The module system actually makes start-up slower (the designers admitted in some presentation) because of the checks it has to perform. Java 9 was a lot slower than 8 and subsequent versions have gotten better but are still slower than 8.

Those numbers are without CDS on Java 8. This is what I get on my machine – Java 13 is 10% faster than Java 8 if you use a jlinked JRE, or 15% slower otherwise:

  $ JAVA=/usr/lib/jvm/java-8-openjdk/bin/java; for i in {1..100}; do time -p "$JAVA" -Xshare:on Hello; done 2>&1|grep real|awk 'BEGIN { sum=0 } { sum += $2 } END { print 1000 * sum / NR " ms" }'
  90.7 ms

  $ JAVA=/usr/lib/jvm/java-13-openjdk/bin/java; for i in {1..100}; do time -p "$JAVA" -Xshare:on Hello; done 2>&1|grep real|awk 'BEGIN { sum=0 } { sum += $2 } END { print 1000 * sum / NR " ms" }'
  106.4 ms

  $ JAVA=/tmp/jlinked-java13-jre/bin/java; for i in {1..100}; do time -p "$JAVA" -Xshare:on Hello; done 2>&1|grep real|awk 'BEGIN { sum=0 } { sum += $2 } END { print 1000 * sum / NR " ms" }'
  82.3 ms

Interestingly, Java 7 is faster than any of the newer versions.

  $ JAVA=/usr/lib/jvm/java-7-openjdk/bin/java; for i in {1..100}; do time -p "$JAVA" -Xshare:on Hello; done 2>&1|grep real|awk 'BEGIN { sum=0 } { sum += $2 } END { print 1000 * sum / NR " ms" }'
  80.6 ms

...and Java 6 is even faster:

  $ JAVA=/opt/java6/bin/java; for i in {1..100}; do time -p "$JAVA" -Xshare:on Hello; done 2>&1|grep real|awk 'BEGIN { sum=0 } { sum += $2 } END { print 1000 * sum / NR " ms" }'
  62.2 ms

So I appreciate that they're finally working on the startup performance regressions, but they apparently have some way to go before achieving parity with the famously lightning-fast startup time of older Java releases.