perf: run installBcc in a subshell

vhdbuilder/packer/install-dependencies.sh

@@ -258,11 +258,17 @@ ls -ltr /opt/gpu/* >> ${VHD_LOGS_FILEPATH}
 installBpftrace
 echo "  - $(bpftrace --version)" >> ${VHD_LOGS_FILEPATH}
 
-installBcc
-cat << EOF >> ${VHD_LOGS_FILEPATH}
-  - bcc-tools
-  - libbcc-examples
-EOF
+PRESENT_DIR=$(pwd)
+# run installBcc in a subshell and continue on with container image pull in order to decrease total build time
+( 
+  cd $PRESENT_DIR || { echo "Subshell in the wrong directory" >&2; exit 1; }
+
+  installBcc
+
+  exit $?
+) > /var/log/bcc_installation.log 2>&1 &
+
+BCC_PID=$!
 
 echo "${CONTAINER_RUNTIME} images pre-pulled:" >> ${VHD_LOGS_FILEPATH}
 stop_watch $capture_time "Pull NVIDIA driver image (mcr), Start installBcc subshell" false
@@ -494,6 +500,19 @@ if [[ $OS == $UBUNTU_OS_NAME ]]; then
   sed -i 's/After=network-online.target/After=multi-user.target/g' /lib/systemd/system/motd-news.service
 fi
 
+wait $BCC_PID
+BCC_EXIT_CODE=$?
+
+if [ $BCC_EXIT_CODE -eq 0 ]; then
+  echo "Bcc tools successfully installed."
+  cat << EOF >> ${VHD_LOGS_FILEPATH}
+  - bcc-tools
+  - libbcc-examples
+EOF
+else
+  echo "Error: installBcc subshell failed with exit code $BCC_EXIT_CODE" >&2
+fi
+
 # use the private_packages_url to download and cache packages
 if [[ -n ${PRIVATE_PACKAGES_URL} ]]; then
   IFS=',' read -ra PRIVATE_URLS <<< "${PRIVATE_PACKAGES_URL}"

vhdbuilder/packer/test/linux-vhd-content-test.sh

@@ -858,6 +858,16 @@ testContainerImagePrefetchScript() {
   return 0
 }
 
+testBccTools () {
+  for line in '- bcc-tools' '- libbcc-examples'; do
+    if ! grep -F -x -e "$line" /opt/azure/vhd-install.complete; then
+      echo "BCC tools were not successfully downloaded."
+      return 1
+    fi
+  done
+  echo "BCC tools were successfully downloaded."
+  return 0
+}
 
 # As we call these tests, we need to bear in mind how the test results are processed by the
 # the caller in run-tests.sh. That code uses az vm run-command invoke to run this script
@@ -867,6 +877,7 @@ testContainerImagePrefetchScript() {
 #
 # We should also avoid early exit from the test run -- like if a command fails with
 # an exit rather than a return -- because that prevents other tests from running.
+testBccTools
 testVHDBuildLogsExist
 testCriticalTools
 testFilesDownloaded $CONTAINER_RUNTIME