Re: [PATCH] validate_abi: build faster by augmenting make with job count

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2016-07-20 19:47, Wiles, Keith:
> On Jul 20, 2016, at 12:48 PM, Neil Horman <nhorman@redhat.com> wrote:
> > On Wed, Jul 20, 2016 at 07:40:49PM +0200, Thomas Monjalon wrote:
> >> 2016-07-20 13:09, Neil Horman:
> >>> From: Neil Horman <nhorman@redhat.com>
> >>> +if [ -z "$MAKE_JOBS" ]
> >>> +then
> >>> +	# This counts the number of cpus on the system
> >>> +	MAKE_JOBS=`lscpu -p=cpu | grep -v "#" | wc -l`
> >>> +fi
> >> 
> >> Is lscpu common enough?
> >> 
> > I'm not sure how to answer that.  lscpu is part of the util-linux package, which
> > is part of any base install.  Theres a variant for BSD, but I'm not sure how
> > common it is there.
> > Neil
> > 
> >> Another acceptable default would be just "-j" without any number.
> >> It would make the number of jobs unlimited.
> 
> I think the best is just use -j as it tries to use the correct number of jobs based on the number of cores, right?

No Keith, -j alone use as much jobs as it can create, i.e. much more than
the number of CPUs.
I have no measure but I remember it is less efficient than giving a number
based on available CPUs (with a multiply factor to avoid idling between jobs).
For a default value, both approaches are fine.