Add method for getting value of cgroup v2 interface file

1 files changed, 46 insertions, 0 deletions

diff --git a/container-disc/src/main/sh/vespa-start-container-daemon.sh b/container-disc/src/main/sh/vespa-start-container-daemon.sh
index 28c2c00a921..54791129a74 100755
--- a/container-disc/src/main/sh/vespa-start-container-daemon.sh
+++ b/container-disc/src/main/sh/vespa-start-container-daemon.sh
@@ -59,6 +59,52 @@ getconfig() {
     eval "$cmds"
 }
 
+# Print the value of the cgroups v2 interface filename $1 for current process,
+# returning 0 on success. $1 is e.g. memory.max.
+vespa_cg2get() {
+    local filename="$1"
+
+    # Verify cgroups v2
+    if ! [ -e /sys/fs/cgroup/cgroup.controllers ]; then
+        return 1
+    fi
+
+    local cgroup_content
+    if ! cgroup_content=$(< /proc/self/cgroup); then
+        echo "No such file: /proc/self/cgroup" >& 2
+        return 1
+    fi
+
+    local slice
+    while read -r; do
+        if [ -n "$slice" ]; then
+            echo "More than one line in /proc/self/cgroup" >&2
+            return 1
+        fi
+        # Ignore prefix of line up to and including the right-most ':'.
+        # Example line: "0::/user.slice/user-1002.slice/session-29.scope"
+        slice="${REPLY##*:}"
+    done <<< "$cgroup_content"
+
+    local root_dir=/sys/fs/cgroup
+    local leaf_dir="$root_dir$slice"
+    local current_dir="$leaf_dir"
+
+    while true; do
+        local path="$current_dir"/"$filename"
+        if [ -r "$path" ]; then
+            cat "$path"
+            return 0
+        fi
+
+        current_dir="${current_dir%/*}"
+        if (( ${#current_dir} < ${#root_dir} )); then
+            echo "No such filename was found at $leaf_dir: $filename" >&2
+            return 1
+        fi
+    done
+}
+
 configure_memory() {
     consider_fallback jvm_minHeapsize 1536
     consider_fallback jvm_heapsize 1536