StagingBuff: support both Mlock & IOUring pin; Use in IoUAssmEngn

We use io_uring_register_buffers() for IoUringAssemblyEngine instead
of using mlock(). This __appears__ to have reduced CPU utilization on
the Dell laptop. Could also be that we recently upgraded total RAM
from 8GiB to 32GiB.

stimBuffApis/livoxGen1/ioUringAssemblyEngine.cpp

@@ -27,8 +27,6 @@
 #include "pcloudStimulusProducer.h"
 #include "livoxGen1.h"
 
-// #define REGISTER_IOURING_BUFFERS
-
 namespace smo {
 namespace stim_buff {
 
@@ -116,10 +114,6 @@ bool IoUringAssemblyEngine::setup()
 		assembledSlotsTracker[i].ioVec.iov_len = slot.nBytes;
 	}
 
-	// Declare iovec early to avoid goto crossing initialization
-#ifdef REGISTER_IOURING_BUFFERS
-	struct iovec iov;
-#endif
 	int ret;
 
 	/**	EXPLANATION:
@@ -134,23 +128,27 @@ bool IoUringAssemblyEngine::setup()
 	if (ret < 0)
 		{ goto cleanup; }
 
-#ifdef REGISTER_IOURING_BUFFERS
-	// Register staging buffer with io_uring for DMA-apt I/O
-	iov = parent.assemblyBuffer.getIoUringRegisterIoVec();
-	ret = io_uring_register_buffers(&ring, &iov, 1);
-	if (ret < 0)
-		{ goto cleanup_ring; }
-#endif
+	try
+	{
+		if (assemblyBufferIoUringPinner)
+		{
+			throw std::runtime_error(std::string(__func__)
+				+ ": assemblyBufferIoUringPinner already exists");
+		}
+
+		assemblyBufferIoUringPinner =
+			parent.assemblyBuffer.makeIoUringPinner(&ring);
+	}
+	catch (const std::exception&)
+	{
+		goto cleanup_ring;
+	}
 
 	// Create eventfd for CQE notifications (used with boost's unified loop)
 	eventfdFd = eventfd(0, EFD_NONBLOCK);
 	if (eventfdFd < 0)
 	{
-#ifdef REGISTER_IOURING_BUFFERS
-		goto cleanup_buffers;
-#else
 		goto cleanup_ring;
-#endif
 	}
 
 	// Register eventfd with io_uring
@@ -164,11 +162,8 @@ bool IoUringAssemblyEngine::setup()
 cleanup_eventfd:
 	close(eventfdFd);
 	eventfdFd = -1;
-#ifdef REGISTER_IOURING_BUFFERS
-cleanup_buffers:
-	io_uring_unregister_buffers(&ring);
-#endif
 cleanup_ring:
+	assemblyBufferIoUringPinner.reset();
 	io_uring_queue_exit(&ring);
 cleanup:
 	return false;
@@ -217,9 +212,7 @@ void IoUringAssemblyEngine::finalize()
 
 	if (wasAcceptingRequests)
 	{
-#ifdef REGISTER_IOURING_BUFFERS
-		io_uring_unregister_buffers(&ring);
-#endif
+		assemblyBufferIoUringPinner.reset();
 		io_uring_queue_exit(&ring);
 	}