International Business Machines Corporation

Andrew James Craik

Vijay Sundaresan

Daniel J Heidinga

Patrick R Doyle

Joseph Devin Micheal Papineau

Nicholas James Coughlin

Mark Graham Stoodley

Graham Alan Chapman

Younes Manton

Rachel E Craik

Yi Zhang

Oluwatobi Ajila

Jose Nelson Amaral

Ashutosh Mehra

Filip Jeremic

Karim Ali

Erick Ochoa

A computer-implemented method and system for resilient adaptive biased locking. The method includes adding, in a system including an adaptive lock reservation scheme having a learning state, a component comprising a per class counter that counts, collectively, a number of learning failures and a number of revocation failures. An embodiment includes initializing the per class counter upon loading a class with a predetermined value representing at least one of a maximum number of learning failures and cancellation instances associated with the class. An embodiment includes initializing, based on a determination of an operational state of the per class counter for an object transitioning from one of the learning state and a biased state to a flatlock state, a lock word of the object directly to the flatlock state while bypassing the biased state.

Resilient adaptive biased locking in multi-thread concurrent program execution

Embodiments relate to a system, program product, and method for implementing loop lock reservations, and, more specifically, for holding a lock reservation across some or all of the iterations of a loop, and under certain conditions, temporarily effect a running thread to yield the reservation and allow other threads to enter the lock.

Loop lock reservation

Provided are a computer program product, system, and method for modifying a series of lock acquire and release operations to use a single lock reservation. A representation of source code is scanned to determine a series of acquire lock program statement and release lock program statement pairs to acquire and release a lock by a thread. A first acquire lock program statement in the series is modified to be an acquire with reserve program statement that when executed by the thread causes the thread to acquire the lock and indicate the lock as reserved for use by the thread. A last release lock program statement in the series is modified to be a release with cancel program statement that when executed by the thread causes the thread to release the lock and indicate the lock as not reserved.

Modifying a series of lock acquire and release operations to use a single lock reservation

An embodiment performs escape analysis of a function as a compiler optimization and stack-allocates an object referenced by the function. At runtime, the embodiment includes detecting a hot code replacement of a portion of the function while the referenced object is stored in stack memory. Responsive to detecting the hot code replacement, the embodiment includes allocating heap memory for the object and moving the object from the stack memory to the allocated heap memory. The embodiment also updates references to the object that were pointing to the object in the stack memory to instead point to the object in the heap memory.

Escape analysis support for method redefinition

An embodiment includes requesting, by a compiler responsive to execution of a first code segment, a first profile dataset associated with the first code segment. The embodiment also includes executing, responsive to receiving an indication that the first profile dataset is not available, a querying process that searches other code segments based on specified criteria relating to an attribute of the first code segment. The embodiment also includes receiving a search result from the querying process, where the search result includes a second code segment. The embodiment also includes generating an extrapolated profile dataset based at least in part on the second code segment. The embodiment stores the extrapolated profile dataset in memory associated with the first code segment, and the compiler performs an optimization process on the first code segment using the extrapolated profile dataset.

Deriving profile data for compiler optimization

A method list is built for a currently executing application within a process virtual machine at a snapshot point, the method list comprising a set of methods capable of being executed by the currently executing application after the snapshot point, the snapshot point comprising an execution state of the currently executing application when a snapshot process is triggered. Profiling data of the currently executing application, collected prior to reaching the snapshot point, is committed, to a designated storage location. Using the profiling data and a just-in-time compiler of the process virtual machine, a method in the method list is compiled. Snapshot data comprising data of the execution state of the currently executing application at the snapshot point, including a result of the compiling, is stored.

Compilation strategy for a sharable application snapshot

An embodiment includes executing a code interpretation engine such that the interpretation engine interprets a first portion of a source code that includes a first comparison between a first pair of operands. The embodiment also includes performing, in memory, a first bitwise comparison between a block Aand a block Bof the first portion of the source code. The embodiment also speeds up execution of the first portion of the source code responsive to the first bitwise comparison producing a negative result. The embodiment speeds up the first portion by omitting at least one of (i) a second bitwise comparison between a block Aand a block B, and (ii) a field-wise comparison between a block Aand a block B

Performance optimization of class instance comparisons

A computer-implemented method and related system for runtime code patching comprises determining, by a runtime, that a runtime event occurred. In response to the determination, performing by the runtime blocking processing of the runtime event, and runtime patching a method in response to an executing thread associated with the method yielding. Each executing thread receives runtime patching and only methods currently executing are runtime patched. Unblocking the runtime event allows execution to continue.

Just-in-time code patching

A method, computer system, and computer program product for estimation of post-inlining transformation benefits are provided. The embodiment may include performing abstract interpretation on a program to find potential post-inlining transformations. The embodiment may also include encoding potential post-inlining transformations into a profitability metric by associating constraints under which a profit is determined to be realized. The embodiment may further include scaling the profitability metric using the relative execution frequency of the program point to which the transformation applies to favor applying transformations in the most frequently executed code paths. The embodiment may also include generating method summaries to store the potential post-inlining transformations in the method summaries. The embodiment may further include creating a method summary map to match each method with each method summary.

Assessment of the benefit of post-inlining program transformation in inlining decisions

A profiling implementation method for reducing overhead while an application is running with profiling instrumentation inserted but disabled; the method for gathering precise profiling data for a subset of observed values at runtime start; generating an index for each observed value; populating one or more data structures within a hash table with the subset of observed values to count; comparing a corresponding key at the index value of an observed value index; evaluating a value limit of the hash table; incrementing a matched key counter; incrementing an alt-counter; locking the hash table; and updating one or more data structures of the hash table.

Lightweight and precise value profiling

A portion of a native memory is configured as a buffer within a native execution environment. Execution of a managed runtime code is initiated by a virtual machine. Data from a managed runtime memory of the virtual machine is marshaled by the virtual machine into the buffer. Control of execution is transferred from the managed runtime code to the native code. The native code is executed. The native code operates directly upon the marshaled data in the buffer.

Managed runtime data marshaling for native code access using a thread local native buffer

An approach is provided for optimizing reference counting. Responsive to receiving code representing a program by a just-in-time compiler, one or more processors in computing machinery supporting transactional memory identify regions of the code having respective sets of reference counting operations executed dynamically. Identifying the regions of the code uses an analysis of semantics of the code. The identified regions are enclosed in respective transactions. The code that was to perform atomic operations, including the reference counting operations in the identified regions, is transformed into new code that performs non-atomic operations that are variants of the atomic operations. Fallback code sequences are inserted into the transformed code. In a non-transactional manner and in response to detections of failures in respective transactions, the fallback code sequences execute original code sequences that were in the code prior to the transformation of the code. The original code sequences include respective multiple atomic operations.

Using hardware transactional memory to optimize reference counting

A computer-implemented method includes: selecting, by a computer device, a set of fields in a program which are marked as final fields to be treated as constants; adding, by the computer device, detection logic to the program, the detection logic including a process that detects writes to the final fields to be treated as constants; compiling, by the computer device, the program into compiled code; executing, by the computer device, the compiled code; detecting, by the computer device, a write to a first one of the final fields to be treated as constants; and transitioning, by the computer device, execution of the compiled code from the compiled code to an interpreter for processing by compensation code that operates on the first one of the final fields to be treated as constants.

Growing community of inventors

North York, Canada

Andrew James Craik