8338389: [JFR] Long strings should be added to the string pool

[jaokim]

When committing JFR events with string data longer than 128 characters, the string isn't added to the JFR string pool. In scenarios with many events containing large string values, this can lead to very large JFR recordings. This is mostly the case for custom events containing f.i. SQL strings or other data. In the case where the string data consist of mostly duplicate data, adding them to the string pool has been shown to reduce the recording size by a factor of 10.

This change will add all longer strings (>128 characters) to the string pool. Strings of length 16-128 are still added using the same pre-cache methodology as before. The raised StringPool.MAX_LIMIT is used by jdk.jfr.internal.event.EventWriter::putString to determine which strings to add to the pool.

Testing

• tier1-tier3
• jdk_jfr
• Internal testing with high load, using custom JFR events containing long strings have been performed

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8338389: [JFR] Long strings should be added to the string pool (Bug - P3)

Reviewers

• Markus Grönlund (@mgronlun - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/20596/head:pull/20596
$ git checkout pull/20596

Update a local copy of the PR:
$ git checkout pull/20596
$ git pull https://git.openjdk.org/jdk.git pull/20596/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 20596

View PR using the GUI difftool:
$ git pr show -t 20596

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/20596.diff

Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back jnordstrom! 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]

@jaokim 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:

8338389: [JFR] Long strings should be added to the string pool

Reviewed-by: mgronlun

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 89 new commits pushed to the master branch:

• fead3cf: 8338745: Intrinsify Continuation.pin() and Continuation.unpin()
• a5e2800: 8338834: Remove unused import declarations in java.compiler
• 9cbf685: 8337658: ZGC: Move soft reference handling out of the driver loop function
• 8e0d019: 8338630: Test java/nio/channels/DatagramChannel/SendReceiveMaxSize.java timeout
• e06652a: 8338810: PPC, s390x: LightweightSynchronizer::exit asserts, missing lock
• ea33709: 8328880: Events::log_exception should limit the size of the logging message
• c89a1c3: 8338696: (fs) BasicFileAttributes.creationTime() falls back to epoch if birth time is unavailable (Linux)
• 813546f: 8338856: [BACKOUT] JDK-8337828: CDS: Trim down minimum GC region alignment
• 0b5c887: 8338380: Update TLSCommon/interop/AbstractServer to specify an interface to listen for connections
• 6041c93: 8335664: Parsing jsr broken: assert(bci>= 0 && bci < c->method()->code_size()) failed: index out of bounds
• ... and 79 more: https://git.openjdk.org/jdk/compare/fbe4f05636c8f692bd40bbe11fb5bb8b77b77042...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.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@mgronlun) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

[openjdk]

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

• hotspot-jfr

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]

Webrevs

• 02: Full - Incremental (190704fd)
• 01: Full - Incremental (1c44df36)
• 00: Full (a55f52a2)

[jaokim]

I've fixed the nits for the test, thanks @turbanoff and @mgronlun!

This now needs a re-review. Thanks!

[jaokim]

Thank you @mgronlun!
Could I also request a sponsor for this? Thanks!

/integrate

[openjdk]

@jaokim
Your change (at version 190704f) is now ready to be sponsored by a Committer.

[mgronlun]

/sponsor

[openjdk]

Going to push as commit d5c6158.
Since your change was applied there have been 114 commits pushed to the master branch:

• 2edf574: 8338814: [PPC64] Unify interface of cmpxchg for different types
• aefdbdc: 8338727: RISC-V: Avoid synthetic data dependency in nmethod barrier on Ztso
• b704bfa: 8298920: Improve microbenchmark build times
• b8e8e96: 8338668: Test javax/swing/JFileChooser/8080628/bug8080628.java doesn't test for GTK L&F
• cd9e241: 8336289: Obliterate most references to _snprintf in the Windows JDK
• 78f53ef: 8338938: The result of the combine method of SettingsControl is not used
• 16df090: 8338947: Deprecate the UseLinuxPosixThreadCPUClocks flag and remove it in a future release
• a827ff0: 8335577: runtime/cds/appcds/TestParallelGCWithCDS.java still fails with JNI error
• 5ecbecf: 8338936: StringConcatFactory optimize the construction of MethodType and MethodTypeDesc
• 0c744ea: 8338928: Update SwingSet2 "About" image to reference openjdk.org
• ... and 104 more: https://git.openjdk.org/jdk/compare/fbe4f05636c8f692bd40bbe11fb5bb8b77b77042...master

Your commit was automatically rebased without conflicts.

[openjdk]

@mgronlun @jaokim Pushed as commit d5c6158.

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