-XX:CMSInitiatingOccupancyFraction=92 Java8

Java8中，-XX:CMSInitiatingOccupancyFraction的默认值是92，详情见官网：

Starting a Concurrent Collection Cycle

With the serial collector a major collection occurs whenever the tenured generation becomes full and all application threads are stopped while the collection is done. In contrast, the start of a concurrent collection must be timed such that the collection can finish before the tenured generation becomes full; otherwise, the application would observe longer pauses due to concurrent mode failure. There are several ways to start a concurrent collection.

Based on recent history, the CMS collector maintains estimates of the time remaining before the tenured generation will be exhausted and of the time needed for a concurrent collection cycle. Using these dynamic estimates, a concurrent collection cycle is started with the aim of completing the collection cycle before the tenured generation is exhausted. These estimates are padded for safety, because concurrent mode failure can be very costly.

A concurrent collection also starts if the occupancy of the tenured generation exceeds an initiating occupancy (a percentage of the tenured generation). The default value for this initiating occupancy threshold is approximately 92%, but the value is subject to change from release to release. This value can be manually adjusted using the command-line option -XX:CMSInitiatingOccupancyFraction=<N>, where <N> is an integral percentage (0 to 100) of the tenured generation size.

https://docs.oracle.com/javase/8/docs/technotes/guides/vm/gctuning/cms.html

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-XX:CMSInitiatingOccupancyFraction=92 Java8

Starting a Concurrent Collection Cycle

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