如何在 jvm 应用程序中诱导长时间的完全 GC 暂停？

Question

I would like to induce long full GC pause in my jvm application. Is there any command I can use? I would like to have more than 1 sec pauses.

Answer 1

To make full GCs longer (I assume that you are using Parallel Scavenge collector), I think you can try to:

1. Disable young GCs before full GCs (-XX:-ScavengeBeforeFullGC). By doing this, full GCs are also responsible to collect the young generation and thus will take longer time than collecting old generation only.

2. Reduce the size of young generation (eg, -XX:NewRatio or -Xmx). So more objects would enter old generation instead of dying in the young generation. As a result, full GCs have more objects to collect and will be longer.

3. Allocate more long-lived objects (if you can modify the source code of your application). For example, try allocating long-lived and large arrays, because large arrays would be allocated in the old generation directly by JVM.