[Gdal-dev] ECW compression - Extremely slow Linux performance
andrew at andrewlarcombe.co.uk
Mon Aug 21 10:22:31 EDT 2006
Andrew Larcombe wrote:
> Frank Warmerdam wrote:
>> Andrew Larcombe wrote:
>>> Frank - according to top the CPU usage varies but never gets above
>>> 20%. Does this shed any more light on the issue?
>> This indicates things are stalling somewhere. My guess then is that it
>> is a thread switching issue of some sort. How confident are you that
>> you are using the latest and greatest ECW SDK?
>> It could also be some sort of IO problem. I think the encoder keeps
>> temp files in /tmp. I trust that is a fast local disk too?
>> Beyond that it gets pretty involved to try and diagnose. I just hate
>> multithreaded libraries.
To get some more consistent results, I've tried comparing the
performance of the latest FWTools on my laptop and the problematic
server. Tests are done on local drives with /tmp also being local. Test
is to convert a 4000x4000 uncompressed TIF to ECW with TARGET=90 set
using gdal_convert found in the bin_safe directory:
Centrino 1.4GHz, 1Gig RAM
Mandriva 2006, glibc-2.3.5
45%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+8878minor)pagefaults 0swaps
4x Dual-Core Xeon 3.66GHz, 8Gig RAM
Redhat Enterprise Linux 3, glibc-2.3.2
ie, the server takes ~2 minutes, the laptop ~1 minute which isn't what
one would expect. Additionally, both are extremely slow compared to the
FWTools shell on Windows XP laptop (1.6GHz, 512MB RAM) which processes
it in ~6 seconds.
Compressing to JPEG using gdal_translate is a different matter -
basically what you would expect. The laptop takes ~4 seconds, the server
Freelance Geospatial, Database & Web Programming
email: andrew at andrewlarcombe.co.uk
mob: +44 (7760) 258623
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