Remove unnecessary buffer copy from EventPipe::WriteEvent pipeline (#13347)

* [WIP] Eliminate extra buffer copy with new api path

* Copy blobs to a flat buffer is Rundown is on

* Refactor to use payload class and dedupe code

* Add contracts

* Fix many small errors

* Make names unambiguous

* Add EventPipe::WriteEventBlob to ecalllist.h

* Address code review

* Add test and fix a buffer copy bug

* Copy data instead of data pointer

* Add optional output file arg to tests

* Change failure return code

* Renamed variables for clarity

13 files changed, 478 insertions, 66 deletions

diff --git a/src/mscorlib/src/System/Diagnostics/Eventing/EventPipe.cs b/src/mscorlib/src/System/Diagnostics/Eventing/EventPipe.cs
index 2f6fdf62ef..0d216c38ab 100644
--- a/src/mscorlib/src/System/Diagnostics/Eventing/EventPipe.cs
+++ b/src/mscorlib/src/System/Diagnostics/Eventing/EventPipe.cs
@@ -171,5 +171,9 @@ namespace System.Diagnostics.Tracing
         [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
         [SuppressUnmanagedCodeSecurity]
         internal static extern unsafe void WriteEvent(IntPtr eventHandle, uint eventID, void* pData, uint length, Guid* activityId, Guid* relatedActivityId);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        [SuppressUnmanagedCodeSecurity]
+        internal static extern unsafe void WriteEventData(IntPtr eventHandle, uint eventID, EventProvider.EventData** pEventData, uint dataCount, Guid* activityId, Guid* relatedActivityId);
     }
 }
diff --git a/src/mscorlib/src/System/Diagnostics/Eventing/EventPipeEventProvider.cs b/src/mscorlib/src/System/Diagnostics/Eventing/EventPipeEventProvider.cs
index d5bc4c2889..1c521bbafc 100644
--- a/src/mscorlib/src/System/Diagnostics/Eventing/EventPipeEventProvider.cs
+++ b/src/mscorlib/src/System/Diagnostics/Eventing/EventPipeEventProvider.cs
@@ -62,28 +62,11 @@ namespace System.Diagnostics.Tracing
             {
                 if (userDataCount == 0)
                 {
-                    EventPipeInternal.WriteEvent(eventHandle, eventID, null, 0, activityId, relatedActivityId);
+                    EventPipeInternal.WriteEventData(eventHandle, eventID, null, 0, activityId, relatedActivityId);
                     return 0;
                 }
 
-                uint length = 0;
-                for (int i = 0; i < userDataCount; i++)
-                {
-                    length += userData[i].Size;
-                }
-
-                byte[] data = new byte[length];
-                fixed (byte *pData = data)
-                {
-                    uint offset = 0;
-                    for (int i = 0; i < userDataCount; i++)
-                    {
-                        byte * singleUserDataPtr = (byte *)(userData[i].Ptr);
-                        uint singleUserDataSize = userData[i].Size;
-                        WriteToBuffer(pData, length, ref offset, singleUserDataPtr, singleUserDataSize);
-                    }
-                    EventPipeInternal.WriteEvent(eventHandle, eventID, pData, length, activityId, relatedActivityId);
-                }
+                EventPipeInternal.WriteEventData(eventHandle, eventID, &userData, (uint) userDataCount, activityId, relatedActivityId);
             }
             return 0;
         }
diff --git a/src/scripts/genEventPipe.py b/src/scripts/genEventPipe.py
index 4c802acaf3..d5785d2799 100644
--- a/src/scripts/genEventPipe.py
+++ b/src/scripts/genEventPipe.py
@@ -110,7 +110,7 @@ def generateClrEventPipeWriteEventsImpl(
             WriteEventImpl.append(
                 "    EventPipe::WriteEvent(*EventPipeEvent" +
                 eventName +
-                ", nullptr, 0);\n")
+                ", (BYTE*) nullptr, 0);\n")
 
         WriteEventImpl.append("\n    return ERROR_SUCCESS;\n}\n\n")
 
diff --git a/src/vm/ecalllist.h b/src/vm/ecalllist.h
index 114d2cf2fd..b76b81cb05 100644
--- a/src/vm/ecalllist.h
+++ b/src/vm/ecalllist.h
@@ -1245,6 +1245,7 @@ FCFuncStart(gEventPipeInternalFuncs)
     QCFuncElement("DefineEvent", EventPipeInternal::DefineEvent)
     QCFuncElement("DeleteProvider", EventPipeInternal::DeleteProvider)
     QCFuncElement("WriteEvent", EventPipeInternal::WriteEvent)
+    QCFuncElement("WriteEventData", EventPipeInternal::WriteEventData)
 FCFuncEnd()
 #endif // FEATURE_PERFTRACING
 
diff --git a/src/vm/eventpipe.cpp b/src/vm/eventpipe.cpp
index 9a94923493..d8d3791d59 100644
--- a/src/vm/eventpipe.cpp
+++ b/src/vm/eventpipe.cpp
@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#include "clrtypes.h"
+#include "safemath.h"
 #include "common.h"
 #include "eventpipe.h"
 #include "eventpipebuffermanager.h"
@@ -38,6 +40,146 @@ extern "C" void InitProvidersAndEvents();
 extern "C" void InitProvidersAndEvents();
 #endif
 
+EventPipeEventPayload::EventPipeEventPayload(BYTE *pData, unsigned int length)
+{
+    CONTRACTL
+    {
+        NOTHROW;
+        GC_NOTRIGGER;
+        MODE_ANY;
+    }
+    CONTRACTL_END;
+
+    m_pData = pData;
+    m_pEventData = NULL;
+    m_eventDataCount = 0;
+    m_allocatedData = false;
+
+    m_size = length;
+}
+
+EventPipeEventPayload::EventPipeEventPayload(EventData **pEventData, unsigned int eventDataCount)
+{
+    CONTRACTL
+    {
+        NOTHROW;
+        GC_NOTRIGGER;
+        MODE_ANY;
+    }
+    CONTRACTL_END;
+
+    m_pData = NULL;
+    m_pEventData = pEventData;
+    m_eventDataCount = eventDataCount;
+    m_allocatedData = false;
+
+    S_UINT32 tmp_size = S_UINT32(0);
+    for (unsigned int i=0; i<m_eventDataCount; i++)
+    {
+        tmp_size += S_UINT32(m_pEventData[i]->Size);
+    }
+
+    if (tmp_size.IsOverflow())
+    {
+        // If there is an overflow, drop the data and create an empty payload
+        m_pEventData = NULL;
+        m_eventDataCount = 0;
+        m_size = 0;
+    }
+    else
+    {
+        m_size = tmp_size.Value();
+    }
+}
+
+EventPipeEventPayload::~EventPipeEventPayload()
+{
+    CONTRACTL
+    {
+        NOTHROW;
+        GC_TRIGGERS;
+        MODE_ANY;
+    }
+    CONTRACTL_END;
+
+    if(m_allocatedData && m_pData != NULL)
+    {
+        delete[] m_pData;
+        m_pData = NULL;
+    }
+}
+
+void EventPipeEventPayload::Flatten()
+{
+    CONTRACTL
+    {
+        NOTHROW;
+        GC_TRIGGERS;
+        MODE_ANY;
+    }
+    CONTRACTL_END;
+
+    if(m_size > 0)
+    {
+        if (!IsFlattened())
+        {
+            BYTE* tmp_pData = new (nothrow) BYTE[m_size];
+            if (tmp_pData != NULL)
+            {
+                m_allocatedData = true;
+                CopyData(tmp_pData);
+                m_pData = tmp_pData;
+            }
+        }
+    }
+}
+
+void EventPipeEventPayload::CopyData(BYTE *pDst)
+{
+    CONTRACTL
+    {
+        NOTHROW;
+        GC_NOTRIGGER;
+        MODE_ANY;
+    }
+    CONTRACTL_END;
+
+    if(m_size > 0)
+    {
+        if(IsFlattened())
+        {
+            memcpy(pDst, m_pData, m_size);
+        }
+
+        else if(m_pEventData != NULL)
+        {
+            unsigned int offset = 0;
+            for(unsigned int i=0; i<m_eventDataCount; i++)
+            {
+                memcpy(pDst + offset, (BYTE*)m_pEventData[i]->Ptr, m_pEventData[i]->Size);
+                offset += m_pEventData[i]->Size;
+            }
+        }
+    }
+}
+
+BYTE* EventPipeEventPayload::GetFlatData()
+{
+    CONTRACTL
+    {
+        NOTHROW;
+        GC_TRIGGERS;
+        MODE_ANY;
+    }
+    CONTRACTL_END;
+
+    if (!IsFlattened())
+    {
+        Flatten();
+    }
+    return m_pData;
+}
+
 void EventPipe::Initialize()
 {
     STANDARD_VM_CONTRACT;
@@ -289,6 +431,34 @@ void EventPipe::WriteEvent(EventPipeEvent &event, BYTE *pData, unsigned int leng
         NOTHROW;
         GC_NOTRIGGER;
         MODE_ANY;
+    }
+    CONTRACTL_END;
+
+    EventPipeEventPayload payload(pData, length);
+    EventPipe::WriteEventInternal(event, payload, pActivityId, pRelatedActivityId);
+}
+
+void EventPipe::WriteEvent(EventPipeEvent &event, EventData **pEventData, unsigned int eventDataCount, LPCGUID pActivityId, LPCGUID pRelatedActivityId)
+{
+    CONTRACTL
+    {
+        NOTHROW;
+        GC_NOTRIGGER;
+        MODE_ANY;
+    }
+    CONTRACTL_END;
+
+    EventPipeEventPayload payload(pEventData, eventDataCount);
+    EventPipe::WriteEventInternal(event, payload, pActivityId, pRelatedActivityId);
+}
+
+void EventPipe::WriteEventInternal(EventPipeEvent &event, EventPipeEventPayload &payload, LPCGUID pActivityId, LPCGUID pRelatedActivityId)
+{
+    CONTRACTL
+    {
+        NOTHROW;
+        GC_NOTRIGGER;
+        MODE_ANY;
         PRECONDITION(s_pBufferManager != NULL);
     }
     CONTRACTL_END;
@@ -309,7 +479,7 @@ void EventPipe::WriteEvent(EventPipeEvent &event, BYTE *pData, unsigned int leng
 
     if(!s_pConfig->RundownEnabled() && s_pBufferManager != NULL)
     {
-        if(!s_pBufferManager->WriteEvent(pThread, event, pData, length, pActivityId, pRelatedActivityId))
+        if(!s_pBufferManager->WriteEvent(pThread, event, payload, pActivityId, pRelatedActivityId))
         {
             // This is used in DEBUG to make sure that we don't log an event synchronously that we didn't log to the buffer.
             return;
@@ -317,19 +487,23 @@ void EventPipe::WriteEvent(EventPipeEvent &event, BYTE *pData, unsigned int leng
     }
     else if(s_pConfig->RundownEnabled())
     {
-        // Write synchronously to the file.
-        // We're under lock and blocking the disabling thread.
-        EventPipeEventInstance instance(
-            event,
-            pThread->GetOSThreadId(),
-            pData,
-            length,
-            pActivityId,
-            pRelatedActivityId);
-
-        if(s_pFile != NULL)
+        BYTE *pData = payload.GetFlatData();
+        if (pData != NULL)
         {
-            s_pFile->WriteEvent(instance);
+            // Write synchronously to the file.
+            // We're under lock and blocking the disabling thread.
+            EventPipeEventInstance instance(
+                event,
+                pThread->GetOSThreadId(),
+                pData,
+                payload.GetSize(),
+                pActivityId,
+                pRelatedActivityId);
+
+            if(s_pFile != NULL)
+            {
+                s_pFile->WriteEvent(instance);
+            }
         }
     }
 
@@ -337,25 +511,29 @@ void EventPipe::WriteEvent(EventPipeEvent &event, BYTE *pData, unsigned int leng
     {
         GCX_PREEMP();
 
-        // Create an instance of the event for the synchronous path.
-        EventPipeEventInstance instance(
-            event,
-            pThread->GetOSThreadId(),
-            pData,
-            length,
-            pActivityId,
-            pRelatedActivityId);
-
-        // Write to the EventPipeFile if it exists.
-        if(s_pSyncFile != NULL)
+        BYTE *pData = payload.GetFlatData();
+        if (pData != NULL)
         {
-            s_pSyncFile->WriteEvent(instance);
-        }
+            // Create an instance of the event for the synchronous path.
+            EventPipeEventInstance instance(
+                event,
+                pThread->GetOSThreadId(),
+                pData,
+                payload.GetSize(),
+                pActivityId,
+                pRelatedActivityId);
+
+            // Write to the EventPipeFile if it exists.
+            if(s_pSyncFile != NULL)
+            {
+                s_pSyncFile->WriteEvent(instance);
+            }
  
-        // Write to the EventPipeJsonFile if it exists.
-        if(s_pJsonFile != NULL)
-        {
-            s_pJsonFile->WriteEvent(instance);
+            // Write to the EventPipeJsonFile if it exists.
+            if(s_pJsonFile != NULL)
+            {
+                s_pJsonFile->WriteEvent(instance);
+            }
         }
     }
 #endif // _DEBUG
@@ -371,12 +549,14 @@ void EventPipe::WriteSampleProfileEvent(Thread *pSamplingThread, EventPipeEvent
     }
     CONTRACTL_END;
 
+    EventPipeEventPayload payload(pData, length);
+
     // Write the event to the thread's buffer.
     if(s_pBufferManager != NULL)
     {
         // Specify the sampling thread as the "current thread", so that we select the right buffer.
         // Specify the target thread so that the event gets properly attributed.
-        if(!s_pBufferManager->WriteEvent(pSamplingThread, *pEvent, pData, length, NULL /* pActivityId */, NULL /* pRelatedActivityId */, pTargetThread, &stackContents))
+        if(!s_pBufferManager->WriteEvent(pSamplingThread, *pEvent, payload, NULL /* pActivityId */, NULL /* pRelatedActivityId */, pTargetThread, &stackContents))
         {
             // This is used in DEBUG to make sure that we don't log an event synchronously that we didn't log to the buffer.
             return;
@@ -595,4 +775,22 @@ void QCALLTYPE EventPipeInternal::WriteEvent(
     END_QCALL;
 }
 
+void QCALLTYPE EventPipeInternal::WriteEventData(
+    INT_PTR eventHandle,
+    unsigned int eventID,
+    EventData **pEventData,
+    unsigned int eventDataCount,
+    LPCGUID pActivityId,
+    LPCGUID pRelatedActivityId)
+{
+    QCALL_CONTRACT;
+    BEGIN_QCALL;
+
+    _ASSERTE(eventHandle != NULL);
+    EventPipeEvent *pEvent = reinterpret_cast<EventPipeEvent *>(eventHandle);
+    EventPipe::WriteEvent(*pEvent, pEventData, eventDataCount, pActivityId, pRelatedActivityId);
+
+    END_QCALL;
+}
+
 #endif // FEATURE_PERFTRACING
diff --git a/src/vm/eventpipe.h b/src/vm/eventpipe.h
index fa7d734280..6ea29ac63b 100644
--- a/src/vm/eventpipe.h
+++ b/src/vm/eventpipe.h
@@ -29,6 +29,69 @@ typedef void (*EventPipeCallback)(
     void *FilterData,
     void *CallbackContext);
 
+struct EventData
+{
+public:
+    unsigned long Ptr;
+    unsigned int Size;
+    unsigned int Reserved;
+};
+
+class EventPipeEventPayload
+{
+private:
+    BYTE *m_pData;
+    EventData **m_pEventData;
+    unsigned int m_eventDataCount;
+    unsigned int m_size;
+    bool m_allocatedData;
+
+    // If the data is stored only as an array of EventData objects, create a flat buffer and copy into it
+    void Flatten();
+
+public:
+    // Build this payload with a flat buffer inside
+    EventPipeEventPayload(BYTE *pData, unsigned int length);
+
+    // Build this payload to contain an array of EventData objects
+    EventPipeEventPayload(EventData **pEventData, unsigned int eventDataCount);
+
+    // If a buffer was allocated internally, delete it
+    ~EventPipeEventPayload();
+    
+    // Copy the data (whether flat or array of objects) into a flat buffer at pDst
+    // Assumes that pDst points to an appropriatly sized buffer
+    void CopyData(BYTE *pDst);
+
+    // Get the flat formatted data in this payload
+    // This method will allocate a buffer if it does not already contain flattened data
+    // This method will return NULL on OOM if a buffer needed to be allocated
+    BYTE* GetFlatData();
+
+    // Return true is the data is stored in a flat buffer
+    bool IsFlattened() const
+    {
+        LIMITED_METHOD_CONTRACT;
+
+        return m_pData != NULL;
+    }
+
+    // The the size of buffer needed to contain the stored data
+    unsigned int GetSize() const
+    {
+        LIMITED_METHOD_CONTRACT;
+
+        return m_size;
+    }
+
+    EventData** GetEventDataArray() const
+    {
+        LIMITED_METHOD_CONTRACT;
+
+        return m_pEventData;
+    }
+};
+
 class StackContents
 {
 private:
@@ -186,10 +249,14 @@ class EventPipe
         // Delete a provider.
         static void DeleteProvider(EventPipeProvider *pProvider);
 
-        // Write out an event.
+        // Write out an event from a flat buffer.
         // Data is written as a serialized blob matching the ETW serialization conventions.
         static void WriteEvent(EventPipeEvent &event, BYTE *pData, unsigned int length, LPCGUID pActivityId = NULL, LPCGUID pRelatedActivityId = NULL);
 
+        // Write out an event from an EventData array.
+        // Data is written as a serialized blob matching the ETW serialization conventions.
+        static void WriteEvent(EventPipeEvent &event, EventData **pEventData, unsigned int eventDataCount, LPCGUID pActivityId = NULL, LPCGUID pRelatedActivityId = NULL);
+
         // Write out a sample profile event.
         static void WriteSampleProfileEvent(Thread *pSamplingThread, EventPipeEvent *pEvent, Thread *pTargetThread, StackContents &stackContents, BYTE *pData = NULL, unsigned int length = 0);
         
@@ -199,6 +266,11 @@ class EventPipe
         // Get the managed call stack for the specified thread.
         static bool WalkManagedStackForThread(Thread *pThread, StackContents &stackContents);
 
+    protected:
+
+        // The counterpart to WriteEvent which after the payload is constructed
+        static void WriteEventInternal(EventPipeEvent &event, EventPipeEventPayload &payload, LPCGUID pActivityId = NULL, LPCGUID pRelatedActivityId = NULL);
+
     private:
 
         // Callback function for the stack walker.  For each frame walked, this callback is invoked.
@@ -307,6 +379,13 @@ public:
         void *pData,
         unsigned int length,
         LPCGUID pActivityId, LPCGUID pRelatedActivityId);
+
+    static void QCALLTYPE WriteEventData(
+        INT_PTR eventHandle,
+        unsigned int eventID,
+        EventData **pEventData,
+        unsigned int eventDataCount,
+        LPCGUID pActivityId, LPCGUID pRelatedActivityId);
 };
 
 #endif // FEATURE_PERFTRACING
diff --git a/src/vm/eventpipebuffer.cpp b/src/vm/eventpipebuffer.cpp
index 00652c9fac..80b4a4f1b7 100644
--- a/src/vm/eventpipebuffer.cpp
+++ b/src/vm/eventpipebuffer.cpp
@@ -4,6 +4,7 @@
 
 
 #include "common.h"
+#include "eventpipe.h"
 #include "eventpipeeventinstance.h"
 #include "eventpipebuffer.h"
 
@@ -46,7 +47,7 @@ EventPipeBuffer::~EventPipeBuffer()
     }
 }
 
-bool EventPipeBuffer::WriteEvent(Thread *pThread, EventPipeEvent &event, BYTE *pData, unsigned int dataLength, LPCGUID pActivityId, LPCGUID pRelatedActivityId, StackContents *pStack)
+bool EventPipeBuffer::WriteEvent(Thread *pThread, EventPipeEvent &event, EventPipeEventPayload &payload, LPCGUID pActivityId, LPCGUID pRelatedActivityId, StackContents *pStack)
 {
     CONTRACTL
     {
@@ -58,7 +59,7 @@ bool EventPipeBuffer::WriteEvent(Thread *pThread, EventPipeEvent &event, BYTE *p
     CONTRACTL_END;
 
     // Calculate the size of the event.
-    unsigned int eventSize = sizeof(EventPipeEventInstance) + dataLength;
+    unsigned int eventSize = sizeof(EventPipeEventInstance) + payload.GetSize();
 
     // Make sure we have enough space to write the event.
     if(m_pCurrent + eventSize >= m_pLimit)
@@ -77,7 +78,7 @@ bool EventPipeBuffer::WriteEvent(Thread *pThread, EventPipeEvent &event, BYTE *p
             event,
             pThread->GetOSThreadId(),
             pDataDest,
-            dataLength,
+            payload.GetSize(),
             pActivityId,
             pRelatedActivityId);
 
@@ -89,9 +90,9 @@ bool EventPipeBuffer::WriteEvent(Thread *pThread, EventPipeEvent &event, BYTE *p
         }
 
         // Write the event payload data to the buffer.
-        if(dataLength > 0)
+        if(payload.GetSize() > 0)
         {
-            memcpy(pDataDest, pData, dataLength);
+            payload.CopyData(pDataDest);
         }
 
         // Save the most recent event timestamp.
diff --git a/src/vm/eventpipebuffer.h b/src/vm/eventpipebuffer.h
index f279a2865c..c96ad26609 100644
--- a/src/vm/eventpipebuffer.h
+++ b/src/vm/eventpipebuffer.h
@@ -7,6 +7,7 @@
 
 #ifdef FEATURE_PERFTRACING
 
+#include "eventpipe.h"
 #include "eventpipeevent.h"
 #include "eventpipeeventinstance.h"
 
@@ -81,7 +82,7 @@ public:
     // Returns:
     //  - true: The write succeeded.
     //  - false: The write failed.  In this case, the buffer should be considered full.
-    bool WriteEvent(Thread *pThread, EventPipeEvent &event, BYTE *pData, unsigned int dataLength, LPCGUID pActivityId, LPCGUID pRelatedActivityId, StackContents *pStack = NULL);
+    bool WriteEvent(Thread *pThread, EventPipeEvent &event, EventPipeEventPayload &payload, LPCGUID pActivityId, LPCGUID pRelatedActivityId, StackContents *pStack = NULL);
 
     // Get the timestamp of the most recent event in the buffer.
     LARGE_INTEGER GetMostRecentTimeStamp() const;
diff --git a/src/vm/eventpipebuffermanager.cpp b/src/vm/eventpipebuffermanager.cpp
index 86a3e03c59..fa4c5e0b68 100644
--- a/src/vm/eventpipebuffermanager.cpp
+++ b/src/vm/eventpipebuffermanager.cpp
@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 #include "common.h"
+#include "eventpipe.h"
 #include "eventpipeconfiguration.h"
 #include "eventpipebuffer.h"
 #include "eventpipebuffermanager.h"
@@ -217,7 +218,7 @@ void EventPipeBufferManager::DeAllocateBuffer(EventPipeBuffer *pBuffer)
     }
 }
 
-bool EventPipeBufferManager::WriteEvent(Thread *pThread, EventPipeEvent &event, BYTE *pData, unsigned int length, LPCGUID pActivityId, LPCGUID pRelatedActivityId, Thread *pEventThread, StackContents *pStack)
+bool EventPipeBufferManager::WriteEvent(Thread *pThread, EventPipeEvent &event, EventPipeEventPayload &payload, LPCGUID pActivityId, LPCGUID pRelatedActivityId, Thread *pEventThread, StackContents *pStack)
 {
     CONTRACTL
     {
@@ -276,7 +277,7 @@ bool EventPipeBufferManager::WriteEvent(Thread *pThread, EventPipeEvent &event,
         else
         {
             // Attempt to write the event to the buffer.  If this fails, we should allocate a new buffer.
-            allocNewBuffer = !pBuffer->WriteEvent(pEventThread, event, pData, length, pActivityId, pRelatedActivityId, pStack);
+            allocNewBuffer = !pBuffer->WriteEvent(pEventThread, event, payload, pActivityId, pRelatedActivityId, pStack);
         }
     }
 
@@ -290,7 +291,7 @@ bool EventPipeBufferManager::WriteEvent(Thread *pThread, EventPipeEvent &event,
         // However, the GC is waiting on this call to return so that it can make forward progress.  Thus it is not safe
         // to switch to preemptive mode here.
 
-        unsigned int requestSize = sizeof(EventPipeEventInstance) + length;
+        unsigned int requestSize = sizeof(EventPipeEventInstance) + payload.GetSize();
         pBuffer = AllocateBufferForThread(pThread, requestSize);
     }
 
@@ -299,7 +300,7 @@ bool EventPipeBufferManager::WriteEvent(Thread *pThread, EventPipeEvent &event,
     // This is the second time if this thread did have one or more buffers, but they were full.
     if(allocNewBuffer && pBuffer != NULL)
     {
-        allocNewBuffer = !pBuffer->WriteEvent(pEventThread, event, pData, length, pActivityId, pRelatedActivityId, pStack);
+        allocNewBuffer = !pBuffer->WriteEvent(pEventThread, event, payload, pActivityId, pRelatedActivityId, pStack);
     }
 
     // Mark that the thread is no longer writing an event.
diff --git a/src/vm/eventpipebuffermanager.h b/src/vm/eventpipebuffermanager.h
index a53721b7b8..23e4e7f3e9 100644
--- a/src/vm/eventpipebuffermanager.h
+++ b/src/vm/eventpipebuffermanager.h
@@ -7,6 +7,7 @@
 
 #ifdef FEATURE_PERFTRACING
 
+#include "eventpipe.h"
 #include "eventpipefile.h"
 #include "eventpipebuffer.h"
 #include "spinlock.h"
@@ -67,7 +68,7 @@ public:
     // This is because the thread that writes the events is not the same as the "event thread".
     // An optional stack trace can be provided for sample profiler events.
     // Otherwise, if a stack trace is needed, one will be automatically collected.
-    bool WriteEvent(Thread *pThread, EventPipeEvent &event, BYTE *pData, unsigned int length, LPCGUID pActivityId, LPCGUID pRelatedActivityId, Thread *pEventThread = NULL, StackContents *pStack = NULL);
+    bool WriteEvent(Thread *pThread, EventPipeEvent &event, EventPipeEventPayload &payload, LPCGUID pActivityId, LPCGUID pRelatedActivityId, Thread *pEventThread = NULL, StackContents *pStack = NULL);
 
     // Write the contents of the managed buffers to the specified file.
     // The stopTimeStamp is used to determine when tracing was stopped to ensure that we
diff --git a/tests/src/tracing/eventpipesmoke/EventPipeSmoke.cs b/tests/src/tracing/eventpipesmoke/EventPipeSmoke.cs
index 5bf11b8f78..78ab88aed9 100644
--- a/tests/src/tracing/eventpipesmoke/EventPipeSmoke.cs
+++ b/tests/src/tracing/eventpipesmoke/EventPipeSmoke.cs
@@ -10,11 +10,19 @@ namespace Tracing.Tests
     {
         private static int allocIterations = 10000;
         private static int trivialSize = 0x100000;
-        private static bool keepOutput = false;
 
         static int Main(string[] args)
         {
-            string outputFilename = System.IO.Path.GetTempPath() + Guid.NewGuid().ToString() + ".netperf";
+            bool keepOutput = false;
+            // Use the first arg as an output filename if there is one
+            string outputFilename = null;
+            if (args.Length >= 1) {
+                outputFilename = args[0];
+                keepOutput = true;
+            }
+            else {
+                outputFilename = System.IO.Path.GetTempPath() + Guid.NewGuid().ToString() + ".netperf";
+            }
 
             Console.WriteLine("\tStart: Enable tracing.");
             TraceControl.EnableDefault(outputFilename);
@@ -49,7 +57,7 @@ namespace Tracing.Tests
                 System.IO.File.Delete(outputFilename);
             }
 
-            return pass ? 100 : 0;
+            return pass ? 100 : -1;
         }
     }
 }
diff --git a/tests/src/tracing/eventsourcesmoke/EventSourceSmoke.cs b/tests/src/tracing/eventsourcesmoke/EventSourceSmoke.cs
new file mode 100644
index 0000000000..c3fe8366ab
--- /dev/null
+++ b/tests/src/tracing/eventsourcesmoke/EventSourceSmoke.cs
@@ -0,0 +1,104 @@
+using System;
+using System.Threading.Tasks;
+using System.IO;
+using System.Diagnostics.Tracing;
+
+using Tracing.Tests.Common;
+
+namespace Tracing.Tests
+{
+    [EventSource(Name = "SimpleEventSource")]
+    class SimpleEventSource : EventSource
+    {
+        public SimpleEventSource() : base(true) { }
+
+        [Event(1)]
+        internal void Message(string msg) { this.WriteEvent(1, msg); }
+    }
+
+    class EventPipeSmoke
+    {
+        private static int messageIterations = 10000;
+        private static int trivialSize = 0x100000;
+
+        public static TraceConfiguration GetConfig(EventSource eventSource, string outputFile="default.netperf")
+        {
+            // Setup the configuration values.
+            uint circularBufferMB = 1024; // 1 GB
+            uint level = 5;//(uint)EventLevel.Informational;
+            TimeSpan profSampleDelay = TimeSpan.FromMilliseconds(1);
+
+            // Create a new instance of EventPipeConfiguration.
+            TraceConfiguration config = new TraceConfiguration(outputFile, circularBufferMB);
+            // Setup the provider values.
+            // Public provider.
+            string providerName = eventSource.Guid.ToString("D");
+            UInt64 keywords = 0xffffffffffffffff;
+
+            // Enable the provider.
+            config.EnableProvider(providerName, keywords, level);
+
+            // Set the sampling rate.
+            config.SetSamplingRate(profSampleDelay);
+
+            return config;
+        }
+
+        static int Main(string[] args)
+        {
+            bool keepOutput = false;
+            // Use the first arg as an output filename if there is one
+            string outputFilename = null;
+            if (args.Length >= 1) {
+                outputFilename = args[0];
+                keepOutput = true;
+            }
+            else {
+                outputFilename = System.IO.Path.GetTempPath() + Guid.NewGuid().ToString() + ".netperf";
+            }
+
+            SimpleEventSource eventSource = new SimpleEventSource();
+
+            Console.WriteLine("\tStart: Enable tracing.");
+            TraceControl.Enable(GetConfig(eventSource, outputFilename));
+            Console.WriteLine("\tEnd: Enable tracing.\n");
+
+            Console.WriteLine("\tStart: Messaging.");
+            // Send messages
+            // Use random numbers and addition as a simple, human readble checksum
+            Random generator = new Random();
+            for(int i=0; i<messageIterations; i++)
+            {
+                int x = generator.Next(1,1000);
+                int y = generator.Next(1,1000);
+                string result = String.Format("{0} + {1} = {2}", x, y, x+y);
+                
+                eventSource.Message(result);
+            }
+            Console.WriteLine("\tEnd: Messaging.\n");
+
+            Console.WriteLine("\tStart: Disable tracing.");
+            TraceControl.Disable();
+            Console.WriteLine("\tEnd: Disable tracing.\n");
+
+            FileInfo outputMeta = new FileInfo(outputFilename);
+            Console.WriteLine("\tCreated {0} bytes of data", outputMeta.Length);
+
+            bool pass = false;
+            if (outputMeta.Length > trivialSize){
+                pass = true;
+            }
+
+            if (keepOutput)
+            {
+                Console.WriteLine(String.Format("\tOutput file: {0}", outputFilename));
+            }
+            else
+            {
+                System.IO.File.Delete(outputFilename);
+            }
+
+            return pass ? 100 : -1;
+        }
+    }
+}
diff --git a/tests/src/tracing/eventsourcesmoke/eventsourcesmoke.csproj b/tests/src/tracing/eventsourcesmoke/eventsourcesmoke.csproj
new file mode 100644
index 0000000000..897ebfd983
--- /dev/null
+++ b/tests/src/tracing/eventsourcesmoke/eventsourcesmoke.csproj
@@ -0,0 +1,31 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="12.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.props))\dir.props" />
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <SchemaVersion>2.0</SchemaVersion>
+    <ProjectGuid>{8E3244CB-407F-4142-BAAB-E7A55901A5FA}</ProjectGuid>
+    <OutputType>Exe</OutputType>
+    <ProjectTypeGuids>{786C830F-07A1-408B-BD7F-6EE04809D6DB};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
+    <SolutionDir Condition="$(SolutionDir) == '' Or $(SolutionDir) == '*Undefined*'">..\..\</SolutionDir>
+    <CLRTestKind>BuildAndRun</CLRTestKind>
+    <DefineConstants>$(DefineConstants);STATIC</DefineConstants>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+  </PropertyGroup>
+  <!-- Default configurations to help VS understand the configurations -->
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|x64'">
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|x64'">
+  </PropertyGroup>
+  <ItemGroup>
+    <CodeAnalysisDependentAssemblyPaths Condition=" '$(VS100COMNTOOLS)' != '' " Include="$(VS100COMNTOOLS)..\IDE\PrivateAssemblies">
+      <Visible>False</Visible>
+    </CodeAnalysisDependentAssemblyPaths>
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="EventSourceSmoke.cs" />
+    <ProjectReference Include="../common/common.csproj" />
+  </ItemGroup>
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
+</Project>