runtime/pprof: export max rss when saving memory profiles.

NB: Adds syscall to deps on runtime/pprof.
Change-Id: I5dd14c2b25eb9c3c446832f5818de45fafd48a27
Reviewed-on: https://go-review.googlesource.com/c/go/+/183844
Run-TryBot: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>

src/go/build/deps_test.go

@@ -195,7 +195,7 @@ var pkgDeps = map[string][]string{
 	"regexp":         {"L2", "regexp/syntax"},
 	"regexp/syntax":  {"L2"},
 	"runtime/debug":  {"L2", "fmt", "io/ioutil", "os", "time"},
-	"runtime/pprof":  {"L2", "compress/gzip", "context", "encoding/binary", "fmt", "io/ioutil", "os", "text/tabwriter", "time"},
+	"runtime/pprof":  {"L2", "compress/gzip", "context", "encoding/binary", "fmt", "io/ioutil", "os", "syscall", "text/tabwriter", "time"},
 	"runtime/trace":  {"L0", "context", "fmt"},
 	"text/tabwriter": {"L2"},
 

src/runtime/pprof/pprof.go

@@ -630,6 +630,9 @@ func writeHeapInternal(w io.Writer, debug int, defaultSampleType string) error {
 	fmt.Fprintf(w, "# GCCPUFraction = %v\n", s.GCCPUFraction)
 	fmt.Fprintf(w, "# DebugGC = %v\n", s.DebugGC)
 
+	// Also flush out MaxRSS on supported platforms.
+	addMaxRSS(w)
+
 	tw.Flush()
 	return b.Flush()
 }

src/runtime/pprof/pprof_norusage.go

@@ -0,0 +1,15 @@
+// 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 !darwin,!linux
+
+package pprof
+
+import (
+	"io"
+)
+
+// Stub call for platforms that don't support rusage.
+func addMaxRSS(w io.Writer) {
+}

src/runtime/pprof/pprof_rusage.go

@@ -0,0 +1,20 @@
+// 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 darwin linux
+
+package pprof
+
+import (
+	"fmt"
+	"io"
+	"syscall"
+)
+
+// Adds MaxRSS to platforms that are supported.
+func addMaxRSS(w io.Writer) {
+	var rusage syscall.Rusage
+	syscall.Getrusage(0, &rusage)
+	fmt.Fprintf(w, "# MaxRSS = %d\n", rusage.Maxrss)
+}