53 results about "Compare-and-swap" patented technology

Producers and consumer processes may synchronize and transfer data using a shared data structure. After locating a potential transfer location that indicates an EMPTY status, a producer may store data to be transferred in the transfer location. A producer may use a compare-and-swap (CAS) operation to store the transfer data to the transfer location. A consumer may subsequently read the transfer data from the transfer location and store, such as by using a CAS operation, a DONE status indicator in the transfer location. The producer may notice the DONE indication and may then set the status location back to EMPTY to indicate that the location is available for future transfers, by the same or a different producer. The producer may also monitor the transfer location and time out if no consumer has picked up the transfer data.

The cache arrangement includes a cache that may be organized as a plurality of memory banks in which each memory bank includes a plurality of slots. Each memory bank has an associated control slot that includes groups of extents of tags. Each cache slot has a corresponding tag that includes a bit value indicating the availability of the associated cache slot, and a time stamp indicating the last time the data in the slot was used. The cache may be shared by multiple processors. Exclusive access of the cache slots is implemented using an atomic compare and swap instruction. The time stamp of slots in the cache may be adjusted to indicate ages of slots affecting the amount of time a particular portion of data remains in the cache. Associated with each processor is a unique extent increment used to determine a next location for that particular processor when attempting to locate an available slot.

A concurrent incremental garbage collector where tracking and summarization of modified references is concurrent with application operations. A card table is arranged with write barriers so that an application's modification of objects in memory cards are memorialized in the card table. The collector performs an atomic operation, e.g., a compare-and-swap (CAS), on the card table to detect modified or written to objects. Card table indicators of dirtied cards are reset or emptied and the corresponding dirtied cards are scanned for the modifications and the remembered sets updated. Another CAS is performed on the same card table and if any dirtied cards are indicated the collector preserves the card table with the dirtied indicators and operates on a distant card table. If the CAS succeeds no modifications were made and the collector operates on the next scheduled card table group.

An object storage system comprises one or more computer processors or threads that can concurrently access a shared memory, the shared memory comprising an array of equally-sized cells. In one embodiment, each cell is of the size used by the processors to represent a pointer, e.g., 64 bits. Using an algorithm performing only one memory write, and using a hardware-provided transactional operation, such as a compare-and-swap instruction, to implement the memory write, concurrent access is safely accommodated in a lock-free manner.

A dummy node is enqueued to a concurrent, non-blocking, lock-free FIFO queue only when necessary to prevent the queue from becoming empty. The dummy node is only enqueued during a dequeue operation and only when the queue contains a single user node during the dequeue operation. This reduces overhead relative to conventional mechanisms that always keep a dummy node in the queue. User nodes are enqueued directly to the queue and can be immediately dequeued on-demand by any thread. Preferably, the enqueueing and dequeueing operations include the use of load-linked/store conditional (LL/SC) synchronization primitives. This solves the ABA problem without requiring the use a unique number, such as a queue-specific number, and contrasts with conventional mechanisms that include the use of compare-and-swap (CAS) synchronization primitives and address the ABA problem through the use of a unique number. In addition, storage ordering fences are preferably inserted to allow the algorithm to run on weakly consistent processors.

A single atomic instruction is used to change up to four disjoint areas in memory concurrently in an extended compare and swap operation, replacing traditional locks for serialization and providing recovery for all queue manipulations. Use count-based responsibility passing is employed so that any number of tasks can read the various message queue chains, concurrent with queue updates being made. A summary queue update sequence number is maintained to provide concurrent chain update detection, so that any number of tasks can add elements to the end, or remove elements from the middle (i.e. any where in the chain) concurrently. Concurrent footprinting is used with chain manipulation, so that all (or none) of the chaining indicators and a footprint are set with a single, non-interruptible instruction, making it possible for recovery to always take the correct action. One such use of concurrent footprinting is the concurrent footprinting of use count changes, while another is the transfer of ownership of message queue control blocks. In a preferred embodiment on an IBM S/390 platform, the Perform Locked Operation (PLO) instruction is used to perform the extended compare and swap operations.

Systems, methods, and computer products that determine how to optimize serialization code that has been ported from other computer systems to the OS/390 UNIX system. General-purpose UNIX systems may not provide sufficient facilities; such as compiler run-time APIs like the Compare and Swap C Run-Time Library API, to accommodate the performance-related features of serialized code in complex applications. When porting a high-performance application from other UNIX platforms to IBM OS/390 UNIX, serialized code performance of the application may be limited. The present invention may be implemented by advantageously determining when substitution of the Compare and Swap C Run-Time Library API calls for pthread_mutex calls will improve the execution of serialized code on the IBM OS/390 UNIX system.

Methods, parallel computers, and computer program products for analyzing update conditions for shared variable directory (SVD) information in a parallel computer are provided. Embodiments include a runtime optimizer receiving a compare-and-swap operation header. The compare-and-swap operation header includes an SVD key, a first SVD address, and an updated first SVD address. The first SVD address is associated with the SVD key in a first SVD associated with a first task. Embodiments also include the runtime optimizer retrieving from a remote address cache associated with the second task, a second SVD address indicating a location within a memory partition associated with the first SVD in response to receiving the compare-and-swap operation header. Embodiments also include the runtime optimizer determining whether the second SVD address matches the first SVD address and transmitting a result indicating whether the second SVD address matches the first SVD address.

A local sorting module includes a set of storage elements storing binary vectors configured in a one-dimensional (1D) or two-dimensional (2D) array structure and separated by respective comparators configured to conditionally compare and sort the binary vectors. The comparators may perform a sort using a compare-and-flip or a compare-and-swap operation. Local sorting modules may be coupled with a global sorting module for enabling a tournament sort algorithm to output values stored in storage elements one at a time until all data is outputted in a predetermined sorting order.

The invention relates to the technical field of data storage, and provides a data writing method, a device, a terminal device and a computer storage medium of a circular queue. The data writing methodcomprises the following steps: when any thread is ready to write data to a circulating queue, judging whether other threads are currently writing data to the circulating queue; If other threads are currently writing data to the circular queue, returning to the step of judging whether other threads are currently writing data to the circular queue and subsequent steps after the preset time length;If no other thread is currently writing data to the circular queue, each thread competing for a first pointer using atomic operation of a compare and swap mechanism, the first pointer pointing to thenext writable data location in the circular queue; and writing data to the circular queue by a thread that successfully competes for the first pointer. The method can effectively improve the data writing efficiency of the circulating queue.

A Lock Free and Wait Free method of the appearance of an atomic double word compare and swap (DCAS) operation on a pointer and ABA avoidance sequence number pair of words while using atomic single word compare and swap (CAS) instructions. To perform this function an area of memory is used by this invention and described as a protected pointer. The protected pointer consists of three words, comprising of: a) a pointer to a memory location, such as a node in linked list, together with b) an ABA avoidance sequence number, and combined together with a third word containing c) a specially crafted hash code derived from the pointer and the ABA avoidance sequence number. The three words together are referred to as a three word protected pointer and are used by this invention for implementing a Lock-Free and Wait-Free method of simulating DCAS using three CAS instructions. The specially crafted hash code, when used in a manner as described in this invention, enable competing threads in a multithreaded environment to advance a partially completed method of the appearance of an atomic double word compare and swap (DCAS) operation on a pointer and ABA avoidance sequence number pair of words while using atomic single word compare and swap (CAS) instructions as partially executed by a different thread. The ability for any thread to complete a partially completed appearance of DCAS provides for wait free operation.

Methods, parallel computers, and computer program products for analyzing update conditions for shared variable directory (SVD) information in a parallel computer are provided. Embodiments include a runtime optimizer receiving a compare-and-swap operation header. The compare-and-swap operation header includes an SVD key, a first SVD address, and an updated first SVD address. The first SVD address is associated with the SVD key in a first SVD associated with a first task. Embodiments also include the runtime optimizer retrieving from a remote address cache associated with the second task, a second SVD address indicating a location within a memory partition associated with the first SVD in response to receiving the compare-and-swap operation header. Embodiments also include the runtime optimizer determining whether the second SVD address matches the first SVD address and transmitting a result indicating whether the second SVD address matches the first SVD address.

Systems, methods, and computer program products are disclosed for intermixing different types of machine instructions. One embodiment of the invention provides a protocol for intermixing the different types of machine instructions. By adhering to the protocol, different types of machine instructions may be intermixed to concurrently update data structures without leading to unpredictable results.

An apparatus, system, and method are disclosed for efficient synchronization of a sliding buffer window to prevent packet re-injection in an IP network. The steps of the method include receiving a data packet which comprises a packet sequence number. The method initializes a replay counter, an update counter, and a circular buffer window. The circular buffer window may comprise at least one window bank and the circular buffer window may also comprise a current window bank. Furthermore, the method may include determining that the packet sequence number is greater than a maximum current bank value. In response, the method may define shifting the circular buffer window such that a current window bank position is incremented. The method may then include determining that the packet sequence number is inside the current window bank and accepting the data packet. Furthermore, a Double Compare and Swap (DCS) operation may update the bit indicator and increment the update counter and replay counter. Also, a Compare and Swap and Store (CSST) operation may increment the update counter and replay counter and set a shifted window bank. Therefore, DCS and CSST operation may still be used without having to resort to traditional locks with higher overhead. In addition, the buffer window may be an arbitrary size and is not limited to the machine architecture limit for compare and swap operations.