Why Heap usage increase continuously?

Question

I create API that just return string("OK").

And I test it with following configuration.

I monitor it with visualVM, and notice that heap usage increase continuously. Eventually jvm perform gc.

Question.

why heap usage increase continuously?

The heap is increasing continuously, because there are allocations, up until the garbage collector runs and reclaims the memory. That’s the normal pattern of garbage collected heaps. Even if your application does not allocate memory on its own, you are looking at the runtime with a tool, the runtime has to communicate with (JMX over RMI), which will create temporary objects. So there still are allocations, even when the application is inactive. — Holger, Nov 02 '21 at 08:06

score 1 · Answer 1 · answered Nov 01 '21 at 08:21

1

Hello，I guess there is other classes in SpringMVC is created。such as threadlocal

answered Nov 01 '21 at 08:21

Charles

21
1

Thank you for your answer. Why Spring MVC use ThreadLocal? Is there any, document about that? – eewwq asd Nov 01 '21 at 09:06

score 1 · Answer 2 · answered Nov 02 '21 at 06:36

1

Better than guessing you can actually use jvisualvm to help you find what objects are there in heap by memory sampling. You can see the number of instances of objects and total size in the profiling section as shown in below screenshot. You can take snapshots while your load test runs and you can then later analyze them. You can even take a heap dump and analyze that with tools like Eclipse Memory Analyzer

answered Nov 02 '21 at 06:36

Shailendra

8,874
2
28
37

Thank you. But, I can't found something special :( – eewwq asd Nov 03 '21 at 09:45
1

To me it looks normal "sawtooth" pattern of garbage collection. To understand more check this out https://stackoverflow.com/questions/7219532/why-a-sawtooth-shaped-graph – Shailendra Nov 03 '21 at 16:10
Oh, thank you! It's so helpful. – eewwq asd Nov 04 '21 at 03:38

Why Heap usage increase continuously?

Question.

2 Answers2