prometheus: log virtual memory limits

Signed-off-by: Simon Pasquier <spasquie@redhat.com>

cmd/prometheus/limits_default.go

@@ -21,12 +21,30 @@ import (
 	"syscall"
 )
 
-// FdLimits returns the soft and hard limits for file descriptors
-func FdLimits() string {
-	flimit := syscall.Rlimit{}
-	err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &flimit)
+var unlimited int64 = syscall.RLIM_INFINITY
+
+func limitToString(v uint64) string {
+	if v == uint64(unlimited) {
+		return "unlimited"
+	}
+	return fmt.Sprintf("%d", v)
+}
+
+func getLimits(resource int) string {
+	rlimit := syscall.Rlimit{}
+	err := syscall.Getrlimit(resource, &rlimit)
 	if err != nil {
 		log.Fatal("Error!")
 	}
-	return fmt.Sprintf("(soft=%d, hard=%d)", flimit.Cur, flimit.Max)
+	return fmt.Sprintf("(soft=%s, hard=%s)", limitToString(rlimit.Cur), limitToString(rlimit.Max))
+}
+
+// FdLimits returns the soft and hard limits for file descriptors.
+func FdLimits() string {
+	return getLimits(syscall.RLIMIT_NOFILE)
+}
+
+// VmLimits returns the soft and hard limits for virtual memory.
+func VmLimits() string {
+	return getLimits(syscall.RLIMIT_AS)
 }

cmd/prometheus/limits_windows.go

@@ -19,3 +19,8 @@ package main
 func FdLimits() string {
 	return "N/A"
 }
+
+// VmLimits not supported on Windows
+func VmLimits() string {
+	return "N/A"
+}

cmd/prometheus/main.go

@@ -223,6 +223,7 @@ func main() {
 	level.Info(logger).Log("build_context", version.BuildContext())
 	level.Info(logger).Log("host_details", Uname())
 	level.Info(logger).Log("fd_limits", FdLimits())
+	level.Info(logger).Log("vm_limits", VmLimits())
 
 	var (
 		localStorage  = &tsdb.ReadyStorage{}