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Bug 1379565 - Overhaul ProfileBuffer::StreamSamplesToJSON. r=mstange. 

The profiler writes ProfileBuffer entries in a particular order, and then later
has to parse them, mostly in StreamSamplesToJSON(). That function's parsing
code is poorly structured and rather gross, at least partly because no explicit
grammar is identified.

This patch identifies the grammar in a comment, and in the same comment also
includes some examples of the more complicated subsequences. Once written down,
the grammar is obviously suboptimal -- the |Sample| entries serve no useful
purpose, for example -- but I will leave grammar improvements as follow-ups.

The patch also rewrites the parser in a more typical fashion that obviously
matches the grammar. The new parser is slightly more verbose but far easier to
understand.

--HG--
extra : rebase_source : 762c21a68cdc18ff25b5feda3c5dfcf33afa53be
This commit is contained in:
Nicholas Nethercote 2017-07-05 21:29:29 +10:00
Родитель f76bc78842
Коммит e893cc5e8d
4 изменённых файлов: 322 добавлений и 177 удалений
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29
tools/profiler/core/ProfileBuffer.cpp
Просмотреть файл

@ -86,32 +86,3 @@ ProfileBuffer::SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
return n;
}
#define DYNAMIC_MAX_STRING 8192
char*
ProfileBuffer::processEmbeddedString(int aReadAheadPos, int* aEntriesConsumed,
char* aStrBuf)
{
int strBufPos = 0;
// Read the string stored in mChars until the null character is seen.
bool seenNullByte = false;
while (aReadAheadPos != mWritePos && !seenNullByte) {
(*aEntriesConsumed)++;
ProfileBufferEntry readAheadEntry = mEntries[aReadAheadPos];
for (size_t pos = 0; pos < ProfileBufferEntry::kNumChars; pos++) {
aStrBuf[strBufPos] = readAheadEntry.u.mChars[pos];
if (aStrBuf[strBufPos] == '\0' || strBufPos == DYNAMIC_MAX_STRING-2) {
seenNullByte = true;
break;
}
strBufPos++;
}
if (!seenNullByte) {
aReadAheadPos = (aReadAheadPos + 1) % mEntrySize;
}
}
return aStrBuf;
}

8
tools/profiler/core/ProfileBuffer.h
Просмотреть файл

@ -42,6 +42,10 @@ public:
// record the resulting generation and index in |aLS| if it's non-null.
void addThreadIdEntry(int aThreadId, LastSample* aLS = nullptr);
// Maximum size of a dynamic string (including the terminating '\0' char)
// that we'll write to the ProfileBuffer.
static const size_t kMaxDynamicStringLength = 8192;
void StreamSamplesToJSON(SpliceableJSONWriter& aWriter, int aThreadId,
double aSinceTime, JSContext* cx,
UniqueStacks& aUniqueStacks);
@ -64,9 +68,7 @@ public:
size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
protected:
char* processEmbeddedString(int aReadaheadPos, int* aEntriesConsumed,
char* aStrBuf);
private:
int FindLastSampleOfThread(int aThreadId, const LastSample& aLS);
public:

459
tools/profiler/core/ProfileBufferEntry.cpp
Просмотреть файл

@ -7,6 +7,7 @@
#include <ostream>
#include "platform.h"
#include "mozilla/HashFunctions.h"
#include "mozilla/Sprintf.h"
#include "nsThreadUtils.h"
#include "nsXULAppAPI.h"
@ -533,7 +534,7 @@ void UniqueStacks::StreamFrame(const OnStackFrameKey& aFrame)
struct ProfileSample
{
uint32_t mStack;
Maybe<double> mTime;
double mTime;
Maybe<double> mResponsiveness;
Maybe<double> mRSS;
Maybe<double> mUSS;
@ -553,9 +554,7 @@ static void WriteSample(SpliceableJSONWriter& aWriter, ProfileSample& aSample)
writer.IntElement(STACK, aSample.mStack);
if (aSample.mTime.isSome()) {
writer.DoubleElement(TIME, *aSample.mTime);
}
writer.DoubleElement(TIME, aSample.mTime);
if (aSample.mResponsiveness.isSome()) {
writer.DoubleElement(RESPONSIVENESS, *aSample.mResponsiveness);
@ -570,146 +569,313 @@ static void WriteSample(SpliceableJSONWriter& aWriter, ProfileSample& aSample)
}
}
void ProfileBuffer::StreamSamplesToJSON(SpliceableJSONWriter& aWriter, int aThreadId,
double aSinceTime, JSContext* aContext,
UniqueStacks& aUniqueStacks)
class EntryGetter
{
Maybe<ProfileSample> sample;
int readPos = mReadPos;
int currentThreadID = -1;
Maybe<double> currentTime;
UniquePtr<char[]> strbuf = MakeUnique<char[]>(DYNAMIC_MAX_STRING);
public:
explicit EntryGetter(ProfileBuffer* aBuffer)
: mEntries(aBuffer->mEntries.get())
, mReadPos(aBuffer->mReadPos)
, mWritePos(aBuffer->mWritePos)
, mEntrySize(aBuffer->mEntrySize)
{}
while (readPos != mWritePos) {
ProfileBufferEntry entry = mEntries[readPos];
if (entry.isThreadId()) {
currentThreadID = entry.u.mInt;
currentTime.reset();
int readAheadPos = (readPos + 1) % mEntrySize;
if (readAheadPos != mWritePos) {
ProfileBufferEntry readAheadEntry = mEntries[readAheadPos];
if (readAheadEntry.isTime()) {
currentTime = Some(readAheadEntry.u.mDouble);
bool Has() const { return mReadPos != mWritePos; }
const ProfileBufferEntry& Get() const { return mEntries[mReadPos]; }
void Next() { mReadPos = (mReadPos + 1) % mEntrySize; }
private:
const ProfileBufferEntry* const mEntries;
int mReadPos;
const int mWritePos;
const int mEntrySize;
};
// Each sample is made up of multiple ProfileBuffer entries. The following
// grammar shows legal sequences.
//
// (
// ThreadId
// Time
// Sample
// ( NativeLeafAddr
// | CodeLocation EmbeddedString* LineNumber? Category?
// | JitReturnAddr
// )+
// Marker*
// Responsiveness?
// ResidentMemory?
// UnsharedMemory?
// )*
//
// The most complicated part is the stack entry sequence that begins with
// CodeLocation. Here are some examples.
//
// - PseudoStack entries without a dynamic string (or with privacy enabled so
// that the dynamic string is hidden):
//
// CodeLocation("js::RunScript")
// Category(ProfileEntry::Category::JS)
//
// CodeLocation("XREMain::XRE_main")
// LineNumber(4660)
// Category(ProfileEntry::Category::OTHER)
//
// CodeLocation("ElementRestyler::ComputeStyleChangeFor")
// LineNumber(3003)
// Category(ProfileEntry::Category::CSS)
//
// - PseudoStack entries with a dynamic string:
//
// CodeLocation("")
// EmbeddedString("nsObserv")
// EmbeddedString("erServic")
// EmbeddedString("e::Notif")
// EmbeddedString("yObserve")
// EmbeddedString("rs profi")
// EmbeddedString("ler-star")
// EmbeddedString "ted")
// LineNumber(291)
// Category(ProfileEntry::Category::OTHER)
//
// CodeLocation("")
// EmbeddedString("closeWin")
// EmbeddedString("dow (chr")
// EmbeddedString("ome://gl")
// EmbeddedString("obal/con")
// EmbeddedString("tent/glo")
// EmbeddedString("balOverl")
// EmbeddedString("ay.js:5)")
// EmbeddedString("") # this string holds the closing '\0'
// LineNumber(25)
// Category(ProfileEntry::Category::JS)
//
// CodeLocation("")
// EmbeddedString("bound (s")
// EmbeddedString("elf-host")
// EmbeddedString("ed:914)")
// LineNumber(945)
// Category(ProfileEntry::Category::JS)
//
// - A wasm JIT frame entry:
//
// CodeLocation("")
// EmbeddedString("wasm-fun")
// EmbeddedString("ction[87")
// EmbeddedString("36] (blo")
// EmbeddedString("b:http:/")
// EmbeddedString("/webasse")
// EmbeddedString("mbly.org")
// EmbeddedString("/3dc5759")
// EmbeddedString("4-ce58-4")
// EmbeddedString("626-975b")
// EmbeddedString("-08ad116")
// EmbeddedString("30bc1:38")
// EmbeddedString("29856)")
//
// - A JS frame entry in a synchronous sample:
//
// CodeLocation("")
// EmbeddedString("u (https")
// EmbeddedString("://perf-")
// EmbeddedString("html.io/")
// EmbeddedString("ac0da204")
// EmbeddedString("aaa44d75")
// EmbeddedString("a800.bun")
// EmbeddedString("dle.js:2")
// EmbeddedString("5)")
//
void
ProfileBuffer::StreamSamplesToJSON(SpliceableJSONWriter& aWriter, int aThreadId,
double aSinceTime, JSContext* aContext,
UniqueStacks& aUniqueStacks)
{
UniquePtr<char[]> strbuf = MakeUnique<char[]>(kMaxDynamicStringLength);
// Because this is a format entirely internal to the Profiler, any parsing
// error indicates a bug in the ProfileBuffer writing or the parser itself,
// or possibly flaky hardware.
#define ERROR_AND_SKIP_TO_NEXT_SAMPLE(msg) \
do { \
fprintf(stderr, "ProfileBuffer parse error: %s", msg); \
MOZ_ASSERT(false, msg); \
goto skip_to_next_sample; \
} while (0)
EntryGetter e(this);
// This block skips entries until we find the start of the next sample. This
// is useful in two situations.
//
// - The circular buffer overwrites old entries, so when we start parsing we
// might be in the middle of a sample, and we must skip forward to the
// start of the next sample.
//
// - We skip samples that don't have an appropriate ThreadId or Time.
//
skip_to_next_sample:
while (e.Has()) {
if (e.Get().isThreadId()) {
break;
} else {
e.Next();
}
}
while (e.Has()) {
if (e.Get().isThreadId()) {
int threadId = e.Get().u.mInt;
e.Next();
// Ignore samples that are for the wrong thread.
if (threadId != aThreadId) {
goto skip_to_next_sample;
}
} else {
// Due to the skip_to_next_sample block above, if we have an entry here
// it must be a ThreadId entry.
MOZ_CRASH();
}
ProfileSample sample;
if (e.Has() && e.Get().isTime()) {
sample.mTime = e.Get().u.mDouble;
e.Next();
// Ignore samples that are too old.
if (sample.mTime < aSinceTime) {
goto skip_to_next_sample;
}
} else {
ERROR_AND_SKIP_TO_NEXT_SAMPLE("expected a Time entry");
}
if (e.Has() && e.Get().isSample()) {
e.Next();
} else {
ERROR_AND_SKIP_TO_NEXT_SAMPLE("expected a Sample entry");
}
UniqueStacks::Stack stack =
aUniqueStacks.BeginStack(UniqueStacks::OnStackFrameKey("(root)"));
int numFrames = 0;
while (e.Has()) {
if (e.Get().isNativeLeafAddr()) {
numFrames++;
// Bug 753041: We need a double cast here to tell GCC that we don't
// want to sign extend 32-bit addresses starting with 0xFXXXXXX.
unsigned long long pc = (unsigned long long)(uintptr_t)e.Get().u.mPtr;
char buf[20];
SprintfLiteral(buf, "%#llx", pc);
stack.AppendFrame(UniqueStacks::OnStackFrameKey(buf));
e.Next();
} else if (e.Get().isCodeLocation()) {
numFrames++;
const char* string = e.Get().u.mString;
e.Next();
strbuf[0] = '\0';
char* p = &strbuf[0];
while (e.Has()) {
if (e.Get().isEmbeddedString()) {
if (p < &strbuf[kMaxDynamicStringLength]) {
// Copy 8 chars at a time. This won't overflow strbuf so long as
// its length is a multiple of 8.
static_assert(kMaxDynamicStringLength % 8 == 0, "bad strbuf sz");
memcpy(p, e.Get().u.mChars, ProfileBufferEntry::kNumChars);
p += ProfileBufferEntry::kNumChars;
}
e.Next();
} else {
break;
}
}
strbuf[kMaxDynamicStringLength - 1] = '\0';
if (strbuf[0] != '\0') {
// When we have EmbeddedStrings, the preceding CodeLocation's string
// is always empty.
MOZ_ASSERT(string[0] == '\0');
string = strbuf.get();
}
UniqueStacks::OnStackFrameKey frameKey(string);
if (e.Has() && e.Get().isLineNumber()) {
frameKey.mLine = Some(unsigned(e.Get().u.mInt));
e.Next();
}
if (e.Has() && e.Get().isCategory()) {
frameKey.mCategory = Some(unsigned(e.Get().u.mInt));
e.Next();
}
stack.AppendFrame(frameKey);
} else if (e.Get().isJitReturnAddr()) {
numFrames++;
// A JIT frame may expand to multiple frames due to inlining.
void* pc = e.Get().u.mPtr;
unsigned depth = aUniqueStacks.LookupJITFrameDepth(pc);
if (depth == 0) {
StreamJSFramesOp framesOp(pc, stack);
MOZ_RELEASE_ASSERT(aContext);
JS::ForEachProfiledFrame(aContext, pc, framesOp);
aUniqueStacks.AddJITFrameDepth(pc, framesOp.depth());
} else {
for (unsigned i = 0; i < depth; i++) {
UniqueStacks::OnStackFrameKey inlineFrameKey(pc, i);
stack.AppendFrame(inlineFrameKey);
}
}
e.Next();
} else {
break;
}
}
if (currentThreadID == aThreadId && (currentTime.isNothing() || *currentTime >= aSinceTime)) {
switch (entry.kind()) {
case ProfileBufferEntry::Kind::Responsiveness:
if (sample.isSome()) {
sample->mResponsiveness = Some(entry.u.mDouble);
}
break;
case ProfileBufferEntry::Kind::ResidentMemory:
if (sample.isSome()) {
sample->mRSS = Some(entry.u.mDouble);
}
break;
case ProfileBufferEntry::Kind::UnsharedMemory:
if (sample.isSome()) {
sample->mUSS = Some(entry.u.mDouble);
}
break;
case ProfileBufferEntry::Kind::Sample:
{
// end the previous sample if there was one
if (sample.isSome()) {
WriteSample(aWriter, *sample);
sample.reset();
}
// begin the next sample
sample.emplace();
sample->mTime = currentTime;
// Process all the remaining entries within this sample.
UniqueStacks::Stack stack =
aUniqueStacks.BeginStack(UniqueStacks::OnStackFrameKey("(root)"));
int entryPos = (readPos + 1) % mEntrySize;
ProfileBufferEntry entry = mEntries[entryPos];
while (entryPos != mWritePos && !entry.isSample() &&
!entry.isThreadId()) {
int incBy = 1;
entry = mEntries[entryPos];
// Read ahead to the next entry. If it's an EmbeddedString entry
// process it now.
const char* string = entry.u.mString;
int readAheadPos = (entryPos + 1) % mEntrySize;
// Make sure the string is always null terminated if it fills up
// DYNAMIC_MAX_STRING-2
strbuf[DYNAMIC_MAX_STRING-1] = '\0';
if (readAheadPos != mWritePos &&
mEntries[readAheadPos].isEmbeddedString()) {
string =
processEmbeddedString(readAheadPos, &incBy, strbuf.get());
}
// Write one entry. It can have either
// 1. only location - a NativeLeafAddr containing a memory address
// 2. location and line number - a CodeLocation followed by
// EmbeddedStrings, an optional LineNumber and an
// optional Category
// 3. a JitReturnAddress containing a native code address
if (entry.isNativeLeafAddr()) {
// Bug 753041
// We need a double cast here to tell GCC that we don't want to sign
// extend 32-bit addresses starting with 0xFXXXXXX.
unsigned long long pc =
(unsigned long long)(uintptr_t)entry.u.mPtr;
snprintf(strbuf.get(), DYNAMIC_MAX_STRING, "%#llx", pc);
stack.AppendFrame(UniqueStacks::OnStackFrameKey(strbuf.get()));
} else if (entry.isCodeLocation()) {
UniqueStacks::OnStackFrameKey frameKey(string);
readAheadPos = (entryPos + incBy) % mEntrySize;
if (readAheadPos != mWritePos &&
mEntries[readAheadPos].isLineNumber()) {
frameKey.mLine = Some((unsigned) mEntries[readAheadPos].u.mInt);
incBy++;
}
readAheadPos = (entryPos + incBy) % mEntrySize;
if (readAheadPos != mWritePos &&
mEntries[readAheadPos].isCategory()) {
frameKey.mCategory =
Some((unsigned) mEntries[readAheadPos].u.mInt);
incBy++;
}
stack.AppendFrame(frameKey);
} else if (entry.isJitReturnAddr()) {
// A JIT frame may expand to multiple frames due to inlining.
void* pc = entry.u.mPtr;
unsigned depth = aUniqueStacks.LookupJITFrameDepth(pc);
if (depth == 0) {
StreamJSFramesOp framesOp(pc, stack);
MOZ_RELEASE_ASSERT(aContext);
JS::ForEachProfiledFrame(aContext, pc, framesOp);
aUniqueStacks.AddJITFrameDepth(pc, framesOp.depth());
} else {
for (unsigned i = 0; i < depth; i++) {
UniqueStacks::OnStackFrameKey inlineFrameKey(pc, i);
stack.AppendFrame(inlineFrameKey);
}
}
}
entryPos = (entryPos + incBy) % mEntrySize;
}
sample->mStack = stack.GetOrAddIndex();
break;
}
default:
break;
} /* switch (entry.kind()) */
if (numFrames == 0) {
ERROR_AND_SKIP_TO_NEXT_SAMPLE("expected one or more frame entries");
}
readPos = (readPos + 1) % mEntrySize;
}
if (sample.isSome()) {
WriteSample(aWriter, *sample);
sample.mStack = stack.GetOrAddIndex();
// Skip over the markers. We process them in StreamMarkersToJSON().
while (e.Has()) {
if (e.Get().isMarker()) {
e.Next();
} else {
break;
}
}
if (e.Has() && e.Get().isResponsiveness()) {
sample.mResponsiveness = Some(e.Get().u.mDouble);
e.Next();
}
if (e.Has() && e.Get().isResidentMemory()) {
sample.mRSS = Some(e.Get().u.mDouble);
e.Next();
}
if (e.Has() && e.Get().isUnsharedMemory()) {
sample.mUSS = Some(e.Get().u.mDouble);
e.Next();
}
WriteSample(aWriter, sample);
}
#undef ERROR_AND_SKIP_TO_NEXT_SAMPLE
}
void
@ -719,19 +885,22 @@ ProfileBuffer::StreamMarkersToJSON(SpliceableJSONWriter& aWriter,
double aSinceTime,
UniqueStacks& aUniqueStacks)
{
int readPos = mReadPos;
EntryGetter e(this);
int currentThreadID = -1;
while (readPos != mWritePos) {
ProfileBufferEntry entry = mEntries[readPos];
if (entry.isThreadId()) {
currentThreadID = entry.u.mInt;
} else if (currentThreadID == aThreadId && entry.isMarker()) {
const ProfilerMarker* marker = entry.u.mMarker;
// Stream all markers whose threadId matches aThreadId. All other entries are
// skipped, because we process them in StreamSamplesToJSON().
while (e.Has()) {
if (e.Get().isThreadId()) {
currentThreadID = e.Get().u.mInt;
} else if (currentThreadID == aThreadId && e.Get().isMarker()) {
const ProfilerMarker* marker = e.Get().u.mMarker;
if (marker->GetTime() >= aSinceTime) {
entry.u.mMarker->StreamJSON(aWriter, aProcessStartTime, aUniqueStacks);
marker->StreamJSON(aWriter, aProcessStartTime, aUniqueStacks);
}
}
readPos = (readPos + 1) % mEntrySize;
e.Next();
}
}

3
tools/profiler/core/platform.cpp
Просмотреть файл

@ -1241,6 +1241,9 @@ DoNativeBacktrace(PSLockRef aLock, const ThreadInfo& aThreadInfo,
// Writes some components shared by periodic and synchronous profiles to
// ActivePS's ProfileBuffer. (This should only be called from DoSyncSample()
// and DoPeriodicSample().)
//
// The grammar for entry sequences is in a comment above
// ProfileBuffer::StreamSamplesToJSON.
static inline void
DoSharedSample(PSLockRef aLock, bool aIsSynchronous,
ThreadInfo& aThreadInfo, const TimeStamp& aNow,