1 files changed, 347 insertions, 63 deletions

diff --git a/runtime/trace.cc b/runtime/trace.cc
index 7326865..5322f9f 100644
--- a/runtime/trace.cc
+++ b/runtime/trace.cc
@@ -31,7 +31,7 @@
 #include "instrumentation.h"
 #include "mirror/art_method-inl.h"
 #include "mirror/class-inl.h"
-#include "mirror/dex_cache.h"
+#include "mirror/dex_cache-inl.h"
 #include "mirror/object_array-inl.h"
 #include "mirror/object-inl.h"
 #include "os.h"
@@ -85,9 +85,12 @@ enum TraceAction {
     kTraceMethodActionMask = 0x03,  // two bits
 };
 
+static constexpr uint8_t kOpNewMethod = 1U;
+static constexpr uint8_t kOpNewThread = 2U;
+
 class BuildStackTraceVisitor : public StackVisitor {
  public:
-  explicit BuildStackTraceVisitor(Thread* thread) : StackVisitor(thread, NULL),
+  explicit BuildStackTraceVisitor(Thread* thread) : StackVisitor(thread, nullptr),
       method_trace_(Trace::AllocStackTrace()) {}
 
   bool VisitFrame() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
@@ -118,7 +121,7 @@ static const uint16_t kTraceRecordSizeDualClock   = 14;  // using v3 with two ti
 
 TraceClockSource Trace::default_clock_source_ = kDefaultTraceClockSource;
 
-Trace* volatile Trace::the_trace_ = NULL;
+Trace* volatile Trace::the_trace_ = nullptr;
 pthread_t Trace::sampling_pthread_ = 0U;
 std::unique_ptr<std::vector<mirror::ArtMethod*>> Trace::temp_stack_trace_;
 
@@ -138,7 +141,7 @@ static uint32_t EncodeTraceMethodAndAction(mirror::ArtMethod* method,
 }
 
 std::vector<mirror::ArtMethod*>* Trace::AllocStackTrace() {
-  if (temp_stack_trace_.get() != NULL) {
+  if (temp_stack_trace_.get() != nullptr) {
     return temp_stack_trace_.release();
   } else {
     return new std::vector<mirror::ArtMethod*>();
@@ -246,7 +249,7 @@ static void GetSample(Thread* thread, void* arg) SHARED_LOCKS_REQUIRED(Locks::mu
 static void ClearThreadStackTraceAndClockBase(Thread* thread, void* arg ATTRIBUTE_UNUSED) {
   thread->SetTraceClockBase(0);
   std::vector<mirror::ArtMethod*>* stack_trace = thread->GetStackTraceSample();
-  thread->SetStackTraceSample(NULL);
+  thread->SetStackTraceSample(nullptr);
   delete stack_trace;
 }
 
@@ -260,7 +263,7 @@ void Trace::CompareAndUpdateStackTrace(Thread* thread,
   uint32_t thread_clock_diff = 0;
   uint32_t wall_clock_diff = 0;
   ReadClocks(thread, &thread_clock_diff, &wall_clock_diff);
-  if (old_stack_trace == NULL) {
+  if (old_stack_trace == nullptr) {
     // If there's no previous stack trace sample for this thread, log an entry event for all
     // methods in the trace.
     for (std::vector<mirror::ArtMethod*>::reverse_iterator rit = stack_trace->rbegin();
@@ -308,7 +311,7 @@ void* Trace::RunSamplingThread(void* arg) {
     {
       MutexLock mu(self, *Locks::trace_lock_);
       the_trace = the_trace_;
-      if (the_trace == NULL) {
+      if (the_trace == nullptr) {
         break;
       }
     }
@@ -323,7 +326,7 @@ void* Trace::RunSamplingThread(void* arg) {
   }
 
   runtime->DetachCurrentThread();
-  return NULL;
+  return nullptr;
 }
 
 void Trace::Start(const char* trace_filename, int trace_fd, int buffer_size, int flags,
@@ -331,7 +334,7 @@ void Trace::Start(const char* trace_filename, int trace_fd, int buffer_size, int
   Thread* self = Thread::Current();
   {
     MutexLock mu(self, *Locks::trace_lock_);
-    if (the_trace_ != NULL) {
+    if (the_trace_ != nullptr) {
       LOG(ERROR) << "Trace already in progress, ignoring this request";
       return;
     }
@@ -354,7 +357,7 @@ void Trace::Start(const char* trace_filename, int trace_fd, int buffer_size, int
       trace_file.reset(new File(trace_fd, "tracefile"));
       trace_file->DisableAutoClose();
     }
-    if (trace_file.get() == NULL) {
+    if (trace_file.get() == nullptr) {
       PLOG(ERROR) << "Unable to open trace file '" << trace_filename << "'";
       ScopedObjectAccess soa(self);
       ThrowRuntimeException("Unable to open trace file '%s'", trace_filename);
@@ -372,20 +375,23 @@ void Trace::Start(const char* trace_filename, int trace_fd, int buffer_size, int
   // Create Trace object.
   {
     MutexLock mu(self, *Locks::trace_lock_);
-    if (the_trace_ != NULL) {
+    if (the_trace_ != nullptr) {
       LOG(ERROR) << "Trace already in progress, ignoring this request";
     } else {
       enable_stats = (flags && kTraceCountAllocs) != 0;
-      the_trace_ = new Trace(trace_file.release(), buffer_size, flags, trace_mode);
+      the_trace_ = new Trace(trace_file.release(), trace_filename, buffer_size, flags, output_mode,
+                             trace_mode);
       if (trace_mode == TraceMode::kSampling) {
-        CHECK_PTHREAD_CALL(pthread_create, (&sampling_pthread_, NULL, &RunSamplingThread,
+        CHECK_PTHREAD_CALL(pthread_create, (&sampling_pthread_, nullptr, &RunSamplingThread,
                                             reinterpret_cast<void*>(interval_us)),
                                             "Sampling profiler thread");
+        the_trace_->interval_us_ = interval_us;
       } else {
         runtime->GetInstrumentation()->AddListener(the_trace_,
                                                    instrumentation::Instrumentation::kMethodEntered |
                                                    instrumentation::Instrumentation::kMethodExited |
                                                    instrumentation::Instrumentation::kMethodUnwind);
+        // TODO: In full-PIC mode, we don't need to fully deopt.
         runtime->GetInstrumentation()->EnableMethodTracing();
       }
     }
@@ -399,18 +405,18 @@ void Trace::Start(const char* trace_filename, int trace_fd, int buffer_size, int
   }
 }
 
-void Trace::Stop() {
+void Trace::StopTracing(bool finish_tracing, bool flush_file) {
   bool stop_alloc_counting = false;
   Runtime* const runtime = Runtime::Current();
   Trace* the_trace = nullptr;
   pthread_t sampling_pthread = 0U;
   {
     MutexLock mu(Thread::Current(), *Locks::trace_lock_);
-    if (the_trace_ == NULL) {
+    if (the_trace_ == nullptr) {
       LOG(ERROR) << "Trace stop requested, but no trace currently running";
     } else {
       the_trace = the_trace_;
-      the_trace_ = NULL;
+      the_trace_ = nullptr;
       sampling_pthread = sampling_pthread_;
     }
   }
@@ -418,13 +424,16 @@ void Trace::Stop() {
   // the sampling thread access a stale pointer. This finishes since the sampling thread exits when
   // the_trace_ is null.
   if (sampling_pthread != 0U) {
-    CHECK_PTHREAD_CALL(pthread_join, (sampling_pthread, NULL), "sampling thread shutdown");
+    CHECK_PTHREAD_CALL(pthread_join, (sampling_pthread, nullptr), "sampling thread shutdown");
     sampling_pthread_ = 0U;
   }
   runtime->GetThreadList()->SuspendAll(__FUNCTION__);
+
   if (the_trace != nullptr) {
-    stop_alloc_counting = (the_trace->flags_ & kTraceCountAllocs) != 0;
-    the_trace->FinishTracing();
+    stop_alloc_counting = (the_trace->flags_ & Trace::kTraceCountAllocs) != 0;
+    if (finish_tracing) {
+      the_trace->FinishTracing();
+    }
 
     if (the_trace->trace_mode_ == TraceMode::kSampling) {
       MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
@@ -438,8 +447,12 @@ void Trace::Stop() {
     }
     if (the_trace->trace_file_.get() != nullptr) {
       // Do not try to erase, so flush and close explicitly.
-      if (the_trace->trace_file_->Flush() != 0) {
-        PLOG(ERROR) << "Could not flush trace file.";
+      if (flush_file) {
+        if (the_trace->trace_file_->Flush() != 0) {
+          PLOG(ERROR) << "Could not flush trace file.";
+        }
+      } else {
+        the_trace->trace_file_->MarkUnchecked();  // Do not trigger guard.
       }
       if (the_trace->trace_file_->Close() != 0) {
         PLOG(ERROR) << "Could not close trace file.";
@@ -454,15 +467,118 @@ void Trace::Stop() {
   }
 }
 
+void Trace::Abort() {
+  // Do not write anything anymore.
+  StopTracing(false, false);
+}
+
+void Trace::Stop() {
+  // Finish writing.
+  StopTracing(true, true);
+}
+
 void Trace::Shutdown() {
   if (GetMethodTracingMode() != kTracingInactive) {
     Stop();
   }
 }
 
+void Trace::Pause() {
+  bool stop_alloc_counting = false;
+  Runtime* runtime = Runtime::Current();
+  Trace* the_trace = nullptr;
+
+  pthread_t sampling_pthread = 0U;
+  {
+    MutexLock mu(Thread::Current(), *Locks::trace_lock_);
+    if (the_trace_ == nullptr) {
+      LOG(ERROR) << "Trace pause requested, but no trace currently running";
+      return;
+    } else {
+      the_trace = the_trace_;
+      sampling_pthread = sampling_pthread_;
+    }
+  }
+
+  if (sampling_pthread != 0U) {
+    {
+      MutexLock mu(Thread::Current(), *Locks::trace_lock_);
+      the_trace_ = nullptr;
+    }
+    CHECK_PTHREAD_CALL(pthread_join, (sampling_pthread, nullptr), "sampling thread shutdown");
+    sampling_pthread_ = 0U;
+    {
+      MutexLock mu(Thread::Current(), *Locks::trace_lock_);
+      the_trace_ = the_trace;
+    }
+  }
+
+  if (the_trace != nullptr) {
+    runtime->GetThreadList()->SuspendAll(__FUNCTION__);
+    stop_alloc_counting = (the_trace->flags_ & Trace::kTraceCountAllocs) != 0;
+
+    if (the_trace->trace_mode_ == TraceMode::kSampling) {
+      MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
+      runtime->GetThreadList()->ForEach(ClearThreadStackTraceAndClockBase, nullptr);
+    } else {
+      runtime->GetInstrumentation()->DisableMethodTracing();
+      runtime->GetInstrumentation()->RemoveListener(the_trace,
+                                                    instrumentation::Instrumentation::kMethodEntered |
+                                                    instrumentation::Instrumentation::kMethodExited |
+                                                    instrumentation::Instrumentation::kMethodUnwind);
+    }
+    runtime->GetThreadList()->ResumeAll();
+  }
+
+  if (stop_alloc_counting) {
+    // Can be racy since SetStatsEnabled is not guarded by any locks.
+    Runtime::Current()->SetStatsEnabled(false);
+  }
+}
+
+void Trace::Resume() {
+  Thread* self = Thread::Current();
+  Trace* the_trace;
+  {
+    MutexLock mu(self, *Locks::trace_lock_);
+    if (the_trace_ == nullptr) {
+      LOG(ERROR) << "No trace to resume (or sampling mode), ignoring this request";
+      return;
+    }
+    the_trace = the_trace_;
+  }
+
+  Runtime* runtime = Runtime::Current();
+
+  // Enable count of allocs if specified in the flags.
+  bool enable_stats = (the_trace->flags_ && kTraceCountAllocs) != 0;
+
+  runtime->GetThreadList()->SuspendAll(__FUNCTION__);
+
+  // Reenable.
+  if (the_trace->trace_mode_ == TraceMode::kSampling) {
+    CHECK_PTHREAD_CALL(pthread_create, (&sampling_pthread_, nullptr, &RunSamplingThread,
+        reinterpret_cast<void*>(the_trace->interval_us_)), "Sampling profiler thread");
+  } else {
+    runtime->GetInstrumentation()->AddListener(the_trace,
+                                               instrumentation::Instrumentation::kMethodEntered |
+                                               instrumentation::Instrumentation::kMethodExited |
+                                               instrumentation::Instrumentation::kMethodUnwind);
+    // TODO: In full-PIC mode, we don't need to fully deopt.
+    runtime->GetInstrumentation()->EnableMethodTracing();
+  }
+
+  runtime->GetThreadList()->ResumeAll();
+
+  // Can't call this when holding the mutator lock.
+  if (enable_stats) {
+    runtime->SetStatsEnabled(true);
+  }
+}
+
 TracingMode Trace::GetMethodTracingMode() {
   MutexLock mu(Thread::Current(), *Locks::trace_lock_);
-  if (the_trace_ == NULL) {
+  if (the_trace_ == nullptr) {
     return kTracingInactive;
   } else {
     switch (the_trace_->trace_mode_) {
@@ -476,13 +592,26 @@ TracingMode Trace::GetMethodTracingMode() {
   }
 }
 
-Trace::Trace(File* trace_file, int buffer_size, int flags, TraceMode trace_mode)
-    : trace_file_(trace_file), buf_(new uint8_t[buffer_size]()), flags_(flags),
-      trace_mode_(trace_mode), clock_source_(default_clock_source_),
-      buffer_size_(buffer_size), start_time_(MicroTime()),
-      clock_overhead_ns_(GetClockOverheadNanoSeconds()), cur_offset_(0), overflow_(false) {
-  // Set up the beginning of the trace.
+static constexpr size_t kStreamingBufferSize = 16 * KB;
+
+Trace::Trace(File* trace_file, const char* trace_name, int buffer_size, int flags,
+             TraceOutputMode output_mode, TraceMode trace_mode)
+    : trace_file_(trace_file),
+      buf_(new uint8_t[output_mode == TraceOutputMode::kStreaming ?
+          kStreamingBufferSize :
+          buffer_size]()),
+      flags_(flags), trace_output_mode_(output_mode), trace_mode_(trace_mode),
+      clock_source_(default_clock_source_),
+      buffer_size_(output_mode == TraceOutputMode::kStreaming ?
+          kStreamingBufferSize :
+          buffer_size),
+      start_time_(MicroTime()), clock_overhead_ns_(GetClockOverheadNanoSeconds()), cur_offset_(0),
+      overflow_(false), interval_us_(0), streaming_lock_(nullptr) {
   uint16_t trace_version = GetTraceVersion(clock_source_);
+  if (output_mode == TraceOutputMode::kStreaming) {
+    trace_version |= 0xF0U;
+  }
+  // Set up the beginning of the trace.
   memset(buf_.get(), 0, kTraceHeaderLength);
   Append4LE(buf_.get(), kTraceMagicValue);
   Append2LE(buf_.get() + 4, trace_version);
@@ -495,6 +624,16 @@ Trace::Trace(File* trace_file, int buffer_size, int flags, TraceMode trace_mode)
 
   // Update current offset.
   cur_offset_.StoreRelaxed(kTraceHeaderLength);
+
+  if (output_mode == TraceOutputMode::kStreaming) {
+    streaming_file_name_ = trace_name;
+    streaming_lock_ = new Mutex("tracing lock");
+    seen_threads_.reset(new ThreadIDBitSet());
+  }
+}
+
+Trace::~Trace() {
+  delete streaming_lock_;
 }
 
 static void DumpBuf(uint8_t* buf, size_t buf_size, TraceClockSource clock_source)
@@ -511,14 +650,38 @@ static void DumpBuf(uint8_t* buf, size_t buf_size, TraceClockSource clock_source
   }
 }
 
-void Trace::FinishTracing() {
-  // Compute elapsed time.
-  uint64_t elapsed = MicroTime() - start_time_;
+static void GetVisitedMethodsFromBitSets(
+    const std::map<mirror::DexCache*, DexIndexBitSet*>& seen_methods,
+    std::set<mirror::ArtMethod*>* visited_methods) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+  for (auto& e : seen_methods) {
+    DexIndexBitSet* bit_set = e.second;
+    for (uint32_t i = 0; i < bit_set->size(); ++i) {
+      if ((*bit_set)[i]) {
+        visited_methods->insert(e.first->GetResolvedMethod(i));
+      }
+    }
+  }
+}
 
-  size_t final_offset = cur_offset_.LoadRelaxed();
+void Trace::FinishTracing() {
+  size_t final_offset = 0;
 
   std::set<mirror::ArtMethod*> visited_methods;
-  GetVisitedMethods(final_offset, &visited_methods);
+  if (trace_output_mode_ == TraceOutputMode::kStreaming) {
+    // Write the secondary file with all the method names.
+    GetVisitedMethodsFromBitSets(seen_methods_, &visited_methods);
+
+    // Clean up.
+    for (auto& e : seen_methods_) {
+      delete e.second;
+    }
+  } else {
+    final_offset = cur_offset_.LoadRelaxed();
+    GetVisitedMethods(final_offset, &visited_methods);
+  }
+
+  // Compute elapsed time.
+  uint64_t elapsed = MicroTime() - start_time_;
 
   std::ostringstream os;
 
@@ -535,8 +698,10 @@ void Trace::FinishTracing() {
     os << StringPrintf("clock=wall\n");
   }
   os << StringPrintf("elapsed-time-usec=%" PRIu64 "\n", elapsed);
-  size_t num_records = (final_offset - kTraceHeaderLength) / GetRecordSize(clock_source_);
-  os << StringPrintf("num-method-calls=%zd\n", num_records);
+  if (trace_output_mode_ != TraceOutputMode::kStreaming) {
+    size_t num_records = (final_offset - kTraceHeaderLength) / GetRecordSize(clock_source_);
+    os << StringPrintf("num-method-calls=%zd\n", num_records);
+  }
   os << StringPrintf("clock-call-overhead-nsec=%d\n", clock_overhead_ns_);
   os << StringPrintf("vm=art\n");
   os << StringPrintf("pid=%d\n", getpid());
@@ -550,27 +715,44 @@ void Trace::FinishTracing() {
   os << StringPrintf("%cmethods\n", kTraceTokenChar);
   DumpMethodList(os, visited_methods);
   os << StringPrintf("%cend\n", kTraceTokenChar);
-
   std::string header(os.str());
-  if (trace_file_.get() == NULL) {
-    iovec iov[2];
-    iov[0].iov_base = reinterpret_cast<void*>(const_cast<char*>(header.c_str()));
-    iov[0].iov_len = header.length();
-    iov[1].iov_base = buf_.get();
-    iov[1].iov_len = final_offset;
-    Dbg::DdmSendChunkV(CHUNK_TYPE("MPSE"), iov, 2);
-    const bool kDumpTraceInfo = false;
-    if (kDumpTraceInfo) {
-      LOG(INFO) << "Trace sent:\n" << header;
-      DumpBuf(buf_.get(), final_offset, clock_source_);
+
+  if (trace_output_mode_ == TraceOutputMode::kStreaming) {
+    File file;
+    if (!file.Open(streaming_file_name_ + ".sec", O_CREAT | O_WRONLY)) {
+      LOG(WARNING) << "Could not open secondary trace file!";
+      return;
     }
-  } else {
-    if (!trace_file_->WriteFully(header.c_str(), header.length()) ||
-        !trace_file_->WriteFully(buf_.get(), final_offset)) {
+    if (!file.WriteFully(header.c_str(), header.length())) {
+      file.Erase();
       std::string detail(StringPrintf("Trace data write failed: %s", strerror(errno)));
       PLOG(ERROR) << detail;
       ThrowRuntimeException("%s", detail.c_str());
     }
+    if (file.FlushCloseOrErase() != 0) {
+      PLOG(ERROR) << "Could not write secondary file";
+    }
+  } else {
+    if (trace_file_.get() == nullptr) {
+      iovec iov[2];
+      iov[0].iov_base = reinterpret_cast<void*>(const_cast<char*>(header.c_str()));
+      iov[0].iov_len = header.length();
+      iov[1].iov_base = buf_.get();
+      iov[1].iov_len = final_offset;
+      Dbg::DdmSendChunkV(CHUNK_TYPE("MPSE"), iov, 2);
+      const bool kDumpTraceInfo = false;
+      if (kDumpTraceInfo) {
+        LOG(INFO) << "Trace sent:\n" << header;
+        DumpBuf(buf_.get(), final_offset, clock_source_);
+      }
+    } else {
+      if (!trace_file_->WriteFully(header.c_str(), header.length()) ||
+          !trace_file_->WriteFully(buf_.get(), final_offset)) {
+        std::string detail(StringPrintf("Trace data write failed: %s", strerror(errno)));
+        PLOG(ERROR) << detail;
+        ThrowRuntimeException("%s", detail.c_str());
+      }
+    }
   }
 }
 
@@ -654,20 +836,76 @@ void Trace::ReadClocks(Thread* thread, uint32_t* thread_clock_diff, uint32_t* wa
   }
 }
 
+bool Trace::RegisterMethod(mirror::ArtMethod* method) {
+  mirror::DexCache* dex_cache = method->GetDexCache();
+  if (dex_cache->GetResolvedMethod(method->GetDexMethodIndex()) != method) {
+    DCHECK(dex_cache->GetResolvedMethod(method->GetDexMethodIndex()) == nullptr);
+    dex_cache->SetResolvedMethod(method->GetDexMethodIndex(), method);
+  }
+  if (seen_methods_.find(dex_cache) == seen_methods_.end()) {
+    seen_methods_.insert(std::make_pair(dex_cache, new DexIndexBitSet()));
+  }
+  DexIndexBitSet* bit_set = seen_methods_.find(dex_cache)->second;
+  if (!(*bit_set)[method->GetDexMethodIndex()]) {
+    bit_set->set(method->GetDexMethodIndex());
+    return true;
+  }
+  return false;
+}
+
+bool Trace::RegisterThread(Thread* thread) {
+  pid_t tid = thread->GetTid();
+  CHECK_LT(0U, static_cast<uint32_t>(tid));
+  CHECK_LT(static_cast<uint32_t>(tid), 65536U);
+
+  if (!(*seen_threads_)[tid]) {
+    seen_threads_->set(tid);
+    return true;
+  }
+  return false;
+}
+
+static std::string GetMethodLine(mirror::ArtMethod* method)
+    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+  return StringPrintf("%p\t%s\t%s\t%s\t%s\n", method,
+      PrettyDescriptor(method->GetDeclaringClassDescriptor()).c_str(), method->GetName(),
+      method->GetSignature().ToString().c_str(), method->GetDeclaringClassSourceFile());
+}
+
+void Trace::WriteToBuf(const uint8_t* src, size_t src_size) {
+  int32_t old_offset = cur_offset_.LoadRelaxed();
+  int32_t new_offset = old_offset + static_cast<int32_t>(src_size);
+  if (new_offset > buffer_size_) {
+    // Flush buffer.
+    if (!trace_file_->WriteFully(buf_.get(), old_offset)) {
+      PLOG(WARNING) << "Failed streaming a tracing event.";
+    }
+    old_offset = 0;
+    new_offset = static_cast<int32_t>(src_size);
+  }
+  cur_offset_.StoreRelease(new_offset);
+  // Fill in data.
+  memcpy(buf_.get() + old_offset, src, src_size);
+}
+
 void Trace::LogMethodTraceEvent(Thread* thread, mirror::ArtMethod* method,
                                 instrumentation::Instrumentation::InstrumentationEvent event,
                                 uint32_t thread_clock_diff, uint32_t wall_clock_diff) {
   // Advance cur_offset_ atomically.
   int32_t new_offset;
-  int32_t old_offset;
-  do {
-    old_offset = cur_offset_.LoadRelaxed();
-    new_offset = old_offset + GetRecordSize(clock_source_);
-    if (new_offset > buffer_size_) {
-      overflow_ = true;
-      return;
-    }
-  } while (!cur_offset_.CompareExchangeWeakSequentiallyConsistent(old_offset, new_offset));
+  int32_t old_offset = 0;
+
+  // We do a busy loop here trying to acquire the next offset.
+  if (trace_output_mode_ != TraceOutputMode::kStreaming) {
+    do {
+      old_offset = cur_offset_.LoadRelaxed();
+      new_offset = old_offset + GetRecordSize(clock_source_);
+      if (new_offset > buffer_size_) {
+        overflow_ = true;
+        return;
+      }
+    } while (!cur_offset_.CompareExchangeWeakSequentiallyConsistent(old_offset, new_offset));
+  }
 
   TraceAction action = kTraceMethodEnter;
   switch (event) {
@@ -687,7 +925,15 @@ void Trace::LogMethodTraceEvent(Thread* thread, mirror::ArtMethod* method,
   uint32_t method_value = EncodeTraceMethodAndAction(method, action);
 
   // Write data
-  uint8_t* ptr = buf_.get() + old_offset;
+  uint8_t* ptr;
+  static constexpr size_t kPacketSize = 14U;  // The maximum size of data in a packet.
+  uint8_t stack_buf[kPacketSize];             // Space to store a packet when in streaming mode.
+  if (trace_output_mode_ == TraceOutputMode::kStreaming) {
+    ptr = stack_buf;
+  } else {
+    ptr = buf_.get() + old_offset;
+  }
+
   Append2LE(ptr, thread->GetTid());
   Append4LE(ptr + 2, method_value);
   ptr += 6;
@@ -699,6 +945,34 @@ void Trace::LogMethodTraceEvent(Thread* thread, mirror::ArtMethod* method,
   if (UseWallClock()) {
     Append4LE(ptr, wall_clock_diff);
   }
+  static_assert(kPacketSize == 2 + 4 + 4 + 4, "Packet size incorrect.");
+
+  if (trace_output_mode_ == TraceOutputMode::kStreaming) {
+    MutexLock mu(Thread::Current(), *streaming_lock_);  // To serialize writing.
+    if (RegisterMethod(method)) {
+      // Write a special block with the name.
+      std::string method_line(GetMethodLine(method));
+      uint8_t buf2[5];
+      Append2LE(buf2, 0);
+      buf2[2] = kOpNewMethod;
+      Append2LE(buf2 + 3, static_cast<uint16_t>(method_line.length()));
+      WriteToBuf(buf2, sizeof(buf2));
+      WriteToBuf(reinterpret_cast<const uint8_t*>(method_line.c_str()), method_line.length());
+    }
+    if (RegisterThread(thread)) {
+      // It might be better to postpone this. Threads might not have received names...
+      std::string thread_name;
+      thread->GetThreadName(thread_name);
+      uint8_t buf2[7];
+      Append2LE(buf2, 0);
+      buf2[2] = kOpNewThread;
+      Append2LE(buf2 + 3, static_cast<uint16_t>(thread->GetTid()));
+      Append2LE(buf2 + 5, static_cast<uint16_t>(thread_name.length()));
+      WriteToBuf(buf2, sizeof(buf2));
+      WriteToBuf(reinterpret_cast<const uint8_t*>(thread_name.c_str()), thread_name.length());
+    }
+    WriteToBuf(stack_buf, sizeof(stack_buf));
+  }
 }
 
 void Trace::GetVisitedMethods(size_t buf_size,
@@ -716,9 +990,7 @@ void Trace::GetVisitedMethods(size_t buf_size,
 
 void Trace::DumpMethodList(std::ostream& os, const std::set<mirror::ArtMethod*>& visited_methods) {
   for (const auto& method : visited_methods) {
-    os << StringPrintf("%p\t%s\t%s\t%s\t%s\n", method,
-        PrettyDescriptor(method->GetDeclaringClassDescriptor()).c_str(), method->GetName(),
-        method->GetSignature().ToString().c_str(), method->GetDeclaringClassSourceFile());
+    os << GetMethodLine(method);
   }
 }
 
@@ -750,4 +1022,16 @@ void Trace::StoreExitingThreadInfo(Thread* thread) {
   }
 }
 
+Trace::TraceOutputMode Trace::GetOutputMode() {
+  MutexLock mu(Thread::Current(), *Locks::trace_lock_);
+  CHECK(the_trace_ != nullptr) << "Trace output mode requested, but no trace currently running";
+  return the_trace_->trace_output_mode_;
+}
+
+Trace::TraceMode Trace::GetMode() {
+  MutexLock mu(Thread::Current(), *Locks::trace_lock_);
+  CHECK(the_trace_ != nullptr) << "Trace mode requested, but no trace currently running";
+  return the_trace_->trace_mode_;
+}
+
 }  // namespace art