On 07/27/2013 07:19 AM, Paul E. McKenney wrote: > From: "Paul E. McKenney" <paul...@linux.vnet.ibm.com> > > At least one CPU must keep the scheduling-clock tick running for > timekeeping purposes whenever there is a non-idle CPU. However, with > the new nohz_full adaptive-idle machinery, it is difficult to distinguish > between all CPUs really being idle as opposed to all non-idle CPUs being > in adaptive-ticks mode. This commit therefore adds a Kconfig parameter > as a first step towards enabling a scalable detection of full-system > idle state. > > Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com> > Cc: Frederic Weisbecker <fweis...@gmail.com> > Cc: Steven Rostedt <rost...@goodmis.org> > --- > kernel/time/Kconfig | 23 +++++++++++++++++++++++ > 1 file changed, 23 insertions(+) > > diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig > index 70f27e8..a613c2a 100644 > --- a/kernel/time/Kconfig > +++ b/kernel/time/Kconfig > @@ -134,6 +134,29 @@ config NO_HZ_FULL_ALL > Note the boot CPU will still be kept outside the range to > handle the timekeeping duty. > > +config NO_HZ_FULL_SYSIDLE > + bool "Detect full-system idle state for full dynticks system" > + depends on NO_HZ_FULL > + default n > + help > + At least one CPU must keep the scheduling-clock tick running > + for timekeeping purposes whenever there is a non-idle CPU, > + where "non-idle" includes CPUs with a single runnable task > + in adaptive-idle mode. Because the underlying adaptive-tick > + support cannot distinguish between all CPUs being idle and > + all CPUs each running a single task in adaptive-idle mode, > + the underlying support simply ensures that there is always > + a CPU handling the scheduling-clock tick, whether or not all > + CPUs are idle. This Kconfig option enables scalable detection > + of the all-CPUs-idle state, thus allowing the scheduling-clock > + tick to be disabled when all CPUs are idle. Note that scalable > + detection of the all-CPUs-idle state means that larger systems > + will be slower to declare the all-CPUs-idle state. > + > + Say Y if you would like to help debug all-CPUs-idle detection.
The code is needed only for debug? I guess not. > + > + Say N if you are unsure. > + > config NO_HZ > bool "Old Idle dynticks config" > depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS -- 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/
