On Wed, 20 Mar 2013, Paul E. McKenney wrote: > > > Another approach is to offload RCU callback processing to "rcuo" kthreads > > > using the CONFIG_RCU_NOCB_CPU=y. The specific CPUs to offload may be > > > selected via several methods:
Why are there multiple rcuo threads? Would a single thread that may be able to run on multiple cpus not be sufficient? > > "Even though the SCHED_FIFO task is the only task running, because the > > SCHED_OTHER tasks are queued on the CPU, it currently will not enter > > adaptive tick mode." > > Again, good point! Uggh. That will cause problems and did cause problems when I tried to use nohz. The OS always has some sched other tasks around that become runnable after a while (like for example the vm statistics update, or the notorious slab scanning). As long as SCHED_FIFO is active and there is no process in the same scheduling class then tick needs to be off. Also wish that this would work with SCHED_OTHER if there is only a single task with a certain renice value (-10?) and the rest is runnable at lower priorities. Maybe in that case stop the tick for a longer period and then give the lower priority tasks a chance to run but then switch off the tick again. -- 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/
