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Date: Thu, 27 Mar 2014 19:12:45 +0100
From: Jilles Tjoelker <jilles@stack.nl>
To: Warner Losh <imp@bsdimp.com>
Subject: Re: svn commit: r263778 - in head: bin lib lib/clang sbin share/mk
 usr.bin usr.sbin
Message-ID: <20140327181245.GA69977@stack.nl>
References: <201403262230.s2QMUdH6021943@svn.freebsd.org>
 <AA90F6B0-3A7A-473D-82C2-CFDFD263E9AC@gmail.com>
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Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org,
 src-committers@freebsd.org, Dimitry Andric <dim@freebsd.org>
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On Thu, Mar 27, 2014 at 11:05:00AM -0600, Warner Losh wrote:
> On Mar 26, 2014, at 4:30 PM, Dimitry Andric <dim@freebsd.org> wrote:
> > Author: dim
> > Date: Wed Mar 26 22:30:38 2014
> > New Revision: 263778
> > URL: http://svnweb.freebsd.org/changeset/base/263778

> > Log:
> >  Add a SUBDIR_PARALLEL option to bsd.subdir.mk, to allow make to process
> >  all the SUBDIR entries in parallel, instead of serially.  Apply this
> >  option to a selected number of Makefiles, which can greatly speed up the
> >  build on multi-core machines, when using make -j.

> >  This can be extended to more Makefiles later on, whenever they are
> >  verified to work correctly with parallel building.

> Why not have this ‘opt out’ rather than ‘opt in’ like it is now? Are
> there any known bad dependencies this introduces?

I'm paranoid about build systems ;) It is easy to add dependencies
across directories and as long as directories are built in sequence,
nothing goes wrong.

In fact, I had enabled SUBDIR_PARALLEL in sys/modules/Makefile as well,
but this caused mysterious failures with some kernels such as mips
ADM5120.

-- 
Jilles Tjoelker