matthew@wil.cx (Matthew Wilcox) wrote on 24.08.00 in <20000824155345.I29677@vodka.thepuffingroup.com>:
> On Thu, Aug 24, 2000 at 08:18:00PM +0200, Kai Henningsen wrote:
> > yodaiken@fsmlabs.com wrote on 23.08.00 in
> > > <20000823172504.A733@hq.fsmlabs.com>: Linux processes are more
> > > lightweight than "threads" on many operating systems. As Rob Pike
> > > pointed out many years ago: a perceived need for "threads" means that
> > > processes are poorly designed.
> >
> > *Only* if the perceived need comes from performance issues.
> >
> > Threads are a rather nice programming abstraction *if used right*, and
> > processes (i.e. threads without shared memory) certainly aren't a
> > reasonable replacement, just as you wouldn't want to replace subroutines
> > with processes.
>
> i think you're misunderstanding pike's point. it is that you don't want
> to have threads because processes are too heavyweight, rather you should
> make processes less heavyweight. sharing VMs between processes is a more
> generally useful feature and shouldn't be restrained to the notion of a
> thread. needless to say, linux's clone() model is based heavily on pike's
> insight and plan9's rfork() model.
This is nothing but word games.
As clone() demonstrates, there are lots of things that you can share
between tasks; when you actually differentiate between "processes" and
"threads", the usual definition is that the former don't share VM, whereas
the latter do.
Can you point me to the text that makes Pike's original point? Google
certainly wasn't able to help me; I mainly found a recent article about OS
research that, IMHO, made enough mistakes to be a bad introdouction to
Pike. (Unless of course the original text is similar.)
MfG Kai
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