RFR: 8305896: Alternative full GC forwarding [v33]

[Erik Österlund]

On Wed, 24 May 2023 14:34:51 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

> > > I guess the alternative would be to not put it under flag to begin with.
> > 
> > 
> > Yes, is there any reason this can't be an improvement in the default case without a flag?
> 
> Dunno. A 7% worst-case performance degradation in the full-GC of Serial (and perhaps G1 and Shenandoah) might be a concern. Also, it is a design principle of the compact headers JEP that all non-trivial changes should be under a runtime flag, where the 'legacy' case is not measurably affected.

In this case, I'd prefer to not have a flag. If we can convince ourselves that the impact is indeed only 7% worst case time for Serial and G1 + Shenandoah failure modes. I'd rather change the goals in the JEP to say we are willing to throw Serial GC non-failure full GC modes under the bust and risk that taking a bit longer, with the reasoning that if you rely on that level of latency or GC performance, then maybe Serial GC simply isn't for you. Does that make sense?

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PR Comment: https://git.openjdk.org/jdk/pull/13582#issuecomment-1561394556