From 9d80f7b2f23595e413ae63d311c03698933b1891 Mon Sep 17 00:00:00 2001 From: Robert Findley Date: Sat, 13 Aug 2022 12:35:57 -0400 Subject: [PATCH] go/types, types2: optimize instance lookup in LookupFieldOrMethod MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit LookupFieldOrMethod appears as a hotspot when benchmarking gopls' auto-completion. In particular, instanceLookup.add was allocating in the common case of structs with no embedding. This is easily fixed, by using a small array in front of the map inside of instanceLookup. Do this, and additionally add a microbenchmark. The benchmark improvement is significant: name old time/op new time/op delta LookupFieldOrMethod-12 388µs ± 6% 154µs ± 3% -60.36% (p=0.000 n=10+10) name old alloc/op new alloc/op delta LookupFieldOrMethod-12 152kB ± 0% 2kB ± 0% -98.77% (p=0.000 n=9+10) name old allocs/op new allocs/op delta LookupFieldOrMethod-12 1.41k ± 0% 0.07k ± 0% -95.38% (p=0.000 n=10+10) It should also be noted that instanceLookup is used elsewhere, in particular by validType. In those contexts, the scope is not just the current type but the entire package, and so the newly added buffer is likely to simply cause extra Identical checks. Nevertheless, those checks are cheap, and on balance the improved LookupFieldOrMethod performance leads overall to improved type-checking performance. Standard library benchmark results varied by package, but type checking speed for many packages improved by ~5%, with allocations improved by ~10%. If this weren't the case we could let the caller control the buffer size, but that optimization doesn't seem necessary at this time. For example: Check/http/funcbodies/noinfo-12 71.5ms ± 4% 67.3ms ± 2% -5.90% (p=0.000 n=20+20) Check/http/funcbodies/noinfo-12 244k ± 0% 219k ± 0% -10.36% (p=0.000 n=19+19) Updates golang/go#53992 Change-Id: I10b6deb3819ab562dbbe1913f12b977cf956dd50 Reviewed-on: https://go-review.googlesource.com/c/go/+/423935 Run-TryBot: Robert Findley TryBot-Result: Gopher Robot Reviewed-by: Robert Griesemer --- src/cmd/compile/internal/types2/lookup.go | 16 ++++- .../compile/internal/types2/lookup_test.go | 55 ++++++++++++++++++ src/go/types/lookup.go | 16 ++++- src/go/types/lookup_test.go | 58 +++++++++++++++++++ 4 files changed, 143 insertions(+), 2 deletions(-) create mode 100644 src/cmd/compile/internal/types2/lookup_test.go create mode 100644 src/go/types/lookup_test.go diff --git a/src/cmd/compile/internal/types2/lookup.go b/src/cmd/compile/internal/types2/lookup.go index 5f767520864a8..3e04798815cde 100644 --- a/src/cmd/compile/internal/types2/lookup.go +++ b/src/cmd/compile/internal/types2/lookup.go @@ -261,10 +261,18 @@ func lookupType(m map[Type]int, typ Type) (int, bool) { } type instanceLookup struct { - m map[*Named][]*Named + // buf is used to avoid allocating the map m in the common case of a small + // number of instances. + buf [3]*Named + m map[*Named][]*Named } func (l *instanceLookup) lookup(inst *Named) *Named { + for _, t := range l.buf { + if t != nil && Identical(inst, t) { + return t + } + } for _, t := range l.m[inst.Origin()] { if Identical(inst, t) { return t @@ -274,6 +282,12 @@ func (l *instanceLookup) lookup(inst *Named) *Named { } func (l *instanceLookup) add(inst *Named) { + for i, t := range l.buf { + if t == nil { + l.buf[i] = inst + return + } + } if l.m == nil { l.m = make(map[*Named][]*Named) } diff --git a/src/cmd/compile/internal/types2/lookup_test.go b/src/cmd/compile/internal/types2/lookup_test.go new file mode 100644 index 0000000000000..56fe48c1e2db5 --- /dev/null +++ b/src/cmd/compile/internal/types2/lookup_test.go @@ -0,0 +1,55 @@ +// Copyright 2022 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. + +package types2_test + +import ( + "path/filepath" + "runtime" + "testing" + + . "cmd/compile/internal/types2" +) + +// BenchmarkLookupFieldOrMethod measures types.LookupFieldOrMethod performance. +// LookupFieldOrMethod is a performance hotspot for both type-checking and +// external API calls. +func BenchmarkLookupFieldOrMethod(b *testing.B) { + // Choose an arbitrary, large package. + path := filepath.Join(runtime.GOROOT(), "src", "net", "http") + + files, err := pkgFiles(path) + if err != nil { + b.Fatal(err) + } + + conf := Config{ + Importer: defaultImporter(), + } + + pkg, err := conf.Check("http", files, nil) + if err != nil { + b.Fatal(err) + } + + scope := pkg.Scope() + names := scope.Names() + + // Look up an arbitrary name for each type referenced in the package scope. + lookup := func() { + for _, name := range names { + typ := scope.Lookup(name).Type() + LookupFieldOrMethod(typ, true, pkg, "m") + } + } + + // Perform a lookup once, to ensure that any lazily-evaluated state is + // complete. + lookup() + + b.ResetTimer() + for i := 0; i < b.N; i++ { + lookup() + } +} diff --git a/src/go/types/lookup.go b/src/go/types/lookup.go index 9e0a06aedb670..828c8813670ed 100644 --- a/src/go/types/lookup.go +++ b/src/go/types/lookup.go @@ -261,10 +261,18 @@ func lookupType(m map[Type]int, typ Type) (int, bool) { } type instanceLookup struct { - m map[*Named][]*Named + // buf is used to avoid allocating the map m in the common case of a small + // number of instances. + buf [3]*Named + m map[*Named][]*Named } func (l *instanceLookup) lookup(inst *Named) *Named { + for _, t := range l.buf { + if t != nil && Identical(inst, t) { + return t + } + } for _, t := range l.m[inst.Origin()] { if Identical(inst, t) { return t @@ -274,6 +282,12 @@ func (l *instanceLookup) lookup(inst *Named) *Named { } func (l *instanceLookup) add(inst *Named) { + for i, t := range l.buf { + if t == nil { + l.buf[i] = inst + return + } + } if l.m == nil { l.m = make(map[*Named][]*Named) } diff --git a/src/go/types/lookup_test.go b/src/go/types/lookup_test.go new file mode 100644 index 0000000000000..cd5e3fb13d611 --- /dev/null +++ b/src/go/types/lookup_test.go @@ -0,0 +1,58 @@ +// Copyright 2022 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. + +package types_test + +import ( + "go/importer" + "go/token" + "path/filepath" + "runtime" + "testing" + + . "go/types" +) + +// BenchmarkLookupFieldOrMethod measures types.LookupFieldOrMethod performance. +// LookupFieldOrMethod is a performance hotspot for both type-checking and +// external API calls. +func BenchmarkLookupFieldOrMethod(b *testing.B) { + // Choose an arbitrary, large package. + path := filepath.Join(runtime.GOROOT(), "src", "net", "http") + + fset := token.NewFileSet() + files, err := pkgFiles(fset, path, 0) + if err != nil { + b.Fatal(err) + } + + conf := Config{ + Importer: importer.Default(), + } + + pkg, err := conf.Check("http", fset, files, nil) + if err != nil { + b.Fatal(err) + } + + scope := pkg.Scope() + names := scope.Names() + + // Look up an arbitrary name for each type referenced in the package scope. + lookup := func() { + for _, name := range names { + typ := scope.Lookup(name).Type() + LookupFieldOrMethod(typ, true, pkg, "m") + } + } + + // Perform a lookup once, to ensure that any lazily-evaluated state is + // complete. + lookup() + + b.ResetTimer() + for i := 0; i < b.N; i++ { + lookup() + } +}