Hi all, I haven't checked the kernel source in the few weeks since ISA 2.06 was released but I suspect that the default Program Priority level hasn't been changed in the kernel yet.
Program Priority: Per ISA 2.06: Section 3.1 (page 671) titled "Program Priority Registers", The 'normal' process priority level has changed from "001 medium" to "100 medium low". There are three levels of priority available to user space and prior to ISA 2.06 the 'normal' priority is the highest priority. This is a relative process priority and 'normal' doesn't immediately set clock rate to an explicit frequency. The ISA change simply re-bases 'normal' to the middle of the three priorities so that user-space can increase or decrease relative program priority without having to explicitly re-base to `100 medium low'. This, of course, means that the kernel should implicitly re-base the priority to the new normal of `100 medium low'. This change can retroactively benefit applications running on POWER6 hardware and since the default program priority is relative it shouldn't effect the performance on older hardware. Sean Curry wrote a patch for GLIBC to increase & decrease thread priority during lock contention loops, i.e. if you don't get the lock, decrease priority. Conversely if you get the lock, increase priority over the critical section. We have some data on cost vs. benefits and we'll supply this when the userspace patch is submitted to GLIBC. We can present that data here in the meantime if requested. Regards, Ryan S. Arnold IBM Linux Technology Center Linux Toolchain development _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
