lib/memory: fall back to reading hierarchical memory limit in cgroups when the default limit isn't set

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/699

lib/cgroup/mem.go

@@ -14,3 +14,18 @@ func GetMemoryLimit() int64 {
 	}
 	return n
 }
+
+// GetHierarchicalMemoryLimit returns hierarchical memory limit
+func GetHierarchicalMemoryLimit() int64 {
+	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/699
+	n, err := readInt64FromCommand("cat /sys/fs/cgroup/memory/memory.stat | grep hierarchical_memory_limit | cut -d' ' -f 2")
+	if err == nil {
+		return n
+	}
+	n, err = readInt64FromCommand(
+		"cat /sys/fs/cgroup/memory$(cat /proc/self/cgroup | grep memory | cut -d: -f3)/memory.stat | grep hierarchical_memory_limit | cut -d' ' -f 2")
+	if err != nil {
+		return 0
+	}
+	return n
+}

lib/cgroup/util.go

@@ -9,15 +9,18 @@ import (
 
 func readInt64(path, altCommand string) (int64, error) {
 	data, err := ioutil.ReadFile(path)
+	if err == nil {
+		data = bytes.TrimSpace(data)
+		return strconv.ParseInt(string(data), 10, 64)
+	}
+	return readInt64FromCommand(altCommand)
+}
+
+func readInt64FromCommand(command string) (int64, error) {
+	cmd := exec.Command("/bin/sh", "-c", command)
+	data, err := cmd.Output()
 	if err != nil {
-		// Read data according to https://unix.stackexchange.com/questions/242718/how-to-find-out-how-much-memory-lxc-container-is-allowed-to-consume
+		return 0, err
-		// This should properly determine the data location inside lxc container.
-		// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/84
-		cmd := exec.Command("/bin/sh", "-c", altCommand)
-		data, err = cmd.Output()
-		if err != nil {
-			return 0, err
-		}
 	}
 	data = bytes.TrimSpace(data)
 	return strconv.ParseInt(string(data), 10, 64)

lib/memory/memory_linux.go

@@ -20,7 +20,12 @@ func sysTotalMemory() int {
 	}
 	mem := cgroup.GetMemoryLimit()
 	if mem <= 0 || int64(int(mem)) != mem || int(mem) > totalMem {
-		return totalMem
+		// Try reading hierachical memory limit.
+		// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/699
+		mem = cgroup.GetHierarchicalMemoryLimit()
+		if mem <= 0 || int64(int(mem)) != mem || int(mem) > totalMem {
+			return totalMem
+		}
 	}
 	return int(mem)
 }