Eclipse J9 is a big deal
by Richard Pajerski
Posted on Friday Mar 15, 2019 at 11:59PM in Technology
Having developed with Java for a number of years in various environments (Notes/Domino, Tomcat, ActiveMQ, Android, desktop, etc.), I was initially skeptical when I read this article and watched the video about the recently-improved Eclipse OpenJ9: https://developer.ibm.com/videos/introduction-to-eclipse-openj9-and-adoptopenjdknet/
Yes, Java has incrementally improved over time but the claims here seemed a bit over the top. To think I might get both noticeably faster startup *and* up to 50% memory reduction just by switching to J9 seemed to be a bit too optimistic. But after downloading (adoptopenjdk.net) and giving it a spin, I was not disappointed.
Sure enough, out-of-the-box startup time for Netbeans 8.2 on Windows 8.1 increased dramatically against Oracle Java 1.8.0_191 (running quad-core I7 on SSD). There was no point in taking measurements -- it was up and ready in three seconds! This didn't seem possible with Netbeans but there it was. Everything worked the same as before ... only faster. Then the real shocker: RAM usage went from roughly 650M down to 268! Huh? If I can eliminate that much RAM usage for hosted server side deployments, it's going to translate into real cash savings.
On top of the performance upgrade and memory savings, I immediately noticed that Swing is visually better in J9 than OpenJDK [edit: with the HotSpot VM]. In particular, the default font rendering is really nice! In the past, OpenJDK has generally lagged behind Oracle Java for desktop applications and still does; but to my eyes, J9 is now at visual parity with Oracle (or perhaps better).
I realize that the J9 has been the JVM in Notes/Domino all these years but I've never attempted to benchmark it against other JVMs since IBM never really promoted it as a JDK for Windows. I'm currently using 9.0.1 FP10 which uses build 22.214.171.124 of J9:
Hopefully, IBM can manage to get the latest J9 into an upcoming fixpack. I sure have lots of Notes and Domino Java code that could benefit from it.
A big congratulations and thank you to Mark Stoodley and all the other engineers and players behind this release!