Hi, The passthrough IO path currently doesn't do any request allocation batching like we do for normal IO. Wire this up through the usual blk_mq_alloc_request() allocation helper. Similarly, we don't currently supported batched completions for passthrough IO. Allow the request->end_io() handler to return back whether or not it retains ownership of the request. By default all handlers are converted to returning RQ_END_IO_NONE, which retains the existing behavior. But with that in place, we can tweak the nvme uring_cmd end_io handler to pass back ownership, and hence enable completion batching for passthrough requests as well. This is good for a 10% improvement for passthrough performance. For a non-drive limited test case, passthrough IO is now more efficient than the regular bdev O_DIRECT path. -- Jens Axboe
