> DirectByteBuffers are still using old `jdk.internal.ref.Cleaner` > implementation. That implementation carries a doubly-linked list, and so > makes DBB suffer from the same issue fixed for generic > `java.lang.ref.Cleaner` users with > [JDK-8343704](https://bugs.openjdk.org/browse/JDK-8343704). See the bug for > the reproducer. > > We can migrate DBBs to use `java.lang.ref.Cleaner`. > > There are two pecularities during this rewrite. > > First, the old ad-hoc `Cleaner` implementation used to exit the VM when > cleaning action failed. I presume it was to avoid memory leak / accidental > reuse of the buffer. I moved the relevant block to `Deallocator` directly. > Unfortunately, I cannot easily test it. > > Second is quite a bit hairy. Old DBB cleaning code was hooked straight into > `Reference` processing loop. This was possible because we could infer that > the weak references we are processing were DBB cleaning actions, since old > `Cleaner` was the only use of this code. With standard `Cleaner`, we have > lost this association, and so we cannot really do this from the reference > processing loop. With the patched version, we now rely on normal `Cleaner` > thread to do cleanups for us. Because of this, there is a new outpacing > opportunity window where reference processing might have been over, but > cleaner thread has not reacted yet. > > Tests show that DirectBufferAlloc tests are still surviving this, possibly > due to exponential sleep-backoff already built in. See the reclamation path > in `Bits.unreserveMemory`: > https://github.com/openjdk/jdk/blob/c207cc7e705d3f449f2387324d86cfb31ce40c44/src/java.base/share/classes/java/nio/Bits.java#L106-L186 > > Additional testing: > - [x] Linux x86_64 server fastdebug, `java/nio java/io` > - [x] Linux AArch64 server fastdebug, `java/nio java/io` > - [x] Linux x86_64 server fastdebug, `all` > - [x] Linux AArch64 server fastdebug, `all`
Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision: Revert waitForReferenceProcessing removals, see JDK-8305186 ------------- Changes: - all: https://git.openjdk.org/jdk/pull/22165/files - new: https://git.openjdk.org/jdk/pull/22165/files/bcfab1ba..dc3dab7f Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=22165&range=10 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22165&range=09-10 Stats: 72 lines in 5 files changed: 70 ins; 0 del; 2 mod Patch: https://git.openjdk.org/jdk/pull/22165.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/22165/head:pull/22165 PR: https://git.openjdk.org/jdk/pull/22165
