JDK-8275056 : Virtualize G1CardSet containers over heap region
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 18
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2021-10-11
  • Updated: 2022-05-18
  • Resolved: 2021-11-15
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JDK 18
18 b24Fixed
Related Reports
Blocks :  
JDK-8276540 - Howl Full CardSet container iteration marks too many cards
Blocks :  
JDK-8276548 - Use range based visitor for Howl-Full cards
Blocks :  
JDK-8275055 - Improve HeapRegionRemSet::split_card()
CSR :  
JDK-8275266 - Virtualize G1CardSet containers over heap region
Duplicate :  
JDK-8272774 - Allow heap region sizes larger than 32M with larger card table entry sizes
Relates :  
JDK-8272773 - Configurable card table card size
Relates :  
JDK-8286943 - G1: With virtualized remembered sets, maximum number of cards configured is wrong
Relates :  
JDK-8017163 - G1: Refactor remembered sets
Sub Tasks
JDK-8276929 :  
Release Note: Allow G1 Heap Regions up to 512MB - Closed
Description
Currently there is a 1:1 mapping between the area G1CardSet can cover and the size of a heap region.
This in effect limits heap region size to the maximum any container can cover, i.e. 2^16 cards, i.e. 2^25 bytes = 32MB.

This is an unnecessary restriction since introduction of JDK-8017163. G1CardSet may as well use "virtual" regions, i.e. subdivide the heap region size in chunks of the size of the maximum any container can cover.

This change also allows arbitrary combinations of the card table size with any heap region size (unless otherwise limited) currently investigated in JDK-8272773.
Comments
Changeset: 1830b8da Author: Thomas Schatzl <tschatzl@openjdk.org> Date: 2021-11-15 18:09:32 +0000 URL: https://git.openjdk.java.net/jdk/commit/1830b8da9028af430ee4791f310b5fc9cb1ff37d
15-11-2021