On Tue, 20 Apr 2010 11:29:02 +0200 Thomas Renninger <trenn@xxxxxxx> wrote: > Have you looked at: > /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_transition_latency > and > /sys/devices/system/cpu/cpu0/cpufreq/ondemand/sampling_rate > Transition latency comes from ACPI tables and sampling rate depends > on it. of course I have; in practice on systems i use it is always a 10 milliseconds interval, which is the minimum it gets. Yes this was a bug, no it wasn't the bug here ;-) > Reducing the sampling rate, significantly reduces performance loss while it does, it is not nearly sufficient for the alternating IO/CPU cases I've looked at. I've looked at many timecharts for various IO/CPU workloads, including my normal own use as well as Andrews and the CPU busy periods are in the 1 - 20 msec range between IOs most of the time, for which a 10 msec sampling is obviously problematic. -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
