[jdk25u] RFR: 8357959: (bf) ByteBuffer.allocateDirect initialization can result in large TTSP spikes

[Oli Gillespie]

On Fri, 22 Aug 2025 13:42:13 GMT, Oli Gillespie <ogillespie at openjdk.org> wrote:

> Hi all,
> 
> This pull request contains a backport of commit [e5ce5c57](https://github.com/openjdk/jdk/commit/e5ce5c57c83972ff52758a804c942986cab74ca7) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.
> 
> The commit being backported was authored by Rohitash Kumar on 12 Jun 2025 and was reviewed by Aleksey Shipilev and Alan Bateman.
> 
> Thanks!
> 
> Clean backport, confirmed that it has the desired effect on [reproducer](https://gist.github.com/rk-kmr/be4322b72a14ae04aeefc0260c01acf6).
> 
> Before: ~1000ms to reach safepoint
> After: 0.2ms to reach safepoint

The one failing test is a timeout on MacOS for GetStackTraceALotWhenBlocking, seems like a recurrence of [JDK-8344577](https://bugs.openjdk.org/browse/JDK-8344577).

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PR Comment: https://git.openjdk.org/jdk25u/pull/125#issuecomment-3214963083