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- // Copyright 2018 Google LLC
- //
- // 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 profiler
-
- import (
- "bytes"
- "context"
- "fmt"
- "runtime"
- "time"
-
- "github.com/google/pprof/profile"
- )
-
- // heapProfile collects an in-use heap profile. The heap profiles returned by
- // the runtime also include the heap allocation metrics. We zero those out
- // since all allocations since program start are recorded, so these make the
- // profile large and there is a separate alloc profile type which shows
- // allocations from a set duration.
- func heapProfile(prof *bytes.Buffer) error {
- p, err := goHeapProfile()
- if err != nil {
- return err
- }
- for _, s := range p.Sample {
- s.Value[0] = 0
- s.Value[1] = 0
- }
-
- // Merge profile with itself to remove samples with only zero values and
- // reduce profile size.
- p, err = profile.Merge([]*profile.Profile{p})
- if err != nil {
- return err
- }
- return p.Write(prof)
- }
-
- // deltaAllocProfile collects an allocation profile by gathering a heap profile,
- // sleeping for the specified duration, gathering another heap profile and
- // subtracting the initial one from that. It then drops the in-use metrics from
- // the profile. If requested, it forces the GC before taking each of the heap
- // profiles, which improves the profile accuracy (see docs in
- // https://golang.org/src/runtime/mprof.go on why).
- func deltaAllocProfile(ctx context.Context, duration time.Duration, forceGC bool, prof *bytes.Buffer) error {
- p1, err := allocProfile(forceGC)
- if err != nil {
- return err
- }
-
- sleep(ctx, duration)
-
- p2, err := allocProfile(forceGC)
- if err != nil {
- return err
- }
-
- p1.Scale(-1)
- p, err := profile.Merge([]*profile.Profile{p1, p2})
- if err != nil {
- return err
- }
- p.DurationNanos = duration.Nanoseconds()
- return p.Write(prof)
- }
-
- // allocProfile collects a single heap profile, and removes all metrics but
- // allocation metrics.
- func allocProfile(forceGC bool) (*profile.Profile, error) {
- if forceGC {
- runtime.GC()
- }
- p, err := goHeapProfile()
- if err != nil {
- return nil, err
- }
- p.SampleType = p.SampleType[:2]
- for _, s := range p.Sample {
- s.Value = s.Value[:2]
- }
- return p, nil
- }
-
- // goHeapProfile collects a heap profile. It returns an error if the metrics
- // in the collected heap profile do not match the expected metrics.
- func goHeapProfile() (*profile.Profile, error) {
- var prof bytes.Buffer
- if err := writeHeapProfile(&prof); err != nil {
- return nil, fmt.Errorf("failed to write heap profile: %v", err)
- }
- p, err := profile.Parse(&prof)
- if err != nil {
- return nil, err
- }
- if got := len(p.SampleType); got != 4 {
- return nil, fmt.Errorf("invalid heap profile: got %d sample types, want 4", got)
- }
- for i, want := range []string{"alloc_objects", "alloc_space", "inuse_objects", "inuse_space"} {
- if got := p.SampleType[i].Type; got != want {
- return nil, fmt.Errorf("invalid heap profile: got %q sample type at index %d, want %q", got, i, want)
- }
- }
- return p, nil
- }
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