2012/11/2 Christoph Lameter <c...@linux.com>: > Also could we have this support without cpusets? There are multiple means > to do system segmentation (f.e. cgroups) and something like hz control is > pretty basic. Control via some cpumask like irq affinities in f.e. > > /sys/devices/system/cpu/nohz > > or a per cpu flag in > > /sys/devices/system/cpu/cpu0/hz > > would be easier and not be tied to something like cpusets.
You really don't want that cpuset interface, do you? ;-) Yeah I think I agree with you. This adds a dependency to cpusets/cgroups, I wish we could avoid that if possible. Also cpuset may be a bit counter intuitive for this usecase. What if a cpu is included in both a nohz cpuset and a non-nohz cpuset? What is the behaviour to adopt? An OR on the nohz flag such that as long as the CPU is in at least one nohz cpuset, it's considered a nohz CPU? Or only shutdown the tick for the tasks attached in the nohz cpusets? Do we really want that per cgroup granularity and the overhead / complexity that comes along? No I think we should stay simple and have a simple per CPU property for that, without involving cgroups aside. So indeed a cpumask in /sys/devices/system/cpu/nohz looks like a better interface. >> This has been long asked for by those in the RT community. If a task >> requires uninterruptible CPU time, this would be able to give a task >> that, even without the full PREEMPT-RT patch set. > > Also those interested in low latency are very very interested in this > feature in particular in support without any preempt support on in the > kernel. Sure, we are trying to make that full dyncticks approach as much generic as possible. -- 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/
