populate_scc.sh

#!/bin/sh
# based in IBMs script.
# original SOURCE: https://github.com/WASdev/ci.docker/blob/fc1f15394dcd59da0bfa865d0f370b26fa6e39d7/ga/latest/kernel/helpers/build/configure.sh
# (C) Copyright IBM Corporation 2020.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
if [ "$VERBOSE" != "true" ]; then
  exec > /dev/null 2>&1
fi

set -ex

SCC_SIZE="80m"  # Default size of the SCC layer.
ITERATIONS=4    # Number of iterations to run to populate it.

# If this directory exists and has at least ug=rwx permissions, assume the base image includes an SCC called 'openj9_system_scc' and build on it.
# If not, build on our own SCC.
if [ -d "/opt/java/.scc" ] && [ "$(stat -L -c "%a" "/opt/java/.scc" | cut -c 1,2)" = "77" ]
then
  SCC="-Xshareclasses:name=openj9_system_scc,cacheDir=/opt/java/.scc"
else
  SCC="-Xshareclasses:name=liberty,cacheDir=/output/.classCache"
fi

# For JDK8, as of OpenJ9 0.20.0 the criteria for determining the max heap size (-Xmx) has changed
# and the JVM has freedom to choose larger max heap sizes.
# Currently in compressedrefs mode there is a dependency between heap size and position and the AOT code stored in the
# SCC, such that if the max heap size/position changes too drastically the AOT code in the SCC becomes invalid and will
# not be loaded. Also, new AOT code will not be generated.
# In order to reduce the chances of this happening we use the -XX:+OriginalJDK8HeapSizeCompatibilityMode
# option to revert to the old criteria, which results in AOT code that is more compatible, on average, with typical heap sizes/positions.
# The option has no effect on later JDKs.
export OPENJ9_JAVA_OPTIONS="-XX:+OriginalJDK8HeapSizeCompatibilityMode $SCC"
export IBM_JAVA_OPTIONS="$OPENJ9_JAVA_OPTIONS"
CREATE_LAYER=$OPENJ9_JAVA_OPTIONS,createLayer
DESTROY_LAYER=$OPENJ9_JAVA_OPTIONS,destroy
PRINT_LAYER_STATS=$OPENJ9_JAVA_OPTIONS,printTopLayerStats

# Explicity create a class cache layer for this image layer here rather than allowing
# `server start` to do it, which will lead to problems because multiple JVMs will be started.
# shellcheck disable=SC2086
java $CREATE_LAYER -Xscmx$SCC_SIZE -version

# TRIM SCC
#echo "Calculating SCC layer upper bound, starting with initial size $SCC_SIZE."
## Populate the newly created class cache layer.
#/opt/scms/bin/scms /tmp/sccinput /tmp/sccoutput
## Find out how full it is.
## shellcheck disable=SC2086
#STATS=$(java $PRINT_LAYER_STATS 2>&1 || true)
#FULL=$( echo "$STATS"  | awk '/^Cache is [0-9.]*% .*full/ {print substr($3, 1, length($3)-1)}')
#echo "SCC layer is $FULL% full. Destroying layer."
## Destroy the layer once we know roughly how much space we need.
## shellcheck disable=SC2086
#java $DESTROY_LAYER || true
## Remove the m suffix.
#SCC_SIZE=$(echo $SCC_SIZE | sed 's/.$//')
## Calculate the new size based on how full the layer was (rounded to nearest m).
#SCC_SIZE=$(awk "BEGIN {print int($SCC_SIZE * $FULL / 100.0 + 0.5)}")
## Make sure size is >0.
#[ "$SCC_SIZE" -eq 0 ] && SCC_SIZE=1
## Add the m suffix back.
#SCC_SIZE="${SCC_SIZE}m"
#echo "Re-creating layer with size $SCC_SIZE."
## Recreate the layer with the new size.
#java "$CREATE_LAYER" -Xscmx$SCC_SIZE -version


# Populate the newly created class cache layer.
# Server start/stop to populate the /output/workarea and make subsequent server starts faster.
i=0
while [ "$i" -ne $ITERATIONS ]; do
    /opt/scms/bin/scms /tmp/sccinput /tmp/sccoutput
    /opt/scms/bin/scms -T1C /tmp/sccinput /tmp/sccoutput
    i=$((i + 1))
done

# Tell the user how full the final layer is.
# shellcheck disable=SC2086
FULL=$( ( java $PRINT_LAYER_STATS || true ) 2>&1 | awk '/^Cache is [0-9.]*% .*full/ {print substr($3, 1, length($3)-1)}')
echo "SCC layer is $FULL% full."