=head2 Problems on RHEL5/CentOS5
-There is a problem with slow performance of certain DBIx::Class
-operations in perl-5.8.8-10 and later on RedHat and related systems, due
-to a bad backport of a "use overload" related bug. The problem is in the
-Perl binary itself, not in DBIx::Class. If your system might suffer this
-problem, you will see a warning on startup, with some options as to what
-to do about it. This problem was eliminated in the perl-5.8.8-15.el5_2.1
-package which was issued in September 2008.
+There used to be an issue with the system perl on Red Hat Enterprise
+Linux 5, some versions of Fedora and derived systems. Further
+information on this can be found in L<DBIx::Class::Manual::Troubleshooting>
=head1 SEE ALSO
... ORDER BY name DESC
+=head2 Perl Performance Issues on Red Hat Systems
+
+There is a problem with slow performance of certain DBIx::Class
+operations using the system perl on some Fedora and Red Hat Enterprise
+Linux system (as well as their derivative distributions such as Centos,
+White Box and Scientific Linix).
+
+Distributions affected include Fedora 5 through to Fedora 8 and RHEL5
+upto and including RHEL5 Update 2. Fedora 9 (which uses perl 5.10) has
+never been affected - this is purely a perl 5.8.8 issue.
+
+As of September 2008 the following packages are known to be fixed and so
+free of this performance issue (this means all Fedora and RHEL5 systems
+with full current updates will not be subject to this problem):-
+
+ Fedora 8 - perl-5.8.8-41.fc8
+ RHEL5 - perl-5.8.8-15.el5_2.1
+
+The issue is due to perl doing an exhaustive search of blessed objects
+under certain circumstances. The problem shows up as performance
+degredation exponential to the number of L<DBIx::Class> row objects in
+memory, so can be unoticeable with certain data sets, but with huge
+performance impacts on other datasets.
+
+A pair of tests for susceptability to the issue, and performance effects
+of the bless/overload problem can be found in the L<DBIx::Class> test
+suite in the file C<t/99rh_perl_perf_bug.t>
+
+Further information on this issue can be found in
+L<https://bugzilla.redhat.com/show_bug.cgi?id=379791>,
+L<https://bugzilla.redhat.com/show_bug.cgi?id=460308> and
+L<http://rhn.redhat.com/errata/RHBA-2008-0876.html>
+
=cut
package DBIx::Class::StartupCheck;
-BEGIN {
-
- { package # don't want this in PAUSE
- TestRHBug; use overload bool => sub { 0 } }
-
- sub _has_bug_34925 {
- my %thing;
- my $r1 = \%thing;
- my $r2 = \%thing;
- bless $r1 => 'TestRHBug';
- return !!$r2;
- }
-
- sub _possibly_has_bad_overload_performance {
- return $] < 5.008009 && ! _has_bug_34925();
- }
-
- unless ($ENV{DBIC_NO_WARN_BAD_PERL}) {
- if (_possibly_has_bad_overload_performance()) {
- print STDERR "\n\nWARNING: " . __PACKAGE__ . ": This version of Perl is likely to exhibit\n" .
- "extremely slow performance for certain critical operations.\n" .
- "Please consider recompiling Perl. For more information, see\n" .
- "https://bugzilla.redhat.com/show_bug.cgi?id=196836 and/or\n" .
- "http://lists.scsys.co.uk/pipermail/dbix-class/2007-October/005119.html.\n" .
- "You can suppress this message by setting DBIC_NO_WARN_BAD_PERL=1 in your\n" .
- "environment.\n\n";
- }
- }
-}
-
=head1 NAME
DBIx::Class::StartupCheck - Run environment checks on startup
=head1 DESCRIPTION
-Currently this module checks for, and if necessary issues a warning for, a
-particular bug found on RedHat systems from perl-5.8.8-10 and up. Other checks
-may be added from time to time.
+This module used to check for, and if necessary issue a warning for, a
+particular bug found on Red Hat and Fedora systems using their system
+perl build. As of September 2008 there are fixed versions of perl for
+all current Red Hat and Fedora distributions, but the old check still
+triggers, incorrectly flagging those versions of perl to be buggy. A
+more comprehensive check has been moved into the test suite in
+C<t/99rh_perl_perf_bug.t> and further information about the bug has been
+put in L<DBIx::Class::Manual::Troubleshooting>
+
+Other checks may be added from time to time.
Any checks herein can be disabled by setting an appropriate environment
-variable. If your system suffers from a particular bug, you will get a warning
-message on startup sent to STDERR, explaining what to do about it and how to
-suppress the message. If you don't see any messages, you have nothing to worry
-about.
+variable. If your system suffers from a particular bug, you will get a
+warning message on startup sent to STDERR, explaining what to do about
+it and how to suppress the message. If you don't see any messages, you
+have nothing to worry about.
=head1 CONTRIBUTORS
--- /dev/null
+#!/usr/bin/perl
+use strict;
+use warnings;
+use Test::More;
+use lib qw(t/lib);
+use DBICTest;
+
+# This is a rather unusual test.
+# It does not test any aspect of DBIx::Class, but instead tests the
+# perl installation this is being run under to see if it is:-
+# 1. Potentially affected by a RH perl build bug
+# 2. If so we do a performance test for the effect of
+# that bug.
+#
+# You can skip these tests by setting the DBIC_NO_WARN_BAD_PERL env
+# variable
+#
+# If these tests fail then please read the section titled
+# Perl Performance Issues on Red Hat Systems in
+# L<DBIx::Class::Manual::Troubleshooting>
+
+plan skip_all =>
+ 'Skipping RH perl performance bug tests as DBIC_NO_WARN_BAD_PERL set'
+ if ( $ENV{DBIC_NO_WARN_BAD_PERL} );
+
+eval "use Benchmark";
+plan skip_all => 'needs Benchmark for testing' if $@;
+
+plan tests => 2;
+
+{
+ package # don't want this in PAUSE
+ TestRHBug;
+ use overload bool => sub { 0 }
+}
+
+sub _has_bug_34925 {
+ my %thing;
+ my $r1 = \%thing;
+ my $r2 = \%thing;
+ bless $r1 => 'TestRHBug';
+ return !!$r2;
+}
+
+sub _possibly_has_bad_overload_performance {
+ return $] < 5.008009 && !_has_bug_34925();
+}
+
+ok( !_possibly_has_bad_overload_performance(),
+ 'Checking not susceptable to bless/overload performance problem' );
+
+my $results = timethese(
+ 0,
+ {
+ overload => sub {
+ use overload q(<) => sub { };
+ my %h;
+ for ( my $i = 0 ; $i < 5000 ; $i++ ) {
+ $h{$i} = bless [] => 'main';
+ }
+ },
+ nooverload => sub {
+ my %h;
+ for ( my $i = 0 ; $i < 5000 ; $i++ ) {
+ $h{$i} = bless [] => 'main';
+ }
+ }
+ }
+);
+
+ok( ( ( $results->{nooverload}->iters / $results->{overload}->iters ) < 2 ),
+ 'Overload/bless performance acceptable' )
projects / dbsrgits/DBIx-Class.git / commitdiff