RFR: 8221360: Eliminate Shared_DirtyCardQ_lock

[Kim Barrett]

On Mon, 23 Aug 2021 12:30:16 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Another reason probably why these cards are put into the shared DCQS was that that card will be processed at a time when that situation can't re-occur. So this change might cause that card (buffer) to be re-enqueued and reprocessed many times while waiting for that object to get fully visible.

Dirty card buffers are processed in fifo order, so this single-card buffer
starts at the end of the line. Also, we generally keep some number of cards in
the queue. So it's going to take some time for this card to make it through
all that and be reconsidered.

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PR: https://git.openjdk.java.net/jdk/pull/5118