JDK-8256287 : [windows] add loop fuse to map_or_reserve_memory_aligned
  • Type: Bug
  • Component: hotspot
  • Sub-Component: runtime
  • Affected Version: 16
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2020-11-12
  • Updated: 2021-05-26
  • Resolved: 2020-11-16
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JDK 11 JDK 16
11.0.12-oracleFixed 16 b25Fixed
Related Reports
Relates :  
JDK-8255954 - [windows] UseNUMAInterleaving causes VM to balloon and hang
Relates :  
JDK-8255978 - [windows] os::release_memory may not release the full range
Description
map_or_reserve_memory_aligned attempts to allocate aligned memory by:
1) reserving larger area
2) releasing it
3) attempting to re-reserve into the vacated address space a smaller area at the aligned start address

Since this may fail (between (2) and (3) someone may have grabbed that address concurrently), we do this in a loop. However, when failing to release it we will loop-reserve endlessly.

This is one of the reasons for JDK-8255954 whose root cause will be fixed with JDK-8255978. But we should guard against endless loops independently from that.
Comments
Fix Request 11u: This bug is important to fix since it may cause in rare situations an endless loop. The fix limits the number of iterations in the release loop. It is very simple. Tests: this fix has been tested in SAP 11u builds since three months. The patch does not apply cleanly, but the rewrite is straightforward: Modified patch: http://cr.openjdk.java.net/~stuefe/webrevs/backports/8256287-windows-add-loop-fuse-to-map_or_reserve_memory_aligned-for-11.diff RFR thread: https://mail.openjdk.java.net/pipermail/jdk-updates-dev/2020-December/004304.html
08-03-2021
Changeset: 0357db35 Author: Thomas Stuefe <stuefe@openjdk.org> Date: 2020-11-16 20:08:49 +0000 URL: https://github.com/openjdk/jdk/commit/0357db35
16-11-2020