Why does JVM program run much faster with a Smaller heap size settings?

Question

I am benchmarking a JVM application which puts very heavy load on both disk IO and CPU.

Normally I benchmark it using 4G max/min heap size, the whole benchmark suit takes in average 73 seconds to run.

Today I was curious and gave it only 1G max/min heap size, and surprisingly the whole benchmark suit takes only 62 seconds to run in average.

So I wonder why does JVM perform better with a smaller heap size?

Extra notes:

The above benchmark results are reliably reproducible on this machine.
Benchmark source code https://github.com/HouzuoGuo/Aurinko2/blob/master/src/test/scala/net/houzuo/aurinko2/test/logic/Benchmark.scala

Environment:

java version "1.7.0_19"
OpenJDK Runtime Environment (fedora-2.3.9.1.fc17-x86_64)
OpenJDK 64-Bit Server VM (build 23.7-b01, mixed mode)

Linux ____ 3.8.4-102.fc17.x86_64 #1 SMP Sun Mar 24 13:09:09 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

Jayan · Accepted Answer · 2013-04-30 02:54:20Z

3

From the docs on Oracle JVM, the note says

Next, you might try decreasing the amount of heap used. A larger heap will cause garbage collection pauses to increase because there is more heap to scan.

It is also function of GC algorithm you use. For example incremental GC may give completely different numbers. (Try -Xincgc and see your numbers)

link

answered Apr 30, 2013 at 2:54

Jayan

18.6k15 gold badges92 silver badges147 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

user972946 Over a year ago

thank you for that, my apologize that I did not mention my JVM environment. Does OpenJDK have similar behaviour?

Jayan Over a year ago

@ Howard Guo - It is really function of JRE not JDK. I expect Oracle and OpenJDK to have similar behavior here. GC etc share same code.

Collectives™ on Stack Overflow

Why does JVM program run much faster with a Smaller heap size settings?

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related