Add startup script with worker core support

Non-empty value of VPP_USE_WORKER_CORE env var enables the use of the
worker core. In this case, exactly 2 logical cores must be allocated
for the VPP container via the cpuset cgroup controller.

Dockerfile

@@ -29,7 +29,7 @@ RUN --mount=target=/var/lib/apt/lists,type=cache,sharing=private \
     python python-cffi python-cffi-backend python-ipaddress \
     python2-minimal python-ply python-pycparser python2.7 python2.7-minimal \
     python3 python3-minimal python3.6 python3-minimal \
-    python3-cffi python3-cffi-backend && \
+    python3-cffi python3-cffi-backend dumb-init && \
     apt-get install -yy clang-9
 
 # TODO: add more packages above that are VPP deps
@@ -43,4 +43,8 @@ RUN --mount=target=/var/lib/apt/lists,type=cache,sharing=private \
     /debs/libvppinfra_*.deb \
     /debs/vpp-api-python_*.deb
 
-ENTRYPOINT /usr/bin/vpp
+COPY start.sh /usr/local/bin/
+RUN chmod +x /usr/local/bin/start.sh
+
+ENTRYPOINT ["dumb-init", "--"]
+CMD ["/usr/local/bin/start.sh"]

Dockerfile.devel

@@ -29,7 +29,7 @@ RUN --mount=target=/var/lib/apt/lists,type=cache,sharing=private \
     python python-cffi python-cffi-backend python-ipaddress \
     python2-minimal python-ply python-pycparser python2.7 python2.7-minimal \
     python3 python3-minimal python3.6 python3-minimal \
-    python3-cffi python3-cffi-backend && \
+    python3-cffi python3-cffi-backend dumb-init && \
     apt-get install -yy clang-9
 
 # TODO: add more packages above that are VPP deps
@@ -45,4 +45,8 @@ RUN --mount=target=/var/lib/apt/lists,type=cache,sharing=private \
     /debs/libvppinfra-dev_*.deb \
     /debs/vpp-api-python_*.deb
 
-ENTRYPOINT /usr/bin/vpp
+COPY start.sh /usr/local/bin/
+RUN chmod +x /usr/local/bin/start.sh
+
+ENTRYPOINT ["dumb-init", "--"]
+CMD ["/usr/local/bin/start.sh"]

start.sh

@@ -0,0 +1,45 @@
+#!/bin/bash -x
+# TODO: remove -x above !
+set -o errexit
+set -o nounset
+set -o pipefail
+set -o errtrace
+
+trap "sleep 10" EXIT
+
+sysctl kernel.core_pattern="/tmp/coredump/core.%t.%e.%p"
+cp /etc/vpp/startup.conf /tmp/startup.conf
+
+echo "cpu {" >>/tmp/startup.conf
+if [[ ${VPP_USE_WORKER_CORE:-} ]]; then
+  # this expands ranges like 10-12,42 in the cpuset core list
+  # into an array by using eval and {x..y} brace expansion
+  cores=($(eval "echo $(sed 's/\([0-9]*\)-\([0-9]*\)/{\1..\2}/g;s/,/ /g' /sys/fs/cgroup/cpuset/cpuset.cpus)"))
+  if (( ${#cores[@]} < 2 )); then
+    echo >&2 "ERROR: need at least 2 cores"
+    exit 1
+  fi
+  main_core=${cores[0]}
+  # try to pick a non-sibling core from the rest of the list
+  for ((i = 1; i < ${#cores[@]}; i++)); do
+    worker_core="${cores[${i}]}"
+    if ! grep -qE "\b(${main_core},${worker_core}|${worker_core},${main_core})\b" \
+         /sys/devices/system/cpu/cpu*/topology/thread_siblings_list; then
+      break
+    fi
+  done
+  if (( ${i} == ${#cores[@]} )); then
+    echo >&2 "ERROR: couldn't find enough cores"
+    echo >&2 "ERROR: the main core ${main_core} and the worker core ${worker_core} are HT siblings!"
+    if [[ ! ${VPP_TOLERATE_HT_SIBLING_CORES:-} ]]; then
+      exit 1
+    fi
+  fi
+  echo "  main-core ${main_core}" >>/tmp/startup.conf
+  echo "  corelist-workers ${worker_core}" >>/tmp/startup.conf
+else
+  echo "  workers 0" >>/tmp/startup.conf
+fi
+echo "}" >>/tmp/startup.conf
+
+/usr/bin/vpp -c /tmp/startup.conf