fixes max memory available detection on linux (#256)

pkg/storage/mem.go

@@ -1,44 +1,13 @@
+// +build !linux
+
 package storage
 
 import (
-	"io/ioutil"
-	"os"
-	"strconv"
-	"strings"
-
-	"github.com/pyroscope-io/pyroscope/pkg/util/file"
 	"github.com/shirou/gopsutil/mem"
-	"github.com/sirupsen/logrus"
 )
 
-const memLimitPath = "/sys/fs/cgroup/memory/memory.limit_in_bytes"
-
-func getCgroupMemLimit() (uint64, error) {
-	f, err := os.Open(memLimitPath)
-	if err != nil {
-		return 0, err
-	}
-	b, err := ioutil.ReadAll(f)
-	if err != nil {
-		return 0, err
-	}
-	r, err := strconv.Atoi(strings.TrimSuffix(string(b), "\n"))
-	if err != nil {
-		return 0, err
-	}
-
-	return uint64(r), nil
-}
-
+// on linux we also look at cgroup mem limit
 func getMemTotal() (uint64, error) {
-	if file.Exists(memLimitPath) {
-		v, err := getCgroupMemLimit()
-		if err == nil {
-			return v, nil
-		}
-		logrus.WithError(err).Warn("Could not read cgroup memory limit")
-	}
-
 	vm, err := mem.VirtualMemory()
 	if err != nil {
 		return 0, err

pkg/storage/mem_linux.go

@@ -0,0 +1,55 @@
+// +build linux
+
+package storage
+
+import (
+	"io/ioutil"
+	"os"
+	"strconv"
+	"strings"
+
+	"github.com/pyroscope-io/pyroscope/pkg/util/file"
+	"github.com/shirou/gopsutil/mem"
+	"github.com/sirupsen/logrus"
+)
+
+const memLimitPath = "/sys/fs/cgroup/memory/memory.limit_in_bytes"
+
+func getCgroupMemLimit() (uint64, error) {
+	f, err := os.Open(memLimitPath)
+	if err != nil {
+		return 0, err
+	}
+	b, err := ioutil.ReadAll(f)
+	if err != nil {
+		return 0, err
+	}
+	r, err := strconv.Atoi(strings.TrimSuffix(string(b), "\n"))
+	if err != nil {
+		return 0, err
+	}
+
+	return uint64(r), nil
+}
+
+func getMemTotal() (uint64, error) {
+	vm, err := mem.VirtualMemory()
+	if err != nil {
+		return 0, err
+	}
+
+	if file.Exists(memLimitPath) {
+		v, err := getCgroupMemLimit()
+		if err == nil {
+			if v < vm.Total {
+				return v, nil
+			}
+			return vm.Total, nil
+		}
+
+		logrus.WithError(err).Warn("Could not read cgroup memory limit")
+		return vm.Total, nil
+	}
+
+	return vm.Total, nil
+}