Add cgroup v2 support for memory limit (#18905)

cmd/handler-api.go

@@ -56,16 +56,31 @@ type apiConfig struct {
 	syncEvents                  bool
 }
 
-const cgroupLimitFile = "/sys/fs/cgroup/memory/memory.limit_in_bytes"
+const (
+	cgroupV1MemLimitFile = "/sys/fs/cgroup/memory/memory.limit_in_bytes"
+	cgroupV2MemLimitFile = "/sys/fs/cgroup/memory.max"
+	cgroupMemNoLimit     = 9223372036854771712
+)
 
-func cgroupLimit(limitFile string) (limit uint64) {
-	buf, err := os.ReadFile(limitFile)
+func cgroupMemLimit() (limit uint64) {
+	buf, err := os.ReadFile(cgroupV2MemLimitFile)
 	if err != nil {
-		return 9223372036854771712
+		buf, err = os.ReadFile(cgroupV1MemLimitFile)
+	}
+	if err != nil {
+		return 0
 	}
 	limit, err = strconv.ParseUint(string(buf), 10, 64)
 	if err != nil {
-		return 9223372036854771712
+		// The kernel can return valid but non integer values
+		// but still, no need to interpret more
+		return 0
+	}
+	if limit == cgroupMemNoLimit {
+		// No limit set, It's the highest positive signed 64-bit
+		// integer (2^63-1), rounded down to multiples of 4096 (2^12),
+		// the most common page size on x86 systems - for cgroup_limits.
+		return 0
 	}
 	return limit
 }
@@ -74,23 +89,19 @@ func availableMemory() (available uint64) {
 	available = 8 << 30 // Default to 8 GiB when we can't find the limits.
 
 	if runtime.GOOS == "linux" {
-		available = cgroupLimit(cgroupLimitFile)
-
-		// No limit set, It's the highest positive signed 64-bit
-		// integer (2^63-1), rounded down to multiples of 4096 (2^12),
-		// the most common page size on x86 systems - for cgroup_limits.
-		if available != 9223372036854771712 {
-			// This means cgroup memory limit is configured.
+		// Useful in container mode
+		limit := cgroupMemLimit()
+		if limit > 0 {
+			// A valid value is found
+			available = limit
 			return
-		} // no-limit set proceed to set the limits based on virtual memory.
-
+		}
 	} // for all other platforms limits are based on virtual memory.
 
 	memStats, err := mem.VirtualMemory()
 	if err != nil {
 		return
 	}
-
 	available = memStats.Available / 2
 	return
 }