Add perf exporter (#1274)

Signed-off-by: Daniel Hodges <hodges.daniel.scott@gmail.com>

vendor/github.com/hodgesds/perf-utils/group_profiler.go

@@ -0,0 +1,170 @@
+// +build linux
+
+package perf
+
+import (
+	"encoding/binary"
+	"fmt"
+	"syscall"
+
+	"go.uber.org/multierr"
+	"golang.org/x/sys/unix"
+)
+
+// ErrNoLeader is returned when a leader of a GroupProfiler is not defined.
+var ErrNoLeader = fmt.Errorf("No leader defined")
+
+// GroupProfileValue is returned from a GroupProfiler.
+type GroupProfileValue struct {
+	Events      uint64
+	TimeEnabled uint64
+	TimeRunning uint64
+	Values      []uint64
+}
+
+// GroupProfiler is used to setup a group profiler.
+type GroupProfiler interface {
+	Start() error
+	Reset() error
+	Stop() error
+	Close() error
+	Profile() (*GroupProfileValue, error)
+}
+
+// groupProfiler implements the GroupProfiler interface.
+type groupProfiler struct {
+	fds []int // leader is always element 0
+}
+
+// NewGroupProfiler returns a GroupProfiler.
+func NewGroupProfiler(pid, cpu, opts int, eventAttrs ...unix.PerfEventAttr) (GroupProfiler, error) {
+	fds := make([]int, len(eventAttrs))
+
+	for i, eventAttr := range eventAttrs {
+		// common configs
+		eventAttr.Size = EventAttrSize
+		eventAttr.Sample_type = PERF_SAMPLE_IDENTIFIER
+
+		// Leader fd must be opened first
+		if i == 0 {
+			// leader specific configs
+			eventAttr.Bits = unix.PerfBitDisabled | unix.PerfBitExcludeHv
+			eventAttr.Read_format = unix.PERF_FORMAT_TOTAL_TIME_RUNNING | unix.PERF_FORMAT_TOTAL_TIME_ENABLED | unix.PERF_FORMAT_GROUP
+
+			fd, err := unix.PerfEventOpen(
+				&eventAttr,
+				pid,
+				cpu,
+				-1,
+				opts,
+			)
+			if err != nil {
+				return nil, err
+			}
+			fds[i] = fd
+			continue
+		}
+
+		// non leader configs
+		eventAttr.Read_format = unix.PERF_FORMAT_TOTAL_TIME_RUNNING | unix.PERF_FORMAT_TOTAL_TIME_ENABLED | unix.PERF_FORMAT_GROUP
+		eventAttr.Bits = unix.PerfBitExcludeHv
+
+		fd, err := unix.PerfEventOpen(
+			&eventAttr,
+			pid,
+			cpu,
+			fds[0],
+			opts,
+		)
+		if err != nil {
+			// cleanup any old Fds
+			for ii, fd2 := range fds {
+				if ii == i {
+					break
+				}
+				err = multierr.Append(err, unix.Close(fd2))
+			}
+			return nil, err
+		}
+		fds[i] = fd
+	}
+
+	return &groupProfiler{
+		fds: fds,
+	}, nil
+}
+
+// Start is used to start the GroupProfiler.
+func (p *groupProfiler) Start() error {
+	if len(p.fds) == 0 {
+		return ErrNoLeader
+	}
+	return unix.IoctlSetInt(p.fds[0], unix.PERF_EVENT_IOC_ENABLE, 0)
+}
+
+// Reset is used to reset the GroupProfiler.
+func (p *groupProfiler) Reset() error {
+	if len(p.fds) == 0 {
+		return ErrNoLeader
+	}
+	return unix.IoctlSetInt(p.fds[0], unix.PERF_EVENT_IOC_RESET, 0)
+}
+
+// Stop is used to stop the GroupProfiler.
+func (p *groupProfiler) Stop() error {
+	if len(p.fds) == 0 {
+		return ErrNoLeader
+	}
+	return unix.IoctlSetInt(p.fds[0], unix.PERF_EVENT_IOC_DISABLE, 0)
+}
+
+// Close is used to close the GroupProfiler.
+func (p *groupProfiler) Close() error {
+	var err error
+	for _, fd := range p.fds {
+		err = multierr.Append(err, unix.Close(fd))
+	}
+	return err
+}
+
+// Profile is used to return the GroupProfileValue of the GroupProfiler.
+func (p *groupProfiler) Profile() (*GroupProfileValue, error) {
+	nEvents := len(p.fds)
+	if nEvents == 0 {
+		return nil, ErrNoLeader
+	}
+
+	// read format of the raw event looks like this:
+	/*
+		     struct read_format {
+			 u64 nr;            // The number of events /
+			 u64 time_enabled;  // if PERF_FORMAT_TOTAL_TIME_ENABLED
+			 u64 time_running;  // if PERF_FORMAT_TOTAL_TIME_RUNNING
+			 struct {
+			     u64 value;     // The value of the event
+			     u64 id;        // if PERF_FORMAT_ID
+			 } values[nr];
+		     };
+	*/
+
+	buf := make([]byte, 24+8*nEvents)
+	_, err := syscall.Read(p.fds[0], buf)
+	if err != nil {
+		return nil, err
+	}
+
+	val := &GroupProfileValue{
+		Events:      binary.LittleEndian.Uint64(buf[0:8]),
+		TimeEnabled: binary.LittleEndian.Uint64(buf[8:16]),
+		TimeRunning: binary.LittleEndian.Uint64(buf[16:24]),
+		Values:      make([]uint64, len(p.fds)),
+	}
+
+	offset := 24
+	for i := range p.fds {
+		val.Values[i] = binary.LittleEndian.Uint64(buf[offset : offset+8])
+		offset += 8
+	}
+
+	return val, nil
+}