9.17.1 Overview
This function changes the output of log data to files so that it can be done asynchronously. Here, asynchronous means that, by preparing a thread dedicated to output processing of log data to files, log data can be output to files without synchronizing the timing of processing with the threads that execute processing other than log output to files. As an example, the following describes the log file output when a GC occurs.
During a GC, program processing stops. In the Hitachi JavaVM log file function, the thread executing the GC also outputs the GC information to the log file, so it is not possible to proceed to the next processing until the processing to output the GC information to the log file is finished.
By enabling this function, the processing to output the GC information to the log file is executed by a dedicated thread. This reduces the processing delays caused by threads that execute other processing waiting for the processing to output the GC information to the log file to finish.
Note that using this function might result in some missing log data. This function temporarily stores the log data in a buffer and then outputs it to a log file. If the amount of log data output is very large, or if the file I/O processing is extremely slow, some log data might not be output. Therefore, we recommend that you use this function if you have tuned the system to achieve 100 msec or less of program processing stop time due to a GC. If you have not performed such tuning, we do not recommend that you use this function.