From c76dd17b2086b760ac38e1e12ec3d4df6268d0b3 Mon Sep 17 00:00:00 2001
From: Justin Lebar <jlebar@google.com>
Date: Mon, 26 Feb 2018 09:24:38 -0800
Subject: [PATCH] [XLA:GPU] Fix HLO profiling when multiple streams are
 involved.

We were enqueueing the timer on the main stream, but not blocking the
substreams, so the results were nonsensical.

PiperOrigin-RevId: 187032412
---
 .../compiler/xla/service/gpu/gpu_executable.cc      | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/tensorflow/compiler/xla/service/gpu/gpu_executable.cc b/tensorflow/compiler/xla/service/gpu/gpu_executable.cc
index 623d671..04b37d9 100644
--- a/tensorflow/compiler/xla/service/gpu/gpu_executable.cc
+++ b/tensorflow/compiler/xla/service/gpu/gpu_executable.cc
@@ -46,12 +46,14 @@ namespace {
 class HloExecutionProfiler {
  public:
   // If profiling is enabled, start an execution timer running.
-  explicit HloExecutionProfiler(bool do_profile, HloExecutionProfile* profile,
-                                se::Stream* stream,
-                                const HloComputation* computation)
+  explicit HloExecutionProfiler(
+      bool do_profile, HloExecutionProfile* profile, se::Stream* stream,
+      const std::vector<Pool<se::Stream>::SmartPtr>& sub_streams,
+      const HloComputation* computation)
       : do_profile_(do_profile),
         profile_(profile),
         stream_(stream),
+        sub_streams_(sub_streams),
         computation_(computation) {
     if (do_profile_) {
       clock_rate_ghz_ =
@@ -70,6 +72,7 @@ class HloExecutionProfiler {
     CHECK(!finished_execution_) << "Call FinishExecution only once!";
     finished_execution_ = true;
     if (do_profile_) {
+      stream_->ThenWaitFor(&sub_streams_);
       stream_->ThenStopTimer(execution_timer_.get());
       stream_->BlockHostUntilDone().IgnoreError();
       profile_->set_total_cycles_executed(
@@ -88,6 +91,7 @@ class HloExecutionProfiler {
   // that the hlo_instruction took to execute in the profile.
   void FinishOperation(const HloInstruction* hlo_instruction) {
     if (do_profile_) {
+      stream_->ThenWaitFor(&sub_streams_);
       stream_->ThenStopTimer(per_op_timer_.get());
       stream_->BlockHostUntilDone().IgnoreError();
       profile_->SetCyclesTakenBy(
@@ -100,6 +104,7 @@ class HloExecutionProfiler {
   double clock_rate_ghz_;
   HloExecutionProfile* profile_;
   se::Stream* stream_;
+  const std::vector<Pool<se::Stream>::SmartPtr>& sub_streams_;
   const HloComputation* computation_;
   std::unique_ptr<se::Timer> execution_timer_;
   std::unique_ptr<se::Timer> per_op_timer_;
@@ -147,13 +152,9 @@ Status GpuExecutable::ExecuteThunks(
     LOG(WARNING) << "PROFILING: profiling is enabled";
   }
 
-  HloExecutionProfiler profiler(do_profile, hlo_execution_profile, main_stream,
-                                hlo_module_->entry_computation());
-
-  uint64 start_micros = tensorflow::Env::Default()->NowMicros();
-
   // Stream 0 indicates `main_stream` and substreams start from stream 1.
   std::vector<Pool<se::Stream>::SmartPtr> sub_streams;
+  sub_streams.reserve(thunk_schedule_->StreamCount() - 1);
   while (sub_streams.size() + 1 < thunk_schedule_->StreamCount()) {
     sub_streams.emplace_back();
     TF_ASSIGN_OR_RETURN(
@@ -161,6 +162,10 @@ Status GpuExecutable::ExecuteThunks(
         run_options->BorrowStream(main_stream->parent()->device_ordinal()));
   }
 
+  HloExecutionProfiler profiler(do_profile, hlo_execution_profile, main_stream,
+                                sub_streams, hlo_module_->entry_computation());
+  uint64 start_micros = tensorflow::Env::Default()->NowMicros();
+
   // The next event enqueued on stream N must not run until the thunk at
   // last_blocking_thunk_for_stream[N] completes.
   std::map<int32, const Thunk*> last_blocking_thunk_for_stream;
-- 
2.7.4