When running this program thread-limit.c on my dedicated debian server, the output says that my system can't create more than around 600 threads. I need to create more threads, and fix my system misconfiguration.

Here are a few informations about my dedicated server:

de801:/# uname -a
Linux de801.ispfr.net 2.6.18-028stab085.5 #1 SMP Thu Apr 14 15:06:33 MSD 2011 x86_64 GNU/Linux
de801:/# java -version
java version "1.6.0_26"
Java(TM) SE Runtime Environment (build 1.6.0_26-b03)
Java HotSpot(TM) 64-Bit Server VM (build 20.1-b02, mixed mode)
de801:/# ldd $(which java)
        linux-vdso.so.1 =>  (0x00007fffbc3fd000)
        libpthread.so.0 => /lib/libpthread.so.0 (0x00002af013225000)
        libjli.so => /usr/lib/jvm/java-6-sun-1.6.0.26/jre/bin/../lib/amd64/jli/libjli.so (0x00002af013441000)
        libdl.so.2 => /lib/libdl.so.2 (0x00002af01354b000)
        libc.so.6 => /lib/libc.so.6 (0x00002af013750000)
        /lib64/ld-linux-x86-64.so.2 (0x00002af013008000)
de801:/# cat /proc/sys/kernel/threads-max
1589248
de801:/# ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 794624
max locked memory       (kbytes, -l) 32
max memory size         (kbytes, -m) unlimited
open files                      (-n) 10240
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 128
cpu time               (seconds, -t) unlimited
max user processes              (-u) unlimited
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

Here is the output of the C program

de801:/test# ./thread-limit
Creating threads ...
Address of c = 1061520 KB
Address of c = 1081300 KB
Address of c = 1080904 KB
Address of c = 1081168 KB
Address of c = 1080508 KB
Address of c = 1080640 KB
Address of c = 1081432 KB
Address of c = 1081036 KB
Address of c = 1080772 KB
100 threads so far ...
200 threads so far ...
300 threads so far ...
400 threads so far ...
500 threads so far ...
600 threads so far ...
Failed with return code 12 creating thread 637.

Any ideas how to fix this please ?