performance of multithreading gets gradually worse under gdb

[Markus Alber <markus@hyperion-imrt.org>]

 Hello,

 I have experienced the following problem:

 I'm debugging a number-crunching application which spawns a lot (36) 
 little
 worker threads per iteration. The system does typically OoM 200 
 iterations.
 Although each of them should take about the same amount of time, the 
 performance
 gets worse with every iteration and becomes excruciatingly slow.

 A system monitor reveals that gdb allocates more memory with every 
 iteration,
 i.e. with every 36 threads started and finished. The CPU load of GDB 
 goes up, too.
 The CPU usage of the application goes down. Compared to the solo 
 performance, it
 gets slower by a factor 20 and more, if run long enough.

 The application behaves perfectly when run by itself. The 
 multi-threaded part is not
 debugging compiled when this behaviour occurs.

 The distribution is SuSE 11.3 / gdb 7.1.

 Is there anything I can change about this behaviour, any options of gdb 
 that need to
 be set in these circumstances?

 Thank you very much for your help in advance,

 Markus