Date: Thu, 23 Nov 2006 16:30:02 -0800 From: Jason Evans <jasone@FreeBSD.org> To: John Birrell <jb@what-creek.com> Cc: arch@freebsd.org Subject: Re: Proposed change to make -j Message-ID: <45663D0A.7010508@FreeBSD.org> In-Reply-To: <20061123232035.GA56985@what-creek.com> References: <20061123232035.GA56985@what-creek.com>
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John Birrell wrote: > Currently 'make -j' reports an error if the number of jobs > isn't specified. > > I'd like to change make(1) to treat -j (without a number) as > meaning "set the number of jobs to the number of processors". > > On sun4v, each processor isn't too powerful and system performance > is only decent when you use all the processors - 32 in my case. > > I've been working on a parallel 'make release' process which > would benefit from having -j set by default. At the moment I > set MAKEFLAGS=j32 in my environment and this achieves the desired > result, but -j would be more general. For gmake, a bare -j says to not limit the number of simultaneous jobs. I don't think that it's a good idea to use a flag name that already has a different (and potentially useful) meaning for gmake. I have some concern that no matter what number of jobs you decide to run simultaneously when your proposed flag is specified (N, N+1, 2N, etc., where N is the number of CPUs), that choice will not be universally useful, since the best choice of argument to -j depends on what 'make' is building. Might it be better to use sysctl(8) in your command line? make -j `sysctl -n hw.ncpu` Jason
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