_CRT_DISABLE_PERFCRIT_LOCKS
Disables performance-critical locking in I/O operations.
#define _CRT_DISABLE_PERFCRIT_LOCKS
Remarks
Defining this symbol can improve performance in single-threaded I/O-bound programs by forcing all I/O operations to assume a single-threaded I/O model. For more information, see Multithreaded Libraries Performance.