Statistics about the heap and permgen sizes


News: Statistics about the heap and permgen sizes

  1. For the task at hand we dug into the 1,024 environments we had gathered statistics from. 662 out of those had overridden the default maximum heap size by setting the -Xmx parameter. Also, 414 had felt that the permanent generation is not properly sized and had specified -XX:MaxPermSize by themselves. 

    We found some interesting aspects from this data:

    • 70% of the heaps were sized between 512MB and 4GB
    • Only 4% of the heaps were larger than this.
    • Maximum heap we discovered from this dataset was 42GB
    • 40% of the users specifying maximum size to the permgen set it to 256MB.
    • ... but there are two guys who either are bad at maths or have done some fine-tuning and set it to 258MB

    If you are interested in the whole study, then it is available in the form of a blog post.

  2. Looking for just this type of info.  thanks