US 12,561,239 B1Granted

Techniques for concurrent multi-generation garbage collection

AssigneeOracle International Corporation

InventorsErik Österlund, Axel Boldt-Christmas, Stefan Mats Rikard Karlsson

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Abstract

Techniques are disclosed for performing a garbage collection process that processes reference objects in multiple generations of a memory area while a program instance is concurrently manipulating runtime objects in the memory area. During one phase of concurrent operations, the system applies one rule set for processing reference objects in one generation of the memory area. During another phase of concurrent operations, the system applies another rule set for processing reference objects residing in another generation of the memory area. To enable the performance of the one phase of concurrent operations and the other phase of concurrent operations at the same time, the system tracks the accessibility of a given runtime object with respect to both of the one generation and the other generation. The system tracks the given runtime object's accessibility with respect to both generations by embedding metadata into a pointer that refers to the given runtime object.

Claims20

Dependent claims

One or more non-transitory computer-readable media comprising instructions that, when executed by one or more hardware processors, cause performance of operations comprising:

performing a first set of garbage operations targeting a first section of a memory area, the first set of garbage collection operations comprising:
identifying a first reference object that holds a first reference to a first referent, the first section of the memory area comprising the first reference object and the first referent, wherein the first reference is classified as a second reference type;
based, at least in part, on determining that the first reference object is classified as a first type of reference object, refraining from adding the first reference object to a first list of one or more reference objects;
breaking a first set of one or more references of the second reference type that are respectively held by a first set of one or more reference objects comprised within the first list of one or more reference objects, wherein the first set of one or more references does not comprise the first reference to the first referent;
performing a second set of garbage collection operations targeting a second section of the memory area, the second set of garbage collection operations comprising operations comprising:
identifying a second reference object that holds a second reference to a second referent, the second section of the memory area comprising the second reference object and the second referent, wherein (a) the second reference object is classified as the first type of reference object and (b) the second reference is classified as the second reference type;
based, at least in part, on at least one of:
(a) a first timestamp corresponding to a prior set of garbage collection operations targeting the second section of the memory area or (b) a second timestamp corresponding to the second reference object being used to access the second referent, adding the second reference object to a second list of one or more reference objects;
breaking a second set of one or more references of the second reference type that are respectively held by a second set of one or more reference objects comprised within the second list of one or more reference objects, wherein the second set of one or more references comprises the second reference to the second referent;
and
updating the first timestamp, wherein the first timestamp subsequently corresponds to the second set of garbage collection operations targeting the second section of the memory area.

8 more elements

A method comprising:

performing a first set of garbage collection operations targeting a first section of a memory area, the first set of garbage collection operations comprising:
identifying a first reference object that holds a first reference to a first referent, the first section of the memory area comprising the first reference object and the first referent, wherein the first reference is classified as a second reference type;
based, at least in part, on determining that the first reference object is classified as a first type of reference object, refraining from adding the first reference object to a first list of one or more reference objects;
breaking a first set of one or more references of the second reference type that are respectively held by a first set of one or more reference objects comprised within the first list of one or more reference objects, wherein the first set of one or more references does not comprise the first reference to the first referent;
performing a second set of garbage collection operations targeting a second section of the memory area, the second set of garbage collection operations comprising:
identifying a second reference object that holds a second reference to a second referent, the second section of the memory area comprising the second reference object and the second referent, wherein (a) the second reference object is classified as the first type of reference object and (b) the second reference is classified as the second reference type;
based, at least in part, on at least one of:
(a) a first timestamp corresponding to a prior set of garbage collection operations targeting the second section of the memory area or (b) a second timestamp corresponding to the second reference object being used to access the second referent, adding the second reference object to a second list of one or more reference objects;
breaking a second set of one or more references of the second reference type that are respectively held by a second set of one or more reference objects comprised within the second list of one or more reference objects, wherein the second set of one or more references comprises the second reference to the second referent;
and
updating the first timestamp, wherein the first timestamp subsequently corresponds to the second set of garbage collection operations targeting the second section of the memory area,
wherein the method is performed by at least one device including a hardware processor.

9 more elements

A system comprising:

at least one device including a hardware processor;
the system being configured to perform operations comprising:
performing a first set of garbage collection operations targeting a first section of a memory area, the first set of garbage collection operations comprising:
identifying a first reference object that holds a first reference to a first referent, the first section of the memory area comprising the first reference object and the first referent, wherein the first reference is classified as a second reference type;
based, at least in part, on determining that the first reference object is classified as a first type of reference object, refraining from adding the first reference object to a first list of one or more reference objects;
breaking a first set of one or more references of the second reference type that are respectively held by a first set of one or more reference objects comprised within the first list of one or more reference objects, wherein the first set of one or more references does not comprise the first reference to the first referent;
performing a second set of garbage collection operations targeting a second section of the memory area, the second set of garbage collection operations comprising:
identifying a second reference object that holds a second reference to a second referent, the second section of the memory area comprising the second reference object and the second referent, wherein (a) the second reference object is classified as the first type of reference object and (b) the second reference is classified as the second reference type;
based, at least in part, on at least one of:
(a) a first timestamp corresponding to a prior set of garbage collection operations targeting the second section of the memory area or (b) a second timestamp corresponding to the second reference object being used to access the second referent, adding the second reference object to a second list of one or more reference objects;
breaking a second set of one or more references of the second reference type that are respectively held by a second set of one or more reference objects comprised within the second list of one or more reference objects, wherein the second set of one or more references comprises the second reference to the second referent;
and
updating the first timestamp, wherein the first timestamp subsequently corresponds to the second set of garbage collection operations targeting the second section of the memory area.

10 more elements

Dependencies are inferred from the claim text.