Bug#663762: debian-policy: default for DEB_BUILD_OPTIONS=parallel=N
On Sun, 25 Mar 2012, Bill Allombert wrote:
> On Sun, Mar 25, 2012 at 09:18:18AM +1030, Ron wrote:
> > On Sat, Mar 17, 2012 at 04:55:19PM -0700, Russ Allbery wrote:
> > > Jakub Wilk <jwilk@debian.org> writes:
> > >
> > > > How should packages behave if there is no explicit "parallel=N" in
> > > > DEB_BUILD_OPTIONS? I saw two different approaches:
> > >
> > > > 1) Behave (roughly) like if parallel=1 was set.
> > >
> > > > 2) Be clever and try to guess the "right" level of parallelism, e.g. by
> > > > using "getconf _NPROCESSORS_ONLN" or parsing /proc/cpuinfo (ugh!).
>
> On an hyperthreaded system, "getconf _NPROCESSORS_ONLN" return the number of threads
> and not the number of cores, so it is not always what the user want.
IMO, this is best left for the local admin. Guessing this kind of stuff
right in every arch is a very hard problem, and the safe choice [which
doesn't break any package builds] is to not do a parallel build at all.
For the record: if you ever thought about using crap like "getconf
_NPROCESSORS_ONLN" for anything, you will probably benefit from looking at
the hwloc and libhwloc* packages.
--
"One disk to rule them all, One disk to find them. One disk to bring
them all and in the darkness grind them. In the Land of Redmond
where the shadows lie." -- The Silicon Valley Tarot
Henrique Holschuh
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