Date: Wed, 17 May 2006 16:15:28 +1000 From: Paul Koch <paul.koch@statseeker.com> To: vd@FreeBSD.org Cc: ports@FreeBSD.org, Edwin Groothuis <edwin@mavetju.org> Subject: Re: Is it safe to compile multiple ports at the same time ? Message-ID: <200605171615.29000.paul.koch@statseeker.com> In-Reply-To: <20060517060026.GA40653@qlovarnika.bg.datamax> References: <200605171353.37745.paul.koch@statseeker.com> <200605171508.07228.paul.koch@statseeker.com> <20060517060026.GA40653@qlovarnika.bg.datamax>
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> > So.... it would be nice to have some type of locking in the ports
> > build. For example, when a make enters
> > /usr/ports/{category}/{port}, it gets an exclusive lock on that
> > port (maybe on the Makefile itself, or a specific lock file) before
> > it attempts to build/install the port. It could be done by using
> > lockf, but that just forks more processes, and there are already
> > lots of them. I'd dare to say.... maybe it could be a function of
> > make itself. As in, extend make so it understands a new keyword
> > that makes it get an exclusive lock, using flock(2).
> >
> > With locking, you should then be able to fire off lots of port
> > builds and use up all those cpu cores :)
>
> Not really, locking will just prevent breakages. Let me illustrate my
> thought with an example:
>
> port A depends on X
> port B depends on X
>
> You start building A which results in building X via exclusive lock
> on X. During the build of X you decide to build B which results in
> building X (X is not yet installed) but you block trying to acquire
> the exclusive lock on X so you wait _idling_ until building of X is
> done. Furthermore what do you suggest to do when the lock is
> released?
>
> Ofcourse if B depends also on Y it can fallback to building Y if it
> cannot gain exclusive lock on X.
Yes, breakage is the main problem.
When the lock is released, then the second make will immediately see
work/.build_done.XXXXXXX is present ??, then return successfully to the
make which called it. I haven't looked to see how it works under the
hood though.
Yep, in your example above, it won't be any faster. But what if I want
to do something like:
port A depends on Q R S T X
port B depends on D E F G X
then lots of simultaneous building can occur until they both hit port X.
Paul.
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