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<DIV><SPAN class=379214204-10102012><FONT size=2 face=Arial>Hi Thomas &
MapCache users,</FONT></SPAN></DIV>
<DIV><SPAN class=379214204-10102012></SPAN><SPAN class=379214204-10102012><FONT
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV><SPAN class=379214204-10102012><FONT size=2 face=Arial>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. </FONT></SPAN></DIV>
<DIV><SPAN class=379214204-10102012><FONT size=2
face=Arial></FONT></SPAN> </DIV>
<DIV><SPAN class=379214204-10102012></SPAN><SPAN class=379214204-10102012><FONT
size=2 face=Arial>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.</FONT></SPAN></DIV>
<DIV><SPAN class=379214204-10102012><FONT size=2
face=Arial></FONT></SPAN> </DIV>
<DIV><SPAN class=379214204-10102012><FONT size=2
face=Arial></FONT></SPAN> </DIV>
<DIV><SPAN class=379214204-10102012><FONT size=2 face=Arial>The issue:
</FONT></SPAN><SPAN class=379214204-10102012><FONT size=2
face=Arial>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.</FONT></SPAN></DIV>
<DIV><SPAN class=379214204-10102012><FONT size=2 face=Arial></FONT></SPAN><SPAN
class=379214204-10102012><FONT size=2 face=Arial></FONT></SPAN> </DIV>
<DIV><SPAN class=379214204-10102012><FONT size=2 face=Arial>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?</FONT></SPAN></DIV>
<DIV><SPAN class=379214204-10102012><FONT size=2
face=Arial></FONT></SPAN> </DIV>
<DIV><SPAN class=379214204-10102012><FONT size=2 face=Arial>Hardware:
</FONT></SPAN></DIV>
<UL>
<LI><SPAN class=379214204-10102012><FONT face=Arial><FONT face=Arial><FONT
face=Arial>Power Edge R820, 4-socket, 2U blade
server</FONT></FONT></FONT></SPAN></LI>
<LI><SPAN class=379214204-10102012><FONT face=Arial>Populated with four Intel
Xeon E5 processors</FONT></LI>
<LI>
<DIV align=left><FONT face=Arial>Processor E5-4650L - 20M Cache, 2.60 GHz,
8.00 GT/s), Clock Speed2.6 GHz. Max</FONT></DIV></LI>
<LI>
<DIV align=left><FONT face=Arial>Turbo Frequency 3.1 GHz,</FONT></DIV></LI>
<LI>
<DIV align=left><FONT face=Arial>Each processor has 8 (microprocessor)
cores,</FONT></DIV></LI>
<LI>
<DIV align=left><FONT face=Arial>Supporting 16 threads per core with hyper
threading,</FONT></DIV></LI>
<LI>
<DIV align=left><FONT face=Arial>A total of 64<SPAN class=379214204-10102012>
threads</SPAN>, and</FONT></DIV></LI>
<LI><FONT face=Arial><SPAN class=379214204-10102012>300GB RAM. (</SPAN>48
DIMMS (<SPAN class=379214204-10102012>upgradable to </SPAN>1.5 TB of
memory)<SPAN class=379214204-10102012>)</SPAN></FONT></LI></UL>
<DIV><SPAN class=379214204-10102012><FONT size=2
face=Arial>OS:</FONT></SPAN></DIV>
<UL>
<LI><SPAN class=379214204-10102012><FONT size=2 face=Arial><SPAN
style="WIDOWS: 2; TEXT-TRANSFORM: none; BACKGROUND-COLOR: rgb(255,255,255); TEXT-INDENT: 0px; DISPLAY: inline !important; FONT: small/19px arial, verdana, sans-serif; WHITE-SPACE: normal; ORPHANS: 2; FLOAT: none; LETTER-SPACING: normal; COLOR: rgb(0,0,0); WORD-SPACING: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px">Red
Hat Enterprise Linux Server release 6.3
(Santiago)</SPAN></FONT></SPAN></LI></UL><SPAN class=379214204-10102012><FONT
size=2><SPAN
style="WIDOWS: 2; TEXT-TRANSFORM: none; BACKGROUND-COLOR: rgb(255,255,255); TEXT-INDENT: 0px; DISPLAY: inline !important; FONT: small/19px arial, verdana, sans-serif; WHITE-SPACE: normal; ORPHANS: 2; FLOAT: none; LETTER-SPACING: normal; COLOR: rgb(0,0,0); WORD-SPACING: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px">
<DIV style="BACKGROUND-COLOR: transparent"><SPAN class=379214204-10102012><FONT
size=2>Software:</FONT></SPAN></DIV>
<UL
style="WIDOWS: 2; TEXT-TRANSFORM: none; BACKGROUND-COLOR: rgb(255,255,255); MARGIN-TOP: 0px; TEXT-INDENT: 0px; FONT: small/19px arial, verdana, sans-serif; WHITE-SPACE: normal; ORPHANS: 2; LETTER-SPACING: normal; COLOR: rgb(0,0,0); WORD-SPACING: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px">
<LI style="BACKGROUND-COLOR: transparent">Apache Server version: Apache/2.2.15
(Unix)</LI>
<UL style="BACKGROUND-COLOR: transparent; MARGIN-TOP: 0px">
<LI style="BACKGROUND-COLOR: transparent">mod_wsgi </LI>
<LI style="BACKGROUND-COLOR: transparent">mod_mapcach<SPAN
class=379214204-10102012>e</SPAN></LI></UL>
<LI style="BACKGROUND-COLOR: transparent">M<SPAN
class=379214204-10102012>apServer</SPAN><SPAN
class=Apple-converted-space> </SPAN>6.0.3</LI>
<LI style="BACKGROUND-COLOR: transparent"><SPAN
style="BORDER-BOTTOM: rgb(221,221,221) 1px solid; BORDER-LEFT: rgb(221,221,221) 0px solid; BORDER-TOP: rgb(221,221,221) 0px solid; BORDER-RIGHT: rgb(221,221,221) 0px solid"
class=foswikiNewLink>MapCache</SPAN><SPAN
class=Apple-converted-space> </SPAN>(current devel 6.2.0beta2)</LI>
<LI style="BACKGROUND-COLOR: transparent">Gdal 1.<SPAN
class=379214204-10102012>8</SPAN>.1</LI>
<LI style="BACKGROUND-COLOR: transparent">Python 2.6.6
<UL style="BACKGROUND-COLOR: transparent; MARGIN-TOP: 0px">
<LI style="BACKGROUND-COLOR: transparent">Python Mapscript</LI></UL></LI>
<LI style="BACKGROUND-COLOR: transparent">Perl 5.10.1
<UL style="BACKGROUND-COLOR: transparent; MARGIN-TOP: 0px">
<LI style="BACKGROUND-COLOR: transparent">Perl Mapscript</LI></UL></LI>
<LI style="BACKGROUND-COLOR: transparent">Postgres 8.4.12/PostGIS
1.5.3</LI></UL>
<DIV><SPAN class=379214204-10102012><FONT size=2>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.
</FONT></SPAN></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><SPAN class=379214204-10102012><FONT size=2>We are using non-linear
resolution steps to avoid seeding too many tiles. Perhaps that is a problem
with depth seeding?</FONT></SPAN></DIV>
<DIV><SPAN class=379214204-10102012></SPAN><SPAN
class=379214204-10102012></SPAN><SPAN class=379214204-10102012><FONT size=2>We
are using a metatile area of 8 x 8.</FONT></SPAN></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><SPAN class=379214204-10102012><FONT size=2>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.</FONT></SPAN></DIV>
<DIV></SPAN></FONT></SPAN></SPAN><SPAN class=379214204-10102012><FONT size=2
face=Arial></FONT></SPAN> </DIV>
<DIV><SPAN class=379214204-10102012><FONT size=2 face=Arial>Best
regards,</FONT></SPAN></DIV>
<DIV><SPAN class=379214204-10102012><FONT size=2
face=Arial>Matt</FONT></SPAN></DIV></BODY></HTML>