On Tue, 11 Jan 2011, Eliot Miranda wrote: (Pine can't quote your mail, sorry.) "The problem with linux is that the pthreads implementation doesn't allow a normal user-level process to create high-priroity threads so that as soon as the Vm starts to spin doing some computation the heartbeat thread is shut-out and if the spinning computation only interrupted when a delay expires it'll never get interrupted because it is blocking the very thread that would signal the delay. Â So until linux's pthreads implementation supports multiple priorities we're stuck with hacks like the interval timer based itimer in the linux Cog VMs." What about keeping the priority of the heartbeat thread at user-level and decreasing the other VM threads' priority slighly? Levente