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
projects / linux-2.6-microblaze.git / blobdiff