gc+heap=debug output is as follows:

[1.600s][debug][gc,heap] GC(134) Heap Before GC invocations=119 (full 29):
[1.600s][debug][gc,heap] GC(134) garbage-first heap total reserved 65536K, committed 65536K, used 64608K [0x00000000fc000000, 0x0000000100000000)
[1.600s][debug][gc,heap] GC(134) region size 1024K, 0 eden (0K), 0 survivors (0K)

For some reason the last line only contains eden and survivor regions, however it is often interesting (e.g. hs_err file) to show existence of other regions as well.

The suggested new output could be:

[1.600s][debug][gc,heap] GC(134) Heap Before GC invocations=119 (full 29):
[1.600s][debug][gc,heap] GC(134) garbage-first heap total reserved 65536K, committed 65536K, used 64608K [0x00000000fc000000, 0x0000000100000000)
[1.600s][debug][gc,heap] GC(134) region size 1024K, 0 eden (0M), 0 survivors (0M), 64 old (64M), 0 humongous (0M), 0 free (0M)

I.e. adding old, humongous and free regions, and showing the sizes in MB - minimum region size is one MB anyway.