8155917: Memory access in free regions during G1 full gc causes regressions in SPECjvm2008 scimark.fft,lu,sor,sparse with 9+116 on Linux-x64 Summary: Do not unnecessarily touch the memory of free regions during the compaction phase in G1 full gc causing some OSes to allocate physical memory for them, decreasing performance in some situations. Reviewed-by: mgerdin, jmasa