Java uses max 8 cores on Debian, even though 16 are available

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http://unix.stackexchange.com – I have two servers at hand, both with 16 cores. The first is running Debian, the second running Ubuntu. I have written a small multithreaded java app that creates 16 threads. On the Debian machine, the program uses at most 8 cores, while on the Ubuntu machine the program uses all 16 cores. Since my program and the hardware are identical, the used cores must somehow be limited by Linux itself. What is the cause for this limit? How can I increase this limit? /proc/cpuinfo (i = 0 to 15): processor : i vendor_id : GenuineIntel cpu family : 6 model : 44 model name : Intel(R) Xeon(R (HowTos)