8273508: Support archived heap objects in SerialGC

[iklam]

When -XX:+UseSerialGC is enabled, load the CDS archived heap objects into SerialHeap::old_gen() during VM bootstrap. This improves VM start-up time, mostly because the module graph can be loaded from the archive.

$ perf stat -r 40 java -XX:+UseSerialGC -version

Before: 0.042484507 seconds time elapsed ( +- 0.72% )
After:  0.031671000 seconds time elapsed ( +- 0.72% )

Changes in the gc subdirectories are contributed by @tschatzl

---

Progress

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Issue

• JDK-8273508: Support archived heap objects in SerialGC

Reviewers

• Thomas Schatzl (@tschatzl - Reviewer) ⚠️ Review applies to 7d841aa
• Calvin Cheung (@calvinccheung - Reviewer) ⚠️ Review applies to 7d841aa

Reviewing

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[mlbridge]

Webrevs

• 03: Full - Incremental (1ae36713)
• 02: Full - Incremental (41ce0bf0)
• 01: Full - Incremental (7d841aae)
• 00: Full (9027660e)

[tschatzl]

Initial pass over GC code.

[tschatzl]

GC changes (and the bits around them) seem good to me.

We already discussed the (existing) pervasive usage of uintptr_t in other code calling the gc code for addresses in the java heap and using size_t/int/intx/whatever for offsets in private which I do not recommend to do. However if there is any change to be made, it's a separate issue.

[openjdk]

@iklam This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8273508: Support archived heap objects in SerialGC

Reviewed-by: tschatzl, ccheung

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At the time when this comment was updated there had been 1 new commit pushed to the master branch:

• 3eca9c3: 8264707: HotSpot Style Guide should permit use of lambda

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[calvinccheung]

Maybe add assert(_loaded_heap_top != 0, “must be”) ?

[calvinccheung]

I've reviewed the CDS related changes. Just one minor comment below.

[iklam]

Thanks @tschatzl and @calvinccheung for the review.
/integrate

[openjdk]

Going to push as commit 6a573b8.
Since your change was applied there has been 1 commit pushed to the master branch:

• 3eca9c3: 8264707: HotSpot Style Guide should permit use of lambda

Your commit was automatically rebased without conflicts.

[openjdk]

@iklam Pushed as commit 6a573b8.

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