Why is IntelliJ 13 IDEA so slow after upgrading from version 12?

Question

While using IntelliJ 13 ultimate edition for a week, it just seems really slow.

First of all, the whole IDE stops for a second or so every once in a while. The Java

Answer 1

In my case massive performance degradation was caused by IntelliJ unintentionally using JDK/JRE 1.8. This seems to affect rendering performance quite badly and also leads to some unexpected crashes and deadlocks.

This would render the IDE unusable (latency of 1-2s on operations) for even a small ~3KLOC project.

Just ensure you are using JDK/JRE 1.7 when running intellij:

JAVA_HOME=/usr/lib/jvm/jdk1.7.0_67 intellij

(or whatever the equivalent is for your OS)

You can check the JRE that is being used to run intellij under Help -> About -> JRE.