Re: Should raw I/O be added to the kernel?

Alan Cox (alan@lxorguk.ukuu.org.uk)
Fri, 18 Dec 1998 16:42:20 +0000 (GMT)

> other OS's for the sake of specific user needs; it makes sense to me that
> certain types of development may take longer [i.e. the development of an
> appropriate high-performance filesystem for Video I/O] but may be more
> successful than they would have been had raw I/O been introduced into the
> mainstream kernel. Then we would have applications crashing the system
> as currently happens with many other OS's.

The point of the raw I/O (be it sendfile, O_DIRECT or otherwise) is to provide
hooks that allow programs to safely access I/O without some of the existing
overhead in specific cases where the program knows best.

Its not about giving direct access to the hardware. O_DIRECT says "This isnt
worth caching, and please get it here efficiently". It doesnt say "excuse me
I want to take over the disk controller".

Alan

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/