From amcglinchy@gmail.com

This is a bug report for perl from amcglinchy@​gmail.com,
generated with the help of perlbug 1.36 running under perl 5.10.0.

When running a threaded perl program in Cygwin that relies heavily on the
split command, a massive decrease in performance has been noted over the
single threaded version. 100_000 splits of a 250 byte string goes from 2.6
seconds to 12.5 seconds when spread across multiple threads. The expected
result of a small increase in performance can be seen with the same code
against the Activestate build.

The following code can reproduce the effect.

## Test code to show split slow when used in muiltiple threads is slow in
cygwin perl
use strict;
use warnings;
use threads;
use Thread​::Queue;
use Time​::HiRes();

my $string = "12356789 "x25;
my $TASK_COUNT =10;

print( (`$^X -v`)[1]);
thread_process(1);
thread_process(4);

sub thread_process {
  my $parallel = shift;
  my $start = Time​::HiRes​::time();
  my @​threads;
  my $queue = Thread​::Queue->new();
  for my $p ( 1 .. $parallel ) {
  push @​threads, threads->create( sub {
  while( my $task_no = $queue->dequeue) {
  for my $n (1..10_000) {
  my @​x= split / /, $string;
  }
  }})
  }
  $queue->enqueue( 1 .. $TASK_COUNT , (undef) x $parallel );
  $_->join for @​threads;
  my $end= Time​::HiRes​::time();
  printf "Processing %d tasks in %d threads completed in %fsecs\n",
$TASK_COUNT, $parallel, $end-$start;
}
__END__

# Here is an example of the output on my dual core XP machine

$ ~/localperl/bin/perl.exe example.split.pl
This is perl 5, version 14, subversion 1 (v5.14.1) built for
cygwin-thread-multi-64int
Processing 10 tasks in 1 threads completed in 2.640625secs
Processing 10 tasks in 4 threads completed in 12.468637secs

$ perl example.split.pl
This is perl, v5.10.0 built for cygwin-thread-multi-64int
Processing 10 tasks in 1 threads completed in 4.578125secs
Processing 10 tasks in 4 threads completed in 25.437345secs

# The defect does not occur with ActivePerl. Instead the expected slightly
faster result occurs
$ c​:/perl/bin/perl example.split.pl
This is perl 5, version 12, subversion 3 (v5.12.3) built for
MSWin32-x86-multi-thread
Processing 10 tasks in 1 threads completed in 2.062500secs
Processing 10 tasks in 4 threads completed in 1.671790secs

Flags​:
  category=core
  severity=medium

Site configuration information for perl 5.10.0​:

Configured by rurban at Mon Jun 30 16​:03​:19 GMT 2008.

Summary of my perl5 (revision 5 version 10 subversion 0 patch 34065)
configuration​:
  Platform​:
  osname=cygwin, osvers=1.5.25(0.15642),
archname=cygwin-thread-multi-64int
  uname='cygwin_nt-5.1 reini 1.5.25(0.15642) 2008-06-12 19​:34 i686 cygwin
'
  config_args='-de -Dmksymlinks -Dusethreads -Dmad=y -Dusedevel'
  hint=recommended, useposix=true, d_sigaction=define
  useithreads=define, usemultiplicity=define
  useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
  use64bitint=define, use64bitall=undef, uselongdouble=undef
  usemymalloc=y, bincompat5005=undef
  Compiler​:
  cc='gcc', ccflags ='-DPERL_USE_SAFE_PUTENV -U__STRICT_ANSI__
-fno-strict-aliasing -pipe -I/usr/local/include',
  optimize='-O3',
  cppflags='-DPERL_USE_SAFE_PUTENV -U__STRICT_ANSI__ -fno-strict-aliasing
-pipe -I/usr/local/include'
  ccversion='', gccversion='3.4.4 (cygming special, gdc 0.12, using dmd
0.125)', gccosandvers=''
  intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=12345678
  d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
  ivtype='long long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t',
lseeksize=8
  alignbytes=8, prototype=define
  Linker and Libraries​:
  ld='g++', ldflags =' -Wl,--enable-auto-import -Wl,--export-all-symbols
-Wl,--stack,8388608 -Wl,--enable-auto-image-base -L/usr/local/lib'
  libpth=/usr/local/lib /usr/lib /lib
  libs=-lgdbm -ldb -ldl -lcrypt -lgdbm_compat
  perllibs=-ldl -lcrypt
  libc=/usr/lib/libc.a, so=dll, useshrplib=true, libperl=libperl.a
  gnulibc_version=''
  Dynamic Linking​:
  dlsrc=dl_dlopen.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' '
  cccdlflags=' ', lddlflags=' --shared -Wl,--enable-auto-import
-Wl,--export-all-symbols -Wl,--stack,8388608 -Wl,--enable-auto-image-base
-L/usr/local/lib'

Locally applied patches​:
  MAINT34065
  CYG11 no-bs
  CYG12 no archlib in otherlibdirs
  CYG14 Dynaloader
  CYG15 static-Win32CORE
  Bug#55162 File​::Spec​::case_tolerant performance

@​INC for perl 5.10.0​:
  /usr/lib/perl5/5.10/i686-cygwin
  /usr/lib/perl5/5.10
  /usr/lib/perl5/site_perl/5.10/i686-cygwin
  /usr/lib/perl5/site_perl/5.10
  /usr/lib/perl5/vendor_perl/5.10/i686-cygwin
  /usr/lib/perl5/vendor_perl/5.10
  /usr/lib/perl5/vendor_perl/5.10
  /usr/lib/perl5/site_perl/5.8
  /usr/lib/perl5/vendor_perl/5.8
  .

Environment for perl 5.10.0​:
  CYGWIN_ROOT=\cygwin
  HOME=/home/Awie
  LANG (unset)
  LANGUAGE (unset)
  LD_LIBRARY_PATH (unset)
  LOGDIR (unset)

PATH=/usr/local/bin​:/usr/bin​:/bin​:/usr/X11R6/bin​:.​:/usr/bin​:/cygdrive/c/bats/​:/cygdrive/c/Program
Files/ActiveState Perl Dev Kit
7.0/bin​:/cygdrive/c/WINDOWS/system32​:/cygdrive/c/WINDOWS​:/cygdrive/c/WINDOWS/System32/Wbem​:/cygdrive/c/Perl/site/bin​:/cygdrive/c/Perl/bin​:/cygdrive/c/Program
Files/TortoiseSVN/bin​:/cygdrive/c/bats​:/cygdrive/c/Parrot-2.5.0/bin​:/cygdrive/c/MinGW/bin​:/cygdrive/c/MySQL5.1/bin​:/cygdrive/c/Program
Files/QuickTime/QTSystem/​:/cygdrive/c/WINDOWS/system32/WindowsPowerShell/v1.0​:/usr/bin​:/usr/bin​:/usr/lib/lapack
  PERL_BADLANG (unset)
  SHELL (unset)

From @tsee

You used perl 5.10. There have been changes in recent versions of Perl
that pertain to allocation and string handling on Windows. It's a bit of
a long shot since what you are seeing involved threads specifically, but
could you maybe try using perl 5.14 to see if you can reproduce the
issue there? Just an idea.

Best regards,
Steffen

The RT System itself - Status changed from 'new' to 'open'

From amcglinchy@gmail.com

Steffen,

On 12 July 2011 08​:25, Steffen Mueller via RT <perlbug-followup@​perl.org>wrote​:

You used perl 5.10. There have been changes in recent versions of Perl
that pertain to allocation and string handling on Windows. It's a bit of
a long shot since what you are seeing involved threads specifically, but
could you maybe try using perl 5.14 to see if you can reproduce the
issue there? Just an idea.

Thanks for the feedback.

Athought I used 5.10 to send the perlbug report, the report shows the
results of three different flavours, the cygwin pre-built 5.10.0 binaries,
my own build of 5.14 and for a control ActivePerl 5.12. These results are
in the __END__ section. You are right string manipulation is substantialy
faster in these later versions of perl but unfortunately this does not
affect the overall defect.

Since then I have also tested in cygwin 5.10.1 which is the latest release
from Redhat and this too has the defect. I have also tested with multiple
versions of ActivePerl (5.8 onwards) and none of them have the defect.

I should also add that if you replace the split with a high CPU math
operation then cygwin perl operates as I expect with a slightly faster
performance in threaded code.

Alistair

From @tsee

Alistair,

On 07/12/2011 11​:02 AM, Alistair McGlinchy wrote​:

On 12 July 2011 08​:25, Steffen Mueller via RT<perlbug-followup@​perl.org>wrote​:

You used perl 5.10. There have been changes in recent versions of Perl
that pertain to allocation and string handling on Windows. It's a bit of
a long shot since what you are seeing involved threads specifically, but
could you maybe try using perl 5.14 to see if you can reproduce the
issue there? Just an idea.

Thanks for the feedback.

Athought I used 5.10 to send the perlbug report, the report shows the
results of three different flavours, the cygwin pre-built 5.10.0 binaries,
my own build of 5.14 and for a control ActivePerl 5.12. These results are
in the __END__ section. You are right string manipulation is substantialy
faster in these later versions of perl but unfortunately this does not
affect the overall defect.

Apologies for missing that. I was too hasty in replying and running off
to work. Given that it's the same defect across many versions, I have no
further clue about the nature of the issue.

Best regards,
Steffen

From @dcollinsn

$ perl 94472.pl
This is perl 5, version 25, subversion 2 (v5.25.2 (v5.25.1-139-gfb899d8)) built for cygwin-thread-multi
Processing 10 tasks in 1 threads completed in 0.673609secs
Processing 10 tasks in 4 threads completed in 18.117090secs

--
Respectfully,
Dan Collins

From [Unknown Contact. See original ticket]

$ perl 94472.pl
This is perl 5, version 25, subversion 2 (v5.25.2 (v5.25.1-139-gfb899d8)) built for cygwin-thread-multi
Processing 10 tasks in 1 threads completed in 0.673609secs
Processing 10 tasks in 4 threads completed in 18.117090secs

--
Respectfully,
Dan Collins