sys/proc: remove GetSystemCPUUsage as it is unused

After e115b52ce2 was merged, this
function was no longer in use, so we should be able to remove it.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

sys/proc.go

@@ -1,80 +0,0 @@
-// +build linux
-
-/*
-   Copyright The containerd Authors.
-
-   Licensed under the Apache License, Version 2.0 (the "License");
-   you may not use this file except in compliance with the License.
-   You may obtain a copy of the License at
-
-       http://www.apache.org/licenses/LICENSE-2.0
-
-   Unless required by applicable law or agreed to in writing, software
-   distributed under the License is distributed on an "AS IS" BASIS,
-   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-   See the License for the specific language governing permissions and
-   limitations under the License.
-*/
-
-package sys
-
-import (
-	"bufio"
-	"fmt"
-	"os"
-	"strconv"
-	"strings"
-
-	"github.com/opencontainers/runc/libcontainer/system"
-)
-
-const nanoSecondsPerSecond = 1e9
-
-var clockTicksPerSecond = uint64(system.GetClockTicks())
-
-// GetSystemCPUUsage returns the host system's cpu usage in
-// nanoseconds. An error is returned if the format of the underlying
-// file does not match.
-//
-// Uses /proc/stat defined by POSIX. Looks for the cpu
-// statistics line and then sums up the first seven fields
-// provided. See `man 5 proc` for details on specific field
-// information.
-func GetSystemCPUUsage() (uint64, error) {
-	var line string
-	f, err := os.Open("/proc/stat")
-	if err != nil {
-		return 0, err
-	}
-	bufReader := bufio.NewReaderSize(nil, 128)
-	defer func() {
-		bufReader.Reset(nil)
-		f.Close()
-	}()
-	bufReader.Reset(f)
-	err = nil
-	for err == nil {
-		line, err = bufReader.ReadString('\n')
-		if err != nil {
-			break
-		}
-		parts := strings.Fields(line)
-		switch parts[0] {
-		case "cpu":
-			if len(parts) < 8 {
-				return 0, fmt.Errorf("bad format of cpu stats")
-			}
-			var totalClockTicks uint64
-			for _, i := range parts[1:8] {
-				v, err := strconv.ParseUint(i, 10, 64)
-				if err != nil {
-					return 0, fmt.Errorf("error parsing cpu stats")
-				}
-				totalClockTicks += v
-			}
-			return (totalClockTicks * nanoSecondsPerSecond) /
-				clockTicksPerSecond, nil
-		}
-	}
-	return 0, fmt.Errorf("bad stats format")
-}