According to one embodiment, a data processing device including a user space including a user space thread including a plurality of coroutines and a file system. The file system is configured to: allocate a plurality of processes generated by an application to the plurality of coroutines; check the plurality of coroutines in order; when a first process included in the plurality of processes is allocated to a first coroutine included in the plurality of coroutines, write a first IO request based on the first process in a submission queue; and when the submission queue is filled, or when checking the plurality of coroutines is finished, transmit the first IO request written in the submission queue to a storage device.