JEP proposed to target JDK 11: 318: Epsilon: An Arbitrarily Low-Overhead Garbage Collector (original) (raw)

Aleksey Shipilev shade at redhat.com
Thu Jan 18 10🔞54 UTC 2018

On 01/18/2018 11:10 AM, Erik Österlund wrote:

I do not feel too comfortable with this being a product flag regardless of the name. There is existing code that assumes that for example System.gc() will actually do something. Similar for assumptions that language features like finalizers and reference objects and queues will do anything at all. That makes me feel uncomfortable. Do you feel comfortable with exposing a product flag that breaks code relying on those features?

I do feel comfortable about this, because JLS and JVMS specify that GC is best-effort, and therefore any other language and library feature that depends on GC is also best-effort. This allows, among other things: no-op GCs, reclaiming GCs that never actually do touch references or finalizers, GCs that fully ignore System.gc (remember -XX:-DisableExplicitGC that is a product option?), etc.

I think users at large understand the choice of GC implementation matters in how responsive (if ever) the language/library features are.

Thanks, -Aleksey

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