generates "new-process signals" which delineate new time intervals. The apparatus responds to data requests generated by the process before the first new-process signal by accessing a requested datum as stored in a first set in memory. An address space manager responds to certain requests, e.g., for write access, in subsequent intervals for copying the requested datum from the most recent set in which it is stored to the current interval and, thereafter, accessing that copy. The manager responds to other requests, e.g., those for read-type access, by accessing the requested datum in the most recent set in which it is stored. A fork element can create a second process that initially duplicates a first one and can initiate generation of a new-process signal in connection with creation of the second process.

Claims44

Dependent claims

A digital data processing apparatus comprising:

A. memory means for storing data,
B. first process means for executing a first process and for generating in connection therewith at least one request for mapped access to said data,
C. fork/checkpoint signalling means for generating one or more new-process signals, each new-process signal delineating a successive process interval,
the interval preceding the first new-process signal being referred to as the first interval,
D. means for responding to a request for access to a datum generated by the first process during said first interval for providing access to the requested datum as stored in a first set of data stored in said memory means,
the first set being referred to as associated with said first interval of the first process,
E. first address space management means, coupled to said first process means and to said fork/checkpoint signalling means, for responding at least to an initial request by that process during a current interval subsequent to said first interval for write-type access to a datum, for
i) accessing the requested datum as stored in a set associated with a prior interval of the first process, and
ii) generating a further datum initially identical to that accessed datum;
F. said first address space management means including means for storing said initially identical datum in a set in said memory means associated with the current interval of the first process, and
G. said first address space management means further including means responsive to said initial request by the first process during said current interval for at least write-type access to a datum, as well as to subsequent requests for any of read-type and write-type access to that same datum by that same process during that same interval, for accessing said initially identical datum as stored in the set associated with the current interval of the first process, and otherwise for accessing the requested datum as stored in a set associated with a prior interval of the first process.

8 more elements

A method for operating a digital data processing apparatus comprising the steps of:

A. providing memory means for storing data,
B. executing a first process and generating in connection therewith at least one request for mapped access to said data,
C. generating one or more new-process signals, each new-process signal delineating a successive process interval,
the interval preceding the first new-process signal being referred to as the first interval,
D. responding to a request for access to a datum generated by the first process during said first interval for providing access to the requested datum as stored in a first set of data stored in said memory means,
the first set being referred to as associated with said first interval of the first process,
E. responding at least to an initial request by said first process during a current interval subsequent to said first interval for write-type access to a datum, for
i) accessing the requested datum as stored in a set associated with a prior interval of the first process, and
ii) generating a further datum initially identical to that accessed datum,
F. storing said initially identical datum in a set in said memory means associated with the current interval of the first process, and
G. responding to said initial request by the first process during said current interval for at least write-type access to a datum, as well as to subsequent requests for any of read-type and write-type access to that same datum by that same process during that same interval, for accessing said initially identical datum as stored in the set associated with the current interval of the first process, and otherwise for accessing the requested datum as stored in a set associated with a prior interval of the first process.

8 more elements

Dependencies are inferred from the claim text.