When loading Ruby source files, we can save the result of successful opens as open(2)/openat(2) are a fairly expensive syscalls. This also avoids a time-of-check-to-time-of-use (TOCTTOU) problem. This reduces open(2) syscalls during `require'; but should be most apparent when users have a small $LOAD_PATH. Users with large $LOAD_PATH will benefit less since there'll be more open(2) failures due to ENOENT. With `strace -c -e openat ruby -e exit' under Linux, this results in a ~14% reduction of openat(2) syscalls (glibc uses openat(2) to implement open(2)). % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 0.00 0.000000 0 296 110 openat 0.00 0.000000 0 254 110 openat Additionally, the introduction of `struct ruby_file_load_state' may make future optimizations more apparent. This change cannot benefit binary (.so) loading since the dlopen(3) API requires a filename and I'm not aware of an alternative that takes a pre-existing FD. In typical situations, Ruby source files outnumber the mount of .so files.