We are experiencing some problems in our production environment, where we get an InvalidPropertyException from one of the compiled jsps (which one differs from time to time) after a bit of time. I have a suspicion that this is caused by something “disappearing” from the heap. Further, I suspect th…
Tag: garbage-collection
What is the recommended max level of heap memory usage? Recommended garbage collection time?
I recently found that one of my services was taking a large amount of time in garbage collection because the max heap size was too small. The service was there before I started, so I was unaware of the low heap size. I would like to set an alarm to warn me if it goes back up past a certain
is there a way to know which objects are in “old” area of Heap
I have long cycles of GC. from checks I saw there are too many objects in the tenured (old) area of the Heap. Is there any utitlity to know which objects are in which area of the heap, or any staticstics about these objects. I am using Sun/Oracle HotSpot JVM (Java 6). EDIT: little bit more details about my pr…
How to calculate HashMap memory usage in Java?
I was asked in an interview to calculate the memory usage for HashMap and how much estimated memory it will consume if you have 2 million items in it. For example: The mapping is like this. How would I estimate the memory usage of this HashMap Object in Java? Answer The short answer To find out how large an o…
Java heap terminology: young, old and permanent generations?
I’m trying to understand What the concepts of young, old and permanent generations are in the Java heap terminology, and more specifically the interactions between the three generations. My questions are: What is the young generation? What is the old generation? What is the permanent generation? How doe…
Definition of Java’s CMS GC log lines?
Examining a Java runtime with CMS (Concurrent-Mark-Sweep) GC enabled, what is the definition of the CMS space in the logs below? Shall I assume it is the tenured space? I see the following lines of a minor-major-minor GC event In particular the [CMS: 10899K->9379K(12448K), 0.2675281 secs] at the 23.492 eve…