JDK-8071462 : Remove G1ParGCAllocator::alloc_buffer_waste
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 9
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2015-01-23
  • Updated: 2015-06-03
  • Resolved: 2015-04-28
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JDK 9
9 b66Fixed
Related Reports
Blocks :  
JDK-8078193 - BACKOUT: Rename and clean up the ParGCAllocBuffer class
Blocks :  
JDK-8074546 - Rename and clean up the ParGCAllocBuffer class
Duplicate :  
JDK-8076316 - G1: Remove unused code from G1ParScanThreadState
Relates :  
JDK-8030849 - Investigate high fragmentation/waste in some situations during allocation during GC in G1
Description
G1ParGCAllocator::alloc_buffer_waste tracks the waste at the end of a PLAB caused by throwing away that TLAB.

Remove it as this information is duplicated by PLABStats::waste(), with the additional problem that alloc_buffer waste does not include all waste. It misses the waste at the end of a PLAB that is reserved to put a filler object into to guarantee parsability of the heap.

The value can be replaced by the sum of survivor/old PLABStats::waste().
Comments
http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2015-April/012686.html
07-04-2015
PLABStats does not contain separate statistic for each thread, it contains summary information for all threads. However, ParGCAllocator contains waste which is added to PLABStats during ParGCAllocBuffer::flush_and_retire_stats(PLABStats* stats). We can use this information to get waste before flush_and_retire_stats.
06-04-2015