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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2013-06-21 11:08:45 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2013-08-18 18:07:02 -0700 |
| commit | b44379af1cf40050794832c38ea6a64e07eb5087 (patch) | |
| tree | 2f7fb3764976a4a0e2d2cf7a7f814564361203a4 /kernel/time | |
| parent | 8bdf7a252b6398dbd4beaa7a2ba0904cea0abd04 (diff) | |
nohz_full: Add Kconfig parameter for scalable detection of all-idle state
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 <paulmck@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
[ paulmck: Update help text per Frederic Weisbecker. ]
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/Kconfig | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index 70f27e89012..c7d2fd67799 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" also includes dynticks CPUs as long as they are + running non-idle tasks. Because the underlying adaptive-tick + support cannot distinguish between all CPUs being idle and + all CPUs each running a single task in dynticks 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. + + Say N if you are unsure. + config NO_HZ bool "Old Idle dynticks config" depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS |