Multiple process logfiles in the same directory

I am getting multiple process logfiles in the same logs directory. Looks like the unique ID somehow doesn't count. To reproduce:

diff --git a/clients/drcachesim/tests/burst_threadfilter.cpp
[..]
\- std::string("-stderr_mask 0xc -client_lib ';;-offline -max_trace_size 256K ");
\+ std::string("-loglevel 3 -logdir logs -stderr_mask 0xc -client_lib ';;-offline -max_trace_size 256K ");
[..]

Then I run

for NUM in `seq 1 1 10000`; do ./clients/bin64/tool.drcacheoff.burst_threadfilter ; echo was here $NUM; done

Example:

ls ../build/logs/tool.drcacheoff.burst_threadfilter.92183.00000000/
log.0.92189.html log.12.92190.html log.15.92186.html log.18.92189.html log.20.92188.html log.23.92191.html log.26.92192.html log.2.92185.html log.31.92188.html log.34.92187.html log.4.92191.html log.7.92192.html tool.drcacheoff.burst_threadfilter.0.92183.html
log.10.92183.html log.13.92188.html log.16.92191.html log.1.92188.html log.21.92187.html log.24.92185.html log.27.92189.html log.29.92183.html log.32.92185.html log.35.92191.html log.5.92187.html log.8.92183.html tool.drcacheoff.burst_threadfilter.0.92189.html
log.11.92187.html log.14.92192.html log.17.92185.html log.19.92186.html log.22.92183.html log.25.92190.html log.28.92186.html log.30.92192.html log.33.92190.html log.3.92186.html log.6.92190.html log.9.92189.html