Method and system for minor garbage collection in a multitasking environment
View Patent ↗A method for minor garbage collection in a multitasking environment involves marking cards as clean, where the cards designate ranges of memory locations in a shared older generation. The method further involves marking a card as dirty when a reference field of an object within the card is modified, where a memory location of the reference field is designated by the card, where the reference field references a live young object in a task-specific young generation, and where the task-specific young generation is associated with a first task. The method further involves marking the card as single-dirty when the card only includes roots of live young objects in the task-specific young generation, and optimizing task-specific minor garbage collection for a second task by skipping the card when the card is marked as single-dirty.
1. A method for minor garbage collection in a multitasking environment comprising:
marking, by a processor, a plurality of cards as clean, wherein the plurality of cards designates ranges of memory locations in a shared older generation;
marking, by the processor, a card selected from the plurality of cards as dirty when a reference field of an object within the card is modified,
wherein a memory location of the reference field is designated by the card,
wherein the reference field references a live young object in a task-specific young generation selected from a plurality of task-specific generations, and
wherein the task-specific young generation is associated with a first task selected from a plurality of tasks;
marking, by the processor, the card as single-dirty when the card only includes roots of live young objects in the task-specific young generation, wherein marking the card as single-dirty comprises recording a unique identifier associated with the first task, wherein the unique identifier is a byte comprising a plurality of possible values, and wherein the plurality of possible values is associated with dirty, clean, and the plurality of tasks; and
optimizing, by the processor, task-specific minor garbage collection for a second task selected from the plurality of tasks by skipping the card when the card is marked as single-dirty.
2. The method of claim 1 , further comprising:
including the card during task-specific minor garbage collection for the first task when the card is marked as single-dirty.
3. The method of claim 1 , further comprising:
including the card during task-specific minor garbage collection for the second task when the card is marked as dirty.
4. The method of claim 1 , further comprising:
scanning the card to identify roots of live young objects when the card is marked as dirty, wherein marking the card as single-dirty is performed based on information gathered while scanning the card.
5. The method of claim 1 , wherein marking the card as single-dirty is performed when the card is filled with promoted objects associated with the first task.
6. A system comprising:
a processor;
a memory comprising:
a plurality of task-specific young generations for storing young objects associated with a plurality of tasks; and
a shared older generation for storing promoted objects associated with the plurality of tasks; and
a garbage collector executing on the processor and configured to perform minor garbage collection by:
marking a plurality of cards as clean, wherein the plurality of cards designates ranges of memory locations in the shared older generation;
marking a card selected from the plurality of cards as dirty when a reference field of an object within the card is modified,
wherein a memory location of the reference field is designated by the card, and
wherein the reference field references a live young object in a task-specific young generation selected from the plurality of task-specific generations;
marking the card as single-dirty when the card only includes roots of live young objects in the task-specific young generation, wherein marking the card as single-dirty comprises recording a unique identifier associated with the first task, wherein the unique identifier is a byte comprising a plurality of possible values, and wherein the plurality of possible values is associated with dirty, clean, and the plurality of tasks; and
optimizing task-specific minor garbage collection for a second task selected from the plurality of tasks by skipping the card when the card is marked as single-dirty.
7. The system of claim 6 , wherein the garbage collector is further configured to perform minor garbage collection by:
including the card during task-specific minor garbage collection for the first task when the card is marked as single-dirty.
8. The system of claim 6 , wherein the garbage collector is further configured to perform minor garbage collection by:
including the card during task-specific minor garbage collection for the second task when the card is marked as dirty.
9. The system of claim 6 , wherein the garbage collector is further configured to perform minor garbage collection by:
scanning the card to identify roots of live young objects when the card is marked as dirty, wherein marking the card as single-dirty is performed based on information gathered while scanning the card.
10. The system of claim 6 , wherein the garbage collector is configured mark the card as single-dirty when the card is filled with promoted objects associated with the first task.
11. A computer readable medium comprising executable instructions for minor garbage collection in a multitasking environment, wherein the executable instructions comprise instructions to:
mark a plurality of cards as clean, wherein the plurality of cards designates ranges of memory locations in a shared older generation;
mark a card selected from the plurality of cards as dirty when a reference field of an object within the card is modified,
wherein a memory location of the reference field is designated by the card,
wherein the reference field references a live young object in a task-specific young generation selected from a plurality of task-specific generations, and
wherein the task-specific young generation is associated with a first task selected from a plurality of tasks;
mark the card as single-dirty when the card only includes roots of live young objects in the task-specific young generation, wherein instructions to mark the card as single-dirty comprise instructions to record a unique identifier associated with the first task, wherein the unique identifier is a byte comprising a plurality of possible values, and wherein the plurality of possible values is associated with dirty, clean, and the plurality of tasks; and
optimize task-specific minor garbage collection for a second task selected from the plurality of tasks by skipping the card when the card is marked as single-dirty.
12. The computer readable medium of claim 11 , wherein the executable instructions further comprise instructions to:
include the card during task-specific minor garbage collection for the first task when the card is marked as single-dirty.
13. The computer readable medium of claim 11 , wherein the executable instructions further comprise instructions to:
include the card during task-specific minor garbage collection for the second task when the card is marked as dirty.
14. The computer readable medium of claim 11 , wherein the executable instructions further comprise instructions to:
scan the card to identify roots of live young objects when the card is marked as dirty, wherein instructions to mark the card as single-dirty are executed based on information gathered while scanning the card.
15. The computer readable medium of claim 11 , wherein instructions to mark the card as single-dirty are executed when the card is filled with promoted objects associated with the first task.