The call to os::reserve_memory_special in ReservedSpace::initialize is ignoring the 'alignment' parameter. Because of this we get an unaligned address back, which results in various crashes.

Repro:

Setup shm large pages according to os_linux.cpp, and run:

sudo java -XX:+UseG1GC -XX:G1HeapRegionSize=16M -Xmx64m -XX:-UseCompressedOops -XX:+UseLargePages
-XX:+UseSHM -XX:+PrintGC SystemGC

ILW: High, Low, Medium => P3, until further evaluated.