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Because a blocked virtual thread would block the OS thread it occupies at the moment, much effort must be taken in the runtime to handle blocking system calls. Typically, a thread from a pool of spare OS threads is used to execute the blocking call for the virtual thread so that the initially executing OS thread is not blocked.
The type of liveness requirements tend to define the data structure. The method calls can be blocking or non-blocking. Data structures are not restricted to one type or the other, and can allow combinations where some method calls are blocking and others are non-blocking (examples can be found in the Java concurrency software library).
Dead stores waste processor time and memory, and may be detected through the use of static program analysis, and removed by an optimizing compiler. If the purpose of a store is intentionally to overwrite data, for example when a password is being removed from memory, dead store optimizations can cause the write not to happen, leading to a ...
Most locking designs block the execution of the thread requesting the lock until it is allowed to access the locked resource. With a spinlock, the thread simply waits ("spins") until the lock becomes available. This is efficient if threads are blocked for a short time, because it avoids the overhead of operating system process re-scheduling.
The memory model specifies synchronization barriers that are established via special, well-defined synchronization operations such as acquiring a lock by entering a synchronized block or method. The memory model stipulates that changes to the values of shared variables only need to be made visible to other threads when such a synchronization ...
The Java memory model describes how threads in the Java programming language interact through memory. Together with the description of single-threaded execution of code, the memory model provides the semantics of the Java programming language.
Data thus structured are said to be blocked. The process of putting data into blocks is called blocking, while deblocking is the process of extracting data from blocks. Blocked data is normally stored in a data buffer, and read or written a whole block at a time. Blocking reduces the overhead and speeds up the handling of the data stream. [3]
For example, the Java Virtual Machine provides three forms of weak references, namely soft references, [1] phantom references, [2] and regular weak references. [3] A softly referenced object is only eligible for reclamation if the garbage collector decides that the program is low on memory.