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List:       openjdk-hotspot-gc-dev
Subject:    Re: RFR (M): 8201491: G1 support for java.lang.ref.Reference precleaning
From:       Aleksey Shipilev <shade () redhat ! com>
Date:       2018-04-26 9:46:03
Message-ID: 475b6476-ead7-a3a8-281e-4f749ffa1f15 () redhat ! com
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On 04/26/2018 11:36 AM, Thomas Schatzl wrote:
> In absence of fully concurrent reference processing this seems to be a
> very good tradeoff between effort and improvement in some cases.
> 
> Since it is planned to be obsoleted in the future, and I do not expect
> other new collectors to implement it (Shenandoah will likely go to
> fully concurrent as well,

Current Shenandoah actually implements Precleaning too, because it uses the same STW RP available in
all JDKs where we backport Shenandoah. It is indeed a good tradeoff between prolonging the
concurrent phase, and dodging long pause processing provably alive references.

> I added a G1 specific experimental option called "G1UseReferencePrecleaning" defaulting to true
> (enabled).

Shenandoah uses the shorter "ShenandoahPreclean", maybe you want to do it shorter too.

-Aleksey


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