Fix EventPipeBuffer to use ClrVirtualAlloc instead of malloc (#28038)

src/vm/eventpipebuffer.cpp

@@ -23,7 +23,9 @@ EventPipeBuffer::EventPipeBuffer(unsigned int bufferSize, EventPipeThread* pWrit
     m_state = EventPipeBufferState::WRITABLE;
     m_pWriterThread = pWriterThread;
     m_eventSequenceNumber = eventSequenceNumber;
-    m_pBuffer = new BYTE[bufferSize];
+    // Use ClrVirtualAlloc instead of malloc to allocate buffer to avoid potential internal fragmentation in the native CRT heap.
+    // (See https://github.com/dotnet/runtime/pull/35924 and https://github.com/microsoft/ApplicationInsights-dotnet/issues/1678 for more details)
+    m_pBuffer = (BYTE*)ClrVirtualAlloc(NULL, bufferSize, MEM_COMMIT, PAGE_READWRITE);
     memset(m_pBuffer, 0, bufferSize);
     m_pLimit = m_pBuffer + bufferSize;
     m_pCurrent = GetNextAlignedAddress(m_pBuffer);
@@ -47,7 +49,7 @@ EventPipeBuffer::~EventPipeBuffer()
     }
     CONTRACTL_END;
 
-    delete[] m_pBuffer;
+    ClrVirtualFree(m_pBuffer, 0, MEM_RELEASE);
 }
 
 bool EventPipeBuffer::WriteEvent(Thread *pThread, EventPipeSession &session, EventPipeEvent &event, EventPipeEventPayload &payload, LPCGUID pActivityId, LPCGUID pRelatedActivityId, StackContents *pStack)

src/vm/eventpipebuffermanager.cpp

@@ -168,6 +168,12 @@ EventPipeBuffer* EventPipeBufferManager::AllocateBufferForThread(EventPipeThread
         const unsigned int maxBufferSize = 1024 * 1024;
         bufferSize = Min(bufferSize, maxBufferSize);
 
+        // Make the buffer size fit into with pagesize-aligned block, 
+        // since ClrVirtualAlloc expects page-aligned sizes to be passed 
+        // as arguments (see ctor of EventPipeBuffer)
+        bufferSize = (bufferSize + g_SystemInfo.dwAllocationGranularity - 1) & ~static_cast<unsigned int>(g_SystemInfo.dwAllocationGranularity - 1);
+
+
         // EX_TRY is used here as opposed to new (nothrow) because
         // the constructor also allocates a private buffer, which
         // could throw, and cannot be easily checked