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Copy pathgroup.go
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114 lines (100 loc) · 3.04 KB
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// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build linux
package perf
import (
"errors"
"fmt"
)
// Group configures a group of events.
type Group struct {
// CountFormat configures the format of counts read from the event
// leader. The Group option is set automatically.
CountFormat CountFormat
// Options configures options for all events in the group.
Options Options
// ClockID configures the clock for samples in the group.
ClockID int32
err error // sticky configuration error
attrs []*Attr
leaderNeedsRing bool
}
// TODO(acln): what other fields belong on Group? SampleFormat perhaps?
// Add adds events to the group, as configured by cfgs.
//
// For each Configurator, a new *Attr is created, the group-specific settings
// are applied, then Configure is called on the *Attr to produce the final
// event attributes.
func (g *Group) Add(cfgs ...Configurator) {
for _, cfg := range cfgs {
g.add(cfg)
}
}
func (g *Group) add(cfg Configurator) {
if g.err != nil {
return
}
a := new(Attr)
a.CountFormat = g.CountFormat
a.Options = g.Options
a.ClockID = g.ClockID
err := cfg.Configure(a)
if err != nil {
g.err = err
return
}
if a.Sample != 0 {
g.leaderNeedsRing = true
}
g.attrs = append(g.attrs, a)
}
// Open opens all the events in the group, and returns their leader.
//
// The returned Event controls the entire group. Callers must use the
// ReadGroupCount method when reading counters from it. Closing it closes
// the entire group.
func (g *Group) Open(pid int, cpu int) (*Event, error) {
if len(g.attrs) == 0 {
return nil, errors.New("perf: empty event group")
}
if g.err != nil {
return nil, fmt.Errorf("perf: configuration error: %v", g.err)
}
leaderattr := g.attrs[0]
leaderattr.CountFormat.Group = true
leader, err := Open(leaderattr, pid, cpu, nil)
if err != nil {
return nil, fmt.Errorf("perf: failed to open event leader: %v", err)
}
if len(g.attrs) < 2 {
return leader, nil
}
if g.leaderNeedsRing {
if err := leader.MapRing(); err != nil {
return nil, fmt.Errorf("perf: failed to map leader ring: %v", err)
}
}
for idx, attr := range g.attrs[1:] {
follower, err := Open(attr, pid, cpu, leader)
if err != nil {
leader.Close()
return nil, fmt.Errorf("perf: failed to open group event #%d (%q): %v", idx, attr.Label, err)
}
leader.owned = append(leader.owned, follower)
if attr.Sample != 0 {
if err := follower.SetOutput(leader); err != nil {
leader.Close()
return nil, fmt.Errorf("perf: failed to route follower %q output to leader %q (pid %d on CPU %d)", attr.Label, leaderattr.Label, pid, cpu)
}
}
}
return leader, nil
}
// A Configurator configures event attributes. Implementations should only
// set the fields they need. See (*Group).Add for more details.
type Configurator interface {
Configure(attr *Attr) error
}
type configuratorFunc func(attr *Attr) error
func (cf configuratorFunc) Configure(attr *Attr) error { return cf(attr) }