RFR: 8257073: ZGC: Try forward object before retaining page

[Per Liden]

On Thu, 26 Nov 2020 12:20:58 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

>> This is a follow up to @albertnetymk's comment in the review of #1228, where he suggested that we could try to forward the object before we go ahead and retain the page. This could be an optimization in two cases:
>> 1) A mutator would avoid a relocation stall in case the page is claimed, but the object the mutator is interested in has already been relocated.
>> 2) The worker thread detaching the page would not have to wait for a mutator that is just forwarding an object.
>
> Marked as reviewed by stefank (Reviewer).

Thanks for reviewing!

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PR: https://git.openjdk.java.net/jdk/pull/1431