> Because that's what benchmarks and real production use of some
> applications with and without direct io show :-)  I don't think
> "cp" is such a good example though, since you lose the readahead.
yes it is. option -D<size> should do copy with direct I/O and given buffer
size (1MB should be ok for modern disk)


> For some (typically database-like) apps it can be a pretty big boost

and: gimp (tempfile), movies, audio editors, everything operating on LARGE
files


> Disclaimer:  We've actually *measured* the performance difference
> for our app only on FreeBSD, Windows, Solaris, and Linux, AFAIK.