ADDITIONAL SYSTEM INFORMATION :
Fedora 26, JDK 8u172

A DESCRIPTION OF THE PROBLEM :
-Xloggc does not output a log when using -XX:G1NewSizePercent with -Xms.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run:
java -Xloggc:gc.log -XX:+PrintGCDetails -XX:+UseG1GC -XX:+UnlockExperimentalVMOptions -XX:G1NewSizePercent=10 -Xms=1g -jar whatever.jar

While the jar is running, run cat gc.log; it will be empty.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
That the gc.log is filled as it would be when running:
java -Xloggc:gc.log -XX:+PrintGCDetails -XX:+UseG1GC -Xms=1g -jar whatever.jar

When running the above, gc.log is filled with GCDetails immediately during execution.
ACTUAL -
cat gc.log returns nothing and the log file is empty

FREQUENCY : always