cmd/go: scale go list with GOMAXPROCS

Benchmark from the go-list-benchmark branch shows the following result:

goos: darwin
goarch: arm64
pkg: cmd/go
cpu: Apple M1 Max
                     │   old.txt   │               new.txt               │
                     │   sec/op    │   sec/op     vs base                │
ListModules/Empty-10   7.768m ± 5%   7.768m ± 6%        ~ (p=0.989 n=20)
ListModules/Cmd-10     272.3m ± 2%   137.8m ± 2%  -49.40% (p=0.000 n=20)
ListModules/K8S-10     10.741 ± 2%    2.525 ± 5%  -76.49% (p=0.000 n=20)
geomean                283.2m        139.3m       -50.82%

                     │   old.txt    │               new.txt               │
                     │  sys-sec/op  │  sys-sec/op   vs base               │
ListModules/Empty-10   2.380m ±  9%   2.443m ±  9%       ~ (p=0.314 n=20)
ListModules/Cmd-10     51.84m ± 13%   47.27m ± 14%       ~ (p=0.289 n=20)
ListModules/K8S-10      1.660 ±  8%    1.485 ± 28%       ~ (p=0.512 n=20)
geomean                58.95m         55.56m        -5.75%

                     │   old.txt    │               new.txt                │
                     │ user-sec/op  │ user-sec/op   vs base                │
ListModules/Empty-10   3.034m ±  4%   3.053m ±  3%        ~ (p=0.445 n=20)
ListModules/Cmd-10     18.01m ± 11%   15.39m ±  5%  -14.55% (p=0.000 n=20)
ListModules/K8S-10     407.6m ± 11%   209.2m ± 49%  -48.67% (p=0.000 n=20)
geomean                28.13m         21.42m        -23.86%

Fixes #63136

Change-Id: Ifd406a52494eb37430306ee1f29a8bf5c1973007
GitHub-Last-Rev: eba40c944e8a8c57c11fa075e98e1ee5420be1a8
GitHub-Pull-Request: golang/go#63137
Reviewed-on: https://go-review.googlesource.com/c/go/+/530037
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
Reviewed-by: qiu laidongfeng2 <2645477756@qq.com>
Reviewed-by: Michael Matloob <matloob@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

diff --git a/src/cmd/go/internal/modload/list.go b/src/cmd/go/internal/modload/list.go
index ef93c25121acc8ebbf58ff8676a9a93a4c3146c7..53cb6c2ffe1406111dac713c44a49075a32d4f55 100644 (file)
--- a/src/cmd/go/internal/modload/list.go
+++ b/src/cmd/go/internal/modload/list.go
@@ -21,6 +21,7 @@ import (
        "cmd/go/internal/modfetch/codehost"
        "cmd/go/internal/modinfo"
        "cmd/go/internal/search"
+       "cmd/internal/par"
        "cmd/internal/pkgpattern"
 
        "golang.org/x/mod/module"
@@ -273,19 +274,29 @@ func listModules(ctx context.Context, rs *Requirements, args []string, mode List
                        continue
                }
 
-               matched := false
+               var matches []module.Version
                for _, m := range mg.BuildList() {
                        if match(m.Path) {
-                               matched = true
                                if !matchedModule[m] {
                                        matchedModule[m] = true
-                                       mods = append(mods, moduleInfo(ctx, rs, m, mode, reuse))
+                                       matches = append(matches, m)
                                }
                        }
                }
-               if !matched {
+
+               if len(matches) == 0 {
                        fmt.Fprintf(os.Stderr, "warning: pattern %q matched no module dependencies\n", arg)
                }
+
+               q := par.NewQueue(runtime.GOMAXPROCS(0))
+               fetchedMods := make([]*modinfo.ModulePublic, len(matches))
+               for i, m := range matches {
+                       q.Add(func() {
+                               fetchedMods[i] = moduleInfo(ctx, rs, m, mode, reuse)
+                       })
+               }
+               <-q.Idle()
+               mods = append(mods, fetchedMods...)
        }
 
        return rs, mods, mgErr