I&#x27;m well aware of this, there is a set of benchmarks in lmbench, which I wrote, that shows something similar to what you are talking about.  I called it open to close performance and it plotted the MB&#x2F;sec as a function of file size for read&#x2F;write vs mmap.<p>One would think that mmap is faster because it does less work but that&#x27;s not true if you include the open&#x2F;mmap, read is always fast in that case (which is surprising to me, it used to be that there was a cross over point).<p>But your whole comment sort of misses the point of sendfile.  If you are doing little file transfers, use read&#x2F;write, they are fine.  The overhead of the syscalls matter if the size is small.  But sendfile is for big data and there the limit, of perf, as the size goes to infinity, is 2x.