Increasing memory usage with TTree:Fill()

Dear ROOT developer,
I have a trouble on increasing memory usage with TTree::Fill().
Is it an expected behavior? How can I stop it?
I use root 5.12/00e or 5.13//02 with gcc3.2.3 in slc3 (lxplus at cern).
A short program and results of memory usage are attached.
Best regards,
rootforum.tar.gz (7.79 KB)

I cannot reproduce your problem. See in attachment the log file produced by your program on my machine running SLC3 and gcc3.2.3.

xwrite.tar.gz (3.13 KB)

Dear Rene,

I’m sorry for the rack of information.
Please modify the line 27 of write.C
const int num=10;
const int num=100;
The result from original code corresponds to the red graph (array szie==10)
and that from the modified version corresponds to the blue graph (array size==100).
Please try the modified version.
Your result is similler to my red graph with root 5.13/02, and
the increase of memory usage is reproduced in your result.
Best Regards,