procfs package

utils/procfs/doc.go

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+// Copyright 2014 Google Inc. All Rights Reserved.
+//
+// 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.
+
+// procfs contains several low level functions to read information from /proc
+// filesystem, and also provides some utility functions like JiffiesToDuration.
+package procfs

utils/procfs/jiffy.go

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+// Copyright 2014 Google Inc. All Rights Reserved.
+//
+// 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 procfs
+
+/*
+#include <unistd.h>
+*/
+import "C"
+import "time"
+
+var userHz uint64
+
+func init() {
+	userHzLong := C.sysconf(C._SC_CLK_TCK)
+	userHz = uint64(userHzLong)
+}
+
+func JiffiesToDuration(jiffies uint64) time.Duration {
+	d := jiffies * 1000000000 / userHz
+	return time.Duration(d)
+}

utils/procfs/schedstats.go

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+// Copyright 2014 Google Inc. All Rights Reserved.
+//
+// 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 procfs
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+)
+
+type ProcessSchedStat struct {
+	// Number of processes
+	NumProcesses int
+
+	// Total time spent on the cpu (Unit: jiffy)
+	Running uint64
+
+	// Total time spent waiting on a runqueue (Unit: jiffy)
+	RunWait uint64
+
+	// # of timeslices run on this cpu (Unit: jiffy)
+	NumTimeSlices uint64
+}
+
+func readUint64List(r io.Reader) ([]uint64, error) {
+	ret := make([]uint64, 0, 4)
+	scanner := bufio.NewScanner(r)
+	scanner.Split(bufio.ScanWords)
+
+	for scanner.Scan() {
+		str := scanner.Text()
+		u, err := strconv.ParseUint(str, 10, 64)
+		if err != nil {
+			return nil, err
+		}
+		ret = append(ret, u)
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, err
+	}
+
+	return ret, nil
+}
+
+// Add() read the schedstat of pid, and add stat to the fields
+// in self parameters. This function is useful if one wants to read stats of
+// a group of processes.
+func (self *ProcessSchedStat) Add(pid int) error {
+	if self == nil {
+		return fmt.Errorf("nil stat")
+	}
+
+	path := fmt.Sprintf("/proc/%d/schedstat", pid)
+	f, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	v, err := readUint64List(f)
+	if err != nil {
+		return err
+	}
+	if len(v) < 3 {
+		return fmt.Errorf("only %v fields read from %v: %v", len(v), path, v)
+	}
+	self.Running += v[0]
+	self.RunWait += v[1]
+	self.NumTimeSlices += v[2]
+	self.NumProcesses++
+	return nil
+}