Hi, I have a SH4 board: $ uname -a Linux LINUX7109 2.6.23.17_stm23_A18B-HMP_7109-STSDK #1 PREEMPT Fri Aug 6 16:08:19 ART 2010 sh4 unknown and suppose I have eaten pretty much all the memory, and have only 9 MB left (aprox.) $ free total used free shared buffers cached Mem: 48072 42276 5796 0 172 3264 -/+ buffers/cache: 38840 9232 Swap: 0 0 0 Now, when I try to launch a single thread with default stack size (8 MB) the pthread_create() call fails with ENOMEM. If I strace my test code, I can see that the function that is failing is mmap: old_mmap(NULL, 8388608, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM (Cannot allocate memory) However, when I set the stack size to a lower value using ulimit -s: ulimit -s 7500 I can now launch 10 threads. Each thread does not allocate anything, so it is only consuming the minimum overhead (aprox. 8 kb per thread, right?). So, my question is: Knowing that mmap doesnt actually consume the memory (due to overcommit=0, right?): Why is pthread_create (or mmap) failing when memory available is above the thread stack size ? Where in linux source is the decision made to permit or not the mmap call ? Thanks! Ezequiel.