8372348: Adjust some UL / JFR string deduplication output messages by MBaesken · Pull Request #28455 · openjdk/jdk

MBaesken · 2025-11-21T15:19:54Z

There is some UL output in the string deduplication code that is not very clear and has room for improvement.
The inspected strings number should be shown and the new unknown strings get a changed text.
(also the new JFR strip dedup event description is slightly adjusted)

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JDK-8372348: Adjust some UL / JFR string deduplication output messages (Enhancement - P4)

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Andreas Steiner (@ansteiner - Author) Review applies to ba0e3410
Francesco Andreuzzi (@fandreuz - Committer)
Lutz Schmidt (@RealLucy - Reviewer)

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bridgekeeper · 2025-11-21T15:21:49Z

👋 Welcome back mbaesken! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2025-11-21T15:22:38Z

@MBaesken 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:

8372348: Adjust some UL / JFR string deduplication output messages

Reviewed-by: fandreuzzi, lucy, asteiner

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 388 new commits pushed to the master branch:

9862f8f: 8373513: C2: Move ProjNode::other_if_proj() to IfProjNode
39306d7: 8373800: Remove ScopedValueBindingsResolver
5e7ae28: 8373677: Clear text HttpServer connection could fail fast if receiving SSL ClientHello
... and 385 more: https://git.openjdk.org/jdk/compare/30410fe265d8d32fb41bae88ab882115271cdf75...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.

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openjdk · 2025-11-21T15:23:23Z

@MBaesken The following label will be automatically applied to this pull request:

hotspot

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

mlbridge · 2025-11-21T15:28:24Z

Webrevs

fandreuz · 2025-11-22T11:33:47Z

src/hotspot/share/gc/shared/stringdedup/stringDedupStat.cpp

+  log_debug(stringdedup)("    Inspected:     %12zu", _inspected);
+  log_debug(stringdedup)("      Known:       %12zu(%5.1f%%)", _known, known_percent);
+  log_debug(stringdedup)("      Shared:      %12zu(%5.1f%%)", _known_shared, known_shared_percent);
+  log_debug(stringdedup)("      New unknown: %12zu(%5.1f%%)" STRDEDUP_BYTES_FORMAT,


I'm wondering if just Unknown would be more self-explanatory than New unknown? We have Known already, and New unknown is the complement of Known

Maybe , but the variables are named _new / _new_bytes and the JFR fields also have 'new' in the name. So it maybe makes sense to keep 'new' in the UL and related output.

The avg (now named total avg) is for some people also a bit mysterious .
It is , taken from total_stat , the deduped bytes / new bytes . Why is it called avg? avg of what ?

Adding total will be helpful already, but why are not the numbers printed on which the avg is based? Because otherwise you don't get an impression what the percentage mean.

total avg of deduped / new unknown bytes maybe ? That mentions what is used for the computation .
We could also print the values of total deduped and new to make it more clear .

Adding total will be helpful already, but why are not the numbers printed on which the avg is based? Because otherwise you don't get an impression what the percentage mean.

I added some more output, please check .

I would appreciate the additional output to get a better understanding of the provided total avg.

So are you fine with the current change ?

MBaesken · 2025-12-17T08:46:36Z

Thanks for the review !

May I have a second review , please ?

fandreuz · 2025-12-17T08:58:15Z

src/hotspot/share/gc/shared/stringdedup/stringDedupStat.cpp

    last_stat->_new, STRDEDUP_BYTES_PARAM(last_stat->_new_bytes),
    last_stat->_deduped, STRDEDUP_BYTES_PARAM(last_stat->_deduped_bytes),
    percent_of(total_stat->_deduped_bytes, total_stat->_new_bytes),
+    total_stat->_deduped_bytes, total_stat->_new_bytes,


Shouldn't these two use STRDEDUP_BYTES_FORMAT and STRDEDUP_BYTES_PARAM?

Yeah seems so, this is what is used for STRDEDUP_BYTES_PARAM(last_stat->_new_bytes), STRDEDUP_BYTES_PARAM(last_stat->_deduped_bytes), .

RealLucy

This looks good.

MBaesken · 2025-12-18T09:13:22Z

Thanks for the reviews !

/integrate

openjdk · 2025-12-18T09:14:37Z

Going to push as commit 3f20eb9.
Since your change was applied there have been 402 commits pushed to the master branch:

a31e6e0: 8373593: Support latest VS2026 MSC_VER in abstract_vm_version.cpp
8598306: 8364766: C2: Improve Value() of DivI and DivL for non-constant inputs
e678050: 8367341: C2: apply KnownBits and unsigned bounds to And / Or operations
... and 399 more: https://git.openjdk.org/jdk/compare/30410fe265d8d32fb41bae88ab882115271cdf75...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-12-18T09:14:48Z

@MBaesken Pushed as commit 3f20eb9.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

JDK-8372348

667f80d

openjdk bot changed the title ~~JDK-8372348: Adjust some UL / JFR string deduplication output messages~~ 8372348: Adjust some UL / JFR string deduplication output messages Nov 21, 2025

openjdk bot added the hotspot hotspot-dev@openjdk.org label Nov 21, 2025

openjdk bot added the rfr Pull request is ready for review label Nov 21, 2025

fandreuz reviewed Nov 22, 2025

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Enhance output

ba0e341

ansteiner approved these changes Dec 17, 2025

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fandreuz reviewed Dec 17, 2025

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Adjust output

2eb2857

fandreuz approved these changes Dec 17, 2025

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RealLucy approved these changes Dec 17, 2025

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openjdk bot added the ready Pull request is ready to be integrated label Dec 17, 2025

openjdk bot added the integrated Pull request has been integrated label Dec 18, 2025

openjdk bot closed this Dec 18, 2025

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Dec 18, 2025

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MBaesken commented Dec 17, 2025

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MBaesken commented Nov 21, 2025 •

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