|author||Linus Torvalds <email@example.com>||2013-09-04 09:36:54 -0700|
|committer||Linus Torvalds <firstname.lastname@example.org>||2013-09-04 09:36:54 -0700|
Merge branch 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timers/nohz changes from Ingo Molnar: "It mostly contains fixes and full dynticks off-case optimizations, by Frederic Weisbecker" * 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits) nohz: Include local CPU in full dynticks global kick nohz: Optimize full dynticks's sched hooks with static keys nohz: Optimize full dynticks state checks with static keys nohz: Rename a few state variables vtime: Always debug check snapshot source _before_ updating it vtime: Always scale generic vtime accounting results vtime: Optimize full dynticks accounting off case with static keys vtime: Describe overriden functions in dedicated arch headers m68k: hardirq_count() only need preempt_mask.h hardirq: Split preempt count mask definitions context_tracking: Split low level state headers vtime: Fix racy cputime delta update vtime: Remove a few unneeded generic vtime state checks context_tracking: User/kernel broundary cross trace events context_tracking: Optimize context switch off case with static keys context_tracking: Optimize guest APIs off case with static key context_tracking: Optimize main APIs off case with static key context_tracking: Ground setup for static key use context_tracking: Remove full dynticks' hacky dependency on wide context tracking nohz: Only enable context tracking on full dynticks CPUs ...
Diffstat (limited to 'init/Kconfig')
1 files changed, 22 insertions, 6 deletions
diff --git a/init/Kconfig b/init/Kconfig
index cc917d3..0a2c4bc 100644
@@ -528,13 +528,29 @@ config RCU_USER_QS
bool "Force context tracking"
depends on CONTEXT_TRACKING
- default CONTEXT_TRACKING
+ default y if !NO_HZ_FULL
- Probe on user/kernel boundaries by default in order to
- test the features that rely on it such as userspace RCU extended
- quiescent states.
- This test is there for debugging until we have a real user like the
- full dynticks mode.
+ The major pre-requirement for full dynticks to work is to
+ support the context tracking subsystem. But there are also
+ other dependencies to provide in order to make the full
+ dynticks working.
+ This option stands for testing when an arch implements the
+ context tracking backend but doesn't yet fullfill all the
+ requirements to make the full dynticks feature working.
+ Without the full dynticks, there is no way to test the support
+ for context tracking and the subsystems that rely on it: RCU
+ userspace extended quiescent state and tickless cputime
+ accounting. This option copes with the absence of the full
+ dynticks subsystem by forcing the context tracking on all
+ CPUs in the system.
+ Say Y only if you're working on the developpement of an
+ architecture backend for the context tracking.
+ Say N otherwise, this option brings an overhead that you
+ don't want in production.
int "Tree-based hierarchical RCU fanout value"