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Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

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Pull RCU updates from Paul E. McKenney:

"
 * Update RCU documentation.  These were posted to LKML at
   https://lkml.org/lkml/2013/8/19/611.

 * Miscellaneous fixes.  These were posted to LKML at
   https://lkml.org/lkml/2013/8/19/619.

 * Full-system idle detection.  This is for use by Frederic
   Weisbecker's adaptive-ticks mechanism.  Its purpose is
   to allow the timekeeping CPU to shut off its tick when
   all other CPUs are idle.  These were posted to LKML at
   https://lkml.org/lkml/2013/8/19/648.

 * Improve rcutorture test coverage.  These were posted to LKML at
   https://lkml.org/lkml/2013/8/19/675.
"

Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar
2013-09-03 07:41:11 +02:00
parent 6e4664525b 25f27ce4a6
commit 7d992feb76
25 changed files with 1609 additions and 832 deletions
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kernel/time/Kconfig
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@@ -134,6 +134,56 @@ 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