International Business Machines Corporation

Harold F Kossman

Timothy John Mullins

Jeffrey Powers Bradford

Richard James Eickemeyer

Gordon Taylor Davis

Jeffrey Douglas Brown

Timothy Hume Heil

Steven R Kunkel

Thomas Basilio Genduso

James Allen Rose

William E Hammer

Ross Evan Johnson

Robert W Todd

An apparatus, program product and method initiate, in connection with a context switch operation, a prefetch of data likely to be used by a thread prior to resuming execution of that thread. As a result, once it is known that a context switch will be performed to a particular thread, data may be prefetched on behalf of that thread so that when execution of the thread is resumed, more of the working state for the thread is likely to be cached, or at least in the process of being retrieved into cache memory, thus reducing cache-related performance penalties associated with context switching.

Context switch data prefetching in multithreaded computer

An apparatus initiates, in connection with a context switch operation, a prefetch of data likely to be used by a thread prior to resuming execution of that thread. As a result, once it is known that a context switch will be performed to a particular thread, data may be prefetched on behalf of that thread so that when execution of the thread is resumed, more of the working state for the thread is likely to be cached, or at least in the process of being retrieved into cache memory, thus reducing cache-related performance penalties associated with context switching.

A method, apparatus and computer program product are provided for implementing polymorphic branch history table (BHT) reconfiguration. A BHT includes a plurality of predetermined configurations corresponding predetermined operational modes. A first BHT configuration is provided. Checking is provided to identify improved performance with another BHT configuration. The BHT is reconfigured to provide improved performance based upon the current workload.

Implementing polymorphic branch history table reconfiguration

An apparatus, program product and method initiate, in connection with a context switch operation, a prefetch of at least one instruction likely to be executed by a thread prior to resuming execution of that thread. As a result, once it is known that a context switch will be performed to a particular thread, one or more instructions may be prefetched on behalf of that thread so that when execution of the thread is resumed, those instructions are more likely to be cached, or at least in the process of being retrieved into cache memory, thus enabling a thread to begin executing instructions more quickly than if the thread was required to fetch those instructions upon resumption of its execution.

Context switch instruction prefetching in multithreaded computer

A prefetch mechanism using prefetch attributes is disclosed. In one aspect, an explicit request for data stored in a memory is provided, and a prefetch attribute in a page table entry associated with the explicit request is examined to determine whether to provide one or more prefetch requests based on the prefetch attribute. Another aspect includes determining dynamic prefetch attributes for use in prefetching data, in which prefetch attributes are adjusted based on memory access requests that target next sequential blocks of memory relative to the most recent previous access in a page of memory.

Prefetch mechanism based on page table attributes

A method and apparatus are provided for implementing thread replacement for optimal performance in a two-tiered multithreading structure. A first tier thread state storage stores a limited number of runnable thread register states. A second tier thread storage facility stores a second number of thread states that is greater than the limited number of runnable thread register states. Each stored thread state includes predefined selection data. A runnable thread selection logic coupled between the first tier thread state storage and the second tier thread storage facility, uses the stored predefined selection data for selectively exchanging thread states between the first tier limited number of runnable thread register states and the second tier thread storage facility.

Method and apparatus for implementing thread replacement for optimal performance in a two-tiered multithreading structure

A method and apparatus are provided for implementing two-tiered thread state multithreading support with a high clock rate. A first tier thread state storage stores a limited number of runnable thread register states. The limited number is less than a threshold value. Next thread selection logic coupled between the first tier thread state storage and a currently executing processor state, picks a next thread to run on a processor from the limited number of runnable thread register states. A second tier thread storage facility stores a second number of thread states that is greater than the limited number of runnable thread register states. A runnable thread selection logic coupled between the first tier thread state storage and the second tier thread storage facility, selectively exchanges thread states between the first tier limited number of runnable thread register states and the second tier thread storage facility.

Method and apparatus for implementing two-tiered thread state multithreading support with high clock rate

A method of using multithreading resources for improving handling instructions is operated by an improved multithreaded processor which includes a context select logic unit being arranged and configured for receiving and responding an interrupt including: a first controller for setting a pending thread latch when a hardware context is not available for executing a new thread for servicing the interrupt.

Multithreaded processor incorporating a thread latch register for

A method and system for enhanced performance multithread operation in a data processing system which includes a processor, a main memory store and at least two levels of cache memory. At least one instruction within an initial thread is executed. Thereafter, the state of the processor at a selected point within the first thread is stored, execution of the first thread is terminated and a second thread is selected for execution only in response to a level two or higher cache miss, thereby minimizing processor delays due to memory latency. The validity state of each thread is preferably maintained in order to minimize the likelihood of returning to a prior thread for execution before the cache miss has been corrected. A least recently executed thread is preferably selected for execution in the event of a nonvalidity indication in association with all remaining threads, in anticipation of a change to the valid status of that thread prior to all other threads. A thread switch bit may also be utilized to selectively inhibit thread switching where execution of a particular thread is deemed necessary.

Method and system for multi-thread switching only when a cache miss

Workstations are connected via workstation controllers to two computer systems where one of the workstation controllers is a primary or controlling workstation controller and the other workstation controller is connected to appear to the primary workstation controller as a workstation and is designated as the secondary or standby workstation controller. The standby workstation controller has its line impedance matching resistor connected to function as a line terminator but it can also function as a line driver resistor when the primary or controlling workstation controller fails, the failure of the primary or controlling workstation controller being detected by the secondary or standby workstation controller upon the failure of being polled by the primary or controlling workstation controller within a predetermined period of time. The line impedance matching resistor of the failing primary or controlling workstation controller then functions as a line terminator resistor. The primary or controlling workstation controller and the secondary or standby workstation controller are connected backwards with respect to the connection of workstation to workstation whereby the line impedance matching resistor of the workstation adjacent to the filing primary or controlling workstation controller can function as a line terminating resistor to permit the failing workstation controller to be removed from the system for repair without creating a line termination problem for the workstations and the standby workstation controller which has become the controlling workstation controller.

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Rochester, MN, United States of America

Harold F Kossman