And even then mmap does not guarantee performance. So for example just don't use mmap for small files, and for larger ones benchmark to see if you really get so

And even then mmap does not guarantee performance. So for example just don't use mmap for small files, and for larger ones benchmark to see if you really get some perf. As for the code, if you just can let it crash, prefer that to attempting to handle it, because this kind of handling is even worse to test and debug than normal error code paths.