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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2013-07-02 16:13:29 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-07-02 16:13:29 -0700 |
| commit | ab3d681e9d41816f90836ea8fe235168d973207f (patch) | |
| tree | c5210911fcb6023f4956a302ee1d4ce3a405aa0f /init/Kconfig | |
| parent | 0c46d68d1930c8a58d0f291328b9759da754e599 (diff) | |
| parent | b1fe9987b78755719e8627d58409174ba00c24de (diff) | |
Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU updates from Ingo Molnar:
"The major changes:
- Simplify RCU's grace-period and callback processing based on the new
numbering for callbacks.
- Removal of TINY_PREEMPT_RCU in favor of TREE_PREEMPT_RCU for
single-CPU low-latency systems.
- SRCU-related changes and fixes.
- Miscellaneous fixes, including converting a few remaining printk()
calls to pr_*().
- Documentation updates"
* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (32 commits)
rcu: Shrink TINY_RCU by reworking CPU-stall ifdefs
rcu: Shrink TINY_RCU by moving exit_rcu()
rcu: Remove TINY_PREEMPT_RCU tracing documentation
rcu: Consolidate rcutiny_plugin.h ifdefs
rcu: Remove rcu_preempt_note_context_switch()
rcu: Remove the CONFIG_TINY_RCU ifdefs in rcutiny.h
rcu: Remove check_cpu_stall_preempt()
rcu: Simplify RCU_TINY RCU callback invocation
rcu: Remove rcu_preempt_process_callbacks()
rcu: Remove rcu_preempt_remove_callbacks()
rcu: Remove rcu_preempt_check_callbacks()
rcu: Remove show_tiny_preempt_stats()
rcu: Remove TINY_PREEMPT_RCU
powerpc,kvm: fix imbalance srcu_read_[un]lock()
rcu: Remove srcu_read_lock_raw() and srcu_read_unlock_raw().
rcu: Apply Dave Jones's NOCB Kconfig help feedback
rcu: Merge adjacent identical ifdefs
rcu: Drive quiescent-state-forcing delay from HZ
rcu: Remove "Experimental" flags
kthread: Add kworker kthreads to OS-jitter documentation
...
Diffstat (limited to 'init/Kconfig')
| -rw-r--r-- | init/Kconfig | 46 |
1 files changed, 27 insertions, 19 deletions
diff --git a/init/Kconfig b/init/Kconfig index 1e825c299ea5..118895cc1f67 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -473,18 +473,10 @@ config TINY_RCU is not required. This option greatly reduces the memory footprint of RCU. -config TINY_PREEMPT_RCU - bool "Preemptible UP-only small-memory-footprint RCU" - depends on PREEMPT && !SMP - help - This option selects the RCU implementation that is designed - for real-time UP systems. This option greatly reduces the - memory footprint of RCU. - endchoice config PREEMPT_RCU - def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU ) + def_bool TREE_PREEMPT_RCU help This option enables preemptible-RCU code that is common between the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations. @@ -670,7 +662,7 @@ config RCU_BOOST_DELAY Accept the default if unsure. config RCU_NOCB_CPU - bool "Offload RCU callback processing from boot-selected CPUs (EXPERIMENTAL" + bool "Offload RCU callback processing from boot-selected CPUs" depends on TREE_RCU || TREE_PREEMPT_RCU default n help @@ -696,9 +688,10 @@ choice prompt "Build-forced no-CBs CPUs" default RCU_NOCB_CPU_NONE help - This option allows no-CBs CPUs to be specified at build time. - Additional no-CBs CPUs may be specified by the rcu_nocbs= - boot parameter. + This option allows no-CBs CPUs (whose RCU callbacks are invoked + from kthreads rather than from softirq context) to be specified + at build time. Additional no-CBs CPUs may be specified by + the rcu_nocbs= boot parameter. config RCU_NOCB_CPU_NONE bool "No build_forced no-CBs CPUs" @@ -706,25 +699,40 @@ config RCU_NOCB_CPU_NONE help This option does not force any of the CPUs to be no-CBs CPUs. Only CPUs designated by the rcu_nocbs= boot parameter will be - no-CBs CPUs. + no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU + kthreads whose names begin with "rcuo". All other CPUs will + invoke their own RCU callbacks in softirq context. + + Select this option if you want to choose no-CBs CPUs at + boot time, for example, to allow testing of different no-CBs + configurations without having to rebuild the kernel each time. config RCU_NOCB_CPU_ZERO bool "CPU 0 is a build_forced no-CBs CPU" depends on RCU_NOCB_CPU && !NO_HZ_FULL help - This option forces CPU 0 to be a no-CBs CPU. Additional CPUs - may be designated as no-CBs CPUs using the rcu_nocbs= boot - parameter will be no-CBs CPUs. + This option forces CPU 0 to be a no-CBs CPU, so that its RCU + callbacks are invoked by a per-CPU kthread whose name begins + with "rcuo". Additional CPUs may be designated as no-CBs + CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs. + All other CPUs will invoke their own RCU callbacks in softirq + context. Select this if CPU 0 needs to be a no-CBs CPU for real-time - or energy-efficiency reasons. + or energy-efficiency reasons, but the real reason it exists + is to ensure that randconfig testing covers mixed systems. config RCU_NOCB_CPU_ALL bool "All CPUs are build_forced no-CBs CPUs" depends on RCU_NOCB_CPU help This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs= - boot parameter will be ignored. + boot parameter will be ignored. All CPUs' RCU callbacks will + be executed in the context of per-CPU rcuo kthreads created for + this purpose. Assuming that the kthreads whose names start with + "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter + on the remaining CPUs, but might decrease memory locality during + RCU-callback invocation, thus potentially degrading throughput. Select this if all CPUs need to be no-CBs CPUs for real-time or energy-efficiency reasons. |