Non-volatile mapped byte buffers would add new JDK-specific file mapping modes that allow the FileChannel API to be used to create MappedByteBuffer instances that refer to non-volatile memory (NVM).One goal is to reduce confusion and concern developers have about NullPointerExceptions. Authors of the proposal are looking to provide helpful information to developers and support staff about the premature termination of a program and improve program understanding by more clearly associating a dynamic exception with static program code. The planned improvement to NullPointerExceptions pertains to improving the usability of the exceptions generated by the JVM by describing exactly which variable was null.If there were a way to read data being recorded from the disk repository without creating a new recording file, much of the overhead could be avoided. There is overhead with creating a recording, such as copying data from the disk repository to a separate recording file. An example of monitoring usage is a dashboard that displays dynamic updates to data. This works well for application profiling, but not for monitoring purposes. Currently, a user must start a recording, stop it, dump the contents to disk, and then parse the recording file. Motivating this proposal is a situation in which the HotSpot VM emits more than 500 data points using JFR, most of them available only by parsing log files. Event streaming must co-exist with non-streaming recordings, both disk-based and memory-based. The event streaming proposal records the same set of events as for the non-streaming case, with overhead of less than one percent if possible.
JFR is a tool for collecting profiling and diagnostic data about a Java application and the JVM as they’re running. JFR Event Streaming provides an API for the continuous consumption of JFR data from both in-process and out-of-process applications.
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