Hi, First of all, many thanks for such useful tools. In the source code of cyclictest, I can see a mistake concerning the error checking of pthread_setaffinity_np(): Upon error, pthread functions return an error ant not -1. So, the following code: if (par->cpu != -1) { CPU_ZERO(&mask); CPU_SET(par->cpu, &mask); thread = pthread_self(); if (pthread_setaffinity_np(thread, sizeof(mask), &mask) == -1) warn("Could not set CPU affinity to CPU #%d\n", par->cpu); } should be fixed as follow: int status; if (par->cpu != -1) { CPU_ZERO(&mask); CPU_SET(par->cpu, &mask); thread = pthread_self(); if ((status = pthread_setaffinity_np(thread, sizeof(mask), &mask)) != 0) warn("Could not set CPU affinity to CPU #%d: %s (%d)\n", par->cpu, strerror(status), status); } Regards, -- Rachid Koucha