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

Erik Osterlund erik.osterlund at
Wed Sep 1 09:15:04 UTC 2021

Hi Andrew,

That was roughly my idea as well. ��


> -----Original Message-----
> From: zgc-dev <zgc-dev-retn at> On Behalf Of Andrew
> Haley
> Sent: Wednesday, 1 September 2021 11:02
> To: zgc-dev at
> Subject: Re: The Holy Grail: a GC that doesn't need Xmx
> 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. <>
> EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671

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