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https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196836
Summary: perl-5.8.8-5 is 30X slower than perl-5.8.8-4 Product: Fedora Core Version: fc5 Platform: i386 OS/Version: Linux Status: NEW Severity: high Priority: normal Component: perl AssignedTo: jvdias@redhat.com ReportedBy: ckuskie@sterlink.net QAContact: dkl@redhat.com CC: fedora-perl-devel-list@redhat.com
Description of problem:
I write and maintain tests for WebGUI, and after upgrading my laptop (running FC5) on June 17th I noticed a huge slowdown in performance in the tests.
From the list of upgraded packages, I traced it down to perl
itself.
Here's data before and after a downgrade back to perl-5.8.8-4:
[colink@redwall t]$ rpm -qf /usr/bin/prove perl-5.8.8-5 [colink@redwall t]$ prove --timer i18n/label.t i18n/label....ok 1125.916s All tests successful. Files=1, Tests=6470, 1125 wallclock secs (1068.49 cusr + 1.27 csys = 1069.76 CPU) [colink@redwall t]$ rpm -qf /usr/bin/prove perl-5.8.8-4 [colink@redwall t]$ !prove prove --timer i18n/label.t i18n/label....ok 38.331s All tests successful. Files=1, Tests=6470, 39 wallclock secs (36.92 cusr + 0.47 csys = 37.39 CPU)
1125/39 =~ 30
Version-Release number of selected component (if applicable): perl-5.8.8-5
How reproducible: Every time.
Steps to Reproduce: 1. Install perl-5.8.8-5 2. Huge slowdown in perl. 3.
Additional info:
The test with the most slowdown uses the Text::Balanced module.
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Summary: perl-5.8.8-5 is 30X slower than perl-5.8.8-4
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196836
jc@oreo.nl changed:
What |Removed |Added ---------------------------------------------------------------------------- CC| |jc@oreo.nl
------- Additional Comments From jc@oreo.nl 2006-06-28 09:25 EST ------- I can confirm this for the X86_64 version. I Use Slim Devices' slimserver (slimserver-6.2.2-1) runs somewhere 20 times faster when just switching between versions perl-5.8.8-4 and perl-5.8.8-5 (and no other rpms are updated) with the perl-5.8.8-5 version being the slower one. Other perl related RPMs I have installed: perl-Digest-SHA1-2.11-1.2 perl-XML-Parser-2.34-6.1.2.2 perl-SGMLSpm-1.03ii-16.2 mod_perl-2.0.2-5.1 perl-Digest-HMAC-1.01-14.2 perl-BSD-Resource-1.24-3.2.2 newt-perl-1.08-9.2.1 perl-Compress-Zlib-1.41-1.2.2 perl-Net-DNS-0.57-1 perl-String-CRC32-1.4-1.FC5 perl-DBI-1.50-2.2 perl-Net-IP-1.24-2.2 perl-libwww-perl-5.805-1.1 perl-HTML-Parser-3.51-1.FC5 perl-DBD-MySQL-3.0004-1.FC5 perl-5.8.8-4 perl-URI-1.35-2.2 perl-HTML-Tagset-3.10-2.1
I am not a perl hacker (I do more in C++ and python), but I am more than willing to provide any trace data that I could generate.
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Summary: perl-5.8.8-5 is 30X slower than perl-5.8.8-4
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196836
------- Additional Comments From jvdias@redhat.com 2006-07-14 18:39 EST ------- Created an attachment (id=132469) --> (https://bugzilla.redhat.com/bugzilla/attachment.cgi?id=132469&action=vie...) Results of perlbench-0.93 when run for perl-5.8.8-5 and perl-5.8.8-4 on a dual processor i386 FC-5 machine
The attached perlbench log shows that the performance of perl-5.8.8-4 compared to perl-5.8.8-5 is virtually identical for common perl operations . Perlbench is a standard benchmark test for perl.
Yes, I have duplicated the severe performance loss when running the WebGUI t/i18n/label.t test.
Reblessing overloaded objects now incurs a performance penalty in 5.8.8-5+ : this is due to the fix for perlbug #34925 'overload and rebless': http://rt.perl.org/rt3/Ticket/Display.html?id=34925 The fix for this bug (change 27512) involves a 'brute force approach' to detect overloaded objects that are then reblessed; the performance penalty is proportional to the number of active scalars in the perl program.
Testing 5.8.8-5 compiled without the 'perl-5.8.8-U27512.patch' applied shows no performance loss when running the WebGUI t/i118n/label.t test over 5.8.8-4 - the 27512 patch is definitely the cause.
Perlbug 34925 severely affects the CPAN DBI::Class module.
As reblessing an overloaded object is quite rare, the brute force approach was deemed acceptable by the upstream perl maintainers, who have applied this overload and rebless detection mechanism to the current maintenance release of perl.
In the upstream 'blead' perl 5.9.4, a fix with no adverse performance impact was applied (change # 27506), but this introduces binary incompatibilities which impact mod_perl; one cannot apply this fix to the 5.8.x releases without
introducing major binary incompatibilities, and I've not been able to see an alternative fix (in 5.8.8, every SV_f* flag bit is already used - in 5.9.4, they've changed the meaning of the flag bits and reserved one to flag the case of overload and rebless).
So, I think we'll have to accept the performance tradeoff for correct operation in the presence of overload and rebless, until perl-5.9.x is released as the stable version of perl-5.
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Summary: perl-5.8.8-5 is 30X slower than perl-5.8.8-4
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196836
------- Additional Comments From stephenclouse@gmail.com 2006-08-22 07:45 EST ------- The real problem seems to be that patch 27512 breaks more than it fixes. I believe the patch itself is bugged; the brute force search seems to be triggering in cases where it doesn't seem to be necessary.
I have a project internal to my employer that makes heavy use of the DateTime module, which was significantly affected by this patch. DateTime does overload but not reblessing, but the search is still triggered (for no apparent reason) whenever the ->clone method is called, even though there's no reason for it (a completely new reference is created by ->clone, it does *not* rebless anything).
DBIx::Class is also bitten by this; see http://forums.slimdevices.com/showpost.php?p=123372&postcount=20
Personally I think this patch needs more testing from upstream before it goes into a stable line update to Fedora.
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Summary: perl-5.8.8-5 is 30X slower than perl-5.8.8-4
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196836
rnorwood@redhat.com changed:
What |Removed |Added ---------------------------------------------------------------------------- AssignedTo|jvdias@redhat.com |rnorwood@redhat.com
------- Additional Comments From rnorwood@redhat.com 2006-08-22 17:21 EST ------- Reopened - assigning to me to keep an eye on this issue.
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Summary: perl-5.8.8-5 is 30X slower than perl-5.8.8-4
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196836
chrismcc@pricegrabber.com changed:
What |Removed |Added ---------------------------------------------------------------------------- CC| |chrismcc@pricegrabber.com
------- Additional Comments From chrismcc@pricegrabber.com 2007-01-12 16:18 EST ------- This shows up in RHEL5 also.
Would another bug be better, or ... overload this one :)
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Summary: perl-5.8.8-5 is 30X slower than perl-5.8.8-4
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196836
bugzilla@redhat.com changed:
What |Removed |Added ---------------------------------------------------------------------------- Priority|normal |medium Product|Fedora Core |Fedora
buribullet@gmail.com changed:
What |Removed |Added ---------------------------------------------------------------------------- CC| |buribullet@gmail.com
------- Additional Comments From buribullet@gmail.com 2007-06-19 19:07 EST ------- perl-5.8.8-10 is 1000X slower! (It seems like O(2^n) slowdown where n is number of onmemory SV) Please rethink. It can kill real apps. (Or Fedora/RedHat is not for Perl?)
# Here is simple benchmark, borrowed and modified from # http://blog.yappo.jp/yappo/archives/000515.html
use Benchmark; timethese(shift || 100000, { 'overload' => sub { push our @array, TestOverload->new }, 'not overload' => sub { push our @array, TestNoverload->new }, });
package TestNoverload; sub new { bless { hoge => 'hoge' }, shift }
package TestOverload; use overload ( q{""} => sub {}, ); sub new { bless { hoge => 'hoge' }, shift }
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Summary: perl-5.8.8-5 is 30X slower than perl-5.8.8-4
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196836
------- Additional Comments From steve@silug.org 2007-06-20 13:07 EST ------- FWIW, I just verified that perl-5.8.8-18.fc7 still has this problem, but a fresh compile of 5.9.4 doesn't.
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Summary: perl-5.8.8-5 is 30X slower than perl-5.8.8-4
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196836
------- Additional Comments From buribullet@gmail.com 2007-06-21 03:26 EST ------- It was not O(2^n) but O(n^2), sorry. See following plot(n=10000 .. 100000)
http://buribullet.net/svntrac/buribullet/attach_get/2/fedora-perl-overload.p...
Of course this should be O(n). O(n^2) for this case is not acceptable overhead.
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Summary: perl-5.8.8-5 is 30X slower than perl-5.8.8-4
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196836
------- Additional Comments From rnorwood@redhat.com 2007-06-22 16:20 EST ------- This is reported upstream here:
http://rt.perl.org/rt3/Public/Bug/Display.html?id=43283
And, as it turns out, Nicholas Clark points out a patch which fixes this issue on my test system:
Benchmark: timing 100000 iterations of not overload, overload... not overload: 1 wallclock secs ( 0.48 usr + 0.24 sys = 0.72 CPU) @ 138888.89/s (n=100000) overload: 2 wallclock secs ( 0.50 usr + 0.22 sys = 0.72 CPU) @ 138888.89/s (n=100000)
Building a fixed version for rawhide/f8 - updates for F7 and FC6 should be available soon.
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Summary: perl-5.8.8-5 is 30X slower than perl-5.8.8-4
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196836
------- Additional Comments From buribullet@gmail.com 2007-06-22 23:59 EST ------- Thank you for your quick action! It will save both community of Perl and Fedora/RedHat.
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Summary: perl-5.8.8-5 is 30X slower than perl-5.8.8-4
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196836
------- Additional Comments From rnorwood@redhat.com 2007-06-23 11:49 EST ------- Update - I'm having a little trouble building the new perl - I'm still working on it, though.
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Summary: perl-5.8.8-5 is 30X slower than perl-5.8.8-4
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196836
------- Additional Comments From buribullet@gmail.com 2007-07-01 02:42 EST -------
a little trouble...
If it is so hard, simply removing U27512 & U27509 will be good enough for most of Perl users, IMHO.
# Following patch is borrowed from http://femo.jp/kazeburo/br51s0s3qh
diff -u -r1.1 perl.spec --- perl.spec 1 Jul 2007 01:47:23 -0000 1.1 +++ perl.spec 1 Jul 2007 01:50:05 -0000 @@ -5,7 +5,7 @@ %define multilib_64_archs x86_64 s390x ppc64 sparc64
%define perlver 5.8.8 -%define perlrel 10 +%define perlrel 11 %define perlepoch 4
%{?!perl_debugging: %define perl_debugging 0} @@ -160,8 +160,8 @@ Patch27116: perl-5.8.8-U27116.patch Patch27391: perl-5.8.8-U27391.patch Patch27426: perl-5.8.8-U27426.patch -Patch27509: perl-5.8.8-U27509.patch -Patch27512: perl-5.8.8-U27512.patch +#Patch27509: perl-5.8.8-U27509.patch +#Patch27512: perl-5.8.8-U27512.patch Patch27604: perl-5.8.8-U27604.patch Patch27605: perl-5.8.8-U27605.patch Patch27914: perl-5.8.8-U27914.patch @@ -367,9 +367,9 @@
%patch27426 -p1
-%patch27509 -p1 +#%patch27509 -p1
-%patch27512 -p1 +#%patch27512 -p1
%patch27604 -p1
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Summary: perl-5.8.8-5 is 30X slower than perl-5.8.8-4
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196836
rnorwood@redhat.com changed:
What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |CLOSED Resolution| |CURRENTRELEASE Fixed In Version| |perl-5.8.8-22.fc8
------- Additional Comments From rnorwood@redhat.com 2007-07-25 15:20 EST ------- This should be fixed in the latest perl in F8/rawhide: perl-5.8.8-22.fc8 or later
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Summary: perl-5.8.8-5 is 30X slower than perl-5.8.8-4
https://bugzilla.redhat.com/show_bug.cgi?id=196836
bugzilla@redhat.com changed:
What |Removed |Added ---------------------------------------------------------------------------- Version|fc5 |5
------- Additional Comments From marcos.marado@sonae.com 2007-12-12 07:36 EST ------- According to the changelog, 4:5.8.8-19 for -fc7 solves this bug, but the latest 4:5.8.8-27 still gives this warning:
WARNING: DBIx::Class::StartupCheck: This version of Perl is likely to exhibit extremely slow performance for certain critical operations. Please consider recompiling Perl. For more information, see https://bugzilla.redhat.com/show_bug.cgi?id=196836 and/or http://lists.scsys.co.uk/pipermail/dbix-class/2007-October/005119.html. You can suppress this message by setting DBIC_NO_WARN_BAD_PERL=1 in your environment.
Any ideas?
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Summary: perl-5.8.8-5 is 30X slower than perl-5.8.8-4
https://bugzilla.redhat.com/show_bug.cgi?id=196836
------- Additional Comments From cweyl@alumni.drew.edu 2007-12-12 11:43 EST ------- Following through that thread, and looking at the source of DBIC::StartupCheck, it appears that it's more of a "MAY" than definite, and that DBIC::StartupClass doesn't know how to check to see if the particular patches have been applied. (AFAICT at least.)
I have DBIx::Class up for review (bug perl-DBIx-Class); if we can verify that indeed Fedora perl has the correct fixes in place (which it does sound like it does) then hopefully we can:
1. override DBIC::StartupCheck's logic in Fedora's packages, until #2 2. create and funnel logic upstream that accurately figures out if this has been applied... Note that this needs to be a near no-op, as these checks are run everytime DBIC is use'd.
perl-devel@lists.fedoraproject.org
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