From 58fbd0414291c8e8b7cc30b914fc6eb4e582cbc5 Mon Sep 17 00:00:00 2001
From: Jacob Dufault <jacobdufault@gmail.com>
Date: Wed, 16 Aug 2017 19:14:54 -0700
Subject: [PATCH] Add ThreadedQueue::EnqueueAll to reduce lock contention.

---
 src/command_line.cc  | 10 +++++-----
 src/threaded_queue.h |  9 +++++++++
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/src/command_line.cc b/src/command_line.cc
index 88773838..aa843512 100644
--- a/src/command_line.cc
+++ b/src/command_line.cc
@@ -998,18 +998,18 @@ bool IndexMain_DoParse(
   entry.args = request->args;
   std::vector<Index_DoIdMap> responses = ParseFile(config, index, file_consumer_shared, timestamp_manager, entry);
 
-  // TODO/FIXME: bulk enqueue so we don't lock so many times
-  for (Index_DoIdMap& response : responses)
-    queue->do_id_map.Enqueue(std::move(response));
+  if (responses.empty())
+    return false;
 
-  return !responses.empty();
+  // EnqueueAll will clear |responses|.
+  queue->do_id_map.EnqueueAll(std::move(responses));
+  return true;
 }
 
 bool IndexMain_DoCreateIndexUpdate(
     Config* config,
     QueueManager* queue,
     TimestampManager* timestamp_manager) {
-  // TODO: Index_OnIdMapped dtor is failing because it seems that its contents have already been destroyed.
   optional<Index_OnIdMapped> response = queue->on_id_mapped.TryDequeue();
   if (!response)
     return false;
diff --git a/src/threaded_queue.h b/src/threaded_queue.h
index 3240c801..93f7a1e3 100644
--- a/src/threaded_queue.h
+++ b/src/threaded_queue.h
@@ -71,6 +71,15 @@ public:
     waiter_->cv.notify_all();
   }
 
+  // Add a set of elements to the queue.
+  void EnqueueAll(std::vector<T>&& elements) {
+    std::lock_guard<std::mutex> lock(mutex_);
+    for (T& element : elements)
+      queue_.push(std::move(element));
+    elements.clear();
+    waiter_->cv.notify_all();
+  }
+
   // Return all elements in the queue.
   std::vector<T> DequeueAll() {
     std::lock_guard<std::mutex> lock(mutex_);