perl bless/overload performance problem on RHEL

Nicholas Clark nick at
Mon Sep 1 10:16:42 BST 2008

On Mon, Sep 01, 2008 at 07:52:51AM +0100, Dave Cross wrote:
> Elliot Moore wrote:
> > 
> > May interest anyone running stock perl on Red Hat 5, Centos 5, or Fedora 9
> > 
> >
> > 
> >  (
> AIUI, the problem is with their builds of 5.8.8 - which is in current
> versions of RHEL and Centos. And was in Fedora 8.
> Fedora 9 contains a build of 5.10.0 which doesn't seem to exhibit this
> problem.

No, the code is different. Full explanation here:

Wishful thinking fix suggestion here:

Slashdot covers it here:

What RedHat did, and why - your guess is as good as mine. But anyone
commenting about the source, cause, or intent of code changes to the
Perl core itself that is in disagreement with what I typed in is wrong.

I wrote *all* the code in question. I should know.

(Both the code in the trunk (that became 5.10.0) and the code in the 5.8.x.
The code that is now in 5.10 is different, and is the conceptually correct
fix to the underlying problem. It can be different, because it involves an
incompatible change in the semantics of SV flag bits. It doesn't actually
involve changing the values of flag bits, so at first glance it doesn't look
binary incompatible. I don't have access to anything running Fedora 9 (or
Fedora anything else) but my understanding is that they have a very clean
build of 5.10.0, so it follows that it cannot have this problem.)

Nicholas Clark

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