US 12,754,838 B2Granted

Garbage collection using detail card tables

AssigneeOracle International Corporation

InventorsThomas Schatzl, Albert Mingkun Yang

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Abstract

Techniques for garbage collection using detail cards are disclosed. A card in a card table and a detail card in a detail card table are associated with a heap segment. Bits in the detail card are associated, respectively, with heap subsegments of the heap segment. A garbage collector marks a first bit in the detail card as dirty. During a sweep cycle, the garbage collector determines that the card is clean, the first bit is dirty, and a second bit in the detail card is clean. During the sweep cycle, based on the card being clean, the first bit being dirty, and the second bit being clean, the garbage collector (a) scans a heap subsegment associated with the first bit for intergenerational references and (b) refrains from scanning a heap subsegment associated with the second bit for intergenerational references.

Claims20

Dependent claims

A method comprising:

marking, by a garbage collector executing in a runtime environment, a first bit in a first plurality of bits of a first detail card as dirty;
wherein a first card in a plurality of cards of a card table is associated with a first heap segment in a plurality of heap segments;
wherein the first plurality of bits of the first detail card are associated, respectively, with a first plurality of heap subsegments of the first heap segment;
and
wherein the first bit is associated with a first heap subsegment in the first plurality of heap subsegments;
determining, by the garbage collector during a sweep cycle, that (a) the first card is clean, (b) the first bit is dirty, and (c) a second bit in the first plurality of bits, associated with a second heap subsegment in the first plurality of heap subsegments, is clean;
and
based on the first card being clean, the first bit being dirty, and the second bit being clean:
scanning, by the garbage collector during the sweep cycle, the first heap subsegment for intergenerational references;
and
refraining from scanning, by the garbage collector during the sweep cycle, the second heap subsegment for intergenerational references;
wherein the method is performed by at least one device including a hardware processor.

9 more elements

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

marking, by a garbage collector executing in a runtime environment, a first bit in a first plurality of bits of a first detail card as dirty;
wherein a first card in a plurality of cards of a card table is associated with a first heap segment in a plurality of heap segments;
wherein the first plurality of bits of the first detail card are associated, respectively, with a first plurality of heap subsegments of the first heap segment;
and
wherein the first bit is associated with a first heap subsegment in the first plurality of heap subsegments;
determining, by the garbage collector during a sweep cycle, that (a) the first card is clean, (b) the first bit is dirty, and (c) a second bit in the first plurality of bits, associated with a second heap subsegment in the first plurality of heap subsegments, is clean;
and
based on the first card being clean, the first bit being dirty, and the second bit being clean:
scanning, by the garbage collector during the sweep cycle, the first heap subsegment for intergenerational references;
and
refraining from scanning, by the garbage collector during the sweep cycle, the second heap subsegment for intergenerational references.

8 more elements

A system comprising:

at least one device including a hardware processor;
the system being configured to perform operations comprising:
marking, by a garbage collector executing in a runtime environment, a first bit in a first plurality of bits of a first detail card as dirty;
wherein a first card in a plurality of cards of a card table is associated with a first heap segment in a plurality of heap segments;
wherein the first plurality of bits of the first detail card are associated, respectively, with a first plurality of heap subsegments of the first heap segment;
and
wherein the first bit is associated with a first heap subsegment in the first plurality of heap subsegments;
determining, by the garbage collector during a sweep cycle, that (a) the first card is clean, (b) the first bit is dirty, and (c) a second bit in the first plurality of bits, associated with a second heap subsegment in the first plurality of heap subsegments, is clean;
and
based on the first card being clean, the first bit being dirty, and the second bit being clean:
scanning, by the garbage collector during the sweep cycle, the first heap subsegment for intergenerational references;
and
refraining from scanning, by the garbage collector during the sweep cycle, the second heap subsegment for intergenerational references.

10 more elements

Dependencies are inferred from the claim text.