2012/11/20 Steven Rostedt <rost...@goodmis.org>: > On Mon, 2012-11-19 at 17:27 -0700, Hakan Akkan wrote: > >> > >> > I suggest to rather define a tunable timekeeping duty CPU affinity in >> > a cpumask file at /sys/devices/system/cpu/timekeeping and a toggle at >> > /sys/devices/system/cpu/cpuX/timekeeping (like the online file). This >> > way the user can decide whether adaptive nohz CPU can handle >> > timekeeping or this must be forced to other CPUs in order to enforce >> > isolation. >> >> Well, users want tickless CPUs because they don't want timekeeping >> (or any other kernel activity for that matter) to run in there. So, I believe >> having that "timekeeping affinity" stay in the regular CPUs is good enough. >> Please let me know how users could utilize these control files to do anything >> other than keeping the timekeeping out of adaptive nohz CPUs. > > I agree. If we already have some /sys cpumask that denotes which CPUs > will be adaptive NO_HZ (or simply isolated) then just keep the tick from > ever going on those CPUs. If all but one CPU is set for nohz, and that > one CPU goes idle, it should still be the one doing the tick.
If you want isolation on your full dynticks CPU it's right. Now you could have lower requirements, a different policy that rather enforce energy saving. But I realize we can integrate such granularity later if users request it and take the behaviour you both describe as the default for now. So let's take that direction. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
