Re: PATCH: Raw device IO for 2.1.131
Matthias Urlichs (smurf@noris.de)
14 Dec 1998 17:23:43 +0100
Jes Sorensen <Jes.Sorensen@cern.ch> writes:
> >>>>> "Richard" == Richard Gooch <rgooch@atnf.csiro.au> writes:
>
> No most of our applications do read(filefd), write(sockfd) and as
> such it could probably be done with sendfile, the main issue is that
> it requires rewriting the code as a special case for Linux.
>
Note that if you have a page-aligned buffer and do a page-aligned read, the
kernel is / should be (don't ask me...) clever enough to toss your existing
page entirely and to map the appropriate page from the file into your space
(copy-on-write, of course). That gives you a zero-copy read, at least.
In fact, the stdio implementation in glibc was explicitly changed to
support this.
--
Matthias Urlichs | noris network GmbH | smurf@noris.de | ICQ: 20193661
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