From b82cc00be9f34937b37a70841447242114aac277 Mon Sep 17 00:00:00 2001
From: falkTX <falktx@gmail.com>
Date: Fri, 11 Apr 2014 13:26:46 +0000
Subject: [PATCH] Experiment with mlock and barriers

---
 source/backend/plugin/BridgePlugin.cpp |  3 +++
 source/utils/CarlaMathUtils.hpp        | 16 ++++++++++++
 source/utils/CarlaRingBuffer.hpp       | 34 ++++++++++++++++++++++++++
 source/utils/Lv2AtomQueue.hpp          | 11 ++++++---
 4 files changed, 61 insertions(+), 3 deletions(-)

diff --git a/source/backend/plugin/BridgePlugin.cpp b/source/backend/plugin/BridgePlugin.cpp
index 8fb3cc989..c5ce60ff2 100644
--- a/source/backend/plugin/BridgePlugin.cpp
+++ b/source/backend/plugin/BridgePlugin.cpp
@@ -1896,6 +1896,9 @@ public:
         carla_stdout("  sizeof(BridgeShmControl): " P_SIZE, sizeof(BridgeShmControl));
         carla_stdout("  sizeof(BridgeTimeInfo):   " P_SIZE, sizeof(BridgeTimeInfo));
 
+        // lock memory
+        fShmControl.lockMemory();
+
         // initial values
         fShmControl.writeOpcode(kPluginBridgeOpcodeNull);
         fShmControl.writeInt(static_cast<int32_t>(sizeof(BridgeShmControl)));
diff --git a/source/utils/CarlaMathUtils.hpp b/source/utils/CarlaMathUtils.hpp
index f691ad98b..ca8c90ac9 100644
--- a/source/utils/CarlaMathUtils.hpp
+++ b/source/utils/CarlaMathUtils.hpp
@@ -79,6 +79,22 @@ const T& carla_fixValue(const T& min, const T& max, const T& value) noexcept
     return value;
 }
 
+/*
+ * Get next power of 2.
+ */
+static inline
+uint32_t carla_nextPowerOf2(uint32_t size)
+{
+    // http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
+    --size;
+    size |= size >> 1;
+    size |= size >> 2;
+    size |= size >> 4;
+    size |= size >> 8;
+    size |= size >> 16;
+    return ++size;
+}
+
 // -----------------------------------------------------------------------
 // math functions (extended)
 
diff --git a/source/utils/CarlaRingBuffer.hpp b/source/utils/CarlaRingBuffer.hpp
index 5c3eff6e6..47142506b 100644
--- a/source/utils/CarlaRingBuffer.hpp
+++ b/source/utils/CarlaRingBuffer.hpp
@@ -20,6 +20,13 @@
 
 #include "CarlaUtils.hpp"
 
+#ifndef CARLA_OS_WIN
+# include <sys/mman.h>
+# ifdef CARLA_OS_MAC
+#  include <libkern/OSAtomic.h>
+# endif
+#endif
+
 // -----------------------------------------------------------------------
 // RingBuffer structs
 
@@ -97,6 +104,7 @@ public:
 
         if (fBuffer->invalidateCommit)
         {
+            memoryBarrier();
             fBuffer->written = fBuffer->head;
             fBuffer->invalidateCommit = false;
             return false;
@@ -115,6 +123,19 @@ public:
         return (fBuffer->head != fBuffer->tail);
     }
 
+    void lockMemory() const noexcept
+    {
+        CARLA_SAFE_ASSERT_RETURN(fBuffer != nullptr,);
+
+#ifdef CARLA_OS_WIN
+        ::VirtualLock(fBuffer, sizeof(BufferStruct));
+        ::VirtualLock(fBuffer->buf, fBuffer->size);
+#else
+        ::mlock(fBuffer, sizeof(BufferStruct));
+        ::mlock(fBuffer->buf, fBuffer->size);
+#endif
+    }
+
     // -------------------------------------------------------------------
 
     char readChar() noexcept
@@ -219,6 +240,7 @@ protected:
             std::memcpy(charbuf, fBuffer->buf + tail, size);
         }
 
+        memoryBarrier();
         fBuffer->tail = static_cast<int32_t>(readto);
     }
 
@@ -261,12 +283,24 @@ protected:
             std::memcpy(fBuffer->buf + wrtn, charbuf, size);
         }
 
+        memoryBarrier();
         fBuffer->written = static_cast<int32_t>(writeto);
     }
 
 private:
     BufferStruct* fBuffer;
 
+    static void memoryBarrier()
+    {
+#if defined(CARLA_OS_MAC)
+        ::OSMemoryBarrier();
+#elif defined(CARLA_OS_WIN)
+        ::MemoryBarrier();
+#elif (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 1)
+        ::__sync_synchronize();
+#endif
+    }
+
     CARLA_PREVENT_HEAP_ALLOCATION
     CARLA_DECLARE_NON_COPY_CLASS(RingBufferControl)
 };
diff --git a/source/utils/Lv2AtomQueue.hpp b/source/utils/Lv2AtomQueue.hpp
index 47704aacb..f3595fe2c 100644
--- a/source/utils/Lv2AtomQueue.hpp
+++ b/source/utils/Lv2AtomQueue.hpp
@@ -18,6 +18,7 @@
 #ifndef LV2_ATOM_QUEUE_HPP_INCLUDED
 #define LV2_ATOM_QUEUE_HPP_INCLUDED
 
+#include "CarlaMathUtils.hpp"
 #include "CarlaMutex.hpp"
 #include "CarlaRingBuffer.hpp"
 
@@ -49,6 +50,9 @@ public:
 
     void createBuffer(const uint32_t size) noexcept
     {
+        if (fLv2Buffer.size == size && ! fIsDummy)
+            return;
+
         if (fLv2Buffer.buf != nullptr)
         {
             if (! fIsDummy)
@@ -59,9 +63,10 @@ public:
         // shouldn't really happen please...
         CARLA_SAFE_ASSERT_RETURN(size > 0,);
 
-        fLv2Buffer.size = size;
-        fLv2Buffer.buf  = new char[size];
+        fLv2Buffer.size = carla_nextPowerOf2(size);
+        fLv2Buffer.buf  = new char[fLv2Buffer.size];
         setRingBuffer(&fLv2Buffer, true);
+        lockMemory();
     }
 
     // used for tmp buffers only
@@ -182,7 +187,7 @@ public:
         if (! fRingBufferCtrl.isDataAvailable())
             return false;
 
-        if (const LV2_Atom* retAtom = fRingBufferCtrl.readAtom(portIndex))
+        if (const LV2_Atom* const retAtom = fRingBufferCtrl.readAtom(portIndex))
         {
             *atom = retAtom;
             return true;