Add a utility to read cpu load stats.
This commit is contained in:
Rohit Jnagal
parent
57c6fb08f4
commit
aeee52161c
92
utils/cpuload/conn.go
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92
utils/cpuload/conn.go
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@ -0,0 +1,92 @@
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// Copyright 2015 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package cpuload
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import (
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"bufio"
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"bytes"
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"encoding/binary"
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"os"
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"syscall"
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)
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type Connection struct {
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// netlink socket
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fd int
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// cache pid to use in every netlink request.
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pid uint32
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// sequence number for netlink messages.
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seq uint32
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addr syscall.SockaddrNetlink
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rbuf *bufio.Reader
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}
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// Create and bind a new netlink socket.
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func newConnection() (*Connection, error) {
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fd, err := syscall.Socket(syscall.AF_NETLINK, syscall.SOCK_DGRAM, syscall.NETLINK_GENERIC)
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if err != nil {
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return nil, err
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}
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conn := new(Connection)
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conn.fd = fd
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conn.seq = 0
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conn.pid = uint32(os.Getpid())
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conn.addr.Family = syscall.AF_NETLINK
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conn.rbuf = bufio.NewReader(conn)
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err = syscall.Bind(fd, &conn.addr)
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if err != nil {
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syscall.Close(fd)
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return nil, err
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}
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return conn, err
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}
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func (self *Connection) Read(b []byte) (n int, err error) {
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n, _, err = syscall.Recvfrom(self.fd, b, 0)
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return n, err
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}
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func (self *Connection) Write(b []byte) (n int, err error) {
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err = syscall.Sendto(self.fd, b, 0, &self.addr)
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return len(b), err
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}
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func (self *Connection) Close() error {
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return syscall.Close(self.fd)
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}
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func (self *Connection) WriteMessage(msg syscall.NetlinkMessage) error {
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w := bytes.NewBuffer(nil)
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msg.Header.Len = uint32(syscall.NLMSG_HDRLEN + len(msg.Data))
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msg.Header.Seq = self.seq
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self.seq++
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msg.Header.Pid = self.pid
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binary.Write(w, binary.LittleEndian, msg.Header)
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_, err := w.Write(msg.Data)
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if err != nil {
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return err
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}
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_, err = self.Write(w.Bytes())
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return err
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}
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func (self *Connection) ReadMessage() (msg syscall.NetlinkMessage, err error) {
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binary.Read(self.rbuf, binary.LittleEndian, &msg.Header)
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msg.Data = make([]byte, msg.Header.Len-syscall.NLMSG_HDRLEN)
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_, err = self.rbuf.Read(msg.Data)
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return msg, err
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}
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90
utils/cpuload/cpuload.go
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90
utils/cpuload/cpuload.go
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// Copyright 2015 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package cpuload
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import (
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"fmt"
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"os"
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"github.com/golang/glog"
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)
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type CpuLoadReader struct {
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familyId uint16
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conn *Connection
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}
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func New() (*CpuLoadReader, error) {
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conn, err := newConnection()
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if err != nil {
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return nil, fmt.Errorf("failed to create a new connection: %s", err)
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}
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id, err := getFamilyId(conn)
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if err != nil {
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return nil, fmt.Errorf("failed to get netlink family id for task stats: %s", err)
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}
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glog.V(2).Infof("Family id for taskstats: %d", id)
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return &CpuLoadReader{
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familyId: id,
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conn: conn,
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}, nil
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}
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func (self *CpuLoadReader) Close() {
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if self.conn != nil {
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self.conn.Close()
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}
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}
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// This mirrors kernel internal structure.
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type LoadStats struct {
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// Number of sleeping tasks.
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NrSleeping uint64 `json:"nr_sleeping"`
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// Number of running tasks.
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NrRunning uint64 `json:"nr_running"`
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// Number of tasks in stopped state
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NrStopped uint64 `json:"nr_stopped"`
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// Number of tasks in uninterruptible state
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NrUinterruptible uint64 `json:"nr_uninterruptible"`
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// Number of tasks waiting on IO
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NrIoWait uint64 `json:"nr_io_wait"`
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}
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// Returns instantaneous number of running tasks in a group.
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// Caller can use historical data to calculate cpu load.
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// path is an absolute filesystem path for a container under the CPU cgroup hierarchy.
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// NOTE: non-hierarchical load is returned. It does not include load for subcontainers.
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func (self *CpuLoadReader) GetCpuLoad(path string) (LoadStats, error) {
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if len(path) == 0 {
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return LoadStats{}, fmt.Errorf("cgroup path can not be empty!")
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}
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cfd, err := os.Open(path)
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if err != nil {
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return LoadStats{}, fmt.Errorf("failed to open cgroup path %s: %q", path, err)
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}
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stats, err := getLoadStats(self.familyId, cfd.Fd(), self.conn)
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if err != nil {
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return LoadStats{}, err
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}
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glog.V(1).Infof("Task stats for %q: %+v", path, stats)
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return stats, nil
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}
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26
utils/cpuload/defs.go
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26
utils/cpuload/defs.go
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// Copyright 2015 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package cpuload
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/*
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#include <linux/taskstats.h>
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*/
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import "C"
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type TaskStats C.struct_taskstats
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const (
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__TASKSTATS_CMD_MAX = C.__TASKSTATS_CMD_MAX
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)
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39
utils/cpuload/example/example.go
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39
utils/cpuload/example/example.go
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// Copyright 2015 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package main
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import (
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"log"
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"github.com/google/cadvisor/utils/cpuload"
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)
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func main() {
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c, err := cpuload.New()
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if err != nil {
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log.Printf("Failed to create cpu load util: %s", err)
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return
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}
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defer c.Close()
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paths := []string{"/sys/fs/cgroup/cpu", "/sys/fs/cgroup/cpu/docker"}
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for _, path := range paths {
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stats, err := c.GetCpuLoad(path)
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if err != nil {
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log.Printf("Error getting cpu load for %q: %s", path, err)
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}
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log.Printf("Task load for %s: %+v", path, stats)
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}
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}
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236
utils/cpuload/netlink.go
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236
utils/cpuload/netlink.go
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// Copyright 2015 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package cpuload
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import (
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"bytes"
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"encoding/binary"
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"fmt"
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"syscall"
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)
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const (
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// Kernel constants for tasks stats.
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genlIdCtrl = syscall.NLMSG_MIN_TYPE // GENL_ID_CTRL
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taskstatsGenlName = "TASKSTATS" // TASKSTATS_GENL_NAME
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cgroupStatsCmdAttrFd = 0x1 // CGROUPSTATS_CMD_ATTR_FD
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ctrlAttrFamilyId = 0x1 // CTRL_ATTR_FAMILY_ID
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ctrlAttrFamilyName = 0x2 // CTRL_ATTR_FAMILY_NAME
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ctrlCmdGetFamily = 0x3 // CTRL_CMD_GETFAMILY
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)
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var (
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// TODO(rjnagal): Verify and fix for other architectures.
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Endian = binary.LittleEndian
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)
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type genMsghdr struct {
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Command uint8
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Version uint8
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Reserved uint16
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}
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type netlinkMessage struct {
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Header syscall.NlMsghdr
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GenHeader genMsghdr
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Data []byte
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}
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func (self netlinkMessage) toRawMsg() (rawmsg syscall.NetlinkMessage) {
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rawmsg.Header = self.Header
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w := bytes.NewBuffer([]byte{})
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binary.Write(w, Endian, self.GenHeader)
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w.Write(self.Data)
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rawmsg.Data = w.Bytes()
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return rawmsg
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}
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type loadStatsResp struct {
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Header syscall.NlMsghdr
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GenHeader genMsghdr
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Stats LoadStats
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}
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// Return required padding to align 'size' to 'alignment'.
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func padding(size int, alignment int) int {
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unalignedPart := size % alignment
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return (alignment - unalignedPart) % alignment
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}
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// Get family id for taskstats subsystem.
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func getFamilyId(conn *Connection) (uint16, error) {
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msg := prepareFamilyMessage()
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conn.WriteMessage(msg.toRawMsg())
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resp, _ := conn.ReadMessage()
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id, err := parseFamilyResp(resp)
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if err != nil {
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return 0, err
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}
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return id, nil
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}
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// Append an attribute to the message.
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// Adds attribute info (length and type), followed by the data and necessary padding.
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// Can be called multiple times to add attributes. Only fixed size and string type
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// attributes are handled. We don't need nested attributes for task stats.
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func addAttribute(buf *bytes.Buffer, attrType uint16, data interface{}, dataSize int) {
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attr := syscall.RtAttr{
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Len: syscall.SizeofRtAttr,
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Type: attrType,
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}
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attr.Len += uint16(dataSize)
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binary.Write(buf, Endian, attr)
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switch data := data.(type) {
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case string:
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binary.Write(buf, Endian, []byte(data))
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buf.WriteByte(0) // terminate
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default:
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binary.Write(buf, Endian, data)
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}
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for i := 0; i < padding(int(attr.Len), syscall.NLMSG_ALIGNTO); i++ {
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buf.WriteByte(0)
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}
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}
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// Prepares the message and generic headers and appends attributes as data.
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func prepareMessage(headerType uint16, cmd uint8, attributes []byte) (msg netlinkMessage) {
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msg.Header.Type = headerType
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msg.Header.Flags = syscall.NLM_F_REQUEST
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msg.GenHeader.Command = cmd
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msg.GenHeader.Version = 0x1
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msg.Data = attributes
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return msg
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}
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// Prepares message to query family id for task stats.
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func prepareFamilyMessage() (msg netlinkMessage) {
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buf := bytes.NewBuffer([]byte{})
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addAttribute(buf, ctrlAttrFamilyName, taskstatsGenlName, len(taskstatsGenlName)+1)
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return prepareMessage(genlIdCtrl, ctrlCmdGetFamily, buf.Bytes())
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}
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// Prepares message to query task stats for a task group.
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func prepareCmdMessage(id uint16, cfd uintptr) (msg netlinkMessage) {
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buf := bytes.NewBuffer([]byte{})
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addAttribute(buf, cgroupStatsCmdAttrFd, uint32(cfd), 4)
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return prepareMessage(id, __TASKSTATS_CMD_MAX+1, buf.Bytes())
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}
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// Extracts returned family id from the response.
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func parseFamilyResp(msg syscall.NetlinkMessage) (uint16, error) {
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m := new(netlinkMessage)
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m.Header = msg.Header
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err := verifyHeader(msg)
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if err != nil {
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return 0, err
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}
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buf := bytes.NewBuffer(msg.Data)
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// extract generic header from data.
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err = binary.Read(buf, Endian, &m.GenHeader)
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if err != nil {
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return 0, err
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}
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id := uint16(0)
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// Extract attributes. kernel reports family name, id, version, etc.
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// Scan till we find id.
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for buf.Len() > syscall.SizeofRtAttr {
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var attr syscall.RtAttr
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err = binary.Read(buf, Endian, &attr)
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if err != nil {
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return 0, err
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}
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if attr.Type == ctrlAttrFamilyId {
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err = binary.Read(buf, Endian, &id)
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if err != nil {
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return 0, err
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}
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return id, nil
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}
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payload := int(attr.Len) - syscall.SizeofRtAttr
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skipLen := payload + padding(payload, syscall.SizeofRtAttr)
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name := make([]byte, skipLen)
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err = binary.Read(buf, Endian, name)
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if err != nil {
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return 0, err
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}
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}
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return 0, fmt.Errorf("family id not found in the response.")
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}
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// Extract task stats from response returned by kernel.
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func parseLoadStatsResp(msg syscall.NetlinkMessage) (*loadStatsResp, error) {
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m := new(loadStatsResp)
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m.Header = msg.Header
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err := verifyHeader(msg)
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if err != nil {
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return m, err
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}
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buf := bytes.NewBuffer(msg.Data)
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// Scan the general header.
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err = binary.Read(buf, Endian, &m.GenHeader)
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if err != nil {
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return m, err
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}
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// cgroup stats response should have just one attribute.
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// Read it directly into the stats structure.
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var attr syscall.RtAttr
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err = binary.Read(buf, Endian, &attr)
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if err != nil {
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return m, err
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}
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err = binary.Read(buf, Endian, &m.Stats)
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if err != nil {
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return m, err
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}
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return m, err
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}
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// Verify and return any error reported by kernel.
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func verifyHeader(msg syscall.NetlinkMessage) error {
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switch msg.Header.Type {
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case syscall.NLMSG_DONE:
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return fmt.Errorf("expected a response, got nil")
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case syscall.NLMSG_ERROR:
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buf := bytes.NewBuffer(msg.Data)
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var errno int32
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binary.Read(buf, Endian, errno)
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return fmt.Errorf("netlink request failed with error %s", syscall.Errno(-errno))
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}
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return nil
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}
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// Get load stats for a task group.
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// id: family id for taskstats.
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// fd: fd to path to the cgroup directory under cpu hierarchy.
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// conn: open netlink connection used to communicate with kernel.
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func getLoadStats(id uint16, fd uintptr, conn *Connection) (LoadStats, error) {
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msg := prepareCmdMessage(id, fd)
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err := conn.WriteMessage(msg.toRawMsg())
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if err != nil {
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return LoadStats{}, err
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}
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resp, err := conn.ReadMessage()
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if err != nil {
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return LoadStats{}, err
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}
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parsedmsg, err := parseLoadStatsResp(resp)
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if err != nil {
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return LoadStats{}, err
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}
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return parsedmsg.Stats, nil
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}
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