hg: jdk9/hs-gc/hotspot: 8059758: Footprint regressions with JDK-8038423

[thomas.schatzl at oracle.com]

Changeset: f605a3199018
Author:    tschatzl
Date:      2014-10-09 11:40 +0200
URL:       http://hg.openjdk.java.net/jdk9/hs-gc/hotspot/rev/f605a3199018

8059758: Footprint regressions with JDK-8038423
Summary: Changes in JDK-8038423 always initialize (zero out) virtual memory used for auxiliary data structures. This causes a footprint regression for G1 in startup benchmarks. This is because they do not touch that memory at all, so the operating system does not actually commit these pages. The fix is to, if the initialization value of the data structures matches the default value of just committed memory (=0), do not do anything.
Reviewed-by: jwilhelm, brutisso

! src/share/vm/gc_implementation/g1/concurrentMark.cpp
! src/share/vm/gc_implementation/g1/concurrentMark.hpp
! src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp
! src/share/vm/gc_implementation/g1/g1CardCounts.cpp
! src/share/vm/gc_implementation/g1/g1CardCounts.hpp
! src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp
! src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp
! src/share/vm/gc_implementation/g1/g1RegionToSpaceMapper.cpp
! src/share/vm/gc_implementation/g1/g1RegionToSpaceMapper.hpp
! src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.cpp
! src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.hpp