JDK-8313669 : Reduced chance for zero-based nKlass encoding since JDK-8296565
  • Type: Bug
  • Component: hotspot
  • Sub-Component: runtime
  • Affected Version: 22
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • CPU: ppc,aarch64
  • Submitted: 2023-08-03
  • Updated: 2023-09-07
  • Resolved: 2023-08-30
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JDK 22
22 b14Fixed
Related Reports
Relates :  
JDK-8312018 - Improve reservation of class space and CDS
Description
In CDS dumptime or off mode, or in CDS runtime relocation (fallback) mode, we call `Metaspace::reserve_address_space_for_compressed_classes(size_t size)` to reserve space suitable for class space and CDS.

https://bugs.openjdk.org/browse/JDK-8296565 randomized the order in which that function attempts to reserve ranges. Before, preference was given to zero-based regions (below 32GB). 

Before, we almost always ran zero-based. Now, we rarely do, depending on RNG.

This only affects AARCH64 and PPC.

This will be fixed as a side effect of JDK-8312018. I opened this bug to track this specific symptom.
Comments
Changeset: 89d18ea4 Author: Thomas Stuefe <stuefe@openjdk.org> Date: 2023-08-30 17:51:28 +0000 URL: https://git.openjdk.org/jdk/commit/89d18ea40f3508f4053824fd47f0b0f85fe1d7c2
30-08-2023
A pull request was submitted for review. URL: https://git.openjdk.org/jdk/pull/15041 Date: 2023-07-26 11:34:18 +0000
10-08-2023