RFR: 8319373: Serial: Refactor dirty cards scanning during Young GC [v2]

[Thomas Schatzl]

On Mon, 6 Nov 2023 12:01:32 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 with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
> 
>  - review
>  - Merge branch 'master' into s1-young-gc
>  - s1-young-gc

src/hotspot/share/gc/serial/cardTableRS.cpp line 352:

> 350:   using Word = uintptr_t;
> 351: 
> 352:   auto is_word_aligned = [] (const void* const p) {

Just my opinion, feel free to ignore: don't use `auto` if unavoidable, in this case use the specific type `bool`. Apart from that I am not sure the gain of defining a single-use-single-line expression is worth the effort.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16492#discussion_r1389108116