The Holy Grail: a GC that doesn't need Xmx

Andrew Haley aph-open at
Wed Sep 1 09:01:34 UTC 2021

On 9/1/21 7:13 AM, Erik Osterlund wrote:
> I have the same dream, and we can get there with ZGC as we make no algorithmic assumptions about the max size of the heap. I have thought about it and have a few ideas how to get there. Currently, adding a young generation is higher up on the priority list though. But this will likely be revisited. Thanks for letting us know that there is demand for such a feature.

A little while ago I was talking to John Rose about GC ergonomics.
I wanted a "compress max" option that conflated the long list of
settings we advise our customers to use for small memory.

We came up with a pretty sweet idea, based on Unix compress. Have
a "-z" setting that specifies the amount of work you're prepared to
do. So "-z9" means do whatever it takes, no matter how long it takes,
to minimize memory, and "-z0" means use as much memory as you want.
I mentioned this to a few people, but never managed to get enough
enthusiasm. So I'm trying again, because I still think it's a neat
idea.  ��

Andrew Haley  (he/him)
Java Platform Lead Engineer
Red Hat UK Ltd. <>
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