Abstract: The present invention provides techniques that allow concurrent collection of cyclic garbage on reference counting systems. In general, candidate objects are found that may be part of cyclic garbage. Each candidate object has a reference count. Two tests are performed to determine if concurrent operations have affected the reference counts of the candidate objects. If concurrent operations have not affected the reference counts, the candidate objects are collected as garbage. Additionally, during garbage collection, the decrements to reference counts are delayed so that increments occur before decrements and so that decrements are held a predetermined time before being applied. This prevents decrementing a reference and collecting a cycle as garbage right before a reference is added to an object in the cycle.

Abstract: Techniques are disclosed for schedule management. By way of example, a method for managing performance of tasks of a thread associated with a processor comprises the following steps. A request to execute a task of a first task type within the thread is received. A determination is made whether the processor is currently executing a critical section of a task of a second task type within the thread. When it is determined that the processor is not executing a critical section of the second task type within the thread, the task of the first task type is executed within the thread. When it is determined that the processor is executing a critical section of the first task type within the thread, a determination is made whether the request for execution of the task of the first task type within the thread is deferrable based on a prior execution of one or more units of the first task type.

Abstract: Techniques are disclosed for schedule management. By way of example, a method for managing performance of tasks in threads associated with at least one processor comprises the following steps. One or more units of a first task type are executed. A count of the one or more units of the first task type executed is maintained. The count represents one or more credits accumulated by the processor for executing the one or more units of a first task type. One or more units of a second task type are executed. During execution of the one or more units of a second task type, a request to execute at least one further unit of the first task type is received. The amount of credits in the count is checked. When it is determined that there is sufficient credit in the count, the request to execute the at least one further unit of the first task type is forgone, and execution of the one or more units of the second task type continues.

Abstract: The present invention provides techniques that allow concurrent collection of cyclic garbage on reference counting systems. In general, candidate objects are found that may be part of cyclic garbage. Each candidate object has a reference count. Two tests are performed to determine if concurrent operations have affected the reference counts of the candidate objects. If concurrent operations have not affected the reference counts, the candidate objects are collected as garbage. Additionally, during garbage collection, the decrements to reference counts are delayed so that increments occur before decrements and so that decrements are held a predetermined time before being applied. This prevents decrementing a reference and collecting a cycle as garbage right before a reference is added to an object in the cycle.

Abstract: The present invention provides techniques that allow concurrent collection of cyclic garbage on reference counting systems. In general, candidate objects are found that may be part of cyclic garbage. Each candidate object has a reference count. Two tests are performed to determine if concurrent operations have affected the reference counts of the candidate objects. If concurrent operations have not affected the reference counts, the candidate objects are collected as garbage. Additionally, during garbage collection, the decrements to reference counts are delayed so that increments occur before decrements and so that decrements are held a predetermined time before being applied. This prevents decrementing a reference and collecting a cycle as garbage right before a reference is added to an object in the cycle.

Abstract: A method for performing garbage collection for a real-time application uses a memory for determining an amount of memory required to run the garbage collection process and waits until the determined amount of memory is available, then allocates memory space for the application by segmenting the memory space into a number of pages of a predetermined size. A mutator is used for assuring that only non-null, unmarked objects are placed into a write buffer. A hybrid collector is used for removing the dead objects and defragmenting the memory space.

Abstract: A garbage collection system that needs to meet real-time requirements uses an eager read barrier that performs a forwarding operation as soon as a quantity is loaded. The barrier maintains a to-space invariant by including a forwarding pointer in the header of objects to be moved or accessed that normally points to the object itself. However, if the object has been moved, the forwarding pointer points to the new object location. The eager read barrier maintains the registers and stack cells such that the registers and stack cells always point into to-space. Barrier-sinking and common sub-expression elimination are used to minimize the overhead associated with the read barrier.

Abstract: A method of performing data and pointer compression includes, in a buffer which is formed between a processor and a level one cache and stores plural tags and full-word values associated with the tags, when the buffer is presented with an address, breaking the address into a line number which indexes a set of the full-word values, and a tag which is used as a key to determine whether a value in the set of full-word values includes a value associated with the presented address, if a tag in the presented address matches a tag in the buffer, returning a full-word value in the buffer which is associated with the tag, and storing the returned full-word value in a destination register of an instruction which originated the presented address, and if a tag in the presented address does not match a tag in the buffer, generating a fault and branching control to a pre-defined handler.

Abstract: A garbage collection system that needs to meet real-time requirements uses an eager read barrier that performs a forwarding operation as soon as a quantity is loaded. The barrier maintains a to-space invariant by including a forwarding pointer in the header of objects to be moved or accessed that normally points to the object itself. However, if the object has been moved, the forwarding pointer points to the new object location. The eager read barrier maintains the registers and stack cells such that the registers and stack cells always point into to-space. Barrier-sinking and common sub-expression elimination are used to minimize the overhead associated with the read barrier.

Abstract: A garbage collection system that needs to meet real-time requirements breaks large objects that need to be moved into a series of arraylets. The arraylets are sized such that the amount of time required to move the arraylets is bounded by a predetermined amount. The arrays are preferably uniformly represented in the header for each array with a series of arraylet pointers that indicate the location of the arraylets. Control-flow graph splitting is used to eliminate multiple tests and allow common sub-expression elimination. Strip-mining can also be used to improve the efficiency of the process.

Abstract: A method of executing a task includes executing, by using a processor, a first task including a low-frequency task in which garbage is collected using a garbage collector, initializing a second task including a high-frequency task by constructing an instance of a class that implements a standard runnable thread interface, and creating a data structure for supporting communication between the second task and lower priority threads, the data structure being accessible by a thread running in a garbage-collected heap in the first task to communicate data between the high-frequency task and the low-frequency task, validating the second task to ensure that the second task is executable without synchronizing with the first task, instantiating the second task to create a class for executing the second task; and after the instantiating the second task, executing the second task, the garbage collector being preemptable by the second task.

Abstract: A method (and system) for executing a task includes executing a first task in which garbage is collected using a garbage collector, and executing a second task, the garbage collector being preemptable (e.g., preempted) by the second task.

Abstract: A garbage collection system that needs to meet real-time requirements uses an eager read barrier that performs a forwarding operation as soon as a quantity is loaded. The barrier maintains a to-space invariant by including a forwarding pointer in the header of objects to be moved or accessed that normally points to the object itself. However, if the object has been moved, the forwarding pointer points to the new object location. The eager read barrier maintains the registers and stack cells such that the registers and stack cells always point into to-space. Barrier-sinking and common sub-expression elimination are used to minimize the overhead associated with the read barrier.

Abstract: Techniques are disclosed for schedule management. By way of example, a method for managing performance of tasks in threads associated with at least one processor comprises the following steps. One or more units of a first task type are executed. A count of the one or more units of the first task type executed is maintained. The count represents one or more credits accumulated by the processor for executing the one or more units of a first task type. One or more units of a second task type are executed. During execution of the one or more units of a second task type, a request to execute at least one further unit of the first task type is received. The amount of credits in the count is checked. When it is determined that there is sufficient credit in the count, the request to execute the at least one further unit of the first task type is forgone, and execution of the one or more units of the second task type continues.

Abstract: Techniques are disclosed for schedule management. By way of example, a method for managing performance of tasks of a thread associated with a processor comprises the following steps. A request to execute a task of a first task type within the thread is received. A determination is made whether the processor is currently executing a critical section of a task of a second task type within the thread. When it is determined that the processor is not executing a critical section of the second task type within the thread, the task of the first task type is executed within the thread. When it is determined that the processor is executing a critical section of the first task type within the thread, a determination is made whether the request for execution of the task of the first task type within the thread is deferrable based on a prior execution of one or more units of the first task type.

Abstract: A garbage collection system that needs to meet real-time requirements utilizes a read barrier that is implemented in an optimizing compiler. The read barrier is implemented with a forwarding pointer positioned in a header of each object. The forwarding pointer points to the object unless the object has been moved. The barrier is optimized by breaking the barrier and applying barrier sinking to sink the read barrier to its point of use and by using sub-expression elimination. A null-check for the read barrier is combined with a null-check required by the real-time application. All objects are located and moved with the collector to minimize variations in mutator utilization.

Abstract: A method for performing garbage collection for a real-time application uses a memory for determining an amount of memory required to run the garbage collection process and waits until the determined amount of memory is available, then allocates memory space for the application by segmenting the memory space into a number of pages of a predetermined size. A mutator is used for assuring that only non-null, unmarked objects are placed into a write buffer. A hybrid collector is used for removing the dead objects and defragmenting the memory space.

Abstract: A garbage collection system that needs to meet real-time requirements with guaranteed space bounds uses a mostly non-copying hybrid collector that performs defragmentation with limited copying of objects. The garbage collection and the real-time application are interleaved on a time-based schedule. An interval for the interleaving is selected based upon a garbage collector processing rate, a garbage generation rate and a memory allocation rate of the real-time application. An amount of memory for the real-time application and the garbage collection process is selected based upon the maximum excess memory requirement of the garbage collection process and the maximum memory requirement for the application. Defragmentation is only performed when an amount of available memory falls below a predetermined level.

Abstract: A system includes a processor for executing a collector program to perform a method (e.g., a method of collection). The method includes using an object model during a collection phase that is different than an object model used during program execution. The processor may also perform a method including assigning a hash code to at least some objects, and consulting a structure that maintains a mapping of objects to hashcode values to determine said hashcode for one of said objects. The processor may also perform a method including storing a class pointer and garbage collector state information in a single word, and accessing said class pointer by masking out non-class bits.

Abstract: A garbage collection process for managing a memory includes a defragmentation cycle. The garbage collection process is interleaved with a running application on a time-based or work-based schedule. The memory is divided into pages which are further divided into blocks falling into one of a number of block size classes. Objects that were not used by applications during the last garbage collection phase are marked. Objects that were used are moved from pages containing the least live objects to pages containing the most live objects. Objects of the largest block size classes are moved first and objects of the smallest block size class are moved last. The garbage collection interval can be selected to satisfy desired CPU utilization or memory overhead requirements.