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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-05-11 11:26:22 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-06-08 18:52:39 -0700
commitfe5ac724d81a3c7803e60c2232718f212f3f38d4 (patch)
tree2e0f8316cd8a2c3f5d67bde225aa5c7cfa7be7a5 /kernel/time/Kconfig
parentf7a10a975036ef9ca957bfe12ab2d4b1a46cccd1 (diff)
rcu: Remove nohz_full full-system-idle state machine
The NO_HZ_FULL_SYSIDLE full-system-idle capability was added in 2013 by commit 0edd1b1784cb ("nohz_full: Add full-system-idle state machine"), but has not been used. This commit therefore removes it. If it turns out to be needed later, this commit can always be reverted. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Rik van Riel <riel@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/time/Kconfig')
-rw-r--r--kernel/time/Kconfig50
1 files changed, 0 insertions, 50 deletions
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 4008d9f95dd7..ac09bc29eb08 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -126,56 +126,6 @@ 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_FULL_SYSIDLE_SMALL
- int "Number of CPUs above which large-system approach is used"
- depends on NO_HZ_FULL_SYSIDLE
- range 1 NR_CPUS
- default 8
- help
- The full-system idle detection mechanism takes a lazy approach
- on large systems, as is required to attain decent scalability.
- However, on smaller systems, scalability is not anywhere near as
- large a concern as is energy efficiency. The sysidle subsystem
- therefore uses a fast but non-scalable algorithm for small
- systems and a lazier but scalable algorithm for large systems.
- This Kconfig parameter defines the number of CPUs in the largest
- system that will be considered to be "small".
-
- The default value will be fine in most cases. Battery-powered
- systems that (1) enable NO_HZ_FULL_SYSIDLE, (2) have larger
- numbers of CPUs, and (3) are suffering from battery-lifetime
- problems due to long sysidle latencies might wish to experiment
- with larger values for this Kconfig parameter. On the other
- hand, they might be even better served by disabling NO_HZ_FULL
- entirely, given that NO_HZ_FULL is intended for HPC and
- real-time workloads that at present do not tend to be run on
- battery-powered systems.
-
- Take the default if you are unsure.
-
config NO_HZ
bool "Old Idle dynticks config"
depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS