8357959: (bf) ByteBuffer.allocateDirect initialization can result in large TTSP spikes

[AAA3M]

Hi all,

This pull request contains a backport of commit e5ce5c57 from the openjdk/jdk repository.

The commit being backported was authored by Rohitash Kumar on 12 Jun 2025 and was reviewed by Aleksey Shipilev and Alan Bateman.

---

Original PR: openjdk/jdk#25487

I ran the reproducer - https://gist.github.com/rk-kmr/be4322b72a14ae04aeefc0260c01acf6

Here is sample output:

DirectByteBufferSafePoint
[0,198s][19971][safepoint,stats] VM Operation                 [ threads: total initial_running ][ time:       sync    cleanup       vmop      total ] page_trap_count
[0,198s][19971][safepoint,stats] ThreadDump                   [             11               1 ][            38375      10792      35583      84750 ]               0
[0,233s][19971][safepoint,stats] ThreadDump                   [             11               1 ][          5691041      11000      33792    5735833 ]               0
[0,245s][19971][safepoint,stats] ThreadDump                   [             11               1 ][           369667       3791      50375     423833 ]               0
[0,258s][19971][safepoint,stats] ThreadDump                   [             11               1 ][           757958       3250      40250     801458 ]               0
[0,281s][19971][safepoint,stats] ThreadDump                   [             11               1 ][         11053792       6958      47917   11108667 ]               0
[0,294s][19971][safepoint,stats] ThreadDump                   [             11               1 ][           118208       3959      34791     156958 ]               0
[0,304s][19971][safepoint,stats] ThreadDump                   [             11               1 ][            41334       3583      25917      70834 ]               0
[0,318s][19971][safepoint,stats] ThreadDump                   [             11               1 ][           489000       2292      36250     527542 ]               0
[0,330s][19971][safepoint,stats] ThreadDump                   [             11               1 ][           110417       5208      38917     154542 ]               0
[0,348s][19971][safepoint,stats] ThreadDump                   [             11               1 ][          4592208       3334      32708    4628250 ]               0
[0,360s][19971][safepoint,stats] ThreadDump                   [             11               1 ][            90875       5250      42875     139000 ]               0
[0,390s][19971][safepoint,stats] ThreadDump                   [             11               1 ][         17300209       5625      42250   17348084 ]               0
[0,412s][19971][safepoint,stats] ThreadDump                   [             11               1 ][         11852416       3834      51125   11907375 ]               0
[0,424s][19971][safepoint,stats] ThreadDump                   [             11               1 ][           473625       3042      33125     509792 ]               0
[0,441s][19971][safepoint,stats] ThreadDump                   [             11               1 ][          3526000       6500      40709    3573209 ]               0
[0,453s][19971][safepoint,stats] ThreadDump                   [             11               1 ][            73917       4500      40000     118417 ]               0
[0,466s][19971][safepoint,stats] ThreadDump                   [             11               1 ][            67917       3791      35792     107500 ]               0

Thanks!

---

Progress

• Change must not contain extraneous whitespace
• JDK-8357959 needs maintainer approval
• Commit message must refer to an issue

Error

 ⚠️ OCA signatory status must be verified

Issue

• JDK-8357959: (bf) ByteBuffer.allocateDirect initialization can result in large TTSP spikes (Enhancement - P4)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk21u-dev.git pull/2259/head:pull/2259
$ git checkout pull/2259

Update a local copy of the PR:
$ git checkout pull/2259
$ git pull https://git.openjdk.org/jdk21u-dev.git pull/2259/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 2259

View PR using the GUI difftool:
$ git pr show -t 2259

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk21u-dev/pull/2259.diff

[bridgekeeper]

Hi @AAA3M, welcome to this OpenJDK project and thanks for contributing!

We do not recognize you as Contributor and need to ensure you have signed the Oracle Contributor Agreement (OCA). If you have not signed the OCA, please follow the instructions. Please fill in your GitHub username in the "Username" field of the application. Once you have signed the OCA, please let us know by writing /signed in a comment in this pull request.

If you already are an OpenJDK Author, Committer or Reviewer, please click here to open a new issue so that we can record that fact. Please use "Add GitHub user AAA3M" as summary for the issue.

If you are contributing this work on behalf of your employer and your employer has signed the OCA, please let us know by writing /covered in a comment in this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

This backport pull request has now been updated with issue from the original commit.

[AAA3M]

Hi @AAA3M, welcome to this OpenJDK project and thanks for contributing!

We do not recognize you as Contributor and need to ensure you have signed the Oracle Contributor Agreement (OCA). If you have not signed the OCA, please follow the instructions. Please fill in your GitHub username in the "Username" field of the application. Once you have signed the OCA, please let us know by writing /signed in a comment in this pull request.

If you already are an OpenJDK Author, Committer or Reviewer, please click here to open a new issue so that we can record that fact. Please use "Add GitHub user AAA3M" as summary for the issue.

If you are contributing this work on behalf of your employer and your employer has signed the OCA, please let us know by writing /covered in a comment in this pull request.

I've submitted a membership request through the company contributor agreement. (Pending approval) so I think I'm covered

[AAA3M]

/covered

[bridgekeeper]

Thank you! Please allow for a few business days to verify that your employer has signed the OCA. Also, please note that pull requests that are pending an OCA check will not usually be evaluated, so your patience is appreciated!

[Rudometov]

/signed