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Re: A sick idea - mmapped file output
On Sun, Nov 05, 2000 at 07:29:19PM -0700, Jeffrey A Law wrote:
> In message <Pine.GSO.4.21.0011030702120.19361-100000@platon>you write:
> > Hi,
> >
> > On Thu, 2 Nov 2000, Zack Weinberg wrote:
> > >
> > > However, you can anticipate running off the end and extend the file
> > > with ftruncate. POSIX and SUS don't guarantee that this works, but
> > > assuming it does, this is indeed faster than write(2) - until you run
> > > out of mapping, at which point you have a problem. Or, even cleverer,
> > > you can catch the signal and extend it then, but this doesn't seem to
> > > be any faster than anticipating the end (not surprising; signals ain't
> > > cheap).
> >
> > Hmm, although it's not really clear if there is a benefit in real
> > situations (like compiling a program with optimizations ;-) ), there is
> > also not a real reason why we shouldn't do it if we can (and the system
> > supports it).
> I disagree strongly.
>
> What Zack is effectively proposing is that we code to specific features
> of implementations instead of a standard. ie, if the spec doesn't spell
> this out as defined behavior, then we should not use it.
The idea's been beaten to death, now. I was blaming the kernel for
stdio's problems. Neil said he was going to do something with
direct-to-write, and we've got the integrated preprocessor going so we
aren't doing I/O anymore.
zw