Matthew, What would help is if you could provide a backtrace from the segfault:
- reconfigure with --enable-debug / recompile / reinstall - gdb mapcache_seed - run [previous args: -n 4 -c /path/to/mapcache.xml etc...] - wait till segfault - bt thanks, thomas On Wed, Oct 10, 2012 at 8:14 AM, Matthew Doyle <[email protected]> wrote: > Hi Thomas & MapCache users, > > A little background: we are developing a weather forecasting tool which > provides a visual representation of a quite a large dataset (NetCDF grid, 7 > days of data every three hours). As such, we have many diferent layers and a > very large number of tiles which require seeding multiple times per day. > > Based on very impressive seeding results from tests carried out on on RHEL 5 > (a VM box with 8 cores), seeding using 8 threads, and encountering no issues > during these tests, the decision was made to purchase the best hardware > available in order to seed our tiles as quickly as possible when going > operational. > > > The issue: mapcache_seed is halting with "segmentation fault (core dumped)" > on our new operational machine when using any number of threads > 1. The > higher the number of threads, the more likely it is to segfault. The issue > appears during the initialisation phase just prior to seeding as once the > seeding run is initialised it will complete successfully, but if the > segfault occurs it will occur and exit almost immediately after execution. > > I will try to provide as much information as possible, please let me know > what would be useful, perhaps the core dump ? or a simple test case > (MapServer mapfile / data file / mapcache xml / seeding parameters) in the > hope that you might be able to reproduce? > > Hardware: > > Power Edge R820, 4-socket, 2U blade server > Populated with four Intel Xeon E5 processors > Processor E5-4650L - 20M Cache, 2.60 GHz, 8.00 GT/s), Clock Speed2.6 GHz. > Max > Turbo Frequency 3.1 GHz, > Each processor has 8 (microprocessor) cores, > Supporting 16 threads per core with hyper threading, > A total of 64 threads, and > 300GB RAM. (48 DIMMS (upgradable to 1.5 TB of memory)) > > OS: > > Red Hat Enterprise Linux Server release 6.3 (Santiago) > > Software: > > Apache Server version: Apache/2.2.15 (Unix) > > mod_wsgi > mod_mapcache > > MapServer 6.0.3 > MapCache (current devel 6.2.0beta2) > Gdal 1.8.1 > Python 2.6.6 > > Python Mapscript > > Perl 5.10.1 > > Perl Mapscript > > Postgres 8.4.12/PostGIS 1.5.3 > > Our WMS service is a very basic Python MapScript wrapper via mod_wsgi, but i > have also tried standard CGI Python and CGI Perl wrappers with the same > results. > > We are using non-linear resolution steps to avoid seeding too many tiles. > Perhaps that is a problem with depth seeding? > We are using a metatile area of 8 x 8. > > Attempting to seed using any number of threads will cause a segfault > (usually any number higher than 4, but i have seen it fail with less). It's > worth mentioning that if n threads is set to 1, then the seeding process > executes and completes without any issues. Any light you can shed on this > situation and any suggestions are greatly appreciated. > > Best regards, > Matt _______________________________________________ mapserver-users mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/mapserver-users
