Xref: utzoo comp.lang.misc:5445 comp.unix.wizards:23734
Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!wuarchive!zaphod.mps.ohio-state.edu!usc!snorkelwacker!apple!uokmax!occrsh!att!cbnewsl!bdsz
From: bdsz@cbnewsl.att.com (bruce.d.szablak)
Newsgroups: comp.lang.misc,comp.unix.wizards
Subject: Re: UNIX semantics do permit full support for asynchronous I/O
Keywords: Buffered I/O, paging, swapping, asynch I/O
Message-ID: <1990Aug30.153902.12686@cbnewsl.att.com>
Date: 30 Aug 90 15:39:02 GMT
References: <126800008@.Prime.COM> <60345@lanl.gov> <1990Aug29.170931.10853@terminator.cc.umich.edu>
Distribution: usa
Organization: AT&T Bell Laboratories
Lines: 11

In article <1990Aug29.170931.10853@terminator.cc.umich.edu>, rsc@merit.edu (Richard Conto) writes:
> In article <27619@nuchat.UUCP> steve@nuchat.UUCP (Steve Nuchia) writes:
> >Have read(2) and write(2) calls map the pages containing the buffers
> >out of the user address space and return immediately.
>  
> A buffer is not necessarily aligned on a page boundary. And a page
> may contain more than one variable.

Actually, the OS only has to mark the pages as copy on write. This sort
of thing is often done when a process forks to avoid making a copy of the data
space for the child. Whether its worth it is another matter.