[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: make -j in Debian packages

On Wed, Jun 28, 2006 at 12:01:31PM +0200, Adam Borowski wrote:
> On Wed, Jun 28, 2006 at 02:06:26AM -0700, Don Armstrong wrote:
> > This has the disadvantage of not automatically using -j for every
> > package and requiring maintainer buy in to see results... but
> > presumably those packages where it actually makes a difference will
> > adopt it just so maintainer builds don't take as long.
> Why would you restrict this just to maintainer builds?  Speeding up
> buildds and user builds would be a worthy goal, too.

"Speeding up" buildds through uninvited make -j is certainly _not_ a
worty goal, simply because you can't do that properly.

SMP buildd systems currently run multiple instances of buildd at the
same time, rather than expecting a package to specify make -j itself.
Having three packages that specify 'make -j 4' on a multiprocessor
buildd host that _already_ runs six builds in parallel is going to be

While parallel builds can indeed help speed up things even on
uniprocessor systems, they do this at a price; they require a _lot_ more
RAM than non-parallel builds. A uniprocessor parallel build will go
faster for as long as your buffercaches can keep make, the compiler, and
the most often used header files in memory; as soon as those need to be
swapped out, your performance will go down dramatically. Since not all
machines have the same amount of RAM, it is impossible to say in a
generic way when this point is going to be.

In any case, I have nothing against doing parallel builds by default (at
least, not as long as it can be properly disabled and regulated), but do
not claim that it's a good thing "also for the buildd's", because you
are sadly mistaken.

Fun will now commence
  -- Seven Of Nine, "Ashes to Ashes", stardate 53679.4

Attachment: signature.asc
Description: Digital signature

Reply to: