G1 GC for 100GB+ heaps

Kees Jan Koster kjkoster at java-monitor.com
Wed Jul 22 16:10:42 UTC 2015

Dear All,

Marcus Lagergren suggested I post this here.

Sorry if this message goes through twice, I had some trouble posting.

We are considering switching to G1 GC for a decently-sized HBase cluster. We run an HBase cluster on the bare metal with 128GB RAM in each machine. Today we use Java 7 with CMS, but we’d like to switch to Java 8 with G1.

* Are there practical limits to the heap size that we can use with G1 can have? Can we just allocate 100GB+ heaps and expect G1 to work untuned?

* Does the G1 GC have failure modes for edge cases that we need to keep in mind?

* What about region size? Should we keep some form of relation between the size of the HBase blocks and the G1 region size?

* What tunables do we have to look at and learn more about when we want to run with this size heap?

* Any gotcha’s or best practices to keep in mind when we switch over to G1?

Kees Jan

kjkoster at kjkoster.org

Human beings make life so interesting. Do you know that in a universe so full of wonders,
they have managed to invent boredom. Quite astonishing... -- Terry Pratchett

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