OpenJDK 15 To Have Better Out-Of-The-Box Performance

Written by Michael Larabel in Oracle on 16 April 2020 at 06:00 PM EDT. 36 Comments
It turns out our recent OpenJDK 8 through OpenJDK 14 benchmarks caught some on Oracle's Java team by surprise. But they were able to replicate the outcome and as a result OpenJDK 15 will be seeing better out-of-the-box performance.

Oracle has made some improvements to their G1 garbage collector that will enhance the out-of-the-box performance as seen by our testing. While Oracle does their own Java benchmarking, most of their work is with a fixed 4G heap size -- not the out-of-the-box configuration -- and thus were taken by surprise with our recent benchmark figures.

Stefan Johansson of Oracle explained the correction they have now made, "We decided to address this problem right away and a change to improve the behavior has already been pushed to JDK 15 (JDK-8241670). The basic idea is to aim for a larger region size by default and this is achieved by: only consider max heap size when determining region size and rounding up the region size to the nearest power of 2 instead of rounding down."

As a result, in SPECjbb and presumably some of the other workloads, the out-of-the-box OpenJDK performance is going to be a hell of a lot better. More details via this blog post.

I'll have our own OpenJDK 15 benchmarks out closer to its September release. For those that appreciate my daily open-source/Linux benchmarking each and every day of the year (the last time there was a single calendar with no original new content was back in May 2012!), please consider showing your support by joining Phoronix Premium or making a PayPal tip. Ad-blockers have really been detrimental for years for the abilities to continue and now with ad rates suffering as a result of COVID19 has put operations on an unstable footing without more joining premium or their support otherwise or at the very least disabling ad-block.
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Michael Larabel

Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via

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