[linux-audio-user] Jack and SHM

Since there has been a lot of post concerning jack usage and optimisation recently it has remind me a problem I got that I never been able to understand. I have never been able to run jackstart with -R option when compiling jack with Sys V shm support. jackd -R as root work with SysV shm but if I want to use jackstart I have to use POSIX shm. The error message I am getting with SysV shm is the classical "cannot lock down memory for RT thread (Cannot allocate memory)". I am running a Mandrake 9.2 multimedia kernel (2.4.22, low latency, preemption and capability patches). Since most of jack users seem to use SysV shm I don't understand why I cannot (I am the only exception ....) Christophe