Hi It seems the recent commit 2c3e17be ('filesetup: add native fallocate') breaks on Cygwin. It works on FreeBSD by the way. --- $ uname CYGWIN_NT-10.0 $ ./fio --name=xxx --ioengine=sync --rw=read --bs=4k --size=1m fio: this platform does not support process shared mutexes, forcing use of threads. Use the 'thread' option to get rid of this warning. xxx: (g=0): rw=read, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=sync, iodepth=1 fio-2.21-80-g2c3e Starting 1 thread This application has requested the Runtime to terminate it in an unusual way. Please contact the application's support team for more information. xxx: Laying out IO file (1 file / 1MiB) fio: unknown fallocate mode: 0 Assertion failed! -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html