tomograph does not work

Hi all, I need to have a visual view of the execution detail of each thread in monetdb so I wish to use Tomograph. I followed this https://www.monetdb.org/Documentation/Manuals/MonetDB/Profiler/tomograph and have installed all required pacakges. But Tomograph does not respond when I finished my queries. All its outputs are empty. However, my Stethoscope works perfectly. Is there anything not listed in the Tomograph documentation that needs to be done to get it work? Thanks! Xuntao