8267186: Add string deduplication support to ZGC

[pliden]

This change adds support for string deduplication to ZGC. It's a pretty straight forward change, but to make reviewing even easier it is broken up into two commits:

ZGC: Introduce ZMarkContext
This commit just moves the ZMarkCache into the new ZMarkContext class, and we now pass a ZMarkContext* around instead of a ZMarkCache*. The ZMarkContext class is a more general container for worker-local data, which in the next commit will be extended to also include the StringDedup::Requests queue.

8267186: Add string deduplication support to ZGC
This commits adds the actual string dedup functionality and enables relevant tests. We use the deduplication_requested bit in the String object to filter out Strings we've already attempted to deduplicate.

Testing:

• Passes all string dedup tests.
• Passes Tier1-7 with ZGC on Linux/x86_64 (with -XX:+UseStringDeduplication enabled by default to get better exposure).

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed

Issue

• JDK-8267186: Add string deduplication support to ZGC

Reviewers

• Erik Österlund (@fisk - Reviewer) ⚠️ Review applies to c8cd63e
• Kim Barrett (@kimbarrett - Reviewer) ⚠️ Review applies to c8cd63e
• Stefan Karlsson (@stefank - Reviewer) ⚠️ Review applies to c164f2c

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/5029/head:pull/5029
$ git checkout pull/5029

Update a local copy of the PR:
$ git checkout pull/5029
$ git pull https://git.openjdk.java.net/jdk pull/5029/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 5029

View PR using the GUI difftool:
$ git pr show -t 5029

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/5029.diff

[bridgekeeper]

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[openjdk]

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[mlbridge]

Webrevs

• 03: Full - Incremental (ea61a000)
• 02: Full - Incremental (c164f2c9)
• 01: Full - Incremental (c8cd63ee)
• 00: Full (5b258cb0)

[fisk]

Now that we have a context object for marking, it would be nice if it also contained the stripes and stacks that we pass around everywhere, that we originally determine just the lines below where the context object is created.

[pliden]

Now that we have a context object for marking, it would be nice if it also contained the stripes and stacks that we pass around everywhere, that we originally determine just the lines below where the context object is created.

Good suggestion, will fix that.

[fisk]

Looks good.

[openjdk]

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

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

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

8267186: Add string deduplication support to ZGC

Reviewed-by: eosterlund, kbarrett, stefank

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 81 new commits pushed to the master branch:

• 5350b99: 8272131: PhaseMacroExpand::generate_slow_arraycopy crash when clone null CallProjections.fallthrough_ioproj
• 1489352: 8271718: Crash when during color transformation the color profile is replaced
• 2a9acc3: 8272050: typo in MachSpillCopyNode::implementation after JDK-8131362
• b62e742: 8213714: AttachingConnector/attach/attach001 failed due to "bind failed: Address already in use"
• 66d1faa: 8271601: Math.floorMod(int, int) and Math.floorMod(long, long) differ in their logic
• 57ae9fb: 8140442: Add getOutermostTypeElement to javax.lang.model utility class
• 67869b4: 8270137: Kerberos Credential Retrieval from Cache not Working in Cross-Realm Setup
• 35b399a: 8269130: Replace usages of Collection.toArray() with Collection.toArray(T[]) to avoid redundant array copying
• 2b05fae: 8260262: Use common code in function unmap_shared() in perfMemory_posix.cpp
• f2599ad: 8272196: Remove unused class ParStrongRootsScope
• ... and 71 more: https://git.openjdk.java.net/jdk/compare/977b8c4e16b02421de8bf78dc60a3866ce25fc1f...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[kimbarrett]

Looks good, except for the include order in zMarkContext.inline.hpp.

[kimbarrett]

The associated .hpp file is supposed to be included first by a .inline.hpp file, per JDK-8267464.

[pliden]

Ah, forgot about that new rule. Fixed.

[stefank]

Looks good.

ZMarkContext serves multiple purposes in the marking code, and if we (maybe in the future) add code for those purposes then it risk being a class of multiple responsibilities. Therefore, I think it would be good to let this class be a simpler data carrier, and move the extra code/logic in ZMarkContext::try_deduplicate out to ZMark, or maybe even a new ZStringDedup class.

[pliden]

[...] I think it would be good to let this class be a simpler data carrier, and move the extra code/logic in ZMarkContext::try_deduplicate out to ZMark, or maybe even a new ZStringDedup class.

Fixed.

[pliden]

Thanks @fisk, @kimbarrett and @stefank for reviewing!

/integrate

[openjdk]

Going to push as commit abebbe2.
Since your change was applied there have been 85 commits pushed to the master branch:

• 0d0f2d0: 8272216: G1: replace G1ParScanThreadState::_dest with a constant
• 3215dbc: 8271928: ErroneousTree with start position -1
• adba09b: 8272146: Disable Fibonacci test on memory constrained systems
• 846cc88: 8272138: ZGC: Adopt relaxed ordering for self-healing
• 5350b99: 8272131: PhaseMacroExpand::generate_slow_arraycopy crash when clone null CallProjections.fallthrough_ioproj
• 1489352: 8271718: Crash when during color transformation the color profile is replaced
• 2a9acc3: 8272050: typo in MachSpillCopyNode::implementation after JDK-8131362
• b62e742: 8213714: AttachingConnector/attach/attach001 failed due to "bind failed: Address already in use"
• 66d1faa: 8271601: Math.floorMod(int, int) and Math.floorMod(long, long) differ in their logic
• 57ae9fb: 8140442: Add getOutermostTypeElement to javax.lang.model utility class
• ... and 75 more: https://git.openjdk.java.net/jdk/compare/977b8c4e16b02421de8bf78dc60a3866ce25fc1f...master

Your commit was automatically rebased without conflicts.

[openjdk]

@pliden Pushed as commit abebbe2.

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