From: Hana (Hyang-Ah) Kim Date: Fri, 13 Jul 2018 20:11:24 +0000 (-0400) Subject: runtime/pprof: add a fake mapping when /proc/self/maps is unavailable X-Git-Tag: go1.11beta2~98 X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=ba02264446fa1863c0a4c8339bbcf2bec57b620a;p=gostls13.git runtime/pprof: add a fake mapping when /proc/self/maps is unavailable Profile's Mapping field is currently populated by reading /proc/self/maps. On systems where /proc/self/maps is not available, the profile generated by Go's runtime will not have any Mapping entry. Pprof command then adds a fake entry and links all Location entries in the profile with the fake entry to be used during symbolization. https://github.com/google/pprof/blob/a8644067d5a3c9a6386e7c88fa4a3d9d37877ca3/internal/driver/fetch.go#L437 The fake entry is not enough to suppress the error or warning messages pprof command produces. We need to tell pprof that Location entries are symbolized already by Go runtime and pprof does not have to attempt to perform further symbolization. In #25743, we made Go runtime mark Mapping entries with HasFunctions=true when all Location entries from the Mapping entries are successfully symbolized. This change makes the Go runtime add a fake mapping entry, otherwise the pprof command tool would add, and set the HasFunctions=true following the same logic taken when the real mapping information is available. Updates #19790. Fixes #26255. Tested pprof doesn't report the error message any more for pure Go program. Change-Id: Ib12b62e15073f5d6c80967e44b3e8709277c11bd Reviewed-on: https://go-review.googlesource.com/123779 Run-TryBot: Hyang-Ah Hana Kim TryBot-Result: Gobot Gobot Reviewed-by: Brad Fitzpatrick --- diff --git a/src/runtime/pprof/proto.go b/src/runtime/pprof/proto.go index 1cf3a5154f..cbd0b83376 100644 --- a/src/runtime/pprof/proto.go +++ b/src/runtime/pprof/proto.go @@ -54,6 +54,7 @@ type memMap struct { file, buildID string funcs symbolizeFlag + fake bool // map entry was faked; /proc/self/maps wasn't available } // symbolizeFlag keeps track of symbolization result. @@ -267,7 +268,7 @@ func (b *profileBuilder) locForPC(addr uintptr) uint64 { frame, more = frames.Next() } for i := range b.mem { - if b.mem[i].start <= addr && addr < b.mem[i].end { + if b.mem[i].start <= addr && addr < b.mem[i].end || b.mem[i].fake { b.pb.uint64Opt(tagLocation_MappingID, uint64(i+1)) m := b.mem[i] @@ -440,6 +441,12 @@ func (b *profileBuilder) build() { func (b *profileBuilder) readMapping() { data, _ := ioutil.ReadFile("/proc/self/maps") parseProcSelfMaps(data, b.addMapping) + if len(b.mem) == 0 { // pprof expects a map entry, so fake one. + b.addMappingEntry(0, 0, 0, "", "", true) + // TODO(hyangah): make addMapping return *memMap or + // take a memMap struct, and get rid of addMappingEntry + // that takes a bunch of positional arguments. + } } func parseProcSelfMaps(data []byte, addMapping func(lo, hi, offset uint64, file, buildID string)) { @@ -540,11 +547,16 @@ func parseProcSelfMaps(data []byte, addMapping func(lo, hi, offset uint64, file, } func (b *profileBuilder) addMapping(lo, hi, offset uint64, file, buildID string) { + b.addMappingEntry(lo, hi, offset, file, buildID, false) +} + +func (b *profileBuilder) addMappingEntry(lo, hi, offset uint64, file, buildID string, fake bool) { b.mem = append(b.mem, memMap{ start: uintptr(lo), end: uintptr(hi), offset: offset, file: file, buildID: buildID, + fake: fake, }) } diff --git a/src/runtime/pprof/proto_test.go b/src/runtime/pprof/proto_test.go index 36c345b6d9..76bd46da02 100644 --- a/src/runtime/pprof/proto_test.go +++ b/src/runtime/pprof/proto_test.go @@ -97,9 +97,16 @@ func testPCs(t *testing.T) (addr1, addr2 uint64, map1, map2 *profile.Mapping) { addr2 = mprof.Mapping[1].Start map2 = mprof.Mapping[1] map2.BuildID, _ = elfBuildID(map2.File) + case "js": + addr1 = uint64(funcPC(f1)) + addr2 = uint64(funcPC(f2)) default: addr1 = uint64(funcPC(f1)) addr2 = uint64(funcPC(f2)) + // Fake mapping - HasFunctions will be true because two PCs from Go + // will be fully symbolized. + fake := &profile.Mapping{ID: 1, HasFunctions: true} + map1, map2 = fake, fake } return } @@ -301,3 +308,41 @@ func symbolized(loc *profile.Location) bool { } return true } + +// TestFakeMapping tests if at least one mapping exists +// (including a fake mapping), and their HasFunctions bits +// are set correctly. +func TestFakeMapping(t *testing.T) { + var buf bytes.Buffer + if err := Lookup("heap").WriteTo(&buf, 0); err != nil { + t.Fatalf("failed to write heap profile: %v", err) + } + prof, err := profile.Parse(&buf) + if err != nil { + t.Fatalf("failed to parse the generated profile data: %v", err) + } + t.Logf("Profile: %s", prof) + if len(prof.Mapping) == 0 { + t.Fatal("want profile with at least one mapping entry, got 0 mapping") + } + + hit := make(map[*profile.Mapping]bool) + miss := make(map[*profile.Mapping]bool) + for _, loc := range prof.Location { + if symbolized(loc) { + hit[loc.Mapping] = true + } else { + miss[loc.Mapping] = true + } + } + for _, m := range prof.Mapping { + if miss[m] && m.HasFunctions { + t.Errorf("mapping %+v has HasFunctions=true, but contains locations with failed symbolization", m) + continue + } + if !miss[m] && hit[m] && !m.HasFunctions { + t.Errorf("mapping %+v has HasFunctions=false, but all referenced locations from this lapping were symbolized successfully", m) + continue + } + } +}