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From: Simon Kuhn <simon@zombe.es>
To: Debian Bug Tracking System <submit@bugs.debian.org>
Subject: imagemagick: large performance degradation when compiled with openmp support
Message-ID: <20110819062606.9978.4587.reportbug@p23.polyvore.com>
X-Mailer: reportbug 4.12.6
Date: Thu, 18 Aug 2011 23:26:06 -0700

Package: imagemagick
Version: 8:6.6.0.4-3
Severity: important


When compiled with OpenMP support (which is the default), and the libgomp available
in Squeeze (among others), ImageMagick will process some operations extremely slowly.
This is most noticable when many ImageMagick operations are run in parallel,
such as when used as part of a web service. A reasonable number of ImageMagick processes
appear to block each other from executing, and result in astronomically high
system load and CPU utilization.

Adding '--disable-openmp' to the end of the configure parameters when building
bypasses the issue completely. I do not think that there is a relevant patch in
later versions of ImageMagick, although it is supposedly working properly
with newer libgomp versions.

This issue has been noted on numerous threads on the ImageMagick forum and elsewhere,
for instance:

http://www.imagemagick.org/discourse-server/viewtopic.php?f=1&t=14307&start=0
http://dlcware.blogspot.com/2010/12/imagemagick-openmp-and-really-bad.html

could you post the command line used ?

Could you run install valgrind and run hellgrind on this case ?

And open a report upstream?



Bastien

affects 638409 +php5-imagick
thanks

Hello,

The openmp support also affects imagemagick php module by segfaulting
the module in specific conditions [1].
After disabling the openmp support in imagemagick, the segfault seems to
never occurs again.

As the problem affects Wheezy too, maybe could you consider disabling
openmp support ?

[1]: http://bugs.debian.org/568349

2011/11/9 Guillaume Delacour <gui@iroqwa.org>:

Ok see a libgomp problem . Why do you report it against imagemagick ?

No thanks. This bug is broader than imagemagick, please fix libgomp
and reassign to libgomp with proper gdb trace. And add affect
imagemagick.



Thanks

Bastien

affects 638409 -php5-imagick
thanks

Le jeudi 10 novembre 2011 à 10:23 +0100, roucaries bastien a écrit :

All backtrace i've collected didn't help me ATM. I saw other users using
other distribution have noted that the openmp support is problematic in
such ways. This is why i've proposed to disable this support.

I've deleted the "affects php5-imagick" on this bug. If i confirm an
issue with libgomp, i'll bug against it.