cmd/trace: common up the mmu page and add it to cmd/trace/v2

This change moves the MMU HTTP handlers and functionality into the
traceviewer package, since unlike the goroutine pages the vast majority
of that functionality is identical between v1 and v2. This change
involves some refactoring so that callers can plug in their own mutator
utilization computation functions (which is the only point of difference
between v1 and v2). The new interface isn't especially nice, but part of
the problem is the MMU handlers depend on specific endpoints to exist. A
follow-up CL will clean this up a bit.

Like the previous CL did for goroutine analysis, modify the v2 mutator
utilization API to accept a slice of trace events. Again, we might as
well reuse what was already parsed and will be needed for other
purposes. It also simplifies the API slightly.

For #60773.
For #63960.

Change-Id: I6c21ec8d1bf7e95eff5363d0e0005c9217fa00e7
Reviewed-on: https://go-review.googlesource.com/c/go/+/541258
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>

src/cmd/trace/main.go

@@ -139,8 +139,13 @@ func main() {
 	log.Printf("Opening browser. Trace viewer is listening on %s", addr)
 	browser.Open(addr)
 
-	// Start http server.
+	// Install MMU handlers.
+	traceviewer.InstallMMUHandlers(http.DefaultServeMux, ranges, mutatorUtil)
+
+	// Install main handler.
 	http.Handle("/", traceviewer.MainHandler(ranges))
+
+	// Start http server.
 	err = http.Serve(ln, nil)
 	dief("failed to start http server: %v\n", err)
 }
@@ -228,3 +233,11 @@ func reportMemoryUsage(msg string) {
 	fmt.Printf("Enter to continue...")
 	fmt.Scanf("%s", &dummy)
 }
+
+func mutatorUtil(flags trace.UtilFlags) ([][]trace.MutatorUtil, error) {
+	events, err := parseEvents()
+	if err != nil {
+		return nil, err
+	}
+	return trace.MutatorUtilization(events, flags), nil
+}

src/cmd/trace/v2/main.go

@@ -70,6 +70,12 @@ func Main(traceFile, httpAddr, pprof string, debug int) error {
 	mux.HandleFunc("/goroutines", GoroutinesHandlerFunc(gSummaries))
 	mux.HandleFunc("/goroutine", GoroutineHandler(gSummaries))
 
+	// Install MMU handlers.
+	mutatorUtil := func(flags trace.UtilFlags) ([][]trace.MutatorUtil, error) {
+		return trace.MutatorUtilizationV2(parsed.events, flags), nil
+	}
+	traceviewer.InstallMMUHandlers(mux, ranges, mutatorUtil)
+
 	err = http.Serve(ln, mux)
 	return fmt.Errorf("failed to start http server: %w", err)
 }

src/internal/trace/gc.go

@@ -7,7 +7,6 @@ package trace
 import (
 	"container/heap"
 	tracev2 "internal/trace/v2"
-	"io"
 	"math"
 	"sort"
 	"strings"
@@ -212,13 +211,7 @@ func MutatorUtilization(events []*Event, flags UtilFlags) [][]MutatorUtil {
 //
 // If the UtilPerProc flag is not given, this always returns a single
 // utilization function. Otherwise, it returns one function per P.
-func MutatorUtilizationV2(trace io.Reader, flags UtilFlags) ([][]MutatorUtil, error) {
-	// Create a reader.
-	r, err := tracev2.NewReader(trace)
-	if err != nil {
-		return nil, err
-	}
-
+func MutatorUtilizationV2(events []tracev2.Event, flags UtilFlags) [][]MutatorUtil {
 	// Set up a bunch of analysis state.
 	type perP struct {
 		// gc > 0 indicates that GC is active on this P.
@@ -255,16 +248,9 @@ func MutatorUtilizationV2(trace io.Reader, flags UtilFlags) ([][]MutatorUtil, er
 	}
 
 	// Iterate through the trace, tracking mutator utilization.
-	var lastEv tracev2.Event
-	for {
-		// Read a single event.
-		ev, err := r.ReadEvent()
-		if err == io.EOF {
-			break
-		}
-		if err != nil {
-			return nil, err
-		}
+	var lastEv *tracev2.Event
+	for i := range events {
+		ev := &events[i]
 		lastEv = ev
 
 		// Process the event.
@@ -451,8 +437,8 @@ func MutatorUtilizationV2(trace io.Reader, flags UtilFlags) ([][]MutatorUtil, er
 	}
 
 	// No events in the stream.
-	if lastEv.Kind() == tracev2.EventBad {
-		return nil, nil
+	if lastEv == nil {
+		return nil
 	}
 
 	// Add final 0 utilization event to any remaining series. This
@@ -463,7 +449,7 @@ func MutatorUtilizationV2(trace io.Reader, flags UtilFlags) ([][]MutatorUtil, er
 	for i := range ps {
 		out[ps[i].series] = addUtil(out[ps[i].series], mu)
 	}
-	return out, nil
+	return out
 }
 
 func addUtil(util []MutatorUtil, mu MutatorUtil) []MutatorUtil {

src/internal/trace/gc_test.go

@@ -6,7 +6,10 @@ package trace
 
 import (
 	"bytes"
+	"internal/trace/v2"
+	tracev2 "internal/trace/v2"
 	"internal/trace/v2/testtrace"
+	"io"
 	"math"
 	"os"
 	"testing"
@@ -133,12 +136,23 @@ func TestMMUTrace(t *testing.T) {
 		if err != nil {
 			t.Fatalf("malformed test %s: bad trace file: %v", testPath, err)
 		}
-		// Pass the trace through MutatorUtilizationV2.
-		mu, err := MutatorUtilizationV2(r, UtilSTW|UtilBackground|UtilAssist)
+		var events []tracev2.Event
+		tr, err := trace.NewReader(r)
 		if err != nil {
-			t.Fatalf("failed to compute mutator utilization or parse trace: %v", err)
+			t.Fatalf("malformed test %s: bad trace file: %v", testPath, err)
 		}
-		check(t, mu)
+		for {
+			ev, err := tr.ReadEvent()
+			if err == io.EOF {
+				break
+			}
+			if err != nil {
+				t.Fatalf("malformed test %s: bad trace file: %v", testPath, err)
+			}
+			events = append(events, ev)
+		}
+		// Pass the trace through MutatorUtilizationV2 and check it.
+		check(t, MutatorUtilizationV2(events, UtilSTW|UtilBackground|UtilAssist))
 	})
 }
 

src/internal/trace/traceviewer/mmu.go

@@ -1,4 +1,4 @@
-// Copyright 2017 The Go Authors. All rights reserved.
+// Copyright 2023 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.
 
@@ -23,13 +23,12 @@
 // could potentially put confidence intervals on these estimates and
 // render this progressively as we refine the distributions.
 
-package main
+package traceviewer
 
 import (
 	"encoding/json"
 	"fmt"
 	"internal/trace"
-	"internal/trace/traceviewer"
 	"log"
 	"math"
 	"net/http"
@@ -39,10 +38,21 @@ import (
 	"time"
 )
 
-func init() {
-	http.HandleFunc("/mmu", httpMMU)
-	http.HandleFunc("/mmuPlot", httpMMUPlot)
-	http.HandleFunc("/mmuDetails", httpMMUDetails)
+type MutatorUtilFunc func(trace.UtilFlags) ([][]trace.MutatorUtil, error)
+
+func InstallMMUHandlers(mux *http.ServeMux, ranges []Range, f MutatorUtilFunc) {
+	mmu := &mmu{
+		cache:  make(map[trace.UtilFlags]*mmuCacheEntry),
+		f:      f,
+		ranges: ranges,
+	}
+	mux.HandleFunc("/mmu", func(w http.ResponseWriter, r *http.Request) {
+		// N.B. templMMU has Javascript that implicitly relies upon the existence
+		// of /mmuPlot and /mmuDetails on the same server.
+		http.ServeContent(w, r, "", time.Time{}, strings.NewReader(templMMU))
+	})
+	mux.HandleFunc("/mmuPlot", mmu.HandlePlot)
+	mux.HandleFunc("/mmuDetails", mmu.HandleDetails)
 }
 
 var utilFlagNames = map[string]trace.UtilFlags{
@@ -53,6 +63,14 @@ var utilFlagNames = map[string]trace.UtilFlags{
 	"sweep":      trace.UtilSweep,
 }
 
+func requestUtilFlags(r *http.Request) trace.UtilFlags {
+	var flags trace.UtilFlags
+	for _, flagStr := range strings.Split(r.FormValue("flags"), "|") {
+		flags |= utilFlagNames[flagStr]
+	}
+	return flags
+}
+
 type mmuCacheEntry struct {
 	init     sync.Once
 	util     [][]trace.MutatorUtil
@@ -60,51 +78,39 @@ type mmuCacheEntry struct {
 	err      error
 }
 
-var mmuCache struct {
-	m    map[trace.UtilFlags]*mmuCacheEntry
-	lock sync.Mutex
+type mmu struct {
+	mu     sync.Mutex
+	cache  map[trace.UtilFlags]*mmuCacheEntry
+	f      MutatorUtilFunc
+	ranges []Range
 }
 
-func init() {
-	mmuCache.m = make(map[trace.UtilFlags]*mmuCacheEntry)
-}
-
-func getMMUCurve(r *http.Request) ([][]trace.MutatorUtil, *trace.MMUCurve, error) {
-	var flags trace.UtilFlags
-	for _, flagStr := range strings.Split(r.FormValue("flags"), "|") {
-		flags |= utilFlagNames[flagStr]
+func (m *mmu) get(flags trace.UtilFlags) ([][]trace.MutatorUtil, *trace.MMUCurve, error) {
+	m.mu.Lock()
+	entry := m.cache[flags]
+	if entry == nil {
+		entry = new(mmuCacheEntry)
+		m.cache[flags] = entry
 	}
+	m.mu.Unlock()
 
-	mmuCache.lock.Lock()
-	c := mmuCache.m[flags]
-	if c == nil {
-		c = new(mmuCacheEntry)
-		mmuCache.m[flags] = c
-	}
-	mmuCache.lock.Unlock()
-
-	c.init.Do(func() {
-		events, err := parseEvents()
+	entry.init.Do(func() {
+		util, err := m.f(flags)
 		if err != nil {
-			c.err = err
+			entry.err = err
 		} else {
-			c.util = trace.MutatorUtilization(events, flags)
-			c.mmuCurve = trace.NewMMUCurve(c.util)
+			entry.util = util
+			entry.mmuCurve = trace.NewMMUCurve(util)
 		}
 	})
-	return c.util, c.mmuCurve, c.err
+	return entry.util, entry.mmuCurve, entry.err
 }
 
-// httpMMU serves the MMU plot page.
-func httpMMU(w http.ResponseWriter, r *http.Request) {
-	http.ServeContent(w, r, "", time.Time{}, strings.NewReader(templMMU))
-}
-
-// httpMMUPlot serves the JSON data for the MMU plot.
-func httpMMUPlot(w http.ResponseWriter, r *http.Request) {
-	mu, mmuCurve, err := getMMUCurve(r)
+// HandlePlot serves the JSON data for the MMU plot.
+func (m *mmu) HandlePlot(w http.ResponseWriter, r *http.Request) {
+	mu, mmuCurve, err := m.get(requestUtilFlags(r))
 	if err != nil {
-		http.Error(w, fmt.Sprintf("failed to parse events: %v", err), http.StatusInternalServerError)
+		http.Error(w, fmt.Sprintf("failed to produce MMU data: %v", err), http.StatusInternalServerError)
 		return
 	}
 
@@ -358,11 +364,11 @@ var templMMU = `<!doctype html>
 </html>
 `
 
-// httpMMUDetails serves details of an MMU graph at a particular window.
-func httpMMUDetails(w http.ResponseWriter, r *http.Request) {
-	_, mmuCurve, err := getMMUCurve(r)
+// HandleDetails serves details of an MMU graph at a particular window.
+func (m *mmu) HandleDetails(w http.ResponseWriter, r *http.Request) {
+	_, mmuCurve, err := m.get(requestUtilFlags(r))
 	if err != nil {
-		http.Error(w, fmt.Sprintf("failed to parse events: %v", err), http.StatusInternalServerError)
+		http.Error(w, fmt.Sprintf("failed to produce MMU data: %v", err), http.StatusInternalServerError)
 		return
 	}
 
@@ -377,7 +383,7 @@ func httpMMUDetails(w http.ResponseWriter, r *http.Request) {
 	// Construct a link for each window.
 	var links []linkedUtilWindow
 	for _, ui := range worst {
-		links = append(links, newLinkedUtilWindow(ui, time.Duration(window)))
+		links = append(links, m.newLinkedUtilWindow(ui, time.Duration(window)))
 	}
 
 	err = json.NewEncoder(w).Encode(links)
@@ -392,10 +398,10 @@ type linkedUtilWindow struct {
 	URL string
 }
 
-func newLinkedUtilWindow(ui trace.UtilWindow, window time.Duration) linkedUtilWindow {
+func (m *mmu) newLinkedUtilWindow(ui trace.UtilWindow, window time.Duration) linkedUtilWindow {
 	// Find the range containing this window.
-	var r traceviewer.Range
-	for _, r = range ranges {
+	var r Range
+	for _, r = range m.ranges {
 		if r.EndTime > ui.Time {
 			break
 		}