Effective nonblocking MPI-I/O in remote I/O operations using a multithreaded mechanism

A flexible intermediate library named Stampi realizes seamless MPI operations on interconnected parallel computers. Dynamic process creation and MPI-I/O operations both inside a computer and among computers are available with it. MPI-I/O operations to a remote computer are realized by MPI-I/O processes of the Stampi library which are invoked on a remote computer using a vendor-supplied MPI-I/O library. If the vendor-supplied one is not available, a single MPI-I/O process is invoked on a remote computer, and it uses UNIX I/O functions instead of the vendor-supplied one. In nonblocking MPI-I/O functions with multiple user processes, the single MPI-I/O process carries out I/O operations required by the processes sequentially. This results in small overlap of computation by the user processes with I/O operations by the MPI-I/O process. Therefore performance of the nonblocking functions is poor with multiple user processes. To realize effective I/O operations, a Pthreads library has been implemented in the MPI-I/O mechanism, and multi-threaded I/O operations have been realized. The newly implemented MPI-I/O mechanism has been evaluated on inter-connected PC clusters, and higher overlap of the computation with the I/O operations has been achieved.