International Business Machines Corporation

Kevin Alexander Stoodley

Marcel Mitran

Chung-Lung K Shum

Vijay Sundaresan

Mark Graham Stoodley

Charles W Gainey, Jr

Allan Henry Kielstra

Michael S Fulton

Levon Sassoon Stepanian

Trent Gray-Donald

Derek Bruce Inglis

Brian Ward Thomson

Nikola Grcevski

Timothy John Slegel

Mark S Farrell

Gheorghe Calin Cascaval

Brian L Smith

David M Mooney

Kevin Paul Hickman

Donald James McCrady

William Sarantakos

Ravi Nair

Raul Esteban Silvera

Yaoqing Gao

Evelyn Duesterwald

Andrew Russell Low

Ali Ijaz Sheikh

Graeme Johnson

Patrick R Doyle

Guansong Zhang

Marius Pirvu

Arie Tal

Siddhartha Chatterjee

John D Keenleyside

Christopher A Lapkowski

Iam R Amelina

Julian Z L Wang

Chung-Ling K Shum

Charles W Gainey

Chung-Lung Kevin Shum

Marcel M Mitran

Charles W Gainey Jr

Brian Leonard Smith

In an approach for utilizing overlay hooks to increase code coverage, a processor inserts an overlay hook in program code at a location within the program code corresponding to a condition statement. A processor executes the program code. Upon reaching the overlay hook, a processor branches to a set of instructions operative to document an outcome of the condition statement. A processor executes the condition statement. A processor records the outcome of the condition statement.

Code coverage through overlay hooks

Embodiments of the invention relate to performing run-time instrumentation. Run-time instrumentation is captured, by a processor, based on an instruction stream of instructions of an application program executing on the processor. The capturing includes storing the run-time instrumentation data in a collection buffer of the processor. A run-time instrumentation sample point trigger is detected by the processor. Contents of the collection buffer are copied into a program buffer as a reporting group based on detecting the run-time instrumentation sample point trigger. The program buffer is located in main storage in an address space that is accessible by the application program.

Hardware based run-time instrumentation facility for managed run-times

The invention relates to implementing run-time instrumentation directed sampling. An aspect of the invention includes fetching a run-time instrumentation next (RINEXT) instruction from an instruction stream. The instruction stream includes the RINEXT instruction followed by a next sequential instruction (NSI) in program order. The method further includes executing the RINEXT instruction by a processor. The executing includes determining whether a current run-time instrumentation state enables setting a sample point for reporting run-time instrumentation information during program execution. Based on the current run-time instrumentation state enabling setting the sample point, the NSI is a sample instruction for causing a run-time instrumentation event. Based on executing the NSI sample instruction, the run-time instrumentation event causes recording of run-time instrumentation information into a run-time instrumentation program buffer as a reporting group.

Run-time instrumentation directed sampling

Aspects of the invention relate to executing a run-time-instrumentation EMIT (RIEMIT) instruction. A processor is configured to capture the run-time-instrumentation information of a stream of instructions. The RIEMIT instruction is fetched and executed. It is determined if the current run-time-instrumentation controls are configured to permit capturing and storing of run-time-instrumentation information in a run-time-instrumentation program buffer. If the controls are configured to store run-time-instrumentation instructions, then a RIEMIT instruction specified value is stored as an emit record of a reporting group in the run-time-instrumentation program buffer.

Run-time-instrumentation controls emit instruction

Aspects relate to executing a run-time-instrumentation EMIT (RIEMIT) instruction. A processor is configured to capture the run-time-instrumentation information of a stream of instructions. The RIEMIT instruction is fetched and executed. It is determined if the current run-time-instrumentation controls are configured to permit capturing and storing of run-time-instrumentation information in a run-time-instrumentation program buffer. If the controls are configured to store run-time-instrumentation instructions, then a RIEMIT instruction specified value is stored as an emit record of a reporting group in the run-time-instrumentation program buffer.

The invention relates to implementing run-time instrumentation directed sampling. An aspect of the invention includes a method for implementing run-time instrumentation directed sampling. The method includes fetching a run-time instrumentation next (RINEXT) instruction from an instruction stream. The instruction stream includes the RINEXT instruction followed by a next sequential instruction (NSI) in program order. The method further includes executing the RINEXT instruction by a processor. The executing includes determining whether a current run-time instrumentation state enables setting a sample point for reporting run-time instrumentation information during program execution. Based on the current run-time instrumentation state enabling setting the sample point, the NSI is a sample instruction for causing a run-time instrumentation event. Based on executing the NSI sample instruction, the run-time instrumentation event causes recording of run-time instrumentation information into a run-time instrumentation program buffer as a reporting group.

Aspects relate to enabling and disabling execution of a run-time instrumentation facility. An instruction for execution by the processor in a lesser privileged state is fetched by the processor. It is determined, by the processor, that the run-time instrumentation facility permits execution of the instruction in the lesser-privileged state and that controls associated with the run-time instrumentation facility are valid. The run-time instrumentation facility is disabled based on the instruction being a run-time instrumentation facility off (RIOFF) instruction. The disabling includes updating a bit in a program status word (PSW) of the processor to indicate that run-time instrumentation data should not be captured by the processor. The run-time instrumentation facility is enabled based on the instruction being a run-time instrumentation facility on (RION) instruction. The enabling includes updating the bit in the PSW to indicate that run-time instrumentation data should be captured by the processor.

Controlling operation of a run-time instrumentation facility from a lesser-privileged state

A process, a computer program product, and a computer system for efficient code cache management implemented by a just-in-time compiler are provided. Embodiments of the present invention provide a practical approach to compile effectively for methods that are frequently executed over a short time period but are subsequently not executed frequently. The disclosed approach reduces the detrimental effects of compilation of such infrequently executed methods on throughput and garbage collection pause times.

Efficient code cache management in presence of infrequently used complied code fragments

An aspect includes enabling and disabling execution of a run-time instrumentation facility. An instruction for execution by the processor in a lesser privileged state is fetched by the processor. The instruction is executed based on determining, by the processor, that the run-time instrumentation facility permits execution of the instruction in the lesser-privileged state and that controls associated with the run-time instrumentation facility are valid. The run-time instrumentation facility is disabled based on the instruction being a run-time instrumentation facility off (RIOFF) instruction. The disabling includes updating a bit in a program status word (PSW) of the processor to indicate that run-time instrumentation data should not be captured by the processor. The run-time instrumentation facility is enabled based on the instruction being a run-time instrumentation facility on (RION) instruction. The enabling includes updating the bit in the PSW to indicate that run-time instrumentation data should be captured by the processor.

Controlling operation of a run-time instrumentation facility

A code region forming part of a computer program is modified during execution of the computer program by a plurality of threads. In one aspect, identical modification instructions are provided to each thread for modifying a site in the code region having a desirable idempotent atomic modification, and the modification instructions direct each thread to make the desirable idempotent atomic modification. In another aspect, a thread is selected to modify the code region, each thread other than the selected thread is directed to execute an alternative execution path that generates output identical to the output of the code region after the code region has been modified, and, responsive to directing each thread other than the selected thread, the selected thread is directed to modify the code region.

Runtime code modification in a multi-threaded environment

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Richmond Hill, Canada

Kevin Alexander Stoodley