Running Out of Threads on Debian

Question

I have a program that creates a specified amount of active threads on my debian machine. When I try to create anything over 100 I get an error saying "Error in creating thread" when it reaches the OS limitation and machine doesn't accept any incoming connections and when executing commands I get "-bash: fork: Cannot allocate memory". Looking at the top command I see tasks are getting maxed out at 32564 and only 20% of my RAM is being utilized. I tried editing ulimit -a & -n to 500000 and -s to 81920 but still doesn't do anything. Any help is greatly appreciated/.

Answer 1

From my own experience, when using threads a good rule of thumb for increased performance for CPU bound processes is to use an equal number of threads as cores, except in the case of a hyper-threaded system in which case one should use twice as many cores. The other rule of thumb that can be concluded is for I/O bound processes. This rule is to quadruple the number threads per cores, except for the case of a hyper-threaded system, then one can quadruple the number of threads per core. So you probably shouldn't be making 100's of threads anyway. Just do "enough".