RFR: 8319373: Serial: Refactor dirty cards scanning during Young GC [v8]

[Thomas Schatzl]

On Fri, 10 Nov 2023 13:33:12 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Reading the new code directly is probably easier. The structure is quite similar to its counterpart in Parallel.
>> 
>> It's mostly perf-neutral, except when dirty cards are scarce. Using `card_scan.java` in [JDK-8310031](https://bugs.openjdk.org/browse/JDK-8310031), I observed ~40% reduction in young-gc pause time with `stride = 32 * 64`.
>
> Albert Mingkun Yang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   next-obj-card

lgtm

-------------

Marked as reviewed by tschatzl (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/16492#pullrequestreview-1726892212