Enhanced Aikar's flag logic to adjust for >12GB memory

For #483

README.md

@@ -1042,10 +1042,16 @@ To enable remote JMX, such as for profiling with VisualVM or JMC, add the enviro
 
 ### Enable Aikar's Flags
 
-[Aikar has does some research](https://aikar.co/2018/07/02/tuning-the-jvm-g1gc-garbage-collector-flags-for-minecraft/) into finding the optimal JVM flags for GC tuning, which becomes more important as more users are connected concurrently. The set of flags documented there can be added using
+[Aikar has does some research](https://mcflags.emc.gs/) into finding the optimal JVM flags for GC tuning, which becomes more important as more users are connected concurrently. The set of flags documented there can be added using
 
     -e USE_AIKAR_FLAGS=true
 
+When `MEMORY` is greater than or equal to 12G, then the Aikar flags will be adjusted according to the article.
+
+Large page support can also be enabled by adding
+
+    -e USE_LARGE_PAGES=true
+
 ### HTTP Proxy
 
 You may configure the use of an HTTP/HTTPS proxy by passing the proxy's URL via the `PROXY`

start-minecraftFinalSetup

@@ -115,22 +115,39 @@ if isTrue ${ENABLE_JMX}; then
   log "JMX is enabled. Make sure you have port forwarding for ${JMX_PORT}"
 fi
 
-if isTrue ${USE_AIKAR_FLAGS}; then
-  # From https://aikar.co/2018/07/02/tuning-the-jvm-g1gc-garbage-collector-flags-for-minecraft/
-  JVM_OPTS="${JVM_XX_OPTS}
+if isTrue "${USE_AIKAR_FLAGS}"; then
+  # From https://mcflags.emc.gs/
+
+  if (( $(normalizeMemSize "${MAX_MEMORY}") >= $(normalizeMemSize 12g) )); then
+    log "Using Aikar's >12GB flags"
+    G1NewSizePercent=40
+    G1MaxNewSizePercent=50
+    G1HeapRegionSize=16M
+    G1ReservePercent=15
+    InitiatingHeapOccupancyPercent=20
+  else
+    log "Using Aikar's flags"
+    G1NewSizePercent=30
+    G1MaxNewSizePercent=40
+    G1HeapRegionSize=8M
+    G1ReservePercent=20
+    InitiatingHeapOccupancyPercent=15
+  fi
+
+  JVM_XX_OPTS="${JVM_XX_OPTS}
   -XX:+UseG1GC -XX:+ParallelRefProcEnabled
   -XX:MaxGCPauseMillis=200
   -XX:+UnlockExperimentalVMOptions
   -XX:+DisableExplicitGC
   -XX:-OmitStackTraceInFastThrow
   -XX:+AlwaysPreTouch
-  -XX:G1NewSizePercent=30
-  -XX:G1MaxNewSizePercent=40
-  -XX:G1HeapRegionSize=8M
-  -XX:G1ReservePercent=20
+  -XX:G1NewSizePercent=${G1NewSizePercent}
+  -XX:G1MaxNewSizePercent=${G1MaxNewSizePercent}
+  -XX:G1HeapRegionSize=${G1HeapRegionSize}
+  -XX:G1ReservePercent=${G1ReservePercent}
   -XX:G1HeapWastePercent=5
   -XX:G1MixedGCCountTarget=8
-  -XX:InitiatingHeapOccupancyPercent=15
+  -XX:InitiatingHeapOccupancyPercent=${InitiatingHeapOccupancyPercent}
   -XX:G1MixedGCLiveThresholdPercent=90
   -XX:G1RSetUpdatingPauseTimePercent=5
   -XX:SurvivorRatio=32
@@ -140,6 +157,12 @@ if isTrue ${USE_AIKAR_FLAGS}; then
   "
 fi
 
+if isTrue "${USE_LARGE_PAGES}"; then
+  JVM_XX_OPTS="${JVM_XX_OPTS}
+  -XX:+UseLargePagesInMetaspace
+  "
+fi
+
 mcServerRunnerArgs="--stop-duration 60s"
 
 if [[ ${TYPE} == "FEED-THE-BEAST" ]]; then

start-utils

@@ -48,3 +48,18 @@ function logn {
 function log {
   echo "[init] $*"
 }
+
+function normalizeMemSize {
+  local scale=1
+  case ${1,,} in
+    *k)
+      scale=1024;;
+    *m)
+      scale=1048576;;
+    *g)
+      scale=1073741824;;
+  esac
+
+  val=${1:0: -1}
+  echo $(( val * scale ))
+}