Re: File System Performance

[Linus Torvalds]

On Mon, 12 Nov 2001, Lionel Bouton wrote:
>
> Seems not the case with gnu tar : write isn't even called once on the fd
> returned by open("/dev/null",...). In fact a "grep write" on the strace
> output is empty in the "tar cf /dev/null" case. Every file in the tar-ed
> tree is stat-ed but no-one is read-ed.

Wow. What a sleazy optimization - it can't be anything but a special case.

How do they do it anyway? By matching on the name Or by knowing what the
minor/major numbers of /dev/null are supposed to be on that particular
operating system?

And what's the _point_ of the optimization? I've never heard of a "tar
benchmark"..

		Linus