JDK-6753547 : NUMA allocator: Invalid chunk size computation during adaptive resizing
  • Type: Bug
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: hs14
  • Priority: P3
  • Status: Resolved
  • Resolution: Fixed
  • OS: generic
  • CPU: generic
  • Submitted: 2008-09-28
  • Updated: 2010-04-03
  • Resolved: 2008-11-04
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JDK 6 JDK 7 Other
6u14Fixed 7Fixed hs14Fixed
The per-lgrp chuck size can be incorrectly computed because of the non-associativity of the floating point operations:

Expression z = x1 * y / x2 with x1 <= x2 can yield z > y, which applied to chunk size computation can result in a chunk size bigger that available.

EVALUATION http://hg.openjdk.java.net/jdk7/hotspot-gc/hotspot/rev/ab4a7734b9c4

SUGGESTED FIX Rearrange operations, so that the precision is not lost: z = x1 / x2 * y;