start building thread support for lang/perl5.12 by default

[Tom Hukins]

On Thu, Oct 21, 2010 at 04:52:20PM +0200, Emanuel Haupt wrote:
> May I suggest to start enabling thread support for lang/perl5.12 by
> default. While thread support was considered unstable for a long time
> it has become more stable with perl 5.12.

I suggest we keep the default of not supporting threaded applications.

The stability of threads doesn't matter: applications written in Perl
either need them or they don't.  If an application doesn't need
threads it won't encounter thread-related instability.  If an
application needs threads, it needs them.

Any perl binary built with threading support runs slower than a
comparable binary without threading support regardless
of whether an application uses threads or not.  Shipping a
thread-enabled perl by default will cause users' applications to run
slower by default.

Specific applications or ports that need threads can install a
threaded perl port or package.

> Finally, many Linux distributions have started to ship perl with thread
> support by default (eg. RHEL5).

We use RedHat at work and build our own perl binary largely to avoid
the slowness of threaded perls.  We also build with PERL_DISABLE_PMC
and NO_MATHOMS for further performance improvements.  One of my
colleagues is an ex-pumpking and has benchmarked these although he
doesn't have any numbers to hand.

Tom