[Gdal-dev] ECW compression - Extremely slow Linux performance

[Andrew Larcombe]

Frank Warmerdam wrote:
> Andrew Larcombe wrote:
>> strace'ing gdal_translate gives this:
>>
>> % time     seconds  usecs/call     calls    errors syscall
>> ------ ----------- ----------- --------- --------- ----------------
>>  35.14    0.357212          14     26030           write
>>  24.54    0.249446           9     26948           sched_yield
>>  18.41    0.187088           7     25948           gettimeofday
>>   9.42    0.095770          17      5505           nanosleep
>>   7.40    0.075248           6     12238           _llseek
>>   1.68    0.017050          11      1576         1 read
>>   1.64    0.016643          65       257           munmap
>>   0.46    0.004717          15       317           mprotect
>>   0.32    0.003283         657         5           unlink
>>   0.29    0.002901          24       119           brk
> ...
>>
>> Do you have any more thoughts on this, or where the problem could lie? 
>> It does seem to be making an awfully large number of gettimeofday 
>> calls, although maybe this is a red herring?
> 
> Andrew,
> 
> There are some interesting points for investigation here, but nothing that
> seems conclusive to me.  Actually, if I were to check something it would
> be all the nanosleep() calls.  This suggests there is a hack somewhere in
> the code to "sleep for a little while" to try and avoid some sort of lock
> or race condition, but a little sleeping a lot of times can easily result
> in the poor cpu utilization we are seeing.
> 
> I appologise for not digging into this at my end, but I don't really have
> time to do an indepth investigation. And since it has been some time since
> 3.3RC2, I hate to do a lot of investigation on an old source tree for the
> SDK.

Hi Frank,

Thanks for your help. Are you saying that there's a more recent SDK 
available? I wasn't aware that there was a more recent version than 
3.3RC2 for Linux? According to 
http://www.ermapper.com/downloads/sdks.aspx it's the most recent version 
for Linux - the 3.3 release is for "Operating Systems: Windows NT, 
Windows 2003 Server, Windows XP, Windows 98, Windows 2000"

Regards,

Andrew

-- 
Andrew Larcombe
andrew at andrewlarcombe.co.uk