Merge pull request #21 from hobu/issue-16

Limit memory consumption by limiting buffer creation

epf/BufferCache.cpp

@@ -23,26 +23,36 @@ namespace epf
 // If we have a buffer in the cache, return it. Otherwise create a new one and return that.
 DataVecPtr BufferCache::fetch()
 {
-    std::lock_guard<std::mutex> lock(m_mutex);
+    std::unique_lock<std::mutex> lock(m_mutex);
 
+    m_cv.wait(lock, [this](){ return m_buffers.size() || m_count < MaxBuffers; });
     if (m_buffers.size())
     {
         DataVecPtr buf(std::move(m_buffers.back()));
         m_buffers.pop_back();
         return buf;
     }
 
+    // m_count tracks the number of created buffers. We only create MaxBuffers buffers.
+    // If we've created that many, we wait until one is available.
+    m_count++;
     return DataVecPtr(new DataVec(BufSize));
 }
 
 // Put a buffer back in the cache.
 void BufferCache::replace(DataVecPtr&& buf)
 {
-    std::lock_guard<std::mutex> lock(m_mutex);
+    std::unique_lock<std::mutex> lock(m_mutex);
 
     //ABELL - Fix this.
     buf->resize(BufSize);
     m_buffers.push_back(std::move(buf));
+
+    if (m_count == MaxBuffers)
+    {
+        lock.unlock();
+        m_cv.notify_one();
+    }
 }
 
 } // namespace epf

epf/BufferCache.hpp

@@ -14,6 +14,8 @@
 #pragma once
 
 #include <deque>
+#include <mutex>
+#include <condition_variable>
 
 #include "EpfTypes.hpp"
 
@@ -26,11 +28,17 @@ namespace epf
 class BufferCache
 {
 public:
-    std::deque<DataVecPtr> m_buffers;
-    std::mutex m_mutex;
+    BufferCache() : m_count(0)
+    {}
 
     DataVecPtr fetch();
     void replace(DataVecPtr&& buf);
+
+private:
+    std::deque<DataVecPtr> m_buffers;
+    std::mutex m_mutex;
+    std::condition_variable m_cv;
+    int m_count;
 };
 
 } // namespace epf

epf/EpfTypes.hpp

@@ -35,6 +35,7 @@ using DataVecPtr = std::unique_ptr<DataVec>;
 using Totals = std::unordered_map<VoxelKey, size_t>;
 constexpr int MaxPointsPerNode = 100000;
 constexpr int BufSize = 4096 * 10;
+constexpr int MaxBuffers = 1000;
 
 struct Error : public std::runtime_error
 {